grindlemire/go-tui code browser

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package provider

import (
	"regexp"
	"sort"
	"strings"

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

// formatSpecifierRegex matches Go format specifiers like %s, %d, %v, %.2f, %#x, etc.
var formatSpecifierRegex = regexp.MustCompile(`%[-+# 0]*(\*|\d+)?(\.\*|\.\d+)?[vTtbcdoqxXUeEfFgGsp%]`)

// stateNewStateRegex matches state declarations like: count := tui.NewState(0)
var stateNewStateRegex = regexp.MustCompile(`(\w+)\s*:=\s*tui\.NewState\((.+)\)`)

// Semantic token types (must match the order in SemanticTokensLegend.TokenTypes).
const (
	TokenTypeNamespace     = 0  // package
	TokenTypeType          = 1  // types
	TokenTypeClass         = 2  // components
	TokenTypeFunction      = 3  // functions
	TokenTypeParameter     = 4  // parameters
	TokenTypeVariable      = 5  // variables
	TokenTypeProperty      = 6  // attributes
	TokenTypeKeyword       = 7  // keywords
	TokenTypeString        = 8  // strings
	TokenTypeNumber        = 9  // numbers
	TokenTypeOperator      = 10 // operators
	TokenTypeDecorator     = 11 // @ prefix
	TokenTypeRegexp        = 12 // format specifiers (often purple)
	TokenTypeComment       = 13 // comments
	TokenTypeLabel         = 14 // named refs
	TokenTypeTypeParameter = 15 // generic type arguments
)

// Semantic token modifiers (bit flags).
const (
	TokenModDeclaration    = 1 << 0 // where defined
	TokenModDefinition     = 1 << 1 // where defined
	TokenModReadonly       = 1 << 2 // const/let
	TokenModModification   = 1 << 3 // where modified
	TokenModDefaultLibrary = 1 << 4 // builtin types (int, bool, string, etc.)
)

// GoBuiltinTypes is the set of Go predeclared type names.
// These receive the defaultLibrary modifier, matching gopls behavior.
var GoBuiltinTypes = map[string]bool{
	"bool":       true,
	"byte":       true,
	"complex64":  true,
	"complex128": true,
	"error":      true,
	"float32":    true,
	"float64":    true,
	"int":        true,
	"int8":       true,
	"int16":      true,
	"int32":      true,
	"int64":      true,
	"rune":       true,
	"string":     true,
	"uint":       true,
	"uint8":      true,
	"uint16":     true,
	"uint32":     true,
	"uint64":     true,
	"uintptr":    true,
	"any":        true,
	"comparable": true,
}

// GoKeywords is the set of Go keywords that should be highlighted as keywords
// when they appear in Go expressions inside .gsx files.
var GoKeywords = map[string]bool{
	"func":        true,
	"return":      true,
	"if":          true,
	"else":        true,
	"for":         true,
	"range":       true,
	"switch":      true,
	"case":        true,
	"default":     true,
	"defer":       true,
	"go":          true,
	"select":      true,
	"chan":        true,
	"map":         true,
	"struct":      true,
	"interface":   true,
	"type":        true,
	"var":         true,
	"const":       true,
	"break":       true,
	"continue":    true,
	"fallthrough": true,
	"goto":        true,
}

// SemanticTokens represents the result of a semantic tokens request.
type SemanticTokens struct {
	Data []int `json:"data"`
}

// SemanticToken represents a single semantic token before encoding.
type SemanticToken struct {
	Line      int
	StartChar int
	Length    int
	TokenType int
	Modifiers int
}

// FunctionNameChecker checks if an identifier is a known function.
type FunctionNameChecker interface {
	IsFunctionName(name string) bool
}

// semanticTokensProvider implements SemanticTokensProvider.
type semanticTokensProvider struct {
	fnChecker      FunctionNameChecker
	docs           DocumentAccessor // optional, for accurate position lookups
	currentURI     string           // set during SemanticTokensFull call
	currentContent string           // set during SemanticTokensFull call
}

// NewSemanticTokensProvider creates a new semantic tokens provider.
func NewSemanticTokensProvider(fnChecker FunctionNameChecker, docs DocumentAccessor) SemanticTokensProvider {
	return &semanticTokensProvider{fnChecker: fnChecker, docs: docs}
}

func (s *semanticTokensProvider) SemanticTokensFull(doc *Document) (*SemanticTokens, error) {
	s.currentURI = doc.URI
	s.currentContent = doc.Content
	log.Server("=== SemanticTokens provider for %s ===", doc.URI)

	if doc.AST == nil {
		return &SemanticTokens{Data: []int{}}, nil
	}

	tokens := s.collectSemanticTokens(doc)

	// Sort tokens by position
	sort.Slice(tokens, func(i, j int) bool {
		if tokens[i].Line != tokens[j].Line {
			return tokens[i].Line < tokens[j].Line
		}
		return tokens[i].StartChar < tokens[j].StartChar
	})

	// Encode tokens into delta format
	data := EncodeSemanticTokens(tokens)

	if len(data) > 0 {
		log.Server("Encoded %d tokens (%d ints). First 25 values: %v", len(tokens), len(data), data[:min(25, len(data))])
	}

	return &SemanticTokens{Data: data}, nil
}

// collectSemanticTokens collects all semantic tokens from a document.
func (s *semanticTokensProvider) collectSemanticTokens(doc *Document) []SemanticToken {
	var tokens []SemanticToken
	ast := doc.AST

	// Collect comment tokens
	s.collectAllCommentTokens(ast, &tokens)

	// Collect package and import tokens
	if s.currentContent != "" {
		lines := strings.Split(s.currentContent, "\n")

		// Package keyword + name
		if ast.Position.Line > 0 {
			pkgLine := ast.Position.Line - 1
			if pkgLine < len(lines) {
				col := strings.Index(lines[pkgLine], "package")
				if col >= 0 {
					tokens = append(tokens, SemanticToken{
						Line:      pkgLine,
						StartChar: col,
						Length:    len("package"),
						TokenType: TokenTypeKeyword,
						Modifiers: 0,
					})
					tokens = append(tokens, SemanticToken{
						Line:      pkgLine,
						StartChar: col + len("package "),
						Length:    len(ast.Package),
						TokenType: TokenTypeNamespace,
						Modifiers: TokenModDeclaration,
					})
				}
			}
		}

		// Import keyword(s)
		for lineIdx, line := range lines {
			trimmed := strings.TrimSpace(line)
			if strings.HasPrefix(trimmed, "import") {
				rest := trimmed[len("import"):]
				if rest == "" || rest[0] == ' ' || rest[0] == '\t' || rest[0] == '(' {
					col := strings.Index(line, "import")
					tokens = append(tokens, SemanticToken{
						Line:      lineIdx,
						StartChar: col,
						Length:    len("import"),
						TokenType: TokenTypeKeyword,
						Modifiers: 0,
					})
				}
			}
		}
	}

	// Collect individual import tokens (alias + path)
	for _, imp := range ast.Imports {
		line := imp.Position.Line - 1
		col := imp.Position.Column - 1
		if imp.Alias != "" {
			tokens = append(tokens, SemanticToken{
				Line:      line,
				StartChar: col,
				Length:    len(imp.Alias),
				TokenType: TokenTypeNamespace,
				Modifiers: 0,
			})
			pathCol := col + len(imp.Alias) + 1
			tokens = append(tokens, SemanticToken{
				Line:      line,
				StartChar: pathCol,
				Length:    len(imp.Path) + 2, // +2 for quotes
				TokenType: TokenTypeString,
				Modifiers: 0,
			})
		} else {
			tokens = append(tokens, SemanticToken{
				Line:      line,
				StartChar: col,
				Length:    len(imp.Path) + 2, // +2 for quotes
				TokenType: TokenTypeString,
				Modifiers: 0,
			})
		}
	}

	// Collect component-related tokens
	for _, comp := range ast.Components {
		line := comp.Position.Line - 1

		// Component keyword (templ)
		tokens = append(tokens, SemanticToken{
			Line:      line,
			StartChar: comp.Position.Column - 1,
			Length:    len("templ"),
			TokenType: TokenTypeKeyword,
			Modifiers: 0,
		})

		// Method receiver tokens (if method templ)
		if comp.ReceiverName != "" && s.currentContent != "" {
			srcLines := strings.Split(s.currentContent, "\n")
			if line < len(srcLines) {
				srcLine := srcLines[line]
				// Find the opening paren of the receiver after "templ"
				searchStart := comp.Position.Column - 1 + len("templ")
				parenIdx := strings.Index(srcLine[searchStart:], "(")
				if parenIdx >= 0 {
					recvStart := searchStart + parenIdx + 1 // after "("
					// Receiver name — use parameter type so it's highlighted at the declaration
					recvNameIdx := strings.Index(srcLine[recvStart:], comp.ReceiverName)
					if recvNameIdx >= 0 {
						tokens = append(tokens, SemanticToken{
							Line:      line,
							StartChar: recvStart + recvNameIdx,
							Length:    len(comp.ReceiverName),
							TokenType: TokenTypeParameter,
							Modifiers: TokenModDeclaration,
						})
					}
					// Receiver type
					recvTypeIdx := strings.Index(srcLine[recvStart:], comp.ReceiverType)
					if recvTypeIdx >= 0 {
						emitGoTypeTokens(comp.ReceiverType, line, recvStart+recvTypeIdx, &tokens)
					}
				}
			}
		}

		// Component name — find position by searching source for "Name("
		nameStart := comp.Position.Column - 1 + len("templ ")
		if comp.ReceiverName != "" && s.currentContent != "" {
			srcLines := strings.Split(s.currentContent, "\n")
			if line < len(srcLines) {
				srcLine := srcLines[line]
				searchFrom := comp.Position.Column - 1 + len("templ")
				nameIdx := strings.Index(srcLine[searchFrom:], comp.Name+"(")
				if nameIdx >= 0 {
					nameStart = searchFrom + nameIdx
				}
			}
		}
		tokens = append(tokens, SemanticToken{
			Line:      line,
			StartChar: nameStart,
			Length:    len(comp.Name),
			TokenType: TokenTypeClass,
			Modifiers: TokenModDeclaration | TokenModDefinition,
		})

		// Parameters (declarations) with type coloring
		for _, param := range comp.Params {
			tokens = append(tokens, SemanticToken{
				Line:      param.Position.Line - 1,
				StartChar: param.Position.Column - 1,
				Length:    len(param.Name),
				TokenType: TokenTypeParameter,
				Modifiers: TokenModDeclaration,
			})
			// Parameter type
			typeStart := param.Position.Column - 1 + len(param.Name) + 1 // +1 for space
			emitGoTypeTokens(param.Type, param.Position.Line-1, typeStart, &tokens)
		}

		// Collect tokens from body — do NOT add receiver to paramNames so it gets
		// default variable coloring in usage (TextMate fallback) while the declaration
		// in the templ signature gets parameter highlighting.
		s.collectTokensFromNodes(comp.Body, comp.Params, &tokens)
	}

	// Collect GoDecl tokens (type, const, var declarations)
	for _, decl := range ast.Decls {
		s.collectTokensFromGoDecl(decl, &tokens)
	}

	// Collect function-related tokens
	for _, fn := range ast.Funcs {
		// func keyword
		tokens = append(tokens, SemanticToken{
			Line:      fn.Position.Line - 1,
			StartChar: fn.Position.Column - 1,
			Length:    len("func"),
			TokenType: TokenTypeKeyword,
			Modifiers: 0,
		})

		// Function name (handles plain funcs, methods with receivers, and generics)
		name, receiverText, typeParamStr, params, returns := parseFuncSignatureForTokens(fn.Code)
		if name != "" {
			line := fn.Position.Line - 1

			// Find name position by searching fn.Code for the name
			// For generics like "func foo[T any](...)", search for "foo[" or "foo("
			nameSearch := name + "("
			if typeParamStr != "" {
				nameSearch = name + "["
			}
			nameInCode := strings.Index(fn.Code, nameSearch)
			nameStart := fn.Position.Column - 1 + len("func ")
			if nameInCode >= 0 {
				nameStart = fn.Position.Column - 1 + nameInCode
			}

			// Emit receiver tokens for methods
			if receiverText != "" {
				recvParts := strings.SplitN(strings.TrimSpace(receiverText), " ", 2)
				if len(recvParts) == 2 {
					recvName := recvParts[0]
					recvType := recvParts[1]
					// Find receiver in the source code
					parenIdx := strings.Index(fn.Code, "(")
					if parenIdx >= 0 {
						recvNameIdx := strings.Index(fn.Code[parenIdx+1:], recvName)
						if recvNameIdx >= 0 {
							tokens = append(tokens, SemanticToken{
								Line:      line,
								StartChar: fn.Position.Column - 1 + parenIdx + 1 + recvNameIdx,
								Length:    len(recvName),
								TokenType: TokenTypeParameter,
								Modifiers: TokenModDeclaration,
							})
						}
						recvTypeIdx := strings.Index(fn.Code[parenIdx+1:], recvType)
						if recvTypeIdx >= 0 {
							emitGoTypeTokens(recvType, line, fn.Position.Column-1+parenIdx+1+recvTypeIdx, &tokens)
						}
					}
				}
			}

			tokens = append(tokens, SemanticToken{
				Line:      line,
				StartChar: nameStart,
				Length:    len(name),
				TokenType: TokenTypeFunction,
				Modifiers: TokenModDeclaration | TokenModDefinition,
			})

			// Type parameters (generics) — emit tokens for [T bool|string] section
			if typeParamStr != "" {
				typeParamStart := nameStart + len(name) // position of '['
				emitGenericTypeParamTokens(typeParamStr, line, typeParamStart, &tokens)
			}

			// Function parameters — names and types
			// For generics, params start after name + typeParams + "("
			paramStart := nameStart + len(name) + 1 // +1 for '('
			if typeParamStr != "" {
				paramStart = nameStart + len(name) + len(typeParamStr) + 1 // +1 for '('
			}
			for _, p := range params {
				// Parameter name
				tokens = append(tokens, SemanticToken{
					Line:      line,
					StartChar: paramStart,
					Length:    len(p.Name),
					TokenType: TokenTypeParameter,
					Modifiers: TokenModDeclaration,
				})
				// Parameter type
				typeStart := paramStart + len(p.Name) + 1 // +1 for space
				emitGoTypeTokens(p.Type, line, typeStart, &tokens)
				paramStart += len(p.Name) + 1 + len(p.Type) + 2 // +2 for ", "
			}

			// Return type
			if returns != "" {
				returnStart := nameStart + len(name) + 1 // "name("
				if typeParamStr != "" {
					returnStart = nameStart + len(name) + len(typeParamStr) + 1 // "name[...]("
				}
				if len(params) > 0 {
					for i, p := range params {
						returnStart += len(p.Name) + 1 + len(p.Type)
						if i < len(params)-1 {
							returnStart += 2 // ", "
						}
					}
				}
				returnStart += 2 // ") " — close paren + space
				emitGoTypeTokens(returns, line, returnStart, &tokens)
			}

			// Build parameter names map for body tokenization.
			// Do NOT add the receiver name — it should get default variable coloring
			// in usage (TextMate fallback) while the declaration gets parameter highlighting.
			paramNames := make(map[string]bool)
			for _, p := range params {
				paramNames[p.Name] = true
			}

			// Tokenize function body
			s.collectTokensFromFuncBody(fn.Code, fn.Position, paramNames, &tokens)
		}
	}

	return tokens
}

// collectTokensFromGoDecl tokenizes a top-level Go declaration (type, const, var).
func (s *semanticTokensProvider) collectTokensFromGoDecl(decl *tuigen.GoDecl, tokens *[]SemanticToken) {
	if decl == nil {
		return
	}

	line := decl.Position.Line - 1
	col := decl.Position.Column - 1

	// Keyword token (type, const, var)
	*tokens = append(*tokens, SemanticToken{
		Line:      line,
		StartChar: col,
		Length:    len(decl.Kind),
		TokenType: TokenTypeKeyword,
		Modifiers: 0,
	})

	// Tokenize the body of the declaration
	code := decl.Code
	paramNames := make(map[string]bool)
	localVars := make(map[string]bool)

	// For multi-line declarations, process each line
	codeLines := strings.Split(code, "\n")
	for lineIdx, codeLine := range codeLines {
		docLine := line + lineIdx
		lineCol := 1
		if lineIdx == 0 {
			lineCol = decl.Position.Column
		}
		linePos := tuigen.Position{Line: docLine + 1, Column: lineCol}
		s.collectTokensInGoCode(codeLine, linePos, 0, paramNames, localVars, tokens)
	}
}

// --- Helper functions ---

// EncodeSemanticTokens encodes tokens into the LSP delta format.
func EncodeSemanticTokens(tokens []SemanticToken) []int {
	if len(tokens) == 0 {
		return []int{}
	}
	data := make([]int, 0, len(tokens)*5)
	prevLine := 0
	prevChar := 0
	for _, t := range tokens {
		deltaLine := t.Line - prevLine
		deltaChar := t.StartChar
		if deltaLine == 0 {
			deltaChar = t.StartChar - prevChar
		}
		data = append(data, deltaLine, deltaChar, t.Length, t.TokenType, t.Modifiers)
		prevLine = t.Line
		prevChar = t.StartChar
	}
	return data
}

func isDigit(c byte) bool {
	return c >= '0' && c <= '9'
}

func isHexDigit(c byte) bool {
	return isDigit(c) || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')
}

func isWordStartChar(c byte) bool {
	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_'
}

// isWordCharByte checks if a byte is a valid word character (for identifiers).
func isWordCharByte(c byte) bool {
	return isWordStartChar(c) || isDigit(c)
}

// isValidIdentifier checks if a string is a valid Go identifier.
func isValidIdentifier(s string) bool {
	if len(s) == 0 {
		return false
	}
	for i, c := range s {
		if i == 0 {
			if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_') {
				return false
			}
		} else {
			if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_') {
				return false
			}
		}
	}
	return true
}