grindlemire/go-tui code browser

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package provider

import (
	"strings"

	"github.com/grindlemire/go-tui/internal/lsp/gopls"
	"github.com/grindlemire/go-tui/internal/lsp/log"
	"github.com/grindlemire/go-tui/internal/tuigen"
)

// definitionProvider implements DefinitionProvider.
type definitionProvider struct {
	index        ComponentIndex
	goplsProxy   GoplsProxyAccessor
	virtualFiles VirtualFileAccessor
	docs         DocumentAccessor
}

// NewDefinitionProvider creates a new definition provider.
func NewDefinitionProvider(index ComponentIndex, proxy GoplsProxyAccessor, vf VirtualFileAccessor, docs DocumentAccessor) DefinitionProvider {
	return &definitionProvider{
		index:        index,
		goplsProxy:   proxy,
		virtualFiles: vf,
		docs:         docs,
	}
}

func (d *definitionProvider) Definition(ctx *CursorContext) ([]Location, error) {
	log.Server("Definition provider: NodeKind=%s, Word=%q, InGoExpr=%v", ctx.NodeKind, ctx.Word, ctx.InGoExpr)

	word := ctx.Word

	// Check local function definitions first (prevents gopls from
	// returning generated .go files instead of .gsx sources).
	// Skip this when inside a Go expression — gopls understands the full
	// context (e.g., field access a.category vs a standalone function call).
	if word != "" && !ctx.InGoExpr {
		funcName := strings.TrimPrefix(word, "@")
		if funcInfo, ok := d.index.LookupFunc(funcName); ok {
			log.Server("Found local function %s at %s (before gopls)", funcName, funcInfo.Location.URI)
			return []Location{funcInfo.Location}, nil
		}
	}

	if word == "" {
		// Without a word, only gopls can resolve (it works by position).
		if ctx.InGoExpr {
			locs, err := d.getGoplsDefinition(ctx)
			if err == nil && len(locs) > 0 {
				return locs, nil
			}
		}
		return nil, nil
	}

	// Dispatch based on node kind. Each case resolves using local knowledge
	// first; unresolved Go expressions fall through to the gopls fallback.
	switch ctx.NodeKind {
	case NodeKindComponentCall:
		return d.definitionComponentCall(ctx)
	case NodeKindRefAttr:
		return d.definitionRefAttr(ctx)
	case NodeKindEventHandler:
		return d.definitionEventHandler(ctx)
	case NodeKindParameter:
		return d.definitionParameter(ctx)
	case NodeKindImportPath:
		return d.definitionImport(ctx)
	case NodeKindStateAccess, NodeKindStateDecl:
		locs, err := d.definitionStateVar(ctx)
		if err == nil && len(locs) > 0 {
			return locs, nil
		}
		// Fall through to gopls for unresolved state references
	case NodeKindGoExpr:
		// Check refs in scope before deferring to gopls (which would
		// return the element tag position from generated code, not the ref site).
		if locs := d.definitionRefFromScope(ctx); len(locs) > 0 {
			return locs, nil
		}
		// Fall through to gopls
	case NodeKindFunction, NodeKindComponent, NodeKindGoDecl:
		// Try local AST-based lookup first (avoids gopls offset issues)
		if ctx.Document.AST != nil && word != "" {
			if loc := d.findGoDeclNameInAST(ctx.Document.AST, word, ctx.Document.URI); loc != nil {
				return []Location{*loc}, nil
			}
		}
		locs, err := d.getGoplsDefinition(ctx)
		if err == nil && len(locs) > 0 {
			return locs, nil
		}
	}

	// Gopls fallback for Go expressions not resolved by handlers above.
	if ctx.InGoExpr {
		locs, err := d.getGoplsDefinition(ctx)
		if err != nil {
			log.Server("gopls definition error: %v", err)
		} else if len(locs) > 0 {
			return locs, nil
		}
	}

	// Word-based fallbacks
	componentName := strings.TrimPrefix(word, "@")

	// Look up component in index
	if info, ok := d.index.Lookup(componentName); ok {
		return []Location{info.Location}, nil
	}

	// Check if it's a function (use componentName with @ stripped)
	if funcInfo, ok := d.index.LookupFunc(componentName); ok {
		return []Location{funcInfo.Location}, nil
	}

	// Check within component scope
	if ctx.Scope.Component != nil {
		compName := ctx.Scope.Component.Name

		// Parameter
		if paramInfo, ok := d.index.LookupParam(compName, word); ok {
			return []Location{paramInfo.Location}, nil
		}

		// Let binding
		if loc := d.findLetBindingDefinition(ctx, word); loc != nil {
			return []Location{*loc}, nil
		}

		// For loop variable
		if loc := d.findLoopVariableDefinition(ctx, word); loc != nil {
			return []Location{*loc}, nil
		}

		// GoCode variable
		if loc := d.findGoCodeVariableDefinition(ctx, word); loc != nil {
			return []Location{*loc}, nil
		}
	}

	// AST-based component/function/type definition within current file
	if ctx.Document.AST != nil {
		if loc := d.findComponentInAST(ctx.Document.AST, componentName, ctx.Document.URI); loc != nil {
			return []Location{*loc}, nil
		}
		if loc := d.findFuncInAST(ctx.Document.AST, word, ctx.Document.URI); loc != nil {
			return []Location{*loc}, nil
		}
		if loc := d.findGoDeclNameInAST(ctx.Document.AST, word, ctx.Document.URI); loc != nil {
			return []Location{*loc}, nil
		}
	}

	return nil, nil
}

// --- Component and function definition ---

func (d *definitionProvider) definitionComponentCall(ctx *CursorContext) ([]Location, error) {
	call, ok := ctx.Node.(*tuigen.ComponentCall)
	if !ok || call == nil {
		return nil, nil
	}

	if info, ok := d.index.Lookup(call.Name); ok {
		return []Location{info.Location}, nil
	}

	// For struct-mount components (e.g., @Sidebar()), the component call name
	// refers to the constructor function, not a templ component name.
	if funcInfo, ok := d.index.LookupFunc(call.Name); ok {
		return []Location{funcInfo.Location}, nil
	}

	return nil, nil
}

// definitionRefFromScope checks if the word under the cursor matches a
// ref variable in the component scope and returns its ref={} definition position.
func (d *definitionProvider) definitionRefFromScope(ctx *CursorContext) []Location {
	if ctx.Scope.Component == nil {
		return nil
	}
	for _, ref := range ctx.Scope.Refs {
		if ref.Name == ctx.Word && ref.Element != nil {
			lineIdx, charIdx, found := findRefAttrPosition(ctx.Document.Content, ref.Element)
			if found {
				refAttr := "ref={" + ref.Name + "}"
				return []Location{{
					URI: ctx.Document.URI,
					Range: Range{
						Start: Position{Line: lineIdx, Character: charIdx},
						End:   Position{Line: lineIdx, Character: charIdx + len(refAttr)},
					},
				}}
			}
		}
	}
	return nil
}

func (d *definitionProvider) definitionRefAttr(ctx *CursorContext) ([]Location, error) {
	elem, ok := ctx.Node.(*tuigen.Element)
	if !ok || elem == nil || elem.RefExpr == nil {
		return nil, nil
	}

	refName := elem.RefExpr.Code

	// Try to find the variable declaration (e.g., content := tui.NewRef())
	if ctx.Scope.Component != nil && ctx.Document.AST != nil {
		if loc := d.findGoCodeVariableDefinition(ctx, refName); loc != nil {
			return []Location{*loc}, nil
		}

		// For dotted names (e.g., c.textareaRef), search struct field definitions
		if strings.Contains(refName, ".") {
			parts := strings.SplitN(refName, ".", 2)
			if len(parts) == 2 {
				fieldName := parts[1]
				if loc := d.findGoDeclNameInAST(ctx.Document.AST, fieldName, ctx.Document.URI); loc != nil {
					return []Location{*loc}, nil
				}
			}
		}
	}

	// Fall back to pointing to the ref={} attribute itself
	lineIdx, charIdx, found := findRefAttrPosition(ctx.Document.Content, elem)
	if !found {
		// Fallback to element tag position
		lineIdx = elem.Position.Line - 1
		charIdx = elem.Position.Column - 1
	}

	refAttr := "ref={" + refName + "}"
	return []Location{{
		URI: ctx.Document.URI,
		Range: Range{
			Start: Position{Line: lineIdx, Character: charIdx},
			End:   Position{Line: lineIdx, Character: charIdx + len(refAttr)},
		},
	}}, nil
}

// findRefAttrPosition finds the source position of ref={name} for an element.
// Searches from the element's tag line through subsequent lines to handle
// multiline elements where ref={} is on its own line.
// Returns 0-indexed line and column.
func findRefAttrPosition(content string, elem *tuigen.Element) (line, col int, found bool) {
	if elem == nil || elem.RefExpr == nil {
		return 0, 0, false
	}

	refAttr := "ref={" + elem.RefExpr.Code + "}"
	lines := strings.Split(content, "\n")
	startLine := elem.Position.Line - 1 // 0-indexed

	maxSearch := min(startLine+20, len(lines))

	for lineIdx := startLine; lineIdx < maxSearch; lineIdx++ {
		idx := strings.Index(lines[lineIdx], refAttr)
		if idx >= 0 {
			return lineIdx, idx, true
		}
	}

	return 0, 0, false
}

func (d *definitionProvider) definitionStateVar(ctx *CursorContext) ([]Location, error) {
	// Find the state variable declaration in scope, matching by name
	for _, sv := range ctx.Scope.StateVars {
		if sv.Name == ctx.Word {
			return []Location{{
				URI: ctx.Document.URI,
				Range: Range{
					Start: Position{Line: sv.Position.Line - 1, Character: sv.Position.Column - 1},
					End:   Position{Line: sv.Position.Line - 1, Character: sv.Position.Column - 1 + len(sv.Name)},
				},
			}}, nil
		}
	}
	return nil, nil
}

func (d *definitionProvider) definitionEventHandler(ctx *CursorContext) ([]Location, error) {
	// Event handler attributes — try to find the handler function in Go expressions
	// For now, fall back to gopls for Go expression resolution
	if ctx.InGoExpr {
		return d.getGoplsDefinition(ctx)
	}
	return nil, nil
}

func (d *definitionProvider) definitionParameter(ctx *CursorContext) ([]Location, error) {
	word := ctx.Word

	// Function parameter
	if ctx.Scope.Function != nil {
		funcName := parseFuncName(ctx.Scope.Function.Code)
		if paramInfo, ok := d.index.LookupFuncParam(funcName, word); ok {
			return []Location{paramInfo.Location}, nil
		}
	}

	// Component parameter
	if ctx.Scope.Component != nil {
		if paramInfo, ok := d.index.LookupParam(ctx.Scope.Component.Name, word); ok {
			return []Location{paramInfo.Location}, nil
		}
	}

	return nil, nil
}

// --- Local variable definitions ---

func (d *definitionProvider) findLetBindingDefinition(ctx *CursorContext, varName string) *Location {
	if ctx.Document.AST == nil || ctx.Scope.Component == nil {
		return nil
	}

	for _, comp := range ctx.Document.AST.Components {
		if comp.Name != ctx.Scope.Component.Name {
			continue
		}

		if binding := findLetBindingInNodes(comp.Body, varName); binding != nil {
			nameOffset := letBindingNameOffset(binding)
			return &Location{
				URI: ctx.Document.URI,
				Range: Range{
					Start: Position{
						Line:      binding.Position.Line - 1,
						Character: binding.Position.Column - 1 + nameOffset,
					},
					End: Position{
						Line:      binding.Position.Line - 1,
						Character: binding.Position.Column - 1 + nameOffset + len(varName),
					},
				},
			}
		}
	}
	return nil
}

func (d *definitionProvider) findLoopVariableDefinition(ctx *CursorContext, varName string) *Location {
	if ctx.Document.AST == nil || ctx.Scope.Component == nil {
		return nil
	}

	for _, comp := range ctx.Document.AST.Components {
		if comp.Name != ctx.Scope.Component.Name {
			continue
		}

		loop := findForLoopWithVariable(comp.Body, varName)
		if loop == nil {
			return nil
		}

		if loop.Index == varName {
			return &Location{
				URI: ctx.Document.URI,
				Range: Range{
					Start: Position{
						Line:      loop.Position.Line - 1,
						Character: loop.Position.Column - 1 + len("for "),
					},
					End: Position{
						Line:      loop.Position.Line - 1,
						Character: loop.Position.Column - 1 + len("for ") + len(varName),
					},
				},
			}
		} else if loop.Value == varName {
			offset := len("for ")
			if loop.Index != "" {
				offset += len(loop.Index) + 2 // ", "
			}
			return &Location{
				URI: ctx.Document.URI,
				Range: Range{
					Start: Position{
						Line:      loop.Position.Line - 1,
						Character: loop.Position.Column - 1 + offset,
					},
					End: Position{
						Line:      loop.Position.Line - 1,
						Character: loop.Position.Column - 1 + offset + len(varName),
					},
				},
			}
		}
	}
	return nil
}

func (d *definitionProvider) findGoCodeVariableDefinition(ctx *CursorContext, varName string) *Location {
	if ctx.Document.AST == nil || ctx.Scope.Component == nil {
		return nil
	}

	for _, comp := range ctx.Document.AST.Components {
		if comp.Name != ctx.Scope.Component.Name {
			continue
		}

		goCode := findGoCodeWithVariable(comp.Body, varName)
		if goCode == nil {
			return nil
		}

		idx := findVarDeclPosition(goCode.Code, varName)
		if idx >= 0 {
			return &Location{
				URI: ctx.Document.URI,
				Range: Range{
					Start: Position{
						Line:      goCode.Position.Line - 1,
						Character: goCode.Position.Column - 1 + idx,
					},
					End: Position{
						Line:      goCode.Position.Line - 1,
						Character: goCode.Position.Column - 1 + idx + len(varName),
					},
				},
			}
		}
	}
	return nil
}

// --- AST lookup helpers ---

func (d *definitionProvider) findComponentInAST(ast *tuigen.File, name string, uri string) *Location {
	for _, comp := range ast.Components {
		if comp.Name == name {
			return &Location{
				URI: uri,
				Range: Range{
					Start: Position{Line: comp.Position.Line - 1, Character: comp.Position.Column - 1},
					End:   Position{Line: comp.Position.Line - 1, Character: comp.Position.Column - 1 + len("templ") + 1 + len(comp.Name)},
				},
			}
		}
	}
	return nil
}

func (d *definitionProvider) findFuncInAST(ast *tuigen.File, name string, uri string) *Location {
	for _, fn := range ast.Funcs {
		fnName := parseFuncName(fn.Code)
		if fnName == name {
			// Find the actual offset of the name in the code. For methods
			// like "func (c *chat) updateHeight()", the name doesn't
			// immediately follow "func ".
			nameIdx := max(strings.Index(fn.Code, fnName+"("), 0)
			startCol := fn.Position.Column - 1 + nameIdx
			return &Location{
				URI: uri,
				Range: Range{
					Start: Position{Line: fn.Position.Line - 1, Character: startCol},
					End:   Position{Line: fn.Position.Line - 1, Character: startCol + len(fnName)},
				},
			}
		}
	}
	return nil
}

// findGoDeclNameInAST searches GoDecl nodes for a type, var, or const name.
// Works for type declarations (type Foo struct{...}), var declarations, etc.
func (d *definitionProvider) findGoDeclNameInAST(ast *tuigen.File, name string, uri string) *Location {
	for _, decl := range ast.Decls {
		code := decl.Code
		// The Code includes the keyword (type/var/const). Extract the declared name.
		// For "type chat struct {" the name is "chat".
		// For "var _ tui.AppBinder = ..." the name is "_".
		trimmed := strings.TrimSpace(code)
		// Remove the keyword prefix
		rest := ""
		if strings.HasPrefix(trimmed, decl.Kind+" ") {
			rest = strings.TrimSpace(trimmed[len(decl.Kind)+1:])
		} else if strings.HasPrefix(trimmed, decl.Kind+"\t") {
			rest = strings.TrimSpace(trimmed[len(decl.Kind)+1:])
		}
		if rest == "" {
			continue
		}

		// Extract the first word (the declared name)
		declName := ""
		for i, ch := range rest {
			if ch == ' ' || ch == '\t' || ch == '(' || ch == '=' {
				declName = rest[:i]
				break
			}
		}
		if declName == "" {
			// Single word (e.g., "const Foo")
			declName = rest
		}

		if declName == name {
			// Find the column of the name in the source
			nameIdx := strings.Index(code, name)
			col := decl.Position.Column - 1
			if nameIdx >= 0 {
				col += nameIdx
			}
			return &Location{
				URI: uri,
				Range: Range{
					Start: Position{Line: decl.Position.Line - 1, Character: col},
					End:   Position{Line: decl.Position.Line - 1, Character: col + len(name)},
				},
			}
		}

		// Also check for struct field definitions within the declaration.
		// For "type chat struct { ... showSettings *tui.State[bool] ... }",
		// search the struct body for field names.
		if strings.Contains(code, "struct {") || strings.Contains(code, "struct{") {
			lines := strings.Split(code, "\n")
			for lineIdx, line := range lines {
				trimmedLine := strings.TrimSpace(line)
				// Skip struct opening/closing and empty lines
				if trimmedLine == "" || trimmedLine == "{" || trimmedLine == "}" ||
					strings.HasPrefix(trimmedLine, "type ") || strings.HasPrefix(trimmedLine, "//") {
					continue
				}
				// First word on the line is the field name
				fields := strings.Fields(trimmedLine)
				if len(fields) >= 2 && fields[0] == name {
					fieldIdx := strings.Index(line, name)
					fieldCol := 0
					if lineIdx == 0 {
						fieldCol = decl.Position.Column - 1
					}
					if fieldIdx >= 0 {
						fieldCol += fieldIdx
					}
					return &Location{
						URI: uri,
						Range: Range{
							Start: Position{Line: decl.Position.Line - 1 + lineIdx, Character: fieldCol},
							End:   Position{Line: decl.Position.Line - 1 + lineIdx, Character: fieldCol + len(name)},
						},
					}
				}
			}
		}
	}
	return nil
}

// --- gopls definition delegation ---

func (d *definitionProvider) getGoplsDefinition(ctx *CursorContext) ([]Location, error) {
	proxy := d.goplsProxy.GetProxy()
	if proxy == nil {
		return nil, nil
	}

	cached := d.virtualFiles.GetVirtualFile(ctx.Document.URI)
	if cached == nil || cached.SourceMap == nil {
		return nil, nil
	}

	goLine, goCol, found := cached.SourceMap.TuiToGo(ctx.Position.Line, ctx.Position.Character)
	if !found {
		return nil, nil
	}

	goplsLocs, err := proxy.Definition(cached.GoURI, gopls.Position{
		Line:      goLine,
		Character: goCol,
	})
	if err != nil {
		return nil, err
	}

	if len(goplsLocs) == 0 {
		return nil, nil
	}

	var locs []Location
	for _, gl := range goplsLocs {
		// Check if this is a virtual file — translate back to .gsx
		if gopls.IsVirtualGoFile(gl.URI) {
			tuiURI := gopls.GoURIToTuiURI(gl.URI)
			cachedFile := d.virtualFiles.GetVirtualFile(tuiURI)
			if cachedFile != nil && cachedFile.SourceMap != nil {
				tuiStartLine, tuiStartCol, startFound := cachedFile.SourceMap.GoToTui(gl.Range.Start.Line, gl.Range.Start.Character)
				tuiEndLine, tuiEndCol, endFound := cachedFile.SourceMap.GoToTui(gl.Range.End.Line, gl.Range.End.Character)
				if startFound && endFound {
					locs = append(locs, Location{
						URI: tuiURI,
						Range: Range{
							Start: Position{Line: tuiStartLine, Character: tuiStartCol},
							End:   Position{Line: tuiEndLine, Character: tuiEndCol},
						},
					})
					continue
				}
			}
			// Translation failed for virtual file — skip instead of returning
			// a nonexistent virtual URI. The caller's word-based fallback will
			// try AST-based lookup.
			log.Server("gopls returned virtual file %s but source map translation failed, skipping", gl.URI)
			continue
		}

		// Real generated _gsx.go files have structural differences from
		// the virtual Go file (different ordering, goimports blank lines),
		// making source map reverse-translation unreliable. Skip these
		// and let the word-based fallback handle them via AST lookup.
		if gopls.IsGeneratedGoFile(gl.URI) {
			log.Server("gopls returned generated file %s, skipping (word-based fallback preferred)", gl.URI)
			continue
		}

		// External file (standard library, etc.) — return as-is
		locs = append(locs, Location{
			URI: gl.URI,
			Range: Range{
				Start: Position{Line: gl.Range.Start.Line, Character: gl.Range.Start.Character},
				End:   Position{Line: gl.Range.End.Line, Character: gl.Range.End.Character},
			},
		})
	}

	return locs, nil
}

// --- Import definition ---

// definitionImport resolves go-to-definition for an import path by finding the
// quoted path in the virtual .go file and asking gopls to resolve it.
func (d *definitionProvider) definitionImport(ctx *CursorContext) ([]Location, error) {
	importPath := ctx.ImportPath
	if importPath == "" {
		return nil, nil
	}

	proxy := d.goplsProxy.GetProxy()
	if proxy == nil {
		log.Server("definitionImport: no gopls proxy available")
		return nil, nil
	}

	cached := d.virtualFiles.GetVirtualFile(ctx.Document.URI)
	if cached == nil {
		log.Server("definitionImport: no virtual file for %s", ctx.Document.URI)
		return nil, nil
	}

	// Find the quoted import path in the virtual Go file content.
	quotedPath := `"` + importPath + `"`
	idx := strings.Index(cached.Content, quotedPath)
	if idx < 0 {
		log.Server("definitionImport: import path %q not found in virtual file", importPath)
		return nil, nil
	}

	// Convert byte offset to line/character and position inside the quotes.
	goLine, goCol := offsetToLineChar(cached.Content, idx+1) // +1 skips opening quote

	log.Server("definitionImport: asking gopls for %q at GoLine=%d GoCol=%d", importPath, goLine, goCol)

	goplsLocs, err := proxy.Definition(cached.GoURI, gopls.Position{
		Line:      goLine,
		Character: goCol,
	})
	if err != nil {
		log.Server("definitionImport: gopls error: %v", err)
		return nil, err
	}

	if len(goplsLocs) == 0 {
		return nil, nil
	}

	// Import definitions always resolve to external .go files, so no
	// source map reverse-translation is needed.
	var locs []Location
	for _, gl := range goplsLocs {
		locs = append(locs, Location{
			URI: gl.URI,
			Range: Range{
				Start: Position{Line: gl.Range.Start.Line, Character: gl.Range.Start.Character},
				End:   Position{Line: gl.Range.End.Line, Character: gl.Range.End.Character},
			},
		})
	}
	return locs, nil
}

// offsetToLineChar converts a byte offset in content to 0-indexed line and character.
func offsetToLineChar(content string, offset int) (int, int) {
	line := 0
	lineStart := 0
	for i := 0; i < offset && i < len(content); i++ {
		if content[i] == '\n' {
			line++
			lineStart = i + 1
		}
	}
	return line, offset - lineStart
}