'use strict';

const direction = {
    NONE: null,
    LEFT: 'left',
    RIGHT: 'right',
    DOWN: 'down',
    UP: 'up'
};

function handleTouchStart(handler, evt) {
    const touchEvent = evt.touches[0];
    handler._xStart = touchEvent.clientX;
    handler._yStart = touchEvent.clientY;
}

function handleTouchMove(handler, evt) {
    if (!handler._xStart || !handler._yStart) {
        return;
    }

    const xDirection = handler._xStart - evt.touches[0].clientX;
    const yDirection = handler._yStart - evt.touches[0].clientY;

    if (Math.abs(xDirection) > Math.abs(yDirection)) {
        if (xDirection > 0) {
            handler._direction = direction.LEFT;
        } else {
            handler._direction = direction.RIGHT;
        }
    } else if (yDirection > 0) {
        handler._direction = direction.DOWN;
    } else {
        handler._direction = direction.UP;
    }
}

function handleTouchEnd(handler) {
    switch (handler._direction) {
    case direction.NONE:
        return;
    case direction.LEFT:
        handler._swipeLeftTask();
        break;
    case direction.RIGHT:
        handler._swipeRightTask();
        break;
    case direction.DOWN:
        handler._swipeDownTask();
        break;
    case direction.UP:
        handler._swipeUpTask();
    // no default
    }

    handler._xStart = null;
    handler._yStart = null;
}

class Touch {
    constructor(target,
        swipeLeft = () => {},
        swipeRight = () => {},
        swipeUp = () => {},
        swipeDown = () => {}) {
        this._target = target;

        this._swipeLeftTask = swipeLeft;
        this._swipeRightTask = swipeRight;
        this._swipeUpTask = swipeUp;
        this._swipeDownTask = swipeDown;

        this._xStart = null;
        this._yStart = null;
        this._direction = direction.NONE;

        this._target.addEventListener('touchstart',
            evt => {
                handleTouchStart(this, evt);
            });
        this._target.addEventListener('touchmove',
            evt => {
                handleTouchMove(this, evt);
            });
        this._target.addEventListener('touchend',
            () => {
                handleTouchEnd(this);
            });
    }
}

module.exports = Touch;