public class Rope
{
    public Room room;
    public Vector2 A, B, lastA, lastB;
    public float totalLength;
    public List<Corner> bends;
    float thickness;

    public RopeDebugVisualizer visualizer;
    public List<Corner> corners;

    public Vector2 AConnect
    {
        get
        {
            if (bends.Count == 0) return B;
            else return bends[0].pos;
        }
    }
    public Vector2 BConnect
    {
        get
        {
            if (bends.Count == 0) return A;
            else return bends[bends.Count - 1].pos;
        }
    }

    public struct Corner
    {
        public FloatRect.CornerLabel dir;
        public Vector2 pos;
        public Corner(FloatRect.CornerLabel dir, Vector2 pos)
        {
            this.dir = dir;
            this.pos = pos;
        }
    }

    public Rope(Room room, Vector2 initA, Vector2 initB, float thickness)
    {
        this.room = room;
        A = initA;
        lastA = initA;
        B = initB;
        lastB = initB;
        totalLength = Vector2.Distance(initA, initB);

        bends = new List<Corner>();
        corners = new List<Corner>();

        this.thickness = thickness;

        //finds all the corners and stores them in a list. This could also be done locally on the fly, for very large spaces with lots of corners that might be preferable performance-wise.
        for (int x = 0; x < room.TileWidth; x++)
            for (int y = 0; y < room.TileHeight; y++)
                if (room.GetTile(x, y).Solid) {
                    if (!room.GetTile(x - 1, y).Solid) {
                        if (!room.GetTile(x, y - 1).Solid && !room.GetTile(x - 1, y - 1).Solid)
                            corners.Add(new Corner(FloatRect.CornerLabel.D, room.MiddleOfTile(x, y) + new Vector2(-10f - thickness, -10f - thickness)));
                        if (!room.GetTile(x, y + 1).Solid && !room.GetTile(x - 1, y + 1).Solid)
                            corners.Add(new Corner(FloatRect.CornerLabel.A, room.MiddleOfTile(x, y) + new Vector2(-10f - thickness, 10f + thickness)));
                    }
                    if (!room.GetTile(x + 1, y).Solid) {
                        if (!room.GetTile(x, y - 1).Solid && !room.GetTile(x + 1, y - 1).Solid)
                            corners.Add(new Corner(FloatRect.CornerLabel.C, room.MiddleOfTile(x, y) + new Vector2(10f + thickness, -10f - thickness)));
                        if (!room.GetTile(x, y + 1).Solid && !room.GetTile(x + 1, y + 1).Solid)
                            corners.Add(new Corner(FloatRect.CornerLabel.B, room.MiddleOfTile(x, y) + new Vector2(10f + thickness, 10f + thickness)));
                    }
                }

        //  visualizer = new RopeDebugVisualizer(this);

    }

    public void Reset()
    {
        bends.Clear();
    }

    public void Update(Vector2 newA, Vector2 newB)
    {
        lastA = A;
        lastB = B;
        A = newA;
        B = newB;

        //sweep terrain to add bend points
        if (bends.Count == 0)
            CollideWithCorners(lastA, A, lastB, B, 0, 0);
        else {
            CollideWithCorners(BConnect, BConnect, lastB, B, bends.Count, 0);
            CollideWithCorners(lastA, A, AConnect, AConnect, 0, 0);
        }

        //delete bend points where the rope has come free of the corner
        if (bends.Count > 0) {//could optimize here by making it only check first and last bend point
            List<int> deleteBends = new List<int>();
            for (int i = 0; i < bends.Count; i++) {
                Vector2 prev = A;
                Vector2 nxt = B;
                if (i > 0) prev = bends[i - 1].pos;
                if (i < bends.Count - 1) nxt = bends[i + 1].pos;
                if (!DoesLineOverlapCorner(prev, nxt, bends[i])) {
                    deleteBends.Add(i);
                }
            }
            for (int i = deleteBends.Count - 1; i >= 0; i--)
                bends.RemoveAt(deleteBends[i]);
        }

        //Calculating new total length of rope
        if (bends.Count == 0)
            totalLength = Vector2.Distance(A, B);
        else {
            totalLength = Vector2.Distance(A, AConnect) + Vector2.Distance(BConnect, B);
            for (int i = 1; i < bends.Count; i++)
                totalLength += Vector2.Distance(bends[i - 1].pos, bends[i].pos);
        }


        if (visualizer != null) visualizer.Update();
    }

    private void CollideWithCorners(Vector2 la, Vector2 a, Vector2 lb, Vector2 b, int bend, int recursion)
    {
        Corner? firstCollision = null;
        float firstCollisionDist = float.MaxValue;
        foreach (Corner c in corners)
            if (DoesLineOverlapCorner(a, b, c)
                && c.pos != la && c.pos != a && c.pos != lb && c.pos != b
                // && Custom.BetweenLines(c.pos, la, a, lb, b) && Custom.BetweenLines(c.pos, la, lb, a, b)//old sweep function that would give some false positives
                && (Custom.PointInTriangle(c.pos, a, la, b) || Custom.PointInTriangle(c.pos, a, lb, b) || Custom.PointInTriangle(c.pos, a, la, lb) || Custom.PointInTriangle(c.pos, la, lb, b))
                && Mathf.Abs(Custom.DistanceToLine(c.pos, la, lb)) < Mathf.Abs(firstCollisionDist)) {
                firstCollision = c;
                firstCollisionDist = Custom.DistanceToLine(c.pos, lastA, lastB);
            }

        if (firstCollision.HasValue) {
            Vector2 bendPoint = firstCollision.Value.pos;
            bends.Insert(bend, firstCollision.Value);

            Vector2 divPoint = Custom.ClosestPointOnLine(la, lb, bendPoint);

            CollideWithCorners(divPoint, bendPoint, lb, b, bend + 1, recursion + 1);
            CollideWithCorners(la, a, divPoint, bendPoint, bend, recursion + 1);
        }
    }

    public bool DoesLineOverlapCorner(Vector2 l1, Vector2 l2, Corner corner)
    {
        IntVector2 cornerDir = new IntVector2((corner.dir == FloatRect.CornerLabel.A || corner.dir == FloatRect.CornerLabel.D) ? -1 : 1,
            (corner.dir == FloatRect.CornerLabel.A || corner.dir == FloatRect.CornerLabel.B) ? 1 : -1);

        if (l1.y != l2.y)
            if ((cornerDir.x < 0 && (Custom.HorizontalCrossPoint(l1, l2, corner.pos.y).x < corner.pos.x))
                || (cornerDir.x > 0 && (Custom.HorizontalCrossPoint(l1, l2, corner.pos.y).x > corner.pos.x)))
                return false;

        if (l1.x != l2.x)
            if ((cornerDir.y < 0 && (Custom.VerticalCrossPoint(l1, l2, corner.pos.x).y < corner.pos.y))
                || (cornerDir.y > 0 && (Custom.VerticalCrossPoint(l1, l2, corner.pos.x).y > corner.pos.y)))
                return false;

        return true;
    }

}