var UserControl = {};

UserControl.lastX = 0;
UserControl.lastY = 0;
UserControl.dragging = false;
UserControl.object = null;
UserControl.forces = [];
UserControl.dirXs = [];
UserControl.dirYs = [];

UserControl.beginDrag = function(x, y, object) {
    UserControl.forces = [0, 0, 0, 0, 0, 0];
    UserControl.dirXs = [0, 0, 0, 0, 0, 0];
    UserControl.dirYs = [0, 0, 0, 0, 0, 0];

    /* User for dragging */
    UserControl.lastX = x;
    UserControl.lastY = y;
    UserControl.dragging = true;
    UserControl.object = object;
    object.dragging = true;
}

UserControl.updateDrag = function(x, y, levelData) {
    if (UserControl.dragging) {
        var dx = (UserControl.lastX - x)/levelData.scale;
        var dy = (UserControl.lastY - y)/levelData.scale;

        /* Force */
        var force = Math.abs(dx) + Math.abs(dy);
        UserControl.forces.push(force);
        UserControl.forces.shift();
        UserControl.dirXs.push(dx);
        UserControl.dirXs.shift();
        UserControl.dirYs.push(dy);
        UserControl.dirYs.shift();

        /* Use for dragging */
        UserControl.lastX = x;
        UserControl.lastY = y;

        if (UserControl.object.dragAllowX) {
            UserControl.object.x -= dx;
        }

        if (UserControl.object.dragAllowY) {
            UserControl.object.y -= dy;
        }
    }
}

UserControl.endDrag = function(x, y) {
    if (UserControl.object) {

        /* Use for force */
        var force = 0;
        var dx = 0;
        var dy = 0;
        for (var i=0; i<UserControl.forces.length; i++) {
            force += UserControl.forces[i];
            dx += UserControl.dirXs[i];
            dy += UserControl.dirYs[i];
        }
        force /= UserControl.forces.length;

        var sub = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
        UserControl.object.dragDirX = dx/sub;
        UserControl.object.dragDirY = dy/sub;
        UserControl.object.dragForce = force;

        /* Use for dragging */
        UserControl.object.dragging = false;
    }   

    UserControl.lastX = x;
    UserControl.lastY = y;
    UserControl.dragging = false;
    UserControl.object = null;
}