const ASSIGNMENT = 'assignment';
const ANSWER = 'answer';
const ALGORITHM_CHECKBOX = 'algorithm';
const CONTAINER_NULL_CHARACTER=0;
const INSTRUCTION_FROM='from';
const INSTRUCTION_MOVE='move';
const INSTRUCTION_TO='to';
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 allAtOnce = document.getElementById(ALGORITHM_CHECKBOX).checked;
  let answer = algorithm(assignment, allAtOnce);

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

/**
 * Calculate the answer to assignment.
 * @param assignment the input from the assignment.
 * @param allAtOnce should all containers be moved at once.
 * @return string the answer
 */
function algorithm(assignment, allAtOnce) {
    let lines = assignment.split(NEWLINE_CHARACTER);
    let containerPlan = Array.from({length:(lines[0].length+1)/4}, () => [])
    console.info("Linecount:" + lines.length);

    let parsec = true;
    for(let i=0; i<lines.length; i++) {
        if(parsec) {

            // Parse containers
            let containerLine = lines[i];

            // Skip numbers
            if(containerLine[1] == '1') {
                parsec = false;
                i+=1;
                console.table(containerPlan);
                continue;
            }

            let containers = parseContainers(containerLine);
            if(containers == -1) {
                // invalid containerline
                // TODO: error
                console.error("Container parse failure.");
                continue;
            }

            // Add containers
            //console.debug(containers);
            for(let j=0; j<containers.length; j++) {
                let container = containers[j];
                //console.debug(container);
                if(container != CONTAINER_NULL_CHARACTER) {
                    //console.debug(j);
                    //console.debug(containerPlan);
                    containerPlan[j].push(container);
                }
            }
            //console.table(containerPlan);
        } else {
            // Parse instructions
            let instructionLine = lines[i];
            let instruction = parseInstruction(instructionLine);

            console.debug(instruction);
            if(instruction == -1) {
                // invalid instructionline
                // TODO: error
                console.error("Instruction parse failure.");
                continue;
            }

            // Execute instruction
            let movecount=0;
            if(allAtOnce) {
                while(instruction.move > 0) {
                    let container = containerPlan[instruction.from].shift();
                    containerPlan[instruction.to].unshift(container);
                    instruction.move--;
                    movecount++;
                }
                console.debug("moved:" + movecount);
            } else {
                let splicedContainers = containerPlan[instruction.from].splice(0, instruction.move);
                containerPlan[instruction.to].unshift(...splicedContainers);
            }

            //console.table(containerPlan);
        }
    }

    let result="";
    for(let k=0; k<containerPlan.length; k++) {
        result += containerPlan[k][0];
    }

    return "Top containers on the stack are: " + result;
}

function parseInstruction(instructionLine) {
    let instruction={
        move:0,
        from:0,
        to:0,
    }

    instructionLine.replace(/\s/g, ''); // Remove whitespace
    let fromIndex = instructionLine.indexOf(INSTRUCTION_FROM);
    let moveIndex = instructionLine.indexOf(INSTRUCTION_MOVE);
    let toIndex = instructionLine.indexOf(INSTRUCTION_TO);

    // Validate
    if(fromIndex < 0 || moveIndex < 0 || toIndex < 0) {
        // Error
        return -1;
    }

    // TODO validate check for numbers after indices.

    // Parse
    instruction.move = parseInt(instructionLine.substring(moveIndex + INSTRUCTION_MOVE.length + 1, fromIndex));
    instruction.from = parseInt(instructionLine.substring(fromIndex + INSTRUCTION_FROM.length + 1, toIndex)) -1;
    instruction.to = parseInt(instructionLine.substring(toIndex + INSTRUCTION_TO.length + 1)) -1;

    return instruction;
}

function parseContainers(containerLine) {
    let containerLineLength = (containerLine.length+1);
    //console.debug("Parse ContainerLine, length: " + containerLineLength);

    if(!containerLine.includes('[') || !containerLine.includes(']') || containerLineLength % 4 != 0) {
        return -1;
    }

    let containers = [];
    for(let i=0; i<containerLineLength; i+=4) {
        let containerLineSubString = containerLine.substring(i, i+4).trim();
        let character = containerLineSubString[1];
        if(containerLineSubString[0] != '[' || containerLineSubString[2] != ']') {
                // Warning invalid container format
                // TODO: warning
        }

        containers.push((!character)? CONTAINER_NULL_CHARACTER: character);
    }
    //console.debug(containers);

    return containers;
}