Mako/parser/parser.go

package parser

import (
	"fmt"
	"strconv"
	"strings"
)

// ParseError represents a parsing error with location information
type ParseError struct {
	Message string
	Line    int
	Column  int
	Token   Token
}

func (pe ParseError) Error() string {
	return fmt.Sprintf("Parse error at line %d, column %d: %s (near '%s')",
		pe.Line, pe.Column, pe.Message, pe.Token.Literal)
}

// Parser implements a recursive descent Pratt parser with optimized AST generation
type Parser struct {
	lexer *Lexer

	curToken  Token
	peekToken Token

	prefixParseFns map[TokenType]func() Expression
	infixParseFns  map[TokenType]func(Expression) Expression

	errors []ParseError

	// Scope tracking
	scopes     []map[string]bool
	scopeTypes []string

	// Struct tracking with ID mapping
	structs   map[string]*StructStatement
	structIDs map[uint16]*StructStatement
	nextID    uint16
}

// NewParser creates a new parser instance
func NewParser(lexer *Lexer) *Parser {
	p := &Parser{
		lexer:      lexer,
		errors:     []ParseError{},
		scopes:     []map[string]bool{make(map[string]bool)},
		scopeTypes: []string{"global"},
		structs:    make(map[string]*StructStatement),
		structIDs:  make(map[uint16]*StructStatement),
		nextID:     1, // 0 reserved for non-struct types
	}

	p.prefixParseFns = make(map[TokenType]func() Expression)
	p.registerPrefix(IDENT, p.parseIdentifier)
	p.registerPrefix(NUMBER, p.parseNumberLiteral)
	p.registerPrefix(STRING, p.parseStringLiteral)
	p.registerPrefix(TRUE, p.parseBooleanLiteral)
	p.registerPrefix(FALSE, p.parseBooleanLiteral)
	p.registerPrefix(NIL, p.parseNilLiteral)
	p.registerPrefix(LPAREN, p.parseGroupedExpression)
	p.registerPrefix(LBRACE, p.parseTableLiteral)
	p.registerPrefix(MINUS, p.parsePrefixExpression)
	p.registerPrefix(NOT, p.parsePrefixExpression)
	p.registerPrefix(FN, p.parseFunctionLiteral)

	p.infixParseFns = make(map[TokenType]func(Expression) Expression)
	p.registerInfix(PLUS, p.parseInfixExpression)
	p.registerInfix(MINUS, p.parseInfixExpression)
	p.registerInfix(SLASH, p.parseInfixExpression)
	p.registerInfix(STAR, p.parseInfixExpression)
	p.registerInfix(MOD, p.parseInfixExpression)
	p.registerInfix(EQ, p.parseInfixExpression)
	p.registerInfix(NOT_EQ, p.parseInfixExpression)
	p.registerInfix(LT, p.parseInfixExpression)
	p.registerInfix(GT, p.parseInfixExpression)
	p.registerInfix(LT_EQ, p.parseInfixExpression)
	p.registerInfix(GT_EQ, p.parseInfixExpression)
	p.registerInfix(AND, p.parseInfixExpression)
	p.registerInfix(OR, p.parseInfixExpression)
	p.registerInfix(DOT, p.parseDotExpression)
	p.registerInfix(LBRACKET, p.parseIndexExpression)
	p.registerInfix(LPAREN, p.parseCallExpression)
	p.registerInfix(LBRACE, p.parseStructConstructor)

	p.nextToken()
	p.nextToken()

	return p
}

// Helper to create position from token
func (p *Parser) pos() Position {
	return Position{Line: p.curToken.Line, Column: p.curToken.Column}
}

// Struct management
func (p *Parser) registerStruct(stmt *StructStatement) {
	stmt.ID = p.nextID
	p.nextID++
	p.structs[stmt.Name] = stmt
	p.structIDs[stmt.ID] = stmt
}

func (p *Parser) getStructByName(name string) *StructStatement {
	return p.structs[name]
}

func (p *Parser) isStructDefined(name string) bool {
	_, exists := p.structs[name]
	return exists
}

// Scope management
func (p *Parser) enterScope(scopeType string) {
	p.scopes = append(p.scopes, make(map[string]bool))
	p.scopeTypes = append(p.scopeTypes, scopeType)
}

func (p *Parser) exitScope() {
	if len(p.scopes) > 1 {
		p.scopes = p.scopes[:len(p.scopes)-1]
		p.scopeTypes = p.scopeTypes[:len(p.scopeTypes)-1]
	}
}

func (p *Parser) currentVariableScope() map[string]bool {
	if len(p.scopeTypes) > 1 && p.scopeTypes[len(p.scopeTypes)-1] == "loop" {
		return p.scopes[len(p.scopes)-2]
	}
	return p.scopes[len(p.scopes)-1]
}

func (p *Parser) isVariableDeclared(name string) bool {
	for i := len(p.scopes) - 1; i >= 0; i-- {
		if p.scopes[i][name] {
			return true
		}
	}
	return false
}

func (p *Parser) declareVariable(name string) {
	p.currentVariableScope()[name] = true
}

func (p *Parser) declareLoopVariable(name string) {
	p.scopes[len(p.scopes)-1][name] = true
}

// parseTypeHint parses optional type hint after colon, returns by value
func (p *Parser) parseTypeHint() TypeInfo {
	if !p.peekTokenIs(COLON) {
		return UnknownType
	}

	p.nextToken() // consume ':'

	if !p.expectPeekIdent() {
		p.addError("expected type name after ':'")
		return UnknownType
	}

	typeName := p.curToken.Literal

	// Check built-in types
	switch typeName {
	case "number":
		return TypeInfo{Type: TypeNumber, Inferred: false}
	case "string":
		return TypeInfo{Type: TypeString, Inferred: false}
	case "bool":
		return TypeInfo{Type: TypeBool, Inferred: false}
	case "nil":
		return TypeInfo{Type: TypeNil, Inferred: false}
	case "table":
		return TypeInfo{Type: TypeTable, Inferred: false}
	case "function":
		return TypeInfo{Type: TypeFunction, Inferred: false}
	case "any":
		return TypeInfo{Type: TypeAny, Inferred: false}
	default:
		// Check if it's a struct type
		if structDef := p.getStructByName(typeName); structDef != nil {
			return TypeInfo{Type: TypeStruct, StructID: structDef.ID, Inferred: false}
		}
		p.addError(fmt.Sprintf("invalid type name '%s'", typeName))
		return UnknownType
	}
}

// registerPrefix/registerInfix
func (p *Parser) registerPrefix(tokenType TokenType, fn func() Expression) {
	p.prefixParseFns[tokenType] = fn
}

func (p *Parser) registerInfix(tokenType TokenType, fn func(Expression) Expression) {
	p.infixParseFns[tokenType] = fn
}

func (p *Parser) nextToken() {
	p.curToken = p.peekToken
	p.peekToken = p.lexer.NextToken()
}

// ParseProgram parses the entire program
func (p *Parser) ParseProgram() *Program {
	program := &Program{Position: p.pos()}
	program.Statements = []Statement{}

	for !p.curTokenIs(EOF) {
		stmt := p.parseStatement()
		if stmt != nil {
			program.Statements = append(program.Statements, stmt)
		}
		p.nextToken()
	}

	return program
}

// parseStatement parses a statement
func (p *Parser) parseStatement() Statement {
	switch p.curToken.Type {
	case STRUCT:
		return p.parseStructStatement()
	case FN:
		return p.parseFunctionStatement()
	case IDENT:
		return p.parseIdentifierStatement()
	case IF:
		return p.parseIfStatement()
	case FOR:
		return p.parseForStatement()
	case WHILE:
		return p.parseWhileStatement()
	case ECHO:
		return p.parseEchoStatement()
	case BREAK:
		return p.parseBreakStatement()
	case EXIT:
		return p.parseExitStatement()
	case RETURN:
		return p.parseReturnStatement()
	case ASSIGN:
		p.addError("assignment operator '=' without left-hand side identifier")
		return nil
	case ILLEGAL:
		p.addError(fmt.Sprintf("unexpected token '%s'", p.curToken.Literal))
		return nil
	case EOF:
		return nil
	default:
		p.addError(fmt.Sprintf("unexpected token '%s', expected statement", p.curToken.Literal))
		return nil
	}
}

// parseStructStatement parses struct definitions
func (p *Parser) parseStructStatement() *StructStatement {
	stmt := &StructStatement{Position: p.pos()}

	if !p.expectPeek(IDENT) {
		p.addError("expected struct name")
		return nil
	}

	stmt.Name = p.curToken.Literal

	if !p.expectPeek(LBRACE) {
		p.addError("expected '{' after struct name")
		return nil
	}

	stmt.Fields = []StructField{}

	if p.peekTokenIs(RBRACE) {
		p.nextToken()
		p.registerStruct(stmt)
		return stmt
	}

	p.nextToken()

	for {
		if p.curTokenIs(EOF) {
			p.addError("unexpected end of input, expected }")
			return nil
		}

		if !p.curTokenIs(IDENT) {
			p.addError("expected field name")
			return nil
		}

		field := StructField{Name: p.curToken.Literal, Position: p.pos()}

		// Parse required type hint
		field.TypeHint = p.parseTypeHint()
		if field.TypeHint.Type == TypeUnknown {
			p.addError("struct fields require type annotation")
			return nil
		}

		stmt.Fields = append(stmt.Fields, field)

		if !p.peekTokenIs(COMMA) {
			break
		}

		p.nextToken() // consume comma
		p.nextToken() // move to next field

		if p.curTokenIs(RBRACE) {
			break
		}

		if p.curTokenIs(EOF) {
			p.addError("expected next token to be }")
			return nil
		}
	}

	if !p.expectPeek(RBRACE) {
		return nil
	}

	p.registerStruct(stmt)
	return stmt
}

// parseFunctionStatement handles both regular functions and methods
func (p *Parser) parseFunctionStatement() Statement {
	pos := p.pos()

	if !p.expectPeek(IDENT) {
		p.addError("expected function name")
		return nil
	}

	funcName := p.curToken.Literal

	// Check if this is a method definition (struct.method)
	if p.peekTokenIs(DOT) {
		p.nextToken() // consume '.'

		if !p.expectPeek(IDENT) {
			p.addError("expected method name after '.'")
			return nil
		}

		methodName := p.curToken.Literal

		// Get struct ID
		structDef := p.getStructByName(funcName)
		if structDef == nil {
			p.addError(fmt.Sprintf("method defined on undefined struct '%s'", funcName))
			return nil
		}

		if !p.expectPeek(LPAREN) {
			p.addError("expected '(' after method name")
			return nil
		}

		// Parse the function literal
		funcLit := &FunctionLiteral{Position: p.pos()}
		funcLit.Parameters, funcLit.Variadic = p.parseFunctionParameters()

		if !p.expectPeek(RPAREN) {
			p.addError("expected ')' after function parameters")
			return nil
		}

		// Check for return type hint
		funcLit.ReturnType = p.parseTypeHint()

		p.nextToken()

		p.enterScope("function")
		for _, param := range funcLit.Parameters {
			p.declareVariable(param.Name)
		}
		funcLit.Body = p.parseBlockStatements(END)
		p.exitScope()

		if !p.curTokenIs(END) {
			p.addError("expected 'end' to close function")
			return nil
		}

		return &MethodDefinition{
			StructID:   structDef.ID,
			MethodName: methodName,
			Function:   funcLit,
			Position:   pos,
		}
	}

	// Regular function - handle as function literal expression statement
	funcLit := p.parseFunctionLiteral()
	if funcLit == nil {
		return nil
	}

	return &ExpressionStatement{Expression: funcLit, Position: pos}
}

// parseIdentifierStatement handles assignments and expression statements
func (p *Parser) parseIdentifierStatement() Statement {
	pos := p.pos()

	// Parse the left-hand side expression first
	expr := p.ParseExpression(LOWEST)
	if expr == nil {
		return nil
	}

	// Check for type hint (only valid on simple identifiers)
	var typeHint TypeInfo = UnknownType
	if _, ok := expr.(*Identifier); ok {
		typeHint = p.parseTypeHint()
	}

	// Check if this is an assignment
	if p.peekTokenIs(ASSIGN) {
		// Create unified assignment
		assignment := &Assignment{
			Target:   expr,
			TypeHint: typeHint,
			Position: pos,
		}

		// Validate assignment target and check if it's a declaration
		switch target := expr.(type) {
		case *Identifier:
			assignment.IsDeclaration = !p.isVariableDeclared(target.Value)
			if assignment.IsDeclaration {
				p.declareVariable(target.Value)
			}
		case *DotExpression, *IndexExpression:
			assignment.IsDeclaration = false
		default:
			p.addError("invalid assignment target")
			return nil
		}

		if !p.expectPeek(ASSIGN) {
			return nil
		}

		p.nextToken()

		assignment.Value = p.ParseExpression(LOWEST)
		if assignment.Value == nil {
			p.addError("expected expression after assignment operator")
			return nil
		}

		return assignment
	} else {
		// This is an expression statement
		return &ExpressionStatement{Expression: expr, Position: pos}
	}
}

// parseEchoStatement parses echo statements
func (p *Parser) parseEchoStatement() *EchoStatement {
	stmt := &EchoStatement{Position: p.pos()}

	p.nextToken() // move past 'echo'

	stmt.Value = p.ParseExpression(LOWEST)
	if stmt.Value == nil {
		p.addError("expected expression after 'echo'")
		return nil
	}

	return stmt
}

// Simple statement parsers
func (p *Parser) parseBreakStatement() *BreakStatement {
	if p.peekTokenIs(IDENT) {
		p.addError("unexpected identifier")
		return nil
	}
	return &BreakStatement{Position: p.pos()}
}

func (p *Parser) parseExitStatement() *ExitStatement {
	stmt := &ExitStatement{Position: p.pos()}

	if p.canStartExpression(p.peekToken.Type) {
		p.nextToken()
		stmt.Value = p.ParseExpression(LOWEST)
		if stmt.Value == nil {
			p.addError("expected expression after 'exit'")
			return nil
		}
	}

	return stmt
}

func (p *Parser) parseReturnStatement() *ReturnStatement {
	stmt := &ReturnStatement{Position: p.pos()}

	if p.canStartExpression(p.peekToken.Type) {
		p.nextToken()
		stmt.Value = p.ParseExpression(LOWEST)
		if stmt.Value == nil {
			p.addError("expected expression after 'return'")
			return nil
		}
	}

	return stmt
}

func (p *Parser) canStartExpression(tokenType TokenType) bool {
	switch tokenType {
	case IDENT, NUMBER, STRING, TRUE, FALSE, NIL, LPAREN, LBRACE, MINUS, NOT, FN:
		return true
	default:
		return false
	}
}

// Loop statement parsers
func (p *Parser) parseWhileStatement() *WhileStatement {
	stmt := &WhileStatement{Position: p.pos()}

	p.nextToken()

	stmt.Condition = p.ParseExpression(LOWEST)
	if stmt.Condition == nil {
		p.addError("expected condition after 'while'")
		return nil
	}

	if !p.expectPeek(DO) {
		p.addError("expected 'do' after while condition")
		return nil
	}

	p.nextToken()

	stmt.Body = p.parseBlockStatements(END)

	if !p.curTokenIs(END) {
		p.addError("expected 'end' to close while loop")
		return nil
	}

	return stmt
}

func (p *Parser) parseForStatement() Statement {
	pos := p.pos()
	p.nextToken()

	if !p.curTokenIs(IDENT) {
		p.addError("expected identifier after 'for'")
		return nil
	}

	firstVar := &Identifier{Value: p.curToken.Literal, Position: p.pos()}

	if p.peekTokenIs(ASSIGN) {
		return p.parseNumericForStatement(firstVar, pos)
	} else if p.peekTokenIs(COMMA) || p.peekTokenIs(IN) {
		return p.parseForInStatement(firstVar, pos)
	} else {
		p.addError("expected '=', ',' or 'in' after for loop variable")
		return nil
	}
}

func (p *Parser) parseNumericForStatement(variable *Identifier, pos Position) *ForStatement {
	stmt := &ForStatement{Variable: variable, Position: pos}

	if !p.expectPeek(ASSIGN) {
		return nil
	}

	p.nextToken()

	stmt.Start = p.ParseExpression(LOWEST)
	if stmt.Start == nil {
		p.addError("expected start expression in for loop")
		return nil
	}

	if !p.expectPeek(COMMA) {
		p.addError("expected ',' after start expression in for loop")
		return nil
	}

	p.nextToken()

	stmt.End = p.ParseExpression(LOWEST)
	if stmt.End == nil {
		p.addError("expected end expression in for loop")
		return nil
	}

	if p.peekTokenIs(COMMA) {
		p.nextToken()
		p.nextToken()

		stmt.Step = p.ParseExpression(LOWEST)
		if stmt.Step == nil {
			p.addError("expected step expression in for loop")
			return nil
		}
	}

	if !p.expectPeek(DO) {
		p.addError("expected 'do' after for loop header")
		return nil
	}

	p.nextToken()

	p.enterScope("loop")
	p.declareLoopVariable(variable.Value)
	stmt.Body = p.parseBlockStatements(END)
	p.exitScope()

	if !p.curTokenIs(END) {
		p.addError("expected 'end' to close for loop")
		return nil
	}

	return stmt
}

func (p *Parser) parseForInStatement(firstVar *Identifier, pos Position) *ForInStatement {
	stmt := &ForInStatement{Position: pos}

	if p.peekTokenIs(COMMA) {
		stmt.Key = firstVar
		p.nextToken()
		p.nextToken()

		if !p.curTokenIs(IDENT) {
			p.addError("expected identifier after ',' in for loop")
			return nil
		}

		stmt.Value = &Identifier{Value: p.curToken.Literal, Position: p.pos()}
	} else {
		stmt.Value = firstVar
	}

	if !p.expectPeek(IN) {
		p.addError("expected 'in' in for loop")
		return nil
	}

	p.nextToken()

	stmt.Iterable = p.ParseExpression(LOWEST)
	if stmt.Iterable == nil {
		p.addError("expected expression after 'in' in for loop")
		return nil
	}

	if !p.expectPeek(DO) {
		p.addError("expected 'do' after for loop header")
		return nil
	}

	p.nextToken()

	p.enterScope("loop")
	if stmt.Key != nil {
		p.declareLoopVariable(stmt.Key.Value)
	}
	p.declareLoopVariable(stmt.Value.Value)
	stmt.Body = p.parseBlockStatements(END)
	p.exitScope()

	if !p.curTokenIs(END) {
		p.addError("expected 'end' to close for loop")
		return nil
	}

	return stmt
}

// parseIfStatement parses if statements
func (p *Parser) parseIfStatement() *IfStatement {
	stmt := &IfStatement{Position: p.pos()}

	p.nextToken()

	stmt.Condition = p.ParseExpression(LOWEST)
	if stmt.Condition == nil {
		p.addError("expected condition after 'if'")
		return nil
	}

	if p.peekTokenIs(THEN) {
		p.nextToken()
	}

	p.nextToken()

	if p.curTokenIs(END) {
		p.addError("expected 'end' to close if statement")
		return nil
	}

	stmt.Body = p.parseBlockStatements(ELSEIF, ELSE, END)

	for p.curTokenIs(ELSEIF) {
		elseif := ElseIfClause{Position: p.pos()}

		p.nextToken()

		elseif.Condition = p.ParseExpression(LOWEST)
		if elseif.Condition == nil {
			p.addError("expected condition after 'elseif'")
			return nil
		}

		if p.peekTokenIs(THEN) {
			p.nextToken()
		}

		p.nextToken()

		elseif.Body = p.parseBlockStatements(ELSEIF, ELSE, END)
		stmt.ElseIfs = append(stmt.ElseIfs, elseif)
	}

	if p.curTokenIs(ELSE) {
		p.nextToken()
		stmt.Else = p.parseBlockStatements(END)
	}

	if !p.curTokenIs(END) {
		p.addError("expected 'end' to close if statement")
		return nil
	}

	return stmt
}

// parseBlockStatements parses statements until terminators
func (p *Parser) parseBlockStatements(terminators ...TokenType) []Statement {
	statements := make([]Statement, 0, 8) // Pre-allocate for performance

	for !p.curTokenIs(EOF) && !p.isTerminator(terminators...) {
		stmt := p.parseStatement()
		if stmt != nil {
			statements = append(statements, stmt)
		}
		p.nextToken()
	}

	return statements
}

func (p *Parser) isTerminator(terminators ...TokenType) bool {
	for _, terminator := range terminators {
		if p.curTokenIs(terminator) {
			return true
		}
	}
	return false
}

// ParseExpression parses expressions using Pratt parsing
func (p *Parser) ParseExpression(precedence Precedence) Expression {
	prefix := p.prefixParseFns[p.curToken.Type]
	if prefix == nil {
		p.noPrefixParseFnError(p.curToken.Type)
		return nil
	}

	leftExp := prefix()
	if leftExp == nil {
		return nil
	}

	for !p.peekTokenIs(EOF) && precedence < p.peekPrecedence() {
		infix := p.infixParseFns[p.peekToken.Type]
		if infix == nil {
			return leftExp
		}

		p.nextToken()
		leftExp = infix(leftExp)
		if leftExp == nil {
			return nil
		}
	}

	return leftExp
}

// Expression parsing functions
func (p *Parser) parseIdentifier() Expression {
	return &Identifier{Value: p.curToken.Literal, Position: p.pos()}
}

func (p *Parser) parseNumberLiteral() Expression {
	lit := &NumberLiteral{Position: p.pos()}
	literal := p.curToken.Literal

	var value float64
	var err error

	if strings.HasPrefix(literal, "0x") || strings.HasPrefix(literal, "0X") {
		if len(literal) <= 2 {
			p.addError(fmt.Sprintf("could not parse '%s' as hexadecimal number", literal))
			return nil
		}
		hexPart := literal[2:]
		for _, ch := range hexPart {
			if !((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F')) {
				p.addError(fmt.Sprintf("could not parse '%s' as hexadecimal number", literal))
				return nil
			}
		}
		intVal, parseErr := strconv.ParseInt(literal, 0, 64)
		if parseErr != nil {
			p.addError(fmt.Sprintf("could not parse '%s' as hexadecimal number", literal))
			return nil
		}
		value = float64(intVal)
	} else if strings.HasPrefix(literal, "0b") || strings.HasPrefix(literal, "0B") {
		if len(literal) <= 2 {
			p.addError(fmt.Sprintf("could not parse '%s' as binary number", literal))
			return nil
		}
		binaryPart := literal[2:]
		for _, ch := range binaryPart {
			if ch != '0' && ch != '1' {
				p.addError(fmt.Sprintf("could not parse '%s' as binary number", literal))
				return nil
			}
		}
		binaryStr := literal[2:]
		intVal, parseErr := strconv.ParseInt(binaryStr, 2, 64)
		if parseErr != nil {
			p.addError(fmt.Sprintf("could not parse '%s' as binary number", literal))
			return nil
		}
		value = float64(intVal)
	} else {
		value, err = strconv.ParseFloat(literal, 64)
		if err != nil {
			p.addError(fmt.Sprintf("could not parse '%s' as number", literal))
			return nil
		}
	}

	lit.Value = value
	return lit
}

func (p *Parser) parseStringLiteral() Expression {
	return &StringLiteral{Value: p.curToken.Literal, Position: p.pos()}
}

func (p *Parser) parseBooleanLiteral() Expression {
	return &BooleanLiteral{Value: p.curTokenIs(TRUE), Position: p.pos()}
}

func (p *Parser) parseNilLiteral() Expression {
	return &NilLiteral{Position: p.pos()}
}

func (p *Parser) parsePrefixExpression() Expression {
	expression := &PrefixExpression{
		Operator: p.curToken.Literal,
		Position: p.pos(),
	}

	p.nextToken()

	expression.Right = p.ParseExpression(PREFIX)
	if expression.Right == nil {
		p.addError(fmt.Sprintf("expected expression after prefix operator '%s'", expression.Operator))
		return nil
	}

	return expression
}

// parseGroupedExpression handles parentheses and assignment expressions
func (p *Parser) parseGroupedExpression() Expression {
	p.nextToken()

	// Check if this is an assignment expression inside parentheses
	if p.curTokenIs(IDENT) && p.peekTokenIs(ASSIGN) {
		return p.parseParenthesizedAssignment()
	}

	// Regular grouped expression
	exp := p.ParseExpression(LOWEST)
	if exp == nil {
		return nil
	}

	if !p.expectPeek(RPAREN) {
		return nil
	}

	return exp
}

// parseParenthesizedAssignment parses assignment expressions in parentheses
func (p *Parser) parseParenthesizedAssignment() Expression {
	pos := p.pos()
	target := p.parseIdentifier()

	if !p.expectPeek(ASSIGN) {
		return nil
	}

	p.nextToken() // move past =

	value := p.ParseExpression(LOWEST)
	if value == nil {
		p.addError("expected expression after assignment operator")
		return nil
	}

	if !p.expectPeek(RPAREN) {
		return nil
	}

	// Create assignment expression
	assignExpr := &Assignment{
		Target:       target,
		Value:        value,
		IsExpression: true,
		Position:     pos,
	}

	// Handle variable declaration for assignment expressions
	if ident, ok := target.(*Identifier); ok {
		assignExpr.IsDeclaration = !p.isVariableDeclared(ident.Value)
		if assignExpr.IsDeclaration {
			p.declareVariable(ident.Value)
		}
	}

	return assignExpr
}

func (p *Parser) parseFunctionLiteral() Expression {
	fn := &FunctionLiteral{Position: p.pos()}

	if !p.expectPeek(LPAREN) {
		p.addError("expected '(' after 'fn'")
		return nil
	}

	fn.Parameters, fn.Variadic = p.parseFunctionParameters()

	if !p.expectPeek(RPAREN) {
		p.addError("expected ')' after function parameters")
		return nil
	}

	// Check for return type hint
	fn.ReturnType = p.parseTypeHint()

	p.nextToken()

	p.enterScope("function")
	for _, param := range fn.Parameters {
		p.declareVariable(param.Name)
	}
	fn.Body = p.parseBlockStatements(END)
	p.exitScope()

	if !p.curTokenIs(END) {
		p.addError("expected 'end' to close function")
		return nil
	}

	return fn
}

func (p *Parser) parseFunctionParameters() ([]FunctionParameter, bool) {
	var params []FunctionParameter
	var variadic bool

	if p.peekTokenIs(RPAREN) {
		return params, false
	}

	p.nextToken()

	for {
		if p.curTokenIs(ELLIPSIS) {
			variadic = true
			break
		}

		if !p.curTokenIs(IDENT) {
			p.addError("expected parameter name")
			return nil, false
		}

		param := FunctionParameter{Name: p.curToken.Literal, Position: p.pos()}

		// Check for type hint
		param.TypeHint = p.parseTypeHint()

		params = append(params, param)

		if !p.peekTokenIs(COMMA) {
			break
		}

		p.nextToken()
		p.nextToken()

		if p.curTokenIs(ELLIPSIS) {
			variadic = true
			break
		}
	}

	return params, variadic
}

func (p *Parser) parseTableLiteral() Expression {
	table := &TableLiteral{Position: p.pos()}
	table.Pairs = make([]TablePair, 0, 4) // Pre-allocate

	if p.peekTokenIs(RBRACE) {
		p.nextToken()
		return table
	}

	p.nextToken()

	for {
		if p.curTokenIs(EOF) {
			p.addError("unexpected end of input, expected }")
			return nil
		}

		pair := TablePair{Position: p.pos()}

		if (p.curTokenIs(IDENT) || p.curTokenIs(STRING)) && p.peekTokenIs(ASSIGN) {
			if p.curTokenIs(IDENT) {
				pair.Key = &Identifier{Value: p.curToken.Literal, Position: p.pos()}
			} else {
				pair.Key = &StringLiteral{Value: p.curToken.Literal, Position: p.pos()}
			}
			p.nextToken()
			p.nextToken()

			if p.curTokenIs(EOF) {
				p.addError("expected expression after assignment operator")
				return nil
			}

			pair.Value = p.ParseExpression(LOWEST)
		} else {
			pair.Value = p.ParseExpression(LOWEST)
		}

		if pair.Value == nil {
			return nil
		}

		table.Pairs = append(table.Pairs, pair)

		if !p.peekTokenIs(COMMA) {
			break
		}

		p.nextToken()
		p.nextToken()

		if p.curTokenIs(RBRACE) {
			break
		}

		if p.curTokenIs(EOF) {
			p.addError("expected next token to be }")
			return nil
		}
	}

	if !p.expectPeek(RBRACE) {
		return nil
	}

	return table
}

// parseStructConstructor handles struct constructor calls
func (p *Parser) parseStructConstructor(left Expression) Expression {
	pos := p.pos()

	ident, ok := left.(*Identifier)
	if !ok {
		return p.parseTableLiteralFromBrace()
	}

	structName := ident.Value
	structDef := p.getStructByName(structName)
	if structDef == nil {
		// Not a struct, parse as table literal
		return p.parseTableLiteralFromBrace()
	}

	constructor := &StructConstructor{
		StructID: structDef.ID,
		Fields:   make([]TablePair, 0, 4),
		typeInfo: TypeInfo{Type: TypeStruct, StructID: structDef.ID, Inferred: true},
		Position: pos,
	}

	if p.peekTokenIs(RBRACE) {
		p.nextToken()
		return constructor
	}

	p.nextToken()

	for {
		if p.curTokenIs(EOF) {
			p.addError("unexpected end of input, expected }")
			return nil
		}

		pair := TablePair{Position: p.pos()}

		if (p.curTokenIs(IDENT) || p.curTokenIs(STRING)) && p.peekTokenIs(ASSIGN) {
			if p.curTokenIs(IDENT) {
				pair.Key = &Identifier{Value: p.curToken.Literal, Position: p.pos()}
			} else {
				pair.Key = &StringLiteral{Value: p.curToken.Literal, Position: p.pos()}
			}
			p.nextToken()
			p.nextToken()

			if p.curTokenIs(EOF) {
				p.addError("expected expression after assignment operator")
				return nil
			}

			pair.Value = p.ParseExpression(LOWEST)
		} else {
			pair.Value = p.ParseExpression(LOWEST)
		}

		if pair.Value == nil {
			return nil
		}

		constructor.Fields = append(constructor.Fields, pair)

		if !p.peekTokenIs(COMMA) {
			break
		}

		p.nextToken()
		p.nextToken()

		if p.curTokenIs(RBRACE) {
			break
		}

		if p.curTokenIs(EOF) {
			p.addError("expected next token to be }")
			return nil
		}
	}

	if !p.expectPeek(RBRACE) {
		return nil
	}

	return constructor
}

func (p *Parser) parseTableLiteralFromBrace() Expression {
	table := &TableLiteral{Position: p.pos()}
	table.Pairs = make([]TablePair, 0, 4)

	if p.peekTokenIs(RBRACE) {
		p.nextToken()
		return table
	}

	p.nextToken()

	for {
		if p.curTokenIs(EOF) {
			p.addError("unexpected end of input, expected }")
			return nil
		}

		pair := TablePair{Position: p.pos()}

		if (p.curTokenIs(IDENT) || p.curTokenIs(STRING)) && p.peekTokenIs(ASSIGN) {
			if p.curTokenIs(IDENT) {
				pair.Key = &Identifier{Value: p.curToken.Literal, Position: p.pos()}
			} else {
				pair.Key = &StringLiteral{Value: p.curToken.Literal, Position: p.pos()}
			}
			p.nextToken()
			p.nextToken()

			if p.curTokenIs(EOF) {
				p.addError("expected expression after assignment operator")
				return nil
			}

			pair.Value = p.ParseExpression(LOWEST)
		} else {
			pair.Value = p.ParseExpression(LOWEST)
		}

		if pair.Value == nil {
			return nil
		}

		table.Pairs = append(table.Pairs, pair)

		if !p.peekTokenIs(COMMA) {
			break
		}

		p.nextToken()
		p.nextToken()

		if p.curTokenIs(RBRACE) {
			break
		}

		if p.curTokenIs(EOF) {
			p.addError("expected next token to be }")
			return nil
		}
	}

	if !p.expectPeek(RBRACE) {
		return nil
	}

	return table
}

func (p *Parser) parseInfixExpression(left Expression) Expression {
	expression := &InfixExpression{
		Left:     left,
		Operator: p.curToken.Literal,
		Position: p.pos(),
	}

	precedence := p.curPrecedence()
	p.nextToken()
	expression.Right = p.ParseExpression(precedence)

	if expression.Right == nil {
		p.addError(fmt.Sprintf("expected expression after operator '%s'", expression.Operator))
		return nil
	}

	return expression
}

func (p *Parser) parseDotExpression(left Expression) Expression {
	pos := p.pos()

	if !p.expectPeekIdent() {
		p.addError("expected identifier after '.'")
		return nil
	}

	return &DotExpression{
		Left:     left,
		Key:      p.curToken.Literal,
		Position: pos,
	}
}

func (p *Parser) parseCallExpression(fn Expression) Expression {
	call := &CallExpression{Function: fn, Position: p.pos()}
	call.Arguments = p.parseExpressionList(RPAREN)
	return call
}

func (p *Parser) parseExpressionList(end TokenType) []Expression {
	var args []Expression

	if p.peekTokenIs(end) {
		p.nextToken()
		return args
	}

	p.nextToken()
	args = append(args, p.ParseExpression(LOWEST))

	for p.peekTokenIs(COMMA) {
		p.nextToken()
		p.nextToken()
		args = append(args, p.ParseExpression(LOWEST))
	}

	if !p.expectPeek(end) {
		return nil
	}

	return args
}

func (p *Parser) parseIndexExpression(left Expression) Expression {
	pos := p.pos()
	p.nextToken()

	index := p.ParseExpression(LOWEST)
	if index == nil {
		p.addError("expected expression inside brackets")
		return nil
	}

	if !p.expectPeek(RBRACKET) {
		p.addError("expected ']' after index expression")
		return nil
	}

	return &IndexExpression{
		Left:     left,
		Index:    index,
		Position: pos,
	}
}

// Helper methods
func (p *Parser) curTokenIs(t TokenType) bool {
	return p.curToken.Type == t
}

func (p *Parser) peekTokenIs(t TokenType) bool {
	return p.peekToken.Type == t
}

func (p *Parser) expectPeek(t TokenType) bool {
	if p.peekTokenIs(t) {
		p.nextToken()
		return true
	}
	p.peekError(t)
	return false
}

func (p *Parser) expectPeekIdent() bool {
	if p.peekTokenIs(IDENT) || p.isKeyword(p.peekToken.Type) {
		p.nextToken()
		return true
	}
	p.peekError(IDENT)
	return false
}

func (p *Parser) isKeyword(t TokenType) bool {
	switch t {
	case TRUE, FALSE, NIL, AND, OR, NOT, IF, THEN, ELSEIF, ELSE, END, ECHO, FOR, WHILE, IN, DO, BREAK, EXIT, FN, RETURN, STRUCT:
		return true
	default:
		return false
	}
}

// Error handling
func (p *Parser) addError(message string) {
	p.errors = append(p.errors, ParseError{
		Message: message,
		Line:    p.curToken.Line,
		Column:  p.curToken.Column,
		Token:   p.curToken,
	})
}

func (p *Parser) peekError(t TokenType) {
	message := fmt.Sprintf("expected next token to be %s, got %s instead",
		tokenTypeString(t), tokenTypeString(p.peekToken.Type))
	p.errors = append(p.errors, ParseError{
		Message: message,
		Line:    p.peekToken.Line,
		Column:  p.peekToken.Column,
		Token:   p.peekToken,
	})
}

func (p *Parser) noPrefixParseFnError(t TokenType) {
	var message string
	switch t {
	case ASSIGN:
		message = "unexpected assignment operator, missing left-hand side identifier"
	case PLUS, MINUS, STAR, SLASH, MOD:
		message = fmt.Sprintf("unexpected operator '%s', missing left operand", tokenTypeString(t))
	case RPAREN:
		message = "unexpected closing parenthesis"
	case RBRACE:
		message = "unexpected closing brace"
	case RBRACKET:
		message = "unexpected closing bracket"
	case EOF:
		message = "unexpected end of input"
	default:
		message = fmt.Sprintf("unexpected token '%s'", tokenTypeString(t))
	}

	p.addError(message)
}

func (p *Parser) peekPrecedence() Precedence {
	if p, ok := precedences[p.peekToken.Type]; ok {
		return p
	}
	return LOWEST
}

func (p *Parser) curPrecedence() Precedence {
	if p, ok := precedences[p.curToken.Type]; ok {
		return p
	}
	return LOWEST
}

// Error reporting
func (p *Parser) Errors() []ParseError { return p.errors }
func (p *Parser) HasErrors() bool      { return len(p.errors) > 0 }
func (p *Parser) ErrorStrings() []string {
	result := make([]string, len(p.errors))
	for i, err := range p.errors {
		result[i] = err.Error()
	}
	return result
}

// tokenTypeString returns human-readable string for token types
func tokenTypeString(t TokenType) string {
	switch t {
	case IDENT:
		return "identifier"
	case NUMBER:
		return "number"
	case STRING:
		return "string"
	case TRUE, FALSE:
		return "boolean"
	case NIL:
		return "nil"
	case ASSIGN:
		return "="
	case PLUS:
		return "+"
	case MINUS:
		return "-"
	case STAR:
		return "*"
	case SLASH:
		return "/"
	case MOD:
		return "%"
	case DOT:
		return "."
	case COLON:
		return ":"
	case EQ:
		return "=="
	case NOT_EQ:
		return "!="
	case LT:
		return "<"
	case GT:
		return ">"
	case LT_EQ:
		return "<="
	case GT_EQ:
		return ">="
	case AND:
		return "and"
	case OR:
		return "or"
	case NOT:
		return "not"
	case LPAREN:
		return "("
	case RPAREN:
		return ")"
	case LBRACE:
		return "{"
	case RBRACE:
		return "}"
	case LBRACKET:
		return "["
	case RBRACKET:
		return "]"
	case COMMA:
		return ","
	case ELLIPSIS:
		return "..."
	case IF:
		return "if"
	case THEN:
		return "then"
	case ELSEIF:
		return "elseif"
	case ELSE:
		return "else"
	case END:
		return "end"
	case ECHO:
		return "echo"
	case FOR:
		return "for"
	case WHILE:
		return "while"
	case IN:
		return "in"
	case DO:
		return "do"
	case BREAK:
		return "break"
	case EXIT:
		return "exit"
	case FN:
		return "fn"
	case RETURN:
		return "return"
	case STRUCT:
		return "struct"
	case EOF:
		return "end of file"
	case ILLEGAL:
		return "illegal token"
	default:
		return "unknown"
	}
}