package token

import file.FilePosition
import token.TokenFactory.BadCharacterException
import token.TokenFactory.EmptyTokenTextException
import util.Characters.AT_SIGN
import util.Characters.BACKQUOTE
import util.Characters.COMMA
import util.Characters.DOUBLE_QUOTE
import util.Characters.LEFT_PARENTHESIS
import util.Characters.RIGHT_PARENTHESIS
import util.Characters.SINGLE_QUOTE
import util.Characters.isLegalIdentifierCharacter
import util.Characters.isNumberPrefix
import java.lang.Character.isDigit

class TokenFactoryImpl : TokenFactory {

    override fun createToken(text: String, position: FilePosition): Token {
        if (text.isEmpty())
            throw EmptyTokenTextException(position)

        val firstCharacter = text[0]

        return when (firstCharacter) {
            LEFT_PARENTHESIS  -> LeftParenthesis(text, position)
            RIGHT_PARENTHESIS -> RightParenthesis(text, position)
            SINGLE_QUOTE      -> QuoteMark(text, position)
            DOUBLE_QUOTE      -> QuotedString(text, position)
            BACKQUOTE         -> Backquote(text, position)
            AT_SIGN           -> AtSign(text, position)
            COMMA             -> Comma(text, position)
            else              -> when {
                isNumeric(firstCharacter, text)            -> Number(text, position)
                isLegalIdentifierCharacter(firstCharacter) -> Identifier(text, position)
                else                                       -> throw BadCharacterException(text, position)
            }
        }
    }

    override fun createEofToken(position: FilePosition): Token {
        return Eof("EOF", position)
    }

    private fun isNumeric(firstCharacter: Char, text: String): Boolean {
        return isDigit(firstCharacter) || isPrefixedNumeric(firstCharacter, text)
    }

    private fun isPrefixedNumeric(firstCharacter: Char, text: String): Boolean {
        return isNumberPrefix(firstCharacter) && isNextCharacterDigit(text)
    }

    private fun isNextCharacterDigit(text: String): Boolean {
        return text.length > 1 && isDigit(text[1])
    }
}