// Package token provides a tokenizer for the monkey language.
package token

// TokenType represents the type of the token
type TokenType string

// Token represents a token, with the type and the literal value of the token
type Token struct {
	Type    TokenType
	Literal string
}

const (
	ILLEGAL = "ILLEGAL"
	EOF     = "EOF"

	IDENT = "IDENT"
	INT   = "INT"

	COMMA     = ","
	SEMICOLON = ";"

	LPAREN = "("
	RPAREN = ")"
	LBRACE = "{"
	RBRACE = "}"

	// The following tokens are keywords
	FUNCTION = "FUNCTION"
	LET      = "LET"
	TRUE     = "TRUE"
	FALSE    = "FALSE"
	IF       = "IF"
	ELSE     = "ELSE"
	RETURN   = "RETURN"

	// The following tokens are for operators
	ASSIGN   = "="
	PLUS     = "+"
	MINUS    = "-"
	BANG     = "!"
	ASTERISK = "*"
	SLASH    = "/"
	LT       = "<"
	GT       = ">"

	EQ     = "=="
	NOT_EQ = "!="
)

// List of our keywords for the language
var keywords = map[string]TokenType{
	"fn":     FUNCTION,
	"let":    LET,
	"true":   TRUE,
	"false":  FALSE,
	"if":     IF,
	"else":   ELSE,
	"return": RETURN,
}

// LookupIdent returns the token type for a given identifier.
// First we check if the identifier is a keyword. If it is, we return they
// keyword TokenType constant. If it isn't, we return the token.IDENT which is
// the TokenType for all user-defined identifiers.
func LookupIdent(ident string) TokenType {
	if tok, ok := keywords[ident]; ok {
		return tok
	}
	return IDENT
}