using System;
using System.Collections;
using Unity.Netcode;
using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.PlayerLoop;
using Random = UnityEngine.Random;
using System.Linq;
using UnityEngine.Serialization;

namespace Game {
	public class Player : NetworkBehaviour {
		
		public enum ESide {Top, Bottom}

		public ESide Side { get; set; }

		private int score;
		
		protected bool goingLeft, goingRight;

		// Units per second
		protected float Speed => 10;
		
		// Unit distance from zero
		private float Border => 10;
		
		private SpeedModification speedModification;
		private BorderModification borderModification;

		private float LeftSide() {
			return X() - transform.localScale.x / 2;
		}

		private float RightSide() {
			return X() + transform.localScale.x / 2;
		}

		protected float X() {
			return transform.position.x;
		}

		protected float Y() {
			return transform.position.y;
		}

		protected void TryMove(float h) {
			Vector2 trans = new Vector2((goingLeft ? -1 : 0) + (goingRight ? 1 : 0), 0);
			trans *= Speed * h;
			transform.Translate(trans);
			if (LeftSide() < -Border)
				transform.Translate(Vector2.right * (-Border - LeftSide()));
			if (RightSide() > Border) 
				transform.Translate(Vector2.left * (RightSide() - Border));
		}

		private void Start() {
			float y = Side switch {
				ESide.Bottom => BorderSize.Singleton.y1,
				ESide.Top => BorderSize.Singleton.y2,
				_ => throw new ArgumentOutOfRangeException()
			};
			transform.position = new Vector2(0, y);
		}
	}

	public class AIPlayer : Player {
		public enum EDifficulty {
			VeryEasy, Easy, Medium, Hard, VeryHard
		}

		public EDifficulty Difficulty { get; set; }

		// True if ball y velocity points towards player
		private bool BallApproaches(Ball ball) {
			var ballVy = ball.rb.velocity.y;
			return Side switch {
				ESide.Bottom => ballVy < 0,
				ESide.Top => ballVy > 0,
				_ => throw new Exception("Side not set on player!")
			};
		}

		// Not manhattan, only Y direction
		private float YDistanceToBall(Ball ball) {
			return Mathf.Abs(ball.rb.position.y - Y());
		}

		// o: Origin, e: End
		public static bool Intersect(Vector2 o1, Vector2 e1, Vector2 o2, Vector2 e2, out Vector2 point) {
			point = Vector2.zero;
			
			Vector2 m1 = e1 - o1;
			Vector2 m2 = e2 - o2;

			/*
			 * o1x + r * m1x = o2x + s * m2x
			 * o1y + r * m1y = o2y + s * m2y
			 *
			 * Solve for r and s:
			 * Formulas below achieved by reordering
			 * Order is irrelevant, but if m1x == 0 then first approach results in division by zero ->
			 * Invert order then, and if division by zero is still a problem, both lines are parallel anyway
			 */
			
			float r, s;
			if (m1.x != 0) {
				s = (o1.y + o2.x * m1.y / m1.x - o1.x * m1.y / m1.x - o2.y) / (m2.y - m2.x * m1.y / m1.x);
				r = (o2.x + s * m2.x - o1.x) / m1.x;
			} else if (m2.x != 0) {
				r = (o2.y + o1.x * m2.y / m2.x - o2.x * m2.y / m2.x - o1.y) / (m1.y - m1.x * m2.y / m2.x);
				s = (o1.x + r * m1.x - o2.x) / m2.x;
			} else {
				return false;
			}

			if (s is > 0 and < 1 && r is > 0 and < 1) {
				point = o1 + r * m1;
				return true;
			}
			
			return false;
		}

		private Vector2 Simulate(Vector2 origin, Vector2 velocity, float radius, float secondsLeft) {
			Vector2 validAreaOrigin = new Vector2(BorderSize.Singleton.x1, BorderSize.Singleton.y1) + new Vector2(radius, radius);
			Vector2 validAreaSize = BorderSize.Singleton.Size - new Vector2(radius, radius) * 2;
			Rect area = new Rect(validAreaOrigin, validAreaSize);

			Vector2 end = origin + velocity * secondsLeft;
			if (area.Contains(end))
				return end;

			float playerY = Side == ESide.Bottom ? area.yMin : area.yMax;
			Vector2 playerLeft = new Vector2(area.xMin, playerY);
			Vector2 playerRight = new Vector2(area.xMax, playerY);

			// Horizontal line (player line) -> stop simulating
			if (Intersect(origin, end, playerLeft, playerRight, out Vector2 point)) {
				return point;
			}

			bool borderHit = false;
			Vector2 borderHitPoint = Vector2.zero;

			// Left vertical border
			if (Intersect(origin, end, new Vector2(area.xMin, area.yMin), new Vector2(area.xMin, area.yMax), out point)) {
				borderHit = true;
				borderHitPoint = point;
			}

			// Right vertical border
			if (Intersect(origin, end, new Vector2(area.xMax, area.yMin), new Vector2(area.xMax, area.yMax), out point)) {
				borderHit = true;
				borderHitPoint = point;
			}

			// Any border -> invert x velocity and simulate all seconds left
			if (borderHit) {
				secondsLeft -= (borderHitPoint - origin).magnitude / Speed;
				velocity = new Vector2(-velocity.x, velocity.y);
				origin = borderHitPoint;
				return Simulate(origin, velocity, radius, secondsLeft);
			}

			// No intersection -> Ball outside of field -> dont simulate further
			return origin;
		}

		private float FutureSeconds => (float)Difficulty * 0.5f;

		private float GetTargetPosition() {
			var balls = GameManager.Singleton.Balls.Where(b => b.IsAlive);
			var approaching = balls.Where(BallApproaches).ToList();
			
			if (approaching.Count == 0)
				return X();

			Ball ball = approaching.Aggregate(approaching[0], (prev, current) => YDistanceToBall(current) < YDistanceToBall(prev) ? current : prev);
			Vector2 origin = ball.rb.position;
			Vector2 velocity = ball.rb.velocity;
			float radius = ball.Radius;
			return Simulate(origin, velocity, radius, FutureSeconds).x;
		}

		private void FixedUpdate() {
			float target = GetTargetPosition();
			const float h = 0.5f;
			goingLeft = target < X() - h;
			goingRight = target > X() + h;
			TryMove(Time.fixedDeltaTime);
		}
	}

	public class RealPlayer : Player {
		public bool isThisClient;
		
		private void FixedUpdate() {
			if (!isThisClient)
				return;
			
			var keyboard = Keyboard.current;
			goingLeft = keyboard.aKey.isPressed;
			goingRight = keyboard.dKey.isPressed;

			TryMove(Time.fixedDeltaTime);
		}
	}
}