esengine/source/src/ECS/Components/TiledMapMover.ts

module es {
    /**
     * 用来存放来自移动调用的所有冲突信息
     */
    export class CollisionState {
        public right: boolean;
        public left: boolean;
        public above: boolean;
        public below: boolean;
        public becameGroundedThisFrame: boolean;
        public wasGroundedLastFrame: boolean;
        public isGroundedOnOnewayPlatform: boolean;
        public slopAngle: number;

        public get hasCollision(): boolean {
            return this.below || this.right || this.left || this.above;
        }

        public _movementRemainderX: SubpixelNumber;
        public _movementRemainderY: SubpixelNumber;

        public reset() {
            this.becameGroundedThisFrame = this.isGroundedOnOnewayPlatform = this.right = this.left = this.above = this.below = false;
            this.slopAngle = 0;
        }

        public toString() {
            return `[CollisionState] r: ${this.right}, l: ${this.left}, a: ${this.above}, b: ${this.below}, angle: ${this.slopAngle}, wasGroundedLastFrame: ${this.wasGroundedLastFrame}, becameGroundedThisFrame: ${this.becameGroundedThisFrame}`;
        }
    }

    /**
     * TiledMapMover是在基于重力的平铺地图中移动对象的助手。
     * 它要求它所在的实体有一个BoxCollider。BoxCollider将与colliderHorizontal/VerticalInset用于所有碰撞检测。
     *
     * 一种方法是通过将你的Transform向下移动1个像素并调用CollisionState.clearLastGroundTile来跳过平台。
     */
    export class TiledMapMover extends Component {
        /**
         * 在垂直移动时，BoxCollider将根据水平面上的嵌入缩小
         */
        public colliderHorizontalInset = 2;

        /**
         * 垂直平面上的嵌入，在水平移动时，BoxCollider将根据该嵌入缩小
         */
        public colliderVerticalInset = 6;

        /**
         * 临时存储
         */
        public _boxColliderBounds: Rectangle;

        constructor() {
            super();
        }

        /**
         * 测试碰撞，然后移动实体
         * @param motion
         * @param boxColliderBounds
         * @param collisionState
         */
        public testCollisions(motion: Vector2, boxColliderBounds: Rectangle, collisionState: CollisionState) {
            this._boxColliderBounds = boxColliderBounds;

            // 保存我们当前的接地状态，我们将用于wasGroundedLastFrame和becameGroundedThisFrame
            collisionState.wasGroundedLastFrame = collisionState.below;

            // 重置碰撞状态
            collisionState.reset();

            // 获取圆角值用于我们的实际检测
            let motionX = motion.x;
            let motionY = motion.y;

            // 首先，检查水平方向中的移动
            if (motionX != 0){
                let direction = motionX > 0 ? Edge.right : Edge.left;
                let sweptBounds = this.collisionRectForSide(direction, motionX);

                let collisionResponse: number = 0;
                if (this.testMapCollision(sweptBounds, direction, collisionState, collisionResponse)){
                    motion.x = collisionResponse - RectangleExt.getSide(boxColliderBounds, direction);
                    collisionState.left = direction == Edge.left;
                    collisionState.right = direction == Edge.right;
                    collisionState._movementRemainderX.reset();
                }else{
                    collisionState.left = false;
                    collisionState.right = false;
                }
            }
        }

        public testMapCollision(collisionRect: Rectangle, direction: Edge, collisionState: CollisionState, collisionResponse: number){
            let side = EdgeExt.oppositeEdge(direction);
            let perpindicularPosition = EdgeExt.isVertical(side) ? collisionRect.center.x : collisionRect.center.y;
            let leadingPosition = RectangleExt.getSide(collisionRect, direction);
            let shouldTestSlopes = EdgeExt.isVertical(side);
        }

        /**
         * 获取展开以考虑运动的给定边的碰撞矩形
         * @param side
         * @param motion
         */
        public collisionRectForSide(side: Edge, motion: number){
            let bounds: Rectangle;

            // 对于水平碰撞检查，我们只使用一个条块作为边界。Vertical得到矩形的一半，就可以正确地向上推，
            // 当相交的斜率，忽略以进行水平移动。
            if (EdgeExt.isHorizontal(side)){
                bounds = RectangleExt.getRectEdgePortion(this._boxColliderBounds, side);
            }else {
                bounds = RectangleExt.getHalfRect(this._boxColliderBounds, side);
            }

            // 我们水平收缩用于垂直移动，垂直收缩用于水平移动
            if (EdgeExt.isVertical(side)){
                RectangleExt.contract(bounds, this.colliderHorizontalInset, 0);
            }else {
                RectangleExt.contract(bounds, 0, this.colliderVerticalInset);
            }

            // 最后在移动方向上扩展边
            RectangleExt.expandSide(bounds, side, motion);

            return bounds;
        }
    }
}