const ASSIGNMENT = 'assignment';
const ANSWER = 'answer';
const ALGORITHM_CHECKBOX = 'algorithm';
const ERROR_MESSAGE_NO_SUCH_CHARACTER_IN_RPS = "Non existant character in rock paper scissor game selected: ";
const ERROR_MESSAGE_TOO_FEW_CHARACTERS_IN_LINE = "Too few characters in line: ";
const NEWLINE_CHARACTER = '\n';
const OPTION_LOSE = 'X';
const OPTION_TIE = 'Y';
const OPTION_WIN = 'Z';

const RPS = Object.freeze({
    ROCK: 1,
    PAPER: 2,
    SCISSORS: 3,

    /**
     * Select winning hand for given hand.
     * @param hand the chosen hand
     * @return RPS the winning hand
     */
    winning_hand: function(hand) {
        hand++;
        if(hand > RPS.SCISSORS) {
            hand = RPS.ROCK;
        }
        return hand;
    },

    /**
     * Select losing hand for given hand.
     * @param hand the chosen hand
     * @return RPS the losing hand
     */
    losing_hand: function(hand) {
        hand--;
        if(hand < RPS.ROCK) {
            hand = RPS.SCISSORS;
        }
        return hand;
    }
});
const RPS_ALIAS_MAP = Object.freeze({
    "A": RPS.ROCK,
    "B": RPS.PAPER,
    "C": RPS.SCISSORS,
    "X": RPS.ROCK,
    "Y": RPS.PAPER,
    "Z": RPS.SCISSORS,
})
const SCORE_LOSE = 0;
const SCORE_TIE = 3;
const SCORE_WIN = 6;

/**
 * Main function
 */
window.onload = function() {
    document.getElementById(ASSIGNMENT).addEventListener("input", calculateAnswer);
    document.getElementById(ALGORITHM_CHECKBOX).addEventListener("click", calculateAnswer);
}

/**
 * Listener function for input in assignment field.
 * @param event the onInput event 
 */
function calculateAnswer(event) {
  console.info("Calculating answer for input...");
  let assignment = document.getElementById(ASSIGNMENT).value;
  let interpret_as_rps = document.getElementById(ALGORITHM_CHECKBOX).checked;
  let answer = algorithm(assignment, interpret_as_rps);

  document.getElementById(ANSWER).innerText = answer;
}

/**
 * Calculate the answer to assignment.
 * @param assignment the input from the assignment.
 * @return string the answer
 */
function algorithm(assignment, interpret_as_rps) {
    let errors = 0;
    let lines = assignment.trim().split(NEWLINE_CHARACTER);
    let score = 0;
    console.info("Linecount:" + lines.length);

    for(let i=0; i<lines.length; i++) {
        let rps_match = lines[i].replace(/\s/g, ''); // remove all whitespace
        if(rps_match.length < 2) {
            console.error(ERROR_MESSAGE_TOO_FEW_CHARACTERS_IN_LINE + i + ", skipped.");
            errors++;
            continue;
        }

        // Assign characters from line
        let opponent_hand = map_hand_character(rps_match[0]); 
        let player_input = rps_match[1]; 
        let player_hand = -1;

        // Validate hand
        if(opponent_hand<0) {
            console.error(ERROR_MESSAGE_NO_SUCH_CHARACTER_IN_RPS + rps_match[0] + " for line: " + i);
            errors++;
            continue;
        }

        // How should we interpret input? match_option or Rock Paper Scissors.
        if(interpret_as_rps) {
            player_hand = interpret_player_hand_as_rps_input(player_input);
        } else {
            player_hand = interpret_player_hand_as_match_input(player_input, opponent_hand);
        }

        if(player_hand<0) { // Invalid input
            console.error(ERROR_MESSAGE_NO_SUCH_CHARACTER_IN_RPS + rps_match[1] + " for line: " + i);
            errors++;
            continue;
        }

        score += rps_result(player_hand, opponent_hand);
    }

    if(errors > 0) {
        return errors.toString() + " Error(s) in input, see console for details."
    }

    return "Player score: " + score;
}

/**
 * Interpret given input for player as a rock paper scissor character.
 * @param char input the input for hand character (A,B,C,X,Y,Z)
 * @return the player hand character or -1 if invalid.
 */
function interpret_player_hand_as_rps_input(input) {
    return map_hand_character(input); 
}

/**
 * Interpret given input for player as a match option.
 * @param char input the input for match option (X,Y,Z)
 * @return the player hand character or -1 if invalid.
 */
function interpret_player_hand_as_match_input(input, opponent_hand) {
    let player_hand = -1;
    switch (input) {
        case OPTION_LOSE:
            player_hand = RPS.losing_hand(opponent_hand);
            break;
        case OPTION_WIN:
            player_hand = RPS.winning_hand(opponent_hand);
            break;
        case OPTION_TIE:
            player_hand = opponent_hand;
            break;
    }

    return player_hand;
}

/**
 * Maps the chosen hand character to 
 * @param hand_character the chosen character
 * @return RPS the rock paper scissor hand or -1 if invalid
 */
function map_hand_character(hand_character) {
    if(!(hand_character in RPS_ALIAS_MAP)) {
        return -1;
    }

    return RPS_ALIAS_MAP[hand_character];
}

/**
 * Calculate the result of rock paper scissor match
 * @param RPS player_hand the player's choice
 * @param RPS opponent_hand the opponent's choice
 * @return score
 */
function rps_result(player_hand, opponent_hand) {
    let score = 0;
    if(player_hand == opponent_hand) {
        score = SCORE_TIE + player_hand;  // TIE
    } else if(player_hand == RPS.winning_hand(opponent_hand)) {
        score = SCORE_WIN + player_hand; // WIN
    } else {
        score = SCORE_LOSE + player_hand; // LOSE
    }

    console.debug("score:" + score + ", player: " + player_hand + ", opponent: " + opponent_hand);
    return score;
}