package token

// TokenType represents the type of a token.
type TokenType int

// Token types.
const (
	// Single-character tokens.
	LEFT_PAREN TokenType = iota
	RIGHT_PAREN
	LEFT_BRACE
	RIGHT_BRACE
	COMMA
	DOT
	MINUS
	PLUS
	SEMICOLON
	SLASH
	STAR

	// One or two character tokens.
	BANG
	BANG_EQUAL
	EQUAL
	EQUAL_EQUAL
	GREATER
	GREATER_EQUAL
	LESS
	LESS_EQUAL

	// Literals.
	IDENTIFIER
	STRING
	NUMBER

	// Keywords.
	AND
	CLASS
	ELSE
	FALSE
	FUN
	FOR
	IF
	NIL
	OR
	PRINT
	RETURN
	SUPER
	THIS
	TRUE
	VAR
	WHILE

	EOF
)

// Token represents a token in the source code.
type Token struct {
	Type    TokenType
	Lexeme  string
	Literal interface{}
	Line    int
}

// New creates a new Token.
func New(t TokenType, lexeme string, literal interface{}, line int) Token {
	return Token{t, lexeme, literal, line}
}

// String returns the string representation of the token.
func (t Token) String() string {
	return t.Lexeme
}

// keywords maps keywords to their respective TokenType.
var keywords = map[string]TokenType{
	"and":    AND,
	"class":  CLASS,
	"else":   ELSE,
	"false":  FALSE,
	"for":    FOR,
	"fun":    FUN,
	"if":     IF,
	"nil":    NIL,
	"or":     OR,
	"print":  PRINT,
	"return": RETURN,
	"super":  SUPER,
	"this":   THIS,
	"true":   TRUE,
	"var":    VAR,
	"while":  WHILE,
}

// LookupKeyword returns the TokenType for the given identifier.
// If the identifier is not a keyword, it returns IDENTIFIER.
func LookupKeyword(identifier string) TokenType {
	if t, ok := keywords[identifier]; ok {
		return t
	}
	return IDENTIFIER
}