package saccharine

import "fmt"

// All tokens in the pseudo-lambda language.
type TokenType int

const (
	TokenOpenParen  TokenType = iota // Denotes the '(' token.
	TokenCloseParen                  // Denotes the ')' token.
	TokenOpenBrace                   // Denotes the '{' token.
	TokenCloseBrace                  // Denotes the '}' token.
	TokenHardBreak                   // Denotes the ';' token.
	TokenAssign                      // Denotes the ':=' token.
	TokenAtom                        // Denotes an alpha-numeric variable.
	TokenSlash                       // Denotes the '/' token.
	TokenDot                         // Denotes the '.' token.
	TokenSoftBreak                   // Denotes a new-line.
)

// A representation of a token in source code.
type Token struct {
	Column int       // Where the token begins in the source text.
	Type   TokenType // What type the token is.
	Value  string    // The value of the token.
}

func NewTokenOpenParen(column int) *Token {
	return &Token{Type: TokenOpenParen, Column: column, Value: "("}
}

func NewTokenCloseParen(column int) *Token {
	return &Token{Type: TokenCloseParen, Column: column, Value: ")"}
}

func NewTokenOpenBrace(column int) *Token {
	return &Token{Type: TokenOpenBrace, Column: column, Value: "{"}
}

func NewTokenCloseBrace(column int) *Token {
	return &Token{Type: TokenCloseBrace, Column: column, Value: "}"}
}

func NewTokenDot(column int) *Token {
	return &Token{Type: TokenDot, Column: column, Value: "."}
}

func NewTokenHardBreak(column int) *Token {
	return &Token{Type: TokenHardBreak, Column: column, Value: ";"}
}

func NewTokenAssign(column int) *Token {
	return &Token{Type: TokenAssign, Column: column, Value: ":="}
}

func NewTokenSlash(column int) *Token {
	return &Token{Type: TokenSlash, Column: column, Value: "\\"}
}

func NewTokenAtom(name string, column int) *Token {
	return &Token{Type: TokenAtom, Column: column, Value: name}
}

func NewTokenSoftBreak(column int) *Token {
	return &Token{Type: TokenSoftBreak, Column: column, Value: "\\n"}
}

func (t TokenType) Name() string {
	switch t {
	case TokenOpenParen:
		return "("
	case TokenCloseParen:
		return ")"
	case TokenSlash:
		return "\\"
	case TokenDot:
		return "."
	case TokenAtom:
		return "ATOM"
	case TokenSoftBreak:
		return "\\n"
	case TokenHardBreak:
		return ";"
	default:
		panic(fmt.Errorf("unknown token type %v", t))
	}
}

func (t Token) Name() string {
	return t.Type.Name()
}