/**
 * The code box class
 */
class CodeBox {
    constructor(codeBoxID, initialStackID, outputID) {
        /**
         * Possible vectors the pointer can move in
         * @type {Object}
         */
        this.directions = {
            NORTH: [-1,  0],
            EAST:  [ 0,  1],
            SOUTH: [ 1,  0],
            WEST:  [ 0, -1],
        };
        /**
         * The current vector of the pointer
         * @type {int[]}
         */
        this.curr_direction = this.directions.EAST;
        /**
         * The Set of instructions to execute
         * 
         * Either a 1 or 2-dimensional array
         * @type {Array|Array[]}
         */
        this.box = [];
        /**
         * The coordinates of the currently executing instruction inside the code box
         * @type {int[]}
         */
        this.pointer = [0,0];
        /**
         * Was the instruction last moving in the left direction
         * 
         * Used by the {@link Fisherman}
         * @type {boolean}
         */
        this.dirWasLeft = false;
        /**
         * Are we currently under the influence of the {@link Fisherman}
         * @type {boolean}
         */
        this.onTheHook = false;
        /**
         * Are we currently processing code box instructions as a string
         *
         * 0 when false, otherwise it holds the char code for string delimiter, either
         * 34 or 39
         *
         * @type {int}
         */
        this.stringMode = 0;
        /**
         * The stack for the code box to work with
         *
         * @TODO Implement multiple stacks
         *
         * @type {Stack}
         */
        this.stack = new Stack();

        this.codeBoxDOM = document.getElementById(codeBoxID);
        if(!this.codeBoxDOM) {
            throw new Error(`Failed to find textarea with ID: ${codeBoxID}`);
        }

        this.outputDOM = document.getElementById(outputID);
        if(!this.outputDOM) {
            throw new Error(`Failed to find textarea with ID: ${outputID}`);
        }

        this.initialStackDOM = document.getElementById(initialStackID);
        if(!this.initialStackDOM) {
            throw new Error(`Failed to find input with ID: ${initialStackID}`);
        }
    }

    /**
     * Print the value to the display 
     *
     * @TODO Set up an actual display
     * @param {*} value 
     */
    Output(value) {
        this.outputDOM.value += value;
    }

    Execute(instruction) {
        let output = null;
        switch(instruction) {
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
            case 6:
            case 7:
            case 8:
            case 9:
            case 0:
            case "a":
            case "b":
            case "c":
            case "d":
            case "e":
            case "f":
                this.stack.Push(parseInt(instruction, 16));
                break;
            case "+": {
                const x = this.stack.Pop();
                const y = this.stack.Pop();
                this.stack.Push(x + y);
                break;
            }
            case "-": {
                const x = this.stack.Pop();
                const y = this.stack.Pop();
                this.stack.Push(x - y);
                break;
            }
            case "n": 
                output = this.stack.Pop();
                break;
            case "o":
                output = String.fromCharCode(this.stack.Pop());
                break;
            case ";":
                output = true;
                break;
            default:
                throw new Error("Something's fishy!");
        }

        return output;
    }

    Swim() {
        const instruction = this.box[this.pointer[0], this.pointer[1]];

        if(this.stringMode != 0 && instruction != this.stringMode) {
            this.stack.Push(dec(instruction));
        }
        else {
            const exeResult = this.Execute(instruction);
            if(exeResult === true) {
                return true;
            }
            else if(exeResult != null) {
                this.Output(exeResult);
            }
        }

        this.Move();
    }

    Move() {
        const newX = this.pointer[0] + this.curr_direction[0];
        const newY = this.pointer[1] + this.curr_direction[1];

        this.SetPointer(newX, newY);
    }

    /**
     * Implement C and .
     */
    SetPointer(x, y) {
        this.pointer = [x, y];
    }

    /**
     * Implement ^
     * 
     * Changes the swim direction upward
     */
    MoveUp() {
        this.curr_direction = this.directions.NORTH;
    }
    /**
     * Implement >
     * 
     * Changes the swim direction rightward
     */
    MoveRight() {
        this.curr_direction = this.directions.EAST;
        this.dirWasLeft = false;
    }
    /**
     * Implement v
     * 
     * Changes the swim direction downward
     */
    MoveDown() {
        this.curr_direction = this.directions.SOUTH;
    }
    /**
     * Implement <
     * 
     * Changes the swim direction leftward
     */
    MoveLeft() {
        this.curr_direction = this.directions.WEST;
        this.dirWasLeft = true;
    }

    /**
     * Implement /
     * 
     * Reflects the swim direction depending on its starting value
     */
    ReflectForward() {
        if (this.curr_direction == this.directions.NORTH) {
            this.MoveRight();
        }
        else if (this.curr_direction == this.directions.EAST) {
            this.MoveUp();
        }
        else if (this.curr_direction == this.directions.SOUTH) {
            this.MoveLeft();
        }
        else {
            this.MoveDown();
        }
    }
    /**
     * Implement \
     * 
     * Reflects the swim direction depending on its starting value
     */
    ReflectBack() {
        if (this.curr_direction == this.directions.NORTH) {
            this.MoveLeft();
        }
        else if (this.curr_direction == this.directions.EAST) {
            this.MoveDown();
        }
        else if (this.curr_direction == this.directions.SOUTH) {
            this.MoveRight();
        }
        else {
            this.MoveUp();
        }
    }

    /**
     * Implement |
     * 
     * Swaps the horizontal swim direction to its opposite
     */
    HorizontalMirror() {
        if (this.curr_direction == this.directions.EAST) {
            this.MoveLeft();
        }
        else {
            this.MoveRight();
        }
    }
    /**
     * Implement _
     * 
     * Swaps the horizontal swim direction to its opposite
     */
    VerticalMirror() {
        if (this.curr_direction == this.directions.NORTH) {
            this.MoveDown();
        }
        else {
            this.MoveUp();
        }
    }
    /**
     * Implement #
     * 
     * A combination of the vertical and the horizontal mirror
     */
    OmniMirror() {
        if (this.curr_direction[0]) {
            this.VerticalMirror();
        }
        else {
            this.HorizontalMirror();
        }
    }

    /**
     * Implement x
     * 
     * Pseudo-randomly switches the swim direction
     */
    ShuffleDirection() {
        this.curr_direction = Object.values(this.directions)[Math.floor(Math.random() * 4)];
    }

    /**
     * Implement `
     * 
     * Changes the swim direction based on the previous direction
     * @see https://esolangs.org/wiki/Starfish#Fisherman
     */
    Fisherman() {
        if (this.curr_direction[0]) {
            if (this.dirWasLeft) {
                this.MoveLeft();
            }
            else {
                this.MoveRight();
            }
        }
        else {
            if (this.onTheHook) {
                this.onTheHook = false;
                this.MoveUp();
            }
            else {
                this.onTheHook = true;    
                this.MoveDown();
            }
        }
    }
}
/**
 * The stack class
 */
class Stack {
    constructor() {
        /**
         * The stack
         * @type {int[]}
         */
        this.stack = [];
        /**
         * A single value saved off the stack
         * @type {int}
         */
        this.register = null;
    }

    /**
     * Wrapper function for Array.prototype.push
     * @param {*} newValue 
     */
    Push(newValue) {
        this.stack.push(newValue);
    }
    /**
     * Wrapper function for Array.prototype.pop
     * @returns {*}
     */
    Pop() {
        return this.stack.pop();
    }

    /**
     * Implement }
     * 
     * Shifts the entire stack leftward by one value
     */
    ShiftLeft() {
        const temp = this.stack.shift();
        this.stack.push(temp);
    }
    /**
     * Implement {
     * 
     * Shifts the entire stack rightward by one value
     */
    ShiftRight() {
        const temp = this.stack.pop();
        this.stack.unshift(temp);
    }
    /**
     * Implement $
     * 
     * Swaps the top two values of the stack
     */
    SwapTwo() {
        // TODO
    }

    /**
     * Implement :
     * 
     * Duplicates the element on the top of the stack
     */
    Duplicate() {
        this.stack.push(this.stack[this.stack.length-1]);
    }
    /**
     * Implements ~
     * 
     * Removes the element on the top of the stack 
     */
    Remove() {
        this.stack.pop();
    }

    /**
     * Implement r
     * 
     * Reverses the entire stack
     */
    Reverse() {
        this.stack.reverse();
    }

    /**
     * Implement l
     * 
     * Pushes the length of the stack onto the top of the stack
     */
    PushLength() {
        this.stack.push(this.stack.length);
    }
}

/**
 * Get the char code of any character
 *
 * Can actually take any length of a value, but only returns the
 * char code of the first character.
 *
 * @param {*} value Any character
 * @returns {int} The value's char code
 */
function dec(value) {
    return value.toString().charCodeAt(0);
}