/**
 * @author       Richard Davey <rich@photonstorm.com>
 * @copyright    2019 Photon Storm Ltd.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */

var CONST = require('./const');

/**
 * Calculates and returns the horizontal overlap between two arcade physics bodies and sets their properties
 * accordingly, including: `touching.left`, `touching.right`, `touching.none` and `overlapX'.
 *
 * @function Phaser.Physics.Arcade.GetOverlapX
 * @since 3.0.0
 *
 * @param {Phaser.Physics.Arcade.Body} body1 - The first Body to separate.
 * @param {Phaser.Physics.Arcade.Body} body2 - The second Body to separate.
 * @param {boolean} overlapOnly - Is this an overlap only check, or part of separation?
 * @param {number} bias - A value added to the delta values during collision checks. Increase it to prevent sprite tunneling(sprites passing through another instead of colliding).
 *
 * @return {number} The amount of overlap.
 */
var GetOverlapX = function (body1, body2, overlapOnly, bias)
{
    var overlap = 0;
    var maxOverlap = body1.deltaAbsX() + body2.deltaAbsX() + bias;

    if (body1._dx === 0 && body2._dx === 0)
    {
        //  They overlap but neither of them are moving
        body1.embedded = true;
        body2.embedded = true;
    }
    else if (body1._dx > body2._dx)
    {
        //  Body1 is moving right and / or Body2 is moving left
        overlap = body1.right - body2.x;

        if ((overlap > maxOverlap && !overlapOnly) || body1.checkCollision.right === false || body2.checkCollision.left === false)
        {
            overlap = 0;
        }
        else
        {
            body1.touching.none = false;
            body1.touching.right = true;

            body2.touching.none = false;
            body2.touching.left = true;

            if (body2.physicsType === CONST.STATIC_BODY)
            {
                body1.blocked.none = false;
                body1.blocked.right = true;
            }

            if (body1.physicsType === CONST.STATIC_BODY)
            {
                body2.blocked.none = false;
                body2.blocked.left = true;
            }
        }
    }
    else if (body1._dx < body2._dx)
    {
        //  Body1 is moving left and/or Body2 is moving right
        overlap = body1.x - body2.width - body2.x;

        if ((-overlap > maxOverlap && !overlapOnly) || body1.checkCollision.left === false || body2.checkCollision.right === false)
        {
            overlap = 0;
        }
        else
        {
            body1.touching.none = false;
            body1.touching.left = true;

            body2.touching.none = false;
            body2.touching.right = true;

            if (body2.physicsType === CONST.STATIC_BODY)
            {
                body1.blocked.none = false;
                body1.blocked.left = true;
            }

            if (body1.physicsType === CONST.STATIC_BODY)
            {
                body2.blocked.none = false;
                body2.blocked.right = true;
            }
        }
    }

    //  Resets the overlapX to zero if there is no overlap, or to the actual pixel value if there is
    body1.overlapX = overlap;
    body2.overlapX = overlap;

    return overlap;
};

module.exports = GetOverlapX;