// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package app

import (
        "slices"
        "unicode"
        "unicode/utf8"

        "github.com/armsnyder/gdshader-language-server/internal/lsp"
        "github.com/samber/lo"
)

type completionContext struct {
        shaderType   string
        functionName string
        lineTokens   []string
}

func (c completionContext) lastToken() string {
        if len(c.lineTokens) == 0 {
                return ""
        }
        return c.lineTokens[len(c.lineTokens)-1]
}

type completionPredicate func(c completionContext) bool

type completionItemPredicate struct {
        predicate completionPredicate
        item      lsp.CompletionItem
}

var alwaysTrue = func(completionContext) bool {
        return true
}

func ifLastTokenOneOf(tokens ...string) completionPredicate {
        return func(c completionContext) bool {
                return slices.Contains(tokens, c.lastToken())
        }
}

func ifFirstTokenOneOf(tokens ...string) completionPredicate {
        return func(c completionContext) bool {
                if len(c.lineTokens) == 0 {
                        return false
                }
                return slices.Contains(tokens, c.lineTokens[0])
        }
}

func ifIsFirst(c completionContext) bool {
        return len(c.lineTokens) == 0
}

func ifShaderType(shaderType string) completionPredicate {
        return func(c completionContext) bool {
                return c.shaderType == shaderType
        }
}

func and(predicates ...completionPredicate) completionPredicate {
        return func(c completionContext) bool {
                for _, predicate := range predicates {
                        if !predicate(c) {
                                return false
                        }
                }
                return true
        }
}

func or(predicates ...completionPredicate) completionPredicate {
        return func(c completionContext) bool {
                for _, predicate := range predicates {
                        if predicate(c) {
                                return true
                        }
                }
                return false
        }
}

func not(predicate completionPredicate) completionPredicate {
        return func(c completionContext) bool {
                return !predicate(c)
        }
}

func ifTokensContain(search string) completionPredicate {
        return func(c completionContext) bool {
                return slices.Contains(c.lineTokens, search)
        }
}

func inFunction(name string) completionPredicate {
        return func(c completionContext) bool {
                return c.functionName == name
        }
}

// https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html#data-types
var dataTypes = map[string]string{
        "void":               "Void datatype, useful only for functions that return nothing.",
        "bool":               "Boolean datatype, can only contain `true` or `false`.",
        "bvec2":              "Two-component vector of booleans.",
        "bvec3":              "Three-component vector of booleans.",
        "bvec4":              "Four-component vector of booleans.",
        "int":                "32 bit signed scalar integer.",
        "ivec2":              "Two-component vector of signed integers.",
        "ivec3":              "Three-component vector of signed integers.",
        "ivec4":              "Four-component vector of signed integers.",
        "uint":               "Unsigned scalar integer; can't contain negative numbers.",
        "uvec2":              "Two-component vector of unsigned integers.",
        "uvec3":              "Three-component vector of unsigned integers.",
        "uvec4":              "Four-component vector of unsigned integers.",
        "float":              "32 bit floating-point scalar.",
        "vec2":               "Two-component vector of floating-point values.",
        "vec3":               "Three-component vector of floating-point values.",
        "vec4":               "Four-component vector of floating-point values.",
        "mat2":               "2x2 matrix, in column major order.",
        "mat3":               "3x3 matrix, in column major order.",
        "mat4":               "4x4 matrix, in column major order.",
        "sampler2D":          "Sampler type for binding 2D textures, which are read as float.",
        "isampler2D":         "Sampler type for binding 2D textures, which are read as signed integer.",
        "usampler2D":         "Sampler type for binding 2D textures, which are read as unsigned integer.",
        "sampler2DArray":     "Sampler type for binding 2D texture arrays, which are read as float.",
        "isampler2DArray":    "Sampler type for binding 2D texture arrays, which are read as signed integer.",
        "usampler2DArray":    "Sampler type for binding 2D texture arrays, which are read as unsigned integer.",
        "sampler3D":          "Sampler type for binding 3D textures, which are read as float.",
        "isampler3D":         "Sampler type for binding 3D textures, which are read as signed integer.",
        "usampler3D":         "Sampler type for binding 3D textures, which are read as unsigned integer.",
        "samplerCube":        "Sampler type for binding Cubemaps, which are read as float.",
        "samplerCubeArray":   "Sampler type for binding Cubemap arrays, which are read as float. Only supported in Forward+ and Mobile, not Compatibility.",
        "samplerExternalOES": "External sampler type. Only supported in Compatibility/Android platform.",
}

func isLastTokenDataType(c completionContext) bool {
        _, ok := dataTypes[c.lastToken()]
        return ok
}

var simpleKeywords = []string{"break", "case", "continue", "default", "do", "else", "for", "if", "return", "switch", "while", "const", "struct"}

func sequence(keyword string, tokens ...string) completionPredicate {
        return func(c completionContext) bool {
                return keyword == tokens[len(tokens)-1] && slices.Equal(c.lineTokens[:len(c.lineTokens)-1], tokens[:len(tokens)-1])
        }
}

func isLastTokenPunctuation(c completionContext) bool {
        if len(c.lineTokens) == 0 {
                return false
        }
        lastToken := c.lastToken()
        r, _ := utf8.DecodeRuneInString(lastToken)
        return unicode.IsPunct(r)
}

var completionItems = func() []completionItemPredicate {
        var items []completionItemPredicate

        for label, doc := range dataTypes {
                items = append(items, completionItemPredicate{
                        predicate: or(
                                isLastTokenPunctuation,
                                ifLastTokenOneOf("uniform", "varying", "in", "out", "inout", "flat", "smooth", "lowp", "mediump", "highp"),
                        ),
                        item: lsp.CompletionItem{
                                Label:         label,
                                Kind:          lsp.CompletionClass,
                                Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: doc},
                        },
                })
        }

        for _, keyword := range simpleKeywords {
                items = append(items, completionItemPredicate{
                        predicate: or(
                                not(or(isLastTokenDataType, ifLastTokenOneOf(simpleKeywords...))),
                                sequence(keyword, "else", "if"),
                        ),
                        item: lsp.CompletionItem{
                                Label: keyword,
                                Kind:  lsp.CompletionKeyword,
                        },
                })
        }

        type predicateDescription struct {
                predicate   completionPredicate
                description string
        }

        isFirstInArgument := ifLastTokenOneOf("(", ",")

        describedKeywords := map[string]predicateDescription{
                // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html#precision
                "lowp":    {alwaysTrue, "low precision, usually 8 bits per component mapped to 0-1"},
                "mediump": {alwaysTrue, "medium precision, usually 16 bits or half float"},
                "highp":   {alwaysTrue, "high precision, uses full float or integer range (32 bit default)"},
                // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html#discarding
                "discard":        {ifIsFirst, "Discards the current fragment, preventing it from being drawn. Used in fragment shaders to skip rendering under certain conditions."},
                "in":             {isFirstInArgument, "An argument only for reading"},
                "out":            {isFirstInArgument, "An argument only for writing"},
                "inout":          {isFirstInArgument, "An argument that is fully passed via reference"},
                "shader_type":    {ifIsFirst, "Declares the type of shader being written, such as `canvas_item`, `spatial`, or `particle`."},
                "render_mode":    {ifIsFirst, "Declares one or more render modes of the shader"},
                "uniform":        {ifIsFirst, "Declares a variable that can be set from outside the shader"},
                "varying":        {ifIsFirst, "Declares a variable that is passed between vertex and fragment shaders"},
                "flat":           {ifLastTokenOneOf("varying"), "The value is not interpolated"},
                "smooth":         {ifLastTokenOneOf("varying"), "The value is interpolated in a perspective-correct fashion. This is the default."},
                "group_uniforms": {ifIsFirst, "Group multiple uniforms together in the inspector"},
        }

        for label, predDesc := range describedKeywords {
                items = append(items, completionItemPredicate{
                        predicate: and(predDesc.predicate, not(func(c completionContext) bool {
                                _, ok := describedKeywords[c.lastToken()]
                                return ok
                        })),
                        item: lsp.CompletionItem{
                                Label: label,
                                Kind:  lsp.CompletionKeyword,
                                Documentation: &lsp.MarkupContent{
                                        Kind:  lsp.MarkupMarkdown,
                                        Value: predDesc.description,
                                },
                        },
                })
        }

        // Non-function uniform himts.
        uniformHints := map[string]string{
                "source_color":                  "Used as color.",
                "hint_normal":                   "Used as normalmap.",
                "hint_default_white":            "As value or albedo color, default to opaque white.",
                "hint_default_black":            "As value or albedo color, default to opaque black.",
                "hint_default_transparent":      "As value or albedo color, default to transparent black.",
                "hint_anisotropy":               "As flowmap, default to right.",
                "repeat_enable":                 "Enabled texture repeating.",
                "repeat_disable":                "Disabled texture repeating.",
                "hint_screen_texture":           "Texture is the screen texture.",
                "hint_depth_texture":            "Texture is the depth texture.",
                "hint_normal_roughness_texture": "Texture is the normal roughness texture (only supported in Forward+).",
        }

        roughnessHints := []string{"r", "g", "b", "a", "normal", "gray"}
        for _, channel := range roughnessHints {
                uniformHints["hint_roughness_"+channel] = "Used for roughness limiter on import (attempts reducing specular aliasing). `_normal` is a normal map that guides the roughness limiter, with roughness increasing in areas that have high-frequency detail."
        }

        filterHints := []string{"nearest", "linear", "nearest_mipmap_nearest", "linear_mipmap_nearest", "nearest_mipmap_linear", "linear_mipmap_linear"}
        for _, filter := range filterHints {
                uniformHints["hint_filter_"+filter] = "Enabled specified texture filtering."
        }

        for label, doc := range uniformHints {
                items = append(items, completionItemPredicate{
                        predicate: and(ifFirstTokenOneOf("uniform"), ifTokensContain(":")),
                        item: lsp.CompletionItem{
                                Label:         label,
                                Kind:          lsp.CompletionKeyword,
                                Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: doc},
                        },
                })
        }

        // Function uniform hints.
        functionUniformHints := map[string]string{
                "hint_enum":  "Displays int input as a dropdown widget in the editor.",
                "hint_range": "Displays float input as a slider in the editor.",
        }

        for label, doc := range functionUniformHints {
                items = append(items, completionItemPredicate{
                        predicate: and(ifFirstTokenOneOf("uniform"), ifTokensContain(":")),
                        item: lsp.CompletionItem{
                                Label:         label,
                                Kind:          lsp.CompletionFunction,
                                Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: doc},
                        },
                })
        }

        // Shader types
        shaderTypes := map[string]string{
                "canvas_item": "Canvas item shader, used for 2D rendering.",
                "spatial":     "Spatial shader, used for 3D rendering.",
                "particles":   "Particle shader, used for particle systems.",
                "sky":         "Sky shader, used for rendering skyboxes or skydomes.",
                "fog":         "Fog shader, used for rendering fog effects.",
        }
        for label, doc := range shaderTypes {
                items = append(items, completionItemPredicate{
                        predicate: ifLastTokenOneOf("shader_type"),
                        item: lsp.CompletionItem{
                                Label:         label,
                                Kind:          lsp.CompletionKeyword,
                                Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: doc},
                        },
                })
        }

        // Built-in variables
        // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html#built-in-variables
        // TODO(asnyder): Set variables based on shader type.

        type renderMode struct {
                mode        string
                description string
        }

        makeRenderModeItems := func(modes ...renderMode) []completionItemPredicate {
                return lo.Map(modes, func(mode renderMode, _ int) completionItemPredicate {
                        return completionItemPredicate{
                                predicate: ifFirstTokenOneOf("render_mode"),
                                item: lsp.CompletionItem{
                                        Label:         mode.mode,
                                        Kind:          lsp.CompletionKeyword,
                                        Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: mode.description},
                                },
                        }
                })
        }

        type constant struct {
                name      string
                shortDesc string
                longDesc  string
        }

        makeConstantItems := func(constants ...constant) []completionItemPredicate {
                return lo.Map(constants, func(c constant, _ int) completionItemPredicate {
                        return completionItemPredicate{
                                predicate: alwaysTrue,
                                item: lsp.CompletionItem{
                                        Label:         c.name,
                                        Kind:          lsp.CompletionConstant,
                                        Detail:        c.shortDesc,
                                        Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: c.longDesc},
                                },
                        }
                })
        }

        makeFunctionConstantItems := func(name string, constants ...constant) []completionItemPredicate {
                return lo.Map(constants, func(c constant, _ int) completionItemPredicate {
                        return completionItemPredicate{
                                predicate: inFunction(name),
                                item: lsp.CompletionItem{
                                        Label:         c.name,
                                        Kind:          lsp.CompletionConstant,
                                        Detail:        c.shortDesc,
                                        Documentation: &lsp.MarkupContent{Kind: lsp.MarkupMarkdown, Value: c.longDesc},
                                },
                        }
                })
        }

        byShaderType := map[string][]completionItemPredicate{
                "spatial": append(
                        // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html#render-modes
                        makeRenderModeItems(
                                renderMode{"blend_mix", "Mix blend mode (alpha is transparency), default."},
                                renderMode{"blend_add", "Additive blend mode."},
                                renderMode{"blend_sub", "Subtractive blend mode."},
                                renderMode{"blend_mul", "Multiplicative blend mode."},
                                renderMode{"blend_premul_alpha", "Premultiplied alpha blend mode (fully transparent = add, fully opaque = mix)."},
                                renderMode{"depth_draw_opaque", "Only draw depth for opaque geometry (not transparent)."},
                                renderMode{"depth_draw_always", "Always draw depth (opaque and transparent)."},
                                renderMode{"depth_draw_never", "Never draw depth."},
                                renderMode{"depth_prepass_alpha", "Do opaque depth pre-pass for transparent geometry."},
                                renderMode{"depth_test_disabled", "Disable depth testing."},
                                renderMode{"sss_mode_skin", "Subsurface Scattering mode for skin (optimizes visuals for human skin, e.g. boosted red channel)."},
                                renderMode{"cull_back", "Cull back-faces (default)."},
                                renderMode{"cull_front", "Cull front-faces."},
                                renderMode{"cull_disabled", "Culling disabled (double sided)."},
                                renderMode{"unshaded", "Result is just albedo. No lighting/shading happens in material, making it faster to render."},
                                renderMode{"wireframe", "Geometry draws using lines (useful for troubleshooting)."},
                                renderMode{"debug_shadow_splits", "Directional shadows are drawn using different colors for each split (useful for troubleshooting)."},
                                renderMode{"diffuse_burley", "Burley (Disney PBS) for diffuse (default)."},
                                renderMode{"diffuse_lambert", "Lambert shading for diffuse."},
                                renderMode{"diffuse_lambert_wrap", "Lambert-wrap shading (roughness-dependent) for diffuse."},
                                renderMode{"diffuse_toon", "Toon shading for diffuse."},
                                renderMode{"specular_schlick_ggx", "Schlick-GGX for direct light specular lobes (default)."},
                                renderMode{"specular_toon", "Toon for direct light specular lobes."},
                                renderMode{"specular_disabled", "Disable direct light specular lobes. Doesn't affect reflected light (use `SPECULAR = 0.0` instead)."},
                                renderMode{"skip_vertex_transform", "`VERTEX`, `NORMAL`, `TANGENT`, and `BITANGENT` need to be transformed manually in the `vertex()` function."},
                                renderMode{"world_vertex_coords", "`VERTEX`, `NORMAL`, `TANGENT`, and `BITANGENT` are modified in world space instead of model space."},
                                renderMode{"ensure_correct_normals", "Use when non-uniform scale is applied to mesh *(note: currently unimplemented)*."},
                                renderMode{"shadows_disabled", "Disable computing shadows in shader. The shader will not receive shadows, but can still cast them."},
                                renderMode{"ambient_light_disabled", "Disable contribution from ambient light and radiance map."},
                                renderMode{"shadow_to_opacity", "Lighting modifies the alpha so shadowed areas are opaque and non-shadowed areas are transparent. Useful for overlaying shadows onto a camera feed in AR."},
                                renderMode{"vertex_lighting", "Use vertex-based lighting instead of per-pixel lighting."},
                                renderMode{"particle_trails", "Enables the trails when used on particles geometry."},
                                renderMode{"alpha_to_coverage", "Alpha antialiasing mode, see [this PR](https://github.com/godotengine/godot/pull/40364) for more."},
                                renderMode{"alpha_to_coverage_and_one", "Alpha antialiasing mode, see [this PR](https://github.com/godotengine/godot/pull/40364) for more."},
                                renderMode{"fog_disabled", "Disable receiving depth-based or volumetric fog. Useful for `blend_add` materials like particles."},
                        ),
                        append(
                                // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html#global-built-ins
                                makeConstantItems(
                                        constant{"TIME", "in float TIME", "Global time since the engine has started, in seconds. It repeats after every `3,600` seconds (which can be changed with the `rollover` setting). It's affected by `time_scale` but not by pausing. If you need a `TIME` variable that is not affected by time scale, add your own global shader uniform and update it each frame."},
                                        constant{"PI", "in float PI", "A `PI` constant (`3.141592`). A ratio of a circle's circumference to its diameter and amount of radians in half turn."},
                                        constant{"TAU", "in float TAU", "A `TAU` constant (`6.283185`). An equivalent of `PI * 2` and amount of radians in full turn."},
                                        constant{"E", "in float E", "An `E` constant (`2.718281`). Euler's number and a base of the natural logarithm."},
                                ),
                                append(
                                        // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html#vertex-built-ins
                                        makeFunctionConstantItems("vertex",
                                                constant{"MODEL_MATRIX", "in mat4 MODEL_MATRIX", "Local space to world space transform. World space is the coordinates you normally use in the editor."},
                                                constant{"CANVAS_MATRIX", "in mat4 CANVAS_MATRIX", "World space to canvas space transform. In canvas space the origin is the upper-left corner of the screen and coordinates ranging from `(0.0, 0.0)` to viewport size."},
                                                constant{"SCREEN_MATRIX", "in mat4 SCREEN_MATRIX", "Canvas space to clip space. In clip space coordinates range from `(-1.0, -1.0)` to `(1.0, 1.0)`."},
                                                constant{"VIEWPORT_SIZE", "in vec2 VIEWPORT_SIZE", "Size of viewport (in pixels)."},
                                                constant{"VIEW_MATRIX", "in mat4 VIEW_MATRIX", "World space to view space transform."},
                                                constant{"INV_VIEW_MATRIX", "in mat4 INV_VIEW_MATRIX", "View space to world space transform."},
                                                constant{"MAIN_CAM_INV_VIEW_MATRIX", "in mat4 MAIN_CAM_INV_VIEW_MATRIX", "View space to world space transform of camera used to draw the current viewport."},
                                                constant{"INV_PROJECTION_MATRIX", "in mat4 INV_PROJECTION_MATRIX", "Clip space to view space transform."},
                                                constant{"NODE_POSITION_WORLD", "in vec3 NODE_POSITION_WORLD", "Node position, in world space."},
                                                constant{"NODE_POSITION_VIEW", "in vec3 NODE_POSITION_VIEW", "Node position, in view space."},
                                                constant{"CAMERA_POSITION_WORLD", "in vec3 CAMERA_POSITION_WORLD", "Camera position, in world space."},
                                                constant{"CAMERA_DIRECTION_WORLD", "in vec3 CAMERA_DIRECTION_WORLD", "Camera direction, in world space."},
                                                constant{"CAMERA_VISIBLE_LAYERS", "in uint CAMERA_VISIBLE_LAYERS", "Cull layers of the camera rendering the current pass."},
                                                constant{"INSTANCE_ID", "in int INSTANCE_ID", "Instance ID for instancing."},
                                                constant{"INSTANCE_CUSTOM", "in vec4 INSTANCE_CUSTOM", "Instance custom data (for particles, mostly)."},
                                                constant{"VIEW_INDEX", "in int VIEW_INDEX", "`VIEW_MONO_LEFT` (`0`) for Mono (not multiview) or left eye, `VIEW_RIGHT` (`1`) for right eye."},
                                                constant{"VIEW_MONO_LEFT", "in int VIEW_MONO_LEFT", "Constant for Mono or left eye, always `0`."},
                                                constant{"VIEW_RIGHT", "in int VIEW_RIGHT", "Constant for right eye, always `1`."},
                                                constant{"EYE_OFFSET", "in vec3 EYE_OFFSET", "Position offset for the eye being rendered. Only applicable for multiview rendering."},
                                                constant{"VERTEX", "inout vec3 VERTEX", "Position of the vertex, in model space. In world space if `world_vertex_coords` is used."},
                                                constant{"VERTEX_ID", "in int VERTEX_ID", "The index of the current vertex in the vertex buffer."},
                                                constant{"NORMAL", "inout vec3 NORMAL", "Normal in model space. In world space if `world_vertex_coords` is used."},
                                                constant{"TANGENT", "inout vec3 TANGENT", "Tangent in model space. In world space if `world_vertex_coords` is used."},
                                                constant{"BINORMAL", "inout vec3 BINORMAL", "Binormal in model space. In world space if `world_vertex_coords` is used."},
                                                constant{"POSITION", "out vec4 POSITION", "If written to, overrides final vertex position in clip space."},
                                                constant{"UV", "inout vec2 UV", "UV main channel."},
                                                constant{"UV2", "inout vec2 UV2", "UV secondary channel."},
                                                constant{"COLOR", "inout vec4 COLOR", "Color from vertices."},
                                                constant{"ROUGHNESS", "out float ROUGHNESS", "Roughness for vertex lighting."},
                                                constant{"POINT_SIZE", "inout float POINT_SIZE", "Point size for point rendering."},
                                                constant{"MODELVIEW_MATRIX", "inout mat4 MODELVIEW_MATRIX", "Model/local space to view space transform (use if possible)."},
                                                constant{"MODELVIEW_NORMAL_MATRIX", "inout mat3 MODELVIEW_NORMAL_MATRIX", ""},
                                                constant{"MODEL_NORMAL_MATRIX", "in mat3 MODEL_NORMAL_MATRIX", ""},
                                                constant{"PROJECTION_MATRIX", "inout mat4 PROJECTION_MATRIX", "View space to clip space transform."},
                                                constant{"BONE_INDICES", "in uvec4 BONE_INDICES", ""},
                                                constant{"BONE_WEIGHTS", "in vec4 BONE_WEIGHTS", ""},
                                                constant{"CUSTOM0", "in vec4 CUSTOM0", "Custom value from vertex primitive. When using extra UVs, `xy` is UV3 and `zw` is UV4."},
                                                constant{"CUSTOM1", "in vec4 CUSTOM1", "Custom value from vertex primitive. When using extra UVs, `xy` is UV5 and `zw` is UV6."},
                                                constant{"CUSTOM2", "in vec4 CUSTOM2", "Custom value from vertex primitive. When using extra UVs, `xy` is UV7 and `zw` is UV8."},
                                                constant{"CUSTOM3", "in vec4 CUSTOM3", "Custom value from vertex primitive."},
                                        ),
                                        append(
                                                // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html#fragment-built-ins
                                                makeFunctionConstantItems("fragment",
                                                        constant{"VIEWPORT_SIZE", "in vec2 VIEWPORT_SIZE", "Size of viewport (in pixels)."},
                                                        constant{"FRAGCOORD", "in vec4 FRAGCOORD", "Coordinate of pixel center in screen space. `xy` specifies position in window (origin is lower-left). `z` is fragment depth and output unless `DEPTH` is written."},
                                                        constant{"FRONT_FACING", "in bool FRONT_FACING", "`true` if current face is front facing, `false` otherwise."},
                                                        constant{"VIEW", "in vec3 VIEW", "Normalized vector from fragment position to camera (in view space)."},
                                                        constant{"UV", "in vec2 UV", "UV that comes from the `vertex()` function."},
                                                        constant{"UV2", "in vec2 UV2", "UV2 that comes from the `vertex()` function."},
                                                        constant{"COLOR", "in vec4 COLOR", "COLOR that comes from the `vertex()` function."},
                                                        constant{"POINT_COORD", "in vec2 POINT_COORD", "Point coordinate for drawing points with `POINT_SIZE`."},
                                                        constant{"MODEL_MATRIX", "in mat4 MODEL_MATRIX", "Model/local space to world space transform."},
                                                        constant{"MODEL_NORMAL_MATRIX", "in mat3 MODEL_NORMAL_MATRIX", "`transpose(inverse(mat3(MODEL_MATRIX)))` for non-uniform scale. Matches `MODEL_MATRIX` otherwise."},
                                                        constant{"VIEW_MATRIX", "in mat4 VIEW_MATRIX", "World space to view space transform."},
                                                        constant{"INV_VIEW_MATRIX", "in mat4 INV_VIEW_MATRIX", "View space to world space transform."},
                                                        constant{"PROJECTION_MATRIX", "in mat4 PROJECTION_MATRIX", "View space to clip space transform."},
                                                        constant{"INV_PROJECTION_MATRIX", "in mat4 INV_PROJECTION_MATRIX", "Clip space to view space transform."},
                                                        constant{"NODE_POSITION_WORLD", "in vec3 NODE_POSITION_WORLD", "Node position, in world space."},
                                                        constant{"NODE_POSITION_VIEW", "in vec3 NODE_POSITION_VIEW", "Node position, in view space."},
                                                        constant{"CAMERA_POSITION_WORLD", "in vec3 CAMERA_POSITION_WORLD", "Camera position, in world space."},
                                                        constant{"CAMERA_DIRECTION_WORLD", "in vec3 CAMERA_DIRECTION_WORLD", "Camera direction, in world space."},
                                                        constant{"CAMERA_VISIBLE_LAYERS", "in uint CAMERA_VISIBLE_LAYERS", "Cull layers of the camera rendering the current pass."},
                                                        constant{"VERTEX", "in vec3 VERTEX", "`VERTEX` from `vertex()` transformed into view space. May differ if `skip_vertex_transform` is enabled."},
                                                        constant{"LIGHT_VERTEX", "inout vec3 LIGHT_VERTEX", "Writable version of `VERTEX` for lighting calculations. Does not change fragment position."},
                                                        constant{"VIEW_INDEX", "in int VIEW_INDEX", "`VIEW_MONO_LEFT` (0) or `VIEW_RIGHT` (1) for stereo rendering."},
                                                        constant{"VIEW_MONO_LEFT", "in int VIEW_MONO_LEFT", "Constant for Mono or left eye, always `0`."},
                                                        constant{"VIEW_RIGHT", "in int VIEW_RIGHT", "Constant for right eye, always `1`."},
                                                        constant{"EYE_OFFSET", "in vec3 EYE_OFFSET", "Position offset for the eye being rendered in multiview rendering."},
                                                        constant{"SCREEN_UV", "in vec2 SCREEN_UV", "Screen UV coordinate for current pixel."},
                                                        constant{"DEPTH", "out float DEPTH", "Custom depth value `[0.0, 1.0]`. Must be set in all branches if written."},
                                                        constant{"NORMAL", "inout vec3 NORMAL", "Normal from `vertex()`, in view space (unless `skip_vertex_transform` is used)."},
                                                        constant{"TANGENT", "inout vec3 TANGENT", "Tangent from `vertex()`, in view space (unless `skip_vertex_transform` is used)."},
                                                        constant{"BINORMAL", "inout vec3 BINORMAL", "Binormal from `vertex()`, in view space (unless `skip_vertex_transform` is used)."},
                                                        constant{"NORMAL_MAP", "out vec3 NORMAL_MAP", "Set normal here when reading from a texture instead of using `NORMAL`."},
                                                        constant{"NORMAL_MAP_DEPTH", "out float NORMAL_MAP_DEPTH", "Depth from `NORMAL_MAP`. Defaults to `1.0`."},
                                                        constant{"ALBEDO", "out vec3 ALBEDO", "Base color (default white)."},
                                                        constant{"ALPHA", "out float ALPHA", "Alpha value `[0.0, 1.0]`. Triggers transparency pipeline if used."},
                                                        constant{"ALPHA_SCISSOR_THRESHOLD", "out float ALPHA_SCISSOR_THRESHOLD", "Alpha discard threshold."},
                                                        constant{"ALPHA_HASH_SCALE", "out float ALPHA_HASH_SCALE", "Alpha hash dither scale (higher = more visible pixels)."},
                                                        constant{"ALPHA_ANTIALIASING_EDGE", "out float ALPHA_ANTIALIASING_EDGE", "Alpha to coverage antialiasing edge threshold. Requires `alpha_to_coverage` render mode."},
                                                        constant{"ALPHA_TEXTURE_COORDINATE", "out vec2 ALPHA_TEXTURE_COORDINATE", "UV for alpha-to-coverage AA. Typically `UV * texture_size`."},
                                                        constant{"PREMUL_ALPHA_FACTOR", "out float PREMUL_ALPHA_FACTOR", "Premultiplied alpha lighting interaction. Used with `blend_premul_alpha`."},
                                                        constant{"METALLIC", "out float METALLIC", "Metallic value `[0.0, 1.0]`."},
                                                        constant{"SPECULAR", "out float SPECULAR", "Specular value (default `0.5`). `0.0` disables reflections."},
                                                        constant{"ROUGHNESS", "out float ROUGHNESS", "Roughness value `[0.0, 1.0]`."},
                                                        constant{"RIM", "out float RIM", "Rim lighting intensity `[0.0, 1.0]`."},
                                                        constant{"RIM_TINT", "out float RIM_TINT", "Rim tint: `0.0` = white, `1.0` = albedo."},
                                                        constant{"CLEARCOAT", "out float CLEARCOAT", "Adds a secondary specular layer."},
                                                        constant{"CLEARCOAT_GLOSS", "out float CLEARCOAT_GLOSS", "Glossiness of clearcoat layer."},
                                                        constant{"ANISOTROPY", "out float ANISOTROPY", "Distortion factor for specular highlight."},
                                                        constant{"ANISOTROPY_FLOW", "out vec2 ANISOTROPY_FLOW", "Direction of anisotropy flow (e.g. from flowmaps)."},
                                                        constant{"SSS_STRENGTH", "out float SSS_STRENGTH", "Subsurface scattering strength."},
                                                        constant{"SSS_TRANSMITTANCE_COLOR", "out vec4 SSS_TRANSMITTANCE_COLOR", "Color for subsurface transmittance effect."},
                                                        constant{"SSS_TRANSMITTANCE_DEPTH", "out float SSS_TRANSMITTANCE_DEPTH", "Depth for transmittance penetration."},
                                                        constant{"SSS_TRANSMITTANCE_BOOST", "out float SSS_TRANSMITTANCE_BOOST", "Boost to force SSS to appear even when lit."},
                                                        constant{"BACKLIGHT", "inout vec3 BACKLIGHT", "Backlighting color for light received on opposite side of surface."},
                                                        constant{"AO", "out float AO", "Ambient occlusion intensity (for pre-baked AO)."},
                                                        constant{"AO_LIGHT_AFFECT", "out float AO_LIGHT_AFFECT", "How much AO dims direct lighting. `[0.0, 1.0]`."},
                                                        constant{"EMISSION", "out vec3 EMISSION", "Emissive color. Can exceed `1.0` for HDR."},
                                                        constant{"FOG", "out vec4 FOG", "If written to, blends final color with `FOG.rgb` using `FOG.a`."},
                                                        constant{"RADIANCE", "out vec4 RADIANCE", "Environment map radiance override."},
                                                        constant{"IRRADIANCE", "out vec4 IRRADIANCE", "Environment map irradiance override."},
                                                ),
                                                // https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html#light-built-ins
                                                makeFunctionConstantItems("light",
                                                        constant{"VIEWPORT_SIZE", "in vec2 VIEWPORT_SIZE", "Size of viewport (in pixels)."},
                                                        constant{"FRAGCOORD", "in vec4 FRAGCOORD", "Pixel center coordinate in screen space. `xy` is position in window, `z` is depth unless `DEPTH` is used. Origin is lower-left."},
                                                        constant{"MODEL_MATRIX", "in mat4 MODEL_MATRIX", "Model/local space to world space transform."},
                                                        constant{"INV_VIEW_MATRIX", "in mat4 INV_VIEW_MATRIX", "View space to world space transform."},
                                                        constant{"VIEW_MATRIX", "in mat4 VIEW_MATRIX", "World space to view space transform."},
                                                        constant{"PROJECTION_MATRIX", "in mat4 PROJECTION_MATRIX", "View space to clip space transform."},
                                                        constant{"INV_PROJECTION_MATRIX", "in mat4 INV_PROJECTION_MATRIX", "Clip space to view space transform."},
                                                        constant{"NORMAL", "in vec3 NORMAL", "Normal vector, in view space."},
                                                        constant{"SCREEN_UV", "in vec2 SCREEN_UV", "Screen UV coordinate for current pixel."},
                                                        constant{"UV", "in vec2 UV", "UV that comes from the `vertex()` function."},
                                                        constant{"UV2", "in vec2 UV2", "UV2 that comes from the `vertex()` function."},
                                                        constant{"VIEW", "in vec3 VIEW", "View vector, in view space."},
                                                        constant{"LIGHT", "in vec3 LIGHT", "Light vector, in view space."},
                                                        constant{"LIGHT_COLOR", "in vec3 LIGHT_COLOR", "`light_color * light_energy * PI`. Includes `PI` because physically-based models divide by `PI`."},
                                                        constant{"SPECULAR_AMOUNT", "in float SPECULAR_AMOUNT", "`2.0 * light_specular` for Omni and Spot lights. `1.0` for Directional lights."},
                                                        constant{"LIGHT_IS_DIRECTIONAL", "in bool LIGHT_IS_DIRECTIONAL", "`true` if this pass is a DirectionalLight3D."},
                                                        constant{"ATTENUATION", "in float ATTENUATION", "Attenuation from distance or shadow."},
                                                        constant{"ALBEDO", "in vec3 ALBEDO", "Base albedo color."},
                                                        constant{"BACKLIGHT", "in vec3 BACKLIGHT", "Backlighting color."},
                                                        constant{"METALLIC", "in float METALLIC", "Metallic factor."},
                                                        constant{"ROUGHNESS", "in float ROUGHNESS", "Roughness factor."},
                                                        constant{"DIFFUSE_LIGHT", "out vec3 DIFFUSE_LIGHT", "Diffuse light result."},
                                                        constant{"SPECULAR_LIGHT", "out vec3 SPECULAR_LIGHT", "Specular light result."},
                                                        constant{"ALPHA", "out float ALPHA", "Alpha value `[0.0, 1.0]`. Enables transparent pipeline if written."},
                                                )...,
                                        )...,
                                )...,
                        )...,
                ),
        }

        for label, typeItems := range byShaderType {
                for _, item := range typeItems {
                        items = append(items, completionItemPredicate{
                                predicate: and(ifShaderType(label), item.predicate),
                                item:      item.item,
                        })
                }
        }

        return items
}()

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package app

import (
        "bytes"
        "context"
        "fmt"
        "io"
        "slices"
        "strings"
        "unicode"
        "unicode/utf8"

        "github.com/armsnyder/gdshader-language-server/internal/lsp"
        "github.com/samber/lo"
)

// Handler encapsulates the logic of the Godot shader language server.
type Handler struct {
        lsp.Filesystem
}

// Initialize implements lsp.Handler.
func (h *Handler) Initialize(context.Context, lsp.ClientCapabilities) (*lsp.ServerCapabilities, error) {
        return &lsp.ServerCapabilities{
                TextDocumentSync: &lsp.TextDocumentSyncOptions{
                        OpenClose: true,
                        Change:    lsp.SyncIncremental,
                },
                CompletionProvider: &lsp.CompletionOptions{},
        }, nil
}

// Completion implements lsp.Handler.
func (h *Handler) Completion(_ context.Context, params lsp.CompletionParams) (*lsp.CompletionList, error) {
        currentWord, c, err := h.getCompletionContext(params)
        if err != nil {
                return nil, fmt.Errorf("failed to get current word: %w", err)
        }

        // TODO(asnyder):
        // - Swizzling https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html#swizzling
        // - Constructors https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shading_language.html#constructing
        // - Array .length()
        // - Reference variables and functions
        // - Struct fields
        // - Built-in functions https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/shader_functions.html#

        return &lsp.CompletionList{
                Items: lo.FilterMap(completionItems, func(item completionItemPredicate, _ int) (lsp.CompletionItem, bool) {
                        return item.item, strings.HasPrefix(item.item.Label, currentWord) && item.predicate(*c)
                }),
        }, nil
}

func (h *Handler) getCompletionContext(params lsp.CompletionParams) (currentWord string, c *completionContext, err error) {
        doc, ok := h.Documents[params.TextDocument.URI]
        if !ok {
                return "", nil, fmt.Errorf("document not found: %s", params.TextDocument.URI)
        }

        lineStartPos := params.Position
        lineStartPos.Character = 0

        line, err := h.readBetweenPositions(doc, lineStartPos, params.Position)
        if err != nil {
                return "", nil, fmt.Errorf("reading current line: %w", err)
        }

        firstLine, err := h.readLine(doc, 0)
        if err != nil {
                return "", nil, fmt.Errorf("reading first line: %w", err)
        }

        c = &completionContext{}

        c.functionName, err = h.getCurrentFunction(doc, params.Position)
        if err != nil {
                return "", nil, fmt.Errorf("getting current function: %w", err)
        }

        firstLineTokens := tokenize(firstLine)
        if i := slices.Index(firstLineTokens, "shader_type"); i >= 0 && i < len(firstLineTokens)-1 {
                c.shaderType = firstLineTokens[i+1]
        }

        tokens := tokenize(line)
        if len(tokens) == 0 {
                return "", c, nil
        }

        c.lineTokens = tokens[:len(tokens)-1]
        return tokens[len(tokens)-1], c, nil
}

func (h *Handler) readBetweenPositions(doc *lsp.Document, startPos, endPos lsp.Position) ([]byte, error) {
        startOffset, err := doc.PositionToOffset(startPos)
        if err != nil {
                return nil, fmt.Errorf("start position to offset: %w", err)
        }
        endOffset, err := doc.PositionToOffset(endPos)
        if err != nil {
                return nil, fmt.Errorf("end position to offset: %w", err)
        }

        return io.ReadAll(io.NewSectionReader(doc, int64(startOffset), int64(endOffset-startOffset)))
}

func (h *Handler) readLine(doc *lsp.Document, lineNumber int) ([]byte, error) {
        startPos := lsp.Position{Line: lineNumber, Character: 0}
        endPos := lsp.Position{Line: lineNumber + 1, Character: 0}

        line, err := h.readBetweenPositions(doc, startPos, endPos)
        if err != nil {
                return nil, fmt.Errorf("reading line %d: %w", lineNumber, err)
        }

        return line, nil
}

func (h *Handler) getCurrentFunction(doc *lsp.Document, pos lsp.Position) (string, error) {
        for lineNumber := pos.Line; lineNumber >= 0; lineNumber-- {
                line, err := h.readLine(doc, lineNumber)
                if err != nil {
                        return "", fmt.Errorf("reading line %d: %w", lineNumber, err)
                }

                tokens := tokenize(line)
                for i := len(tokens) - 2; i > 1; i-- {
                        if tokens[i] == ")" && tokens[i+1] == "{" {
                                return tokens[1], nil
                        }
                }
        }

        return "", nil
}

func tokenize(line []byte) []string {
        var tokens []string

        isNotWord := func(r rune) bool {
                return !unicode.IsLetter(r) && !unicode.IsDigit(r) && r != '_'
        }

        for {
                // Skip over any whitespace.
                line = bytes.TrimLeftFunc(line, unicode.IsSpace)
                // Capture each punctuation as a separate token.
                if i := bytes.IndexFunc(line, isNotWord); i == 0 {
                        r, size := utf8.DecodeRune(line)
                        tokens = append(tokens, string(r))
                        line = line[size:]
                        continue
                }
                // Capture the word.
                if i := bytes.IndexFunc(line, isNotWord); i >= 0 {
                        tokens = append(tokens, string(line[:i]))
                        line = line[i:]
                        continue
                }
                // This is the last token
                if len(line) > 0 {
                        tokens = append(tokens, string(line))
                }
                return tokens
        }
}

var _ lsp.Handler = &Handler{}

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package ast

import (
        "io"

        "github.com/alecthomas/participle/v2"
)

var parser *participle.Parser[File]

func init() {
        parser = participle.MustBuild[File]()
}

// Parse parses a .gdshader file into a tree of AST nodes.
func Parse(filename string, reader io.Reader) (*File, error) {
        return parser.Parse(filename, reader, participle.AllowTrailing(true))
}

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package lsp

import (
        "bytes"
        "context"
        "errors"
        "fmt"
        "io"
        "slices"
        "strings"
        "unicode/utf8"

        "github.com/zyedidia/rope"
)

// BufferType represents a buffer implementation.
type BufferType int

const (
        // BufferTypeDefault chooses a buffer for you.
        BufferTypeDefault BufferType = iota
        // BufferTypeGap uses a gap buffer for amortized O(1) insertions and
        // deletions and fast reads, at the cost of poorer random access.
        BufferTypeGap
        // BufferTypeRope uses a rope data structure for efficient random
        // access and insertions/deletions in large documents.
        BufferTypeRope
)

// Filesystem can be embedded into handlers in order to implement the basic
// document sync methods of the LSP.
type Filesystem struct {
        Documents  map[string]*Document
        BufferType BufferType
}

// DidOpenTextDocument implements DocumentSyncHandler.
func (f *Filesystem) DidOpenTextDocument(_ context.Context, params DidOpenTextDocumentParams) error {
        var buf Buffer
        switch f.BufferType {
        case BufferTypeGap:
                buf = &GapBuffer{}
        case BufferTypeRope:
                buf = &RopeBuffer{}
        }

        if f.Documents == nil {
                f.Documents = make(map[string]*Document)
        }
        f.Documents[params.TextDocument.URI] = NewDocument([]byte(params.TextDocument.Text), buf)

        return nil
}

// DidCloseTextDocument implements lsp.Handler.
func (f *Filesystem) DidCloseTextDocument(_ context.Context, params DidCloseTextDocumentParams) error {
        delete(f.Documents, params.TextDocument.URI)
        return nil
}

// DidChangeTextDocument implements lsp.Handler.
func (f *Filesystem) DidChangeTextDocument(_ context.Context, params DidChangeTextDocumentParams) error {
        doc, ok := f.Documents[params.TextDocument.URI]
        if !ok {
                return fmt.Errorf("document not found: %s", params.TextDocument.URI)
        }

        for _, change := range params.ContentChanges {
                if err := doc.ApplyChange(change); err != nil {
                        return err
                }
        }

        return nil
}

var _ DocumentSyncHandler = (*Filesystem)(nil)

// Buffer implements large text storage with methods for random access.
type Buffer interface {
        io.ReaderAt
        io.WriterAt
        // Reset reinitializes the buffer with the given text.
        Reset(b []byte)
        // Bytes returns the full content of the buffer as a byte slice.
        Bytes() []byte
        // Delete deletes a range of bytes from the buffer.
        Delete(start, end int)
        // Len returns the number of bytes in the buffer.
        Len() int
}

// Document represents a text document with methods to manipulate its content.
type Document struct {
        buffer    Buffer
        lineStart []int
        cache     []byte
        charBuf   []byte
}

// NewDocument creates a new Document with the given initial text and buffer.
// If buf is nil, a GapBuffer is used.
func NewDocument(text []byte, buf Buffer) *Document {
        if buf == nil {
                buf = &GapBuffer{}
        }
        doc := &Document{buffer: buf, charBuf: make([]byte, 1024)}
        doc.Reset(text)
        return doc
}

// Reset reinitializes the document with the given text.
func (d *Document) Reset(text []byte) {
        d.cache = nil
        d.buffer.Reset(text)
        d.lineStart = computeLineStart(text)
}

// Bytes returns the full content of the document.
func (d *Document) Bytes() []byte {
        if d.cache != nil {
                return d.cache
        }
        d.cache = d.buffer.Bytes()
        return d.cache
}

// ReadAt implements io.ReaderAt.
func (d *Document) ReadAt(p []byte, off int64) (n int, err error) {
        if d.cache != nil {
                return copy(p, d.cache[off:]), nil
        }
        return d.buffer.ReadAt(p, off)
}

// Len returns the number of bytes in the document.
func (d *Document) Len() int {
        if d.cache != nil {
                return len(d.cache)
        }
        return d.buffer.Len()
}

// ApplyChange applies a content change to the document.
func (d *Document) ApplyChange(change TextDocumentContentChangeEvent) error {
        d.cache = nil

        if len(d.charBuf) == 0 {
                d.charBuf = make([]byte, 1024)
        }

        if change.Range == nil {
                d.Reset([]byte(change.Text))
                return nil
        }

        startOffset, endOffset, err := d.getChangeOffsets(change)
        if err != nil {
                return fmt.Errorf("get change offsets: %w", err)
        }

        if startOffset != endOffset {
                d.buffer.Delete(startOffset, endOffset)
        }

        if change.Text != "" {
                if err := d.writeText(change.Text, startOffset); err != nil {
                        return fmt.Errorf("write text at offset %d: %w", startOffset, err)
                }
        }

        d.lineStart = updateLineStart(d.lineStart, change, startOffset, endOffset)

        return nil
}

func (d *Document) getChangeOffsets(change TextDocumentContentChangeEvent) (start, end int, err error) {
        startOffset, err := d.PositionToOffset(change.Range.Start)
        if err != nil {
                return 0, 0, err
        }

        // Optimize for basic typing, where end == start
        endOffset := startOffset
        if change.Range.End != change.Range.Start {
                endOffset, err = d.PositionToOffset(change.Range.End)
                if err != nil {
                        return 0, 0, err
                }
        }

        return startOffset, endOffset, nil
}

func (d *Document) writeText(text string, off int) error {
        var toWrite []byte
        if len([]byte(text)) <= len(d.charBuf) {
                n := copy(d.charBuf, text)
                toWrite = d.charBuf[:n]
        } else {
                toWrite = []byte(text)
        }
        _, err := d.buffer.WriteAt(toWrite, int64(off))
        return err
}

// PositionToOffset converts a Position (line and character) to a byte offset
// in the document. It correctly handles UTF-16 character widths.
func (d *Document) PositionToOffset(pos Position) (int, error) {
        if pos.Line >= len(d.lineStart) {
                return 0, fmt.Errorf("invalid line: %d", pos.Line)
        }

        start, end := d.lineBounds(pos.Line)

        offset, u16Count := start, 0
        for offset < end {
                chunkSize := min(len(d.charBuf), end-offset)

                n, err := d.buffer.ReadAt(d.charBuf[:chunkSize], int64(offset))
                if err != nil && !errors.Is(err, io.EOF) {
                        return 0, fmt.Errorf("buffer read at line %d: %w", pos.Line, err)
                }

                if n == 0 {
                        break
                }

                deltaOffset, done, err := decodeUntilTargetOffset(d.charBuf[:n], pos.Character, &u16Count)
                if err != nil {
                        return 0, err
                }
                if done {
                        return offset + deltaOffset, nil
                }

                offset += n
        }

        if u16Count >= pos.Character {
                return offset, nil
        }

        return 0, fmt.Errorf("line %d: target units %d out of bounds (only %d utf16 units)", pos.Line, pos.Character, u16Count)
}

func (d *Document) lineBounds(line int) (start, end int) {
        start = d.lineStart[line]
        if line+1 < len(d.lineStart) {
                return start, d.lineStart[line+1]
        }
        return start, d.buffer.Len()
}

func decodeUntilTargetOffset(buf []byte, targetU16Offset int, u16Count *int) (deltaOffset int, done bool, err error) {
        for i := 0; i < len(buf); {
                r, size := utf8.DecodeRune(buf[i:])
                if r == utf8.RuneError && size == 1 {
                        return 0, false, fmt.Errorf("invalid utf-8 at byte offset %d", i)
                }
                if *u16Count >= targetU16Offset {
                        return i, true, nil
                }
                *u16Count += utf16Width(r)
                i += size
        }
        return 0, false, nil
}

func utf16Width(r rune) int {
        if r <= 0xFFFF {
                return 1
        }
        return 2
}

// ArrayBuffer is the simplest implementation of Buffer, using a byte slice
// for storage. It is optimized for reads. Insertions and deletions are O(n)
// due to slice copying.
//
// This implementation is not recommended and is mainly used as a testing
// benchmark baseline for smarter buffer implementations.
type ArrayBuffer struct {
        data []byte
}

// Bytes implements Buffer.
func (a *ArrayBuffer) Bytes() []byte {
        return a.data
}

// Delete implements Buffer.
func (a *ArrayBuffer) Delete(start, end int) {
        a.data = slices.Delete(a.data, start, end)
}

// Len implements Buffer.
func (a *ArrayBuffer) Len() int {
        return len(a.data)
}

// ReadAt implements Buffer.
func (a *ArrayBuffer) ReadAt(p []byte, off int64) (n int, err error) {
        n = copy(p, a.data[off:])
        return n, nil
}

// Reset implements Buffer.
func (a *ArrayBuffer) Reset(b []byte) {
        a.data = b
}

// WriteAt implements Buffer.
func (a *ArrayBuffer) WriteAt(p []byte, off int64) (n int, err error) {
        a.data = slices.Insert(a.data, int(off), p...)
        return len(p), nil
}

var _ Buffer = (*ArrayBuffer)(nil)

// GapBuffer implements a gap buffer for amortized O(1) insertions and
// deletions at the cursor position and O(n) for random access. Its reads
// are fast compared to [RopeBuffer].
type GapBuffer struct {
        buf      []byte
        gapStart int
        gapEnd   int
}

const initialGapSize = 128

// Bytes implements Buffer.
func (g *GapBuffer) Bytes() []byte {
        return append(g.buf[:g.gapStart], g.buf[g.gapEnd:]...)
}

// Delete implements Buffer.
func (g *GapBuffer) Delete(start, end int) {
        count := end - start
        switch g.gapStart {
        // Specific cases where we do not need to copy data
        case start:
                g.gapEnd += count
        case end:
                g.gapStart -= count
        // General case where we put the buffer into a state optimized for a
        // follow-up write to the start offset.
        default:
                g.moveGapTo(start)
                g.gapEnd += count
        }
}

// Len implements Buffer.
func (g *GapBuffer) Len() int {
        return len(g.buf) - g.gapSize()
}

// ReadAt implements Buffer.
func (g *GapBuffer) ReadAt(p []byte, off int64) (n int, err error) {
        if int(off) < g.gapStart {
                n = copy(p, g.buf[int(off):g.gapStart])
                n += copy(p[n:], g.buf[g.gapEnd:])
        } else {
                n = copy(p, g.buf[g.physicalOffset(int(off)):])
        }
        if n < len(p) {
                err = io.EOF
        }
        return n, err
}

// Reset implements Buffer.
func (g *GapBuffer) Reset(b []byte) {
        g.buf = make([]byte, len(b)+initialGapSize) // preallocate a gap
        copy(g.buf, b)
        g.gapStart = len(b)
        g.gapEnd = len(g.buf)
}

// WriteAt implements Buffer.
func (g *GapBuffer) WriteAt(p []byte, off int64) (n int, err error) {
        g.moveGapTo(int(off))
        g.growGap(len(p) - g.gapSize())
        n = copy(g.buf[g.gapStart:], p)
        g.gapStart += n
        g.shrinkGapTo(1024)
        return n, nil
}

func (g *GapBuffer) physicalOffset(off int) int {
        if off < g.gapStart {
                return off
        }
        return off + g.gapSize()
}

func (g *GapBuffer) gapSize() int {
        return g.gapEnd - g.gapStart
}

func (g *GapBuffer) moveGapTo(off int) {
        count := off - g.gapStart
        switch {
        case count < 0:
                copy(g.buf[g.gapEnd+count:], g.buf[off:g.gapStart])
        case count > 0:
                copy(g.buf[g.gapStart:g.gapStart+count], g.buf[g.gapEnd:g.gapEnd+count])
        }
        g.gapEnd += count
        g.gapStart += count
}

func (g *GapBuffer) shrinkGapTo(n int) {
        excess := g.gapSize() - n
        if excess <= 0 {
                return
        }
        g.buf = slices.Delete(g.buf, g.gapStart, g.gapStart+excess)
        g.gapEnd -= excess
}

func (g *GapBuffer) growGap(n int) {
        if n <= 0 {
                return
        }
        n += initialGapSize
        g.buf = slices.Insert(g.buf, g.gapEnd, make([]byte, n)...)
        g.gapEnd += n
}

var _ Buffer = (*GapBuffer)(nil)

// RopeBuffer implements Buffer using a rope data structure. This is best at
// scale, for large documents with frequent random insertions and deletions.
type RopeBuffer struct {
        node *rope.Node
}

// Bytes implements Buffer.
func (r *RopeBuffer) Bytes() []byte {
        return r.node.Value()
}

// Delete implements Buffer.
func (r *RopeBuffer) Delete(start, end int) {
        r.node.Remove(start, end)
}

// Len implements Buffer.
func (r *RopeBuffer) Len() int {
        return r.node.Len()
}

// ReadAt implements Buffer.
func (r *RopeBuffer) ReadAt(p []byte, off int64) (n int, err error) {
        return r.node.ReadAt(p, off)
}

// Reset implements Buffer.
func (r *RopeBuffer) Reset(b []byte) {
        r.node = rope.New(b)
}

// WriteAt implements Buffer.
func (r *RopeBuffer) WriteAt(p []byte, off int64) (n int, err error) {
        r.node.Insert(int(off), p)
        return len(p), nil
}

var _ Buffer = (*RopeBuffer)(nil)

func computeLineStart(text []byte) []int {
        lineStart := []int{0}
        for i, b := range text {
                if b == '\n' {
                        lineStart = append(lineStart, i+1)
                }
        }
        return lineStart
}

func updateLineStart(lineStart []int, change TextDocumentContentChangeEvent, startOffset, endOffset int) []int {
        // 1. We know all offsets before the change will remain the same.
        // 2. Since we know the text inserted, we can calculate any new line
        //    offsets that are created by the change.
        // 3. Since we know the length of the text inserted, and we are passed
        //    the length of the text removed, we can use those to update the
        //    offsets of the lines after the change.

        newLinesInserted := strings.Count(change.Text, "\n")
        newLinesRemoved := change.Range.End.Line - change.Range.Start.Line
        growth := newLinesInserted - newLinesRemoved

        switch {
        case growth > 0:
                // Shift the existing elements right
                lineStart = slices.Insert(lineStart, change.Range.End.Line+1, make([]int, growth)...)
        case growth < 0:
                // Shift the existing elements left
                lineStart = slices.Delete(lineStart, change.Range.End.Line+growth+1, change.Range.End.Line+1)
        }

        if newLinesInserted > 0 {
                // Save the new offsets
                asBytes := []byte(change.Text)
                off := 0
                for i := range newLinesInserted {
                        off += bytes.IndexByte(asBytes[off:], '\n') + 1
                        lineStart[change.Range.Start.Line+i+1] = startOffset + off
                }
        }

        // Update the offsets for lines after the change
        for i := change.Range.End.Line + 1 + growth; i < len(lineStart); i++ {
                lineStart[i] += len([]byte(change.Text)) + startOffset - endOffset
        }

        return lineStart
}

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package lsp

import (
        "bufio"
        "bytes"
        "context"
        "encoding/json"
        "errors"
        "fmt"
        "io"
        "log/slog"
        "net/textproto"
        "os"
        "strconv"
)

// DocumentSyncHandler defines methods for handling document synchronization.
type DocumentSyncHandler interface {
        DidOpenTextDocument(ctx context.Context, params DidOpenTextDocumentParams) error
        DidCloseTextDocument(ctx context.Context, params DidCloseTextDocumentParams) error
        DidChangeTextDocument(ctx context.Context, params DidChangeTextDocumentParams) error
}

// Handler provides the logic for handling LSP requests and notifications.
type Handler interface {
        DocumentSyncHandler
        Initialize(ctx context.Context, clientCapabilities ClientCapabilities) (*ServerCapabilities, error)
        Completion(ctx context.Context, params CompletionParams) (*CompletionList, error)
}

// Server manages the LSP server lifecycle and dispatching requests and
// notifications to a handler.
type Server struct {
        Stdin   io.Reader
        Stdout  io.Writer
        Info    ServerInfo
        Handler Handler
}

// Serve runs the LSP server. It blocks until the client receives an "exit".
func (s *Server) Serve() error {
        if s.Stdin == nil {
                s.Stdin = os.Stdin
        }

        scanner := bufio.NewScanner(s.Stdin)
        scanner.Split(jsonRPCSplit)

        slog.Info("Server is running", "name", s.Info.Name, "version", s.Info.Version)

        for scanner.Scan() {
                if !s.processMessage(scanner.Bytes()) {
                        return nil
                }
        }

        slog.Error("Scanner error", "error", scanner.Err())

        return scanner.Err()
}

func (s *Server) processMessage(payload []byte) bool {
        // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#requestMessage
        var request struct {
                ID     json.RawMessage `json:"id"`
                Method string          `json:"method"`
                Params json.RawMessage `json:"params"`
        }

        if err := json.Unmarshal(payload, &request); err != nil {
                slog.Error("Bad request", "error", err)
                return true
        }

        if len(request.ID) == 0 {
                logger := slog.With("method", request.Method)
                logger.Debug("Received notification", "params", string(request.Params))

                if request.Method == "exit" {
                        logger.Info("Exiting")
                        return false
                }

                if err := s.handleNotification(request.Method, request.Params); err != nil {
                        logger.Error("Error handling notification", "error", err)
                }

                return true
        }

        logger := slog.With("request_id", request.ID, "method", request.Method)
        debugEnabled := logger.Enabled(context.TODO(), slog.LevelDebug)

        if debugEnabled {
                logger.Debug("Received request", "params", string(request.Params))
        }

        response, err := s.handleRequest(request.Method, request.Params)
        if err != nil {
                logger.Error("Error handling request", "error", err)
                var asResponseError *ResponseError
                if errors.As(err, &asResponseError) {
                        response = asResponseError
                } else {
                        response = &ResponseError{
                                Code:    CodeInternalError,
                                Message: err.Error(),
                        }
                }
        }

        if err := s.write(request.ID, response); err != nil {
                logger.Error("Write error", "error", err)
                return true
        }

        if debugEnabled {
                logger.Debug("Sent response", "response", fmt.Sprintf("%#v", response))
        }

        return true
}

func jsonRPCSplit(data []byte, _ bool) (advance int, token []byte, err error) {
        const headerDelimiter = "\r\n\r\n"

        i := bytes.Index(data, []byte(headerDelimiter))
        if i == -1 {
                return 0, nil, nil
        }

        payloadIndex := i + len(headerDelimiter)

        header, err := textproto.NewReader(bufio.NewReader(bytes.NewReader(data[:payloadIndex]))).ReadMIMEHeader()
        if err != nil {
                return 0, nil, fmt.Errorf("bad header: %w", err)
        }

        contentLength, err := strconv.Atoi(header.Get("content-length"))
        if err != nil {
                return 0, nil, fmt.Errorf("bad content-length: %w", err)
        }

        restBytes := data[payloadIndex:]

        if len(restBytes) < contentLength {
                return 0, nil, nil
        }

        return payloadIndex + contentLength, restBytes[:contentLength], nil
}

func (s *Server) handleNotification(method string, paramsRaw json.RawMessage) error {
        switch method {
        case "initialized":

        case "cancelRequest":
                // TODO(asnyder): Handle cancelRequest and make everything
                // async.

        case "textDocument/didOpen":
                var params DidOpenTextDocumentParams
                if err := parseParams(paramsRaw, &params); err != nil {
                        return err
                }
                return s.Handler.DidOpenTextDocument(context.TODO(), params)

        case "textDocument/didClose":
                var params DidCloseTextDocumentParams
                if err := parseParams(paramsRaw, &params); err != nil {
                        return err
                }
                return s.Handler.DidCloseTextDocument(context.TODO(), params)

        case "textDocument/didChange":
                var params DidChangeTextDocumentParams
                if err := parseParams(paramsRaw, &params); err != nil {
                        return err
                }
                return s.Handler.DidChangeTextDocument(context.TODO(), params)

        default:
                slog.Warn("Unknown notification", "method", method)
        }
        return nil
}

func (s *Server) handleRequest(method string, paramsRaw json.RawMessage) (any, error) {
        switch method {
        case "initialize":
                // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#initializeParams
                var params struct {
                        ClientInfo struct {
                                Name    string `json:"name"`
                                Version string `json:"version"`
                        } `json:"clientInfo"`
                        Capabilities ClientCapabilities `json:"capabilities"`
                }
                if err := parseParams(paramsRaw, &params); err != nil {
                        return nil, err
                }

                slog.Info("Client info", "name", params.ClientInfo.Name, "version", params.ClientInfo.Version)

                serverCapabilities, err := s.Handler.Initialize(context.TODO(), params.Capabilities)
                if err != nil {
                        return nil, err
                }

                // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#initializeResult
                return struct {
                        Capabilities *ServerCapabilities `json:"capabilities"`
                        ServerInfo   ServerInfo          `json:"serverInfo"`
                }{Capabilities: serverCapabilities, ServerInfo: s.Info}, nil

        case "shutdown":
                return nil, nil

        case "textDocument/completion":
                var params CompletionParams
                if err := parseParams(paramsRaw, &params); err != nil {
                        return nil, err
                }
                return s.Handler.Completion(context.TODO(), params)

        default:
                return nil, &ResponseError{
                        Code:    CodeMethodNotFound,
                        Message: fmt.Sprintf("Unknown method %q", method),
                }
        }
}

func parseParams(paramsRaw json.RawMessage, result any) error {
        if err := json.Unmarshal(paramsRaw, result); err != nil {
                return &ResponseError{
                        Code:          CodeInvalidParams,
                        Message:       err.Error(),
                        InternalError: err,
                }
        }
        return nil
}

func (s *Server) write(requestID json.RawMessage, result any) error {
        // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#responseMessage
        message := struct {
                JSONRPC string          `json:"jsonrpc"`
                ID      json.RawMessage `json:"id"`
                Result  any             `json:"result"`
        }{JSONRPC: "2.0", ID: requestID, Result: result}

        data, err := json.Marshal(message)
        if err != nil {
                return fmt.Errorf("invalid response: %w", err)
        }

        if s.Stdout == nil {
                s.Stdout = os.Stdout
        }

        _, err = s.Stdout.Write(append([]byte("Content-Length: "+strconv.Itoa(len(data))+"\r\nContent-Type: application/vscode-jsonrpc; charset=utf-8\r\n\r\n"), data...))
        return err
}

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package lsp

import "fmt"

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#clientCapabilities
type ClientCapabilities struct{}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#serverCapabilities
type ServerCapabilities struct {
        TextDocumentSync      *TextDocumentSyncOptions `json:"textDocumentSync,omitempty"`
        CompletionProvider    *CompletionOptions       `json:"completionProvider,omitempty"`
        HoverProvider         bool                     `json:"hoverProvider,omitempty"`
        DefinitionProvider    bool                     `json:"definitionProvider,omitempty"`
        ReferencesProvider    bool                     `json:"referencesProvider,omitempty"`
        SignatureHelpProvider bool                     `json:"signatureHelpProvider,omitempty"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentSyncOptions
type TextDocumentSyncOptions struct {
        OpenClose bool                 `json:"openClose,omitempty"`
        Change    TextDocumentSyncKind `json:"change"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionOptions
type CompletionOptions struct{}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentSyncKind
type TextDocumentSyncKind int

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentSyncKind
const (
        SyncNone        TextDocumentSyncKind = 0
        SyncFull        TextDocumentSyncKind = 1
        SyncIncremental TextDocumentSyncKind = 2
)

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#initializeResult
type ServerInfo struct {
        Name    string `json:"name"`
        Version string `json:"version"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#responseError
type ResponseError struct {
        Code          ErrorCode `json:"code"`
        Message       string    `json:"message"`
        InternalError error     `json:"-"`
}

func (e *ResponseError) Error() string {
        msg := fmt.Sprintf("error code %d: %s", e.Code, e.Message)
        if e.InternalError != nil {
                msg += fmt.Sprintf(": %s", e.InternalError.Error())
        }
        return msg
}

func (e *ResponseError) Unwrap() error {
        return e.InternalError
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#errorCodes
type ErrorCode int

// LSP error codes.
const (
        CodeParseError     ErrorCode = -32700
        CodeInvalidRequest ErrorCode = -32600
        CodeMethodNotFound ErrorCode = -32601
        CodeInvalidParams  ErrorCode = -32602
        CodeInternalError  ErrorCode = -32603
)

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#didOpenTextDocumentParams
type DidOpenTextDocumentParams struct {
        TextDocument TextDocumentItem `json:"textDocument"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#didChangeTextDocumentParams
type DidChangeTextDocumentParams struct {
        TextDocument   TextDocumentIdentifier           `json:"textDocument"`
        ContentChanges []TextDocumentContentChangeEvent `json:"contentChanges"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentContentChangeEvent
type TextDocumentContentChangeEvent struct {
        Text  string `json:"text"`
        Range *Range `json:"range,omitempty"`
}

func (e TextDocumentContentChangeEvent) String() string {
        return fmt.Sprintf("%q @ %s", e.Text, e.Range)
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#didCloseTextDocumentParams
type DidCloseTextDocumentParams struct {
        TextDocument TextDocumentIdentifier `json:"textDocument"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#position
type Position struct {
        Line      int `json:"line"`
        Character int `json:"character"`
}

func (p Position) String() string {
        return fmt.Sprintf("%d:%d", p.Line, p.Character)
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#range
type Range struct {
        Start Position `json:"start"`
        End   Position `json:"end"`
}

func (r Range) String() string {
        return fmt.Sprintf("%s-%s", r.Start, r.End)
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentItem
type TextDocumentItem struct {
        URI  string `json:"uri"`
        Text string `json:"text"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentIdentifier
type TextDocumentIdentifier struct {
        URI string `json:"uri"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentPositionParams
type TextDocumentPositionParams struct {
        TextDocument TextDocumentIdentifier `json:"textDocument"`
        Position     Position               `json:"position"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#location
type Location struct {
        URI   string `json:"uri"`
        Range Range  `json:"range"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionParams
type CompletionParams struct {
        TextDocumentPositionParams
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionList
type CompletionList struct {
        IsIncomplete bool             `json:"isIncomplete"`
        Items        []CompletionItem `json:"items"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionItem
type CompletionItem struct {
        Label         string             `json:"label"`
        Kind          CompletionItemKind `json:"kind,omitempty"`
        Detail        string             `json:"detail,omitempty"`
        Documentation *MarkupContent     `json:"documentation,omitempty"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionItemKind
type CompletionItemKind int

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionItemKind
const (
        CompletionText          CompletionItemKind = 1
        CompletionMethod        CompletionItemKind = 2
        CompletionFunction      CompletionItemKind = 3
        CompletionConstructor   CompletionItemKind = 4
        CompletionField         CompletionItemKind = 5
        CompletionVariable      CompletionItemKind = 6
        CompletionClass         CompletionItemKind = 7
        CompletionInterface     CompletionItemKind = 8
        CompletionModule        CompletionItemKind = 9
        CompletionProperty      CompletionItemKind = 10
        CompletionUnit          CompletionItemKind = 11
        CompletionValue         CompletionItemKind = 12
        CompletionEnum          CompletionItemKind = 13
        CompletionKeyword       CompletionItemKind = 14
        CompletionSnippet       CompletionItemKind = 15
        CompletionColor         CompletionItemKind = 16
        CompletionFile          CompletionItemKind = 17
        CompletionReference     CompletionItemKind = 18
        CompletionFolder        CompletionItemKind = 19
        CompletionEnumMember    CompletionItemKind = 20
        CompletionConstant      CompletionItemKind = 21
        CompletionStruct        CompletionItemKind = 22
        CompletionEvent         CompletionItemKind = 23
        CompletionOperator      CompletionItemKind = 24
        CompletionTypeParameter CompletionItemKind = 25
)

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#markupContentInnerDefinition
type MarkupContent struct {
        Kind  MarkupKind `json:"kind"`
        Value string     `json:"value"`
}

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#markupContent
type MarkupKind string

// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#markupContent
const (
        MarkupPlainText MarkupKind = "plaintext"
        MarkupMarkdown  MarkupKind = "markdown"
)

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package testutil

import (
        "io"
        "log/slog"
        "path/filepath"
        "testing"
)

// SetupLogger configures the default slog logger for testing.
func SetupLogger(t testing.TB) {
        originalHandler := slog.Default().Handler()

        t.Cleanup(func() {
                slog.SetDefault(slog.New(originalHandler))
        })

        slog.SetDefault(slog.New(slog.NewTextHandler(TestWriter{t}, &slog.HandlerOptions{
                Level:     slog.LevelDebug,
                AddSource: true,
                ReplaceAttr: func(_ []string, a slog.Attr) slog.Attr {
                        switch a.Key {
                        case slog.TimeKey:
                                // Suppress time
                                return slog.Attr{}
                        case slog.SourceKey:
                                // Simplify file name
                                source := a.Value.Any().(*slog.Source) //nolint:revive
                                source.File = filepath.Base(source.File)
                        }
                        return a
                },
        })))
}

// TestWriter is an io.Writer that writes to test logs.
type TestWriter struct {
        T testing.TB
}

// Write implements io.Writer.
func (t TestWriter) Write(p []byte) (n int, err error) {
        t.T.Helper()
        t.T.Logf("%s", p)
        return len(p), nil
}

var _ io.Writer = TestWriter{}

// MIT License
//
// Copyright (c) 2025 Adam Snyder
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package main

import (
        _ "embed"
        "flag"
        "log/slog"
        "os"
        "path/filepath"
        "strings"

        "github.com/armsnyder/gdshader-language-server/internal/app"
        "github.com/armsnyder/gdshader-language-server/internal/lsp"
)

//go:embed version.txt
var version string

func main() {
        var flags struct {
                Debug bool
        }

        flag.BoolVar(&flags.Debug, "debug", false, "Enable debug logging")

        flag.Parse()

        setupLogger(flags.Debug)

        server := &lsp.Server{
                Info: lsp.ServerInfo{
                        Name:    "gdshader-language-server",
                        Version: strings.TrimSpace(version),
                },
                Handler: &app.Handler{},
        }

        if err := server.Serve(); err != nil {
                os.Exit(1)
        }
}

func setupLogger(debug bool) { //nolint:revive
        level := slog.LevelInfo
        if debug {
                level = slog.LevelDebug
        }

        slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
                Level:     level,
                AddSource: true,
                ReplaceAttr: func(_ []string, a slog.Attr) slog.Attr {
                        switch a.Key {
                        case slog.TimeKey:
                                // Suppress time
                                return slog.Attr{}
                        case slog.SourceKey:
                                // Simplify file name
                                source := a.Value.Any().(*slog.Source) //nolint:revive
                                source.File = filepath.Base(source.File)
                        }
                        return a
                },
        })))
}