/**
 * A splitter control.
 * Turns an existing HTML element into an horizontal splitter control.
 * @constructor Splitter
 * @param {Object} params   Available parameters:
 *                          {Element} container  HTML container representing
 *                                               the splitter
 *                          {Number} [snap]      Number of pixels to snap to
 *                                               the edges (0 or 1)
 *                          {function} [change]  Callback method called when
 *                                               the splitter value has changed.
 *                                               The callback is called with
 *                                               the new value as parameter
 */
function Splitter (params) {
    if (!params || !params.container) {
        throw new Error('params.container undefined in Splitter constructor');
    }

    var me = this;
    jsoneditor.util.addEventListener(params.container, "mousedown", function (event) {
        me.onMouseDown(event);
    });

    this.container = params.container;
    this.snap = Number(params.snap) || 200; // px
    this.width = undefined;
    this.value = undefined;
    this.onChange = (params.change) ? params.change : function () {};
    this.params = {};
}

/**
 * Handle mouse down event. Start dragging the splitter.
 * @param {Event} event
 * @private
 */
Splitter.prototype.onMouseDown = function (event) {
    var me = this;
    var leftButtonDown = event.which ? (event.which == 1) : (event.button == 1);
    if (!leftButtonDown) {
        return;
    }
    jsoneditor.util.addClassName(this.container, 'active');

    if (!this.params.mousedown) {
        this.params.mousedown = true;
        this.params.mousemove =
            jsoneditor.util.addEventListener(document, 'mousemove', function (event) {
                me.onMouseMove(event);
            });
        this.params.mouseup =
            jsoneditor.util.addEventListener(document, 'mouseup', function (event) {
                me.onMouseUp(event);
            });
        this.params.screenX = event.screenX;
        this.params.changed = false;
        this.params.value = this.getValue();
    }
    jsoneditor.util.preventDefault(event);
    jsoneditor.util.stopPropagation(event);
};

/**
 * Handle on mouse move event. Used to drag the splitter
 * @param {Event} event
 * @private
 */
Splitter.prototype.onMouseMove = function (event) {
    if (this.width != undefined) {
        var diff = event.screenX - this.params.screenX;

        var value = this.params.value + diff / this.width;
        value = this.setValue(value);

        if (value != this.params.value) {
            // value has been changed
            this.params.changed = true;
        }

        this.onChange(value);
    }

    jsoneditor.util.preventDefault(event);
    jsoneditor.util.stopPropagation(event);
};

/**
 * Handle on mouse up event
 * @param {Event} event
 * @private
 */
Splitter.prototype.onMouseUp = function (event) {
    jsoneditor.util.removeClassName(this.container, 'active');

    if (this.params.mousedown) {
        jsoneditor.util.removeEventListener(document, 'mousemove', this.params.mousemove);
        jsoneditor.util.removeEventListener(document, 'mouseup', this.params.mouseup);
        this.params.mousemove = undefined;
        this.params.mouseup = undefined;
        this.params.mousedown = false;

        var value = this.getValue();
        if (!this.params.changed) {
            // value is unchanged -> unsnap when currently snapped
            if (value == 0) {
                value = this.setValue(0.2);
                this.onChange(value);
            }
            if (value == 1) {
                value = this.setValue(0.8);
                this.onChange(value);
            }
        }
    }
    jsoneditor.util.preventDefault(event);
    jsoneditor.util.stopPropagation(event);
};

/**
 * Set the window width for the splitter
 * @param {Number} width
 */
Splitter.prototype.setWidth = function (width) {
    this.width = width;
};

/**
 * Set a value for the splitter (UI is not adjusted)
 * @param {Number} value   A number between 0 and 1
 * @return {Number} value  The stored value
 */
Splitter.prototype.setValue = function (value) {
    value = Number(value);

    // snap to 0 or 1 when close
    if (this.width != undefined && this.width > this.snap) {
        if (value < this.snap / this.width) {
            value = 0;
        }
        if (value > (this.width - this.snap) / this.width) {
            value = 1;
        }
    }

    this.value = value;

    try {
        localStorage['splitterValue'] = value;
    }
    catch (e) {
        console.log(e);
    }
    return value;
};

/**
 * Get the splitter value from local storage
 * @return {Number} value   A value between 0.1 and 0.9
 */
Splitter.prototype.getValue = function () {
    var value = this.value;
    if (value == undefined) {
        // read from localStorage once
        try {
            if (localStorage['splitterValue'] != undefined) {
                value = Number(localStorage['splitterValue']); // read
                value = this.setValue(value);          // verify and store
            }
        }
        catch (e) {
            console.log(e);
        }
    }
    if (value == undefined) {
        value = this.setValue(0.5);
    }
    return value;
};