const ASSIGNMENT = 'assignment';
const ANSWER = 'answer';
const ALGORITHM_CHECKBOX = 'algorithm';
const CHARCODE_START=64;
const CHARCODE_UPPER_CORRECTION=6;
const ERROR_MESSAGE_INVALID_INPUT_SIZE = "Invalid input size, should be higher than 2 for: ";
const ERROR_MESSAGE_INVALID_ITEM_CHARACTER = "Invalid item character found: ";
const NEWLINE_CHARACTER = '\n';

/**
 * 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 byCompartiments = document.getElementById(ALGORITHM_CHECKBOX).checked;
  let answer = algorithm(assignment, byCompartiments);

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

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

    let increment = (byCompartiments)? 1:3;
    for(let i=0; i<lines.length; i+=increment) {
        let inputs = [];
        let rucksack = lines[i].replace(/\s/g, ''); // Remove whitespace

        if(byCompartiments) {
            let compartiment1 = rucksack.slice(0, rucksack.length/2);
            let compartiment2 = rucksack.slice(rucksack.length/2);
            inputs = [compartiment1, compartiment2];
        } else {
            inputs = [rucksack, lines[i+1].replace(/\s/g, ''), lines[i+2].replace(/\s/g, '')];
        }

        let duplicate = getDuplicateCharacter(inputs);
        if(duplicate < 0) {
            console.error(ERROR_MESSAGE_INVALID_INPUT_SIZE + inputs + " on line: " + i);
        }

        let priorityScore = getPriorityScore(duplicate);
        if(priorityScore < 0) {
            console.error(ERROR_MESSAGE_INVALID_ITEM_CHARACTER + duplicate + " on line: " + i);
            continue;
        }
        priorityScoreSum += priorityScore;
    }

    return "SUM priorityscore: " + priorityScoreSum;
}

/**
 * Calculate the answer to assignment.
 * @param assignment the input from the assignment.
 * @return string the answer
 */
 function algorithm1(assignment) {
    let priorityScoreSum = 0;
    let lines = assignment.trim().split(NEWLINE_CHARACTER);
    console.info("Linecount:" + lines.length);

    for(let i=0; i<lines.length; i++) {
        let rucksack = lines[i].replace(/\s/g, ''); // Remove whitespace
        let compartiment1 = rucksack.slice(0, rucksack.length/2);
        let compartiment2 = rucksack.slice(rucksack.length/2);

        console.debug("Check rucksack" + i, ": " + rucksack + " \n with compartiment1: " + compartiment1 + "\n and compartiment2: " + compartiment2);
        
        for(item of compartiment2) {
            if(compartiment1.includes(item)) {
                console.debug("Found duplicate: " + item + " in rucksack" + i);
                let priorityScore = getPriorityScore(item);
                if(priorityScore < 0) {
                    console.error(ERROR_MESSAGE_INVALID_ITEM_CHARACTER + item + " on line: " + i);
                    continue;
                }
                priorityScoreSum += priorityScore;
                break;
            }
        }
    }

    return "SUM priorityscore: " + priorityScoreSum;
}

/**
 * Find duplicate character in inputs.
 * @param string[] inputs the inputs to find duplicates in. 
 * @return char the duplicate character
 */
function getDuplicateCharacter(inputs) {
    console.debug("Checking inputs: " + inputs);
    if(inputs.length < 2) {
        return -1;
    }

    for(let item of inputs[0]) {
        let duplicate = true
        for(let j=1; j<inputs.length; j++) {
            duplicate = duplicate && inputs[j].includes(item);
        }

        if(duplicate) {
            console.debug("Found duplicate: " + item);
            return item;
        }
    }
}

/**
 * Returns priorityscore for given character.
 * @param char character the character
 * @return int the priorityscore for character or -1 if invalid 
 */
function getPriorityScore(character) {
    let result=0;
    let uppercase = character.toUpperCase();
    let lowercase = character.toLowerCase();
    
    // validate character
    if( uppercase == lowercase ) {
        return -1;
    }
    
    if(character == uppercase) { // Switch results for upper and lowercase characters
        result -= CHARCODE_UPPER_CORRECTION;
        character = lowercase;
    } else {
        character = uppercase;
    }

    result += character.charCodeAt() - CHARCODE_START;

    return result;
}