using System;
using System.Collections.Generic;
using System.Linq;
using SlimDX;

namespace Asteroids {
	class WrapingUniverse {
		private readonly Random RNG = new Random();
		public readonly float Width=25000f, Height=15000f;

		/// <summary>
		/// ~= a - b
		/// </summary>
		public Vector2 NearDelta( Vector2 a, Vector2 b ) {
			var nd = a-b;
			var w_2 = Width/2;
			var h_2 = Height/2;
			nd.X
				= nd.X > +Width/2 ? nd.X-Width
				: nd.X < -Width/2 ? nd.X+Width
				: nd.X
				;
			nd.Y
				= nd.Y > +Height/2 ? nd.Y-Height
				: nd.Y < -Height/2 ? nd.Y+Height
				: nd.Y
				;
			return nd;
		}

		public void SpawnRandomAsteroid() {
			Asteroids.Add( new Asteroid(100)
				{ Position = new Vector2(RNG.NextFloat(0,Width),RNG.NextFloat(0,Height))
				, Velocity = new Vector2(RNG.NextFloat(-50,+50), RNG.NextFloat(-50,+50))
				});
		}
		public readonly WrapingSpatialBag<Asteroid > Asteroids;
		public readonly List<Bullet   > Bullets    = new List<Bullet>();
		public readonly List<Explosion> Explosions = new List<Explosion>();
		public readonly HashSet<Ship     > Ships      = new HashSet<Ship>();

		public WrapingUniverse() {
			Asteroids = new WrapingSpatialBag<Asteroid>(this)
				{ new Asteroid( 10) { Position = new Vector2(-100,-100) }
				, new Asteroid( 10) { Position = new Vector2(+100,-100) }
				, new Asteroid( 10) { Position = new Vector2(-100,+100) }
				, new Asteroid( 10) { Position = new Vector2(+100,+100) }
				, new Asteroid(100) { Position = new Vector2(   0,-200) }
				, new Asteroid(100) { Position = new Vector2(   0,+200) }
				, new Asteroid(100) { Position = new Vector2(-200,   0) }
				, new Asteroid(100) { Position = new Vector2(+200,   0) }
				};
		}

		public void Update( TimeSpan time ) {
			float dt = (float)time.TotalSeconds;

			foreach ( var s in Ships ) foreach ( var hit in s.SweepAgainst( this, Asteroids, 0f, dt ) ) {
				Explosions.Add( new Explosion(ExplosionAnimation.Default) { Position = s.Position, Velocity = s.Velocity } );
				s.Dead = true;
				break;
			}
			for ( int i=0, n=Bullets.Count ; i<n ; ++i ) {
				var bullet = Bullets[i];
				foreach ( var hit in bullet.SweepAgainst( this, Asteroids.GetObjectsNear(bullet)/*.ToArray()*/, 0f, dt ) ) {
					var asteroid = hit.Target;
					Explosions.Add( new Explosion(ExplosionAnimation.Default) { Position = bullet.Position, Velocity = bullet.Velocity } );
					bullet.Dead = true;

					float newr = asteroid.Radius/2;
					if ( newr > 15 ) {
						Asteroids.Remove(asteroid);
						var children = RNG.Next(2,4);
						for ( int j=0 ; j<children ; ++j ) {
							Asteroids.Add( new Asteroid(newr) { Position = asteroid.Position, Velocity = new Vector2(RNG.NextFloat(-50,+50),RNG.NextFloat(-50,+50)) } );
						}
					} else {
						Asteroids.Remove(asteroid);
						SpawnRandomAsteroid();
					}

					break;
				}
				Bullets[i] = bullet;
			}
			Bullets.RemoveAll(b=>b.Dead);
			//Ships.RemoveAll(s=>s.Dead);
			Ships.RemoveWhere(s=>s.Dead);

			foreach ( var a in Asteroids ) Asteroids.Relocate(a,()=>{
				var p = a.Position;
				p += dt*a.Velocity;
				if ( (p.X %= Width ) < 0 ) p.X += Width;
				if ( (p.Y %= Height) < 0 ) p.Y += Height;
				a.Position = p;
			});

			for ( int i=0, n=Bullets.Count ; i<n ; ++i ) {
				var b = Bullets[i];
				var p = b.Position;
				p += dt*b.Velocity;
				if ( (p.X %= Width ) < 0 ) p.X += Width;
				if ( (p.Y %= Height) < 0 ) p.Y += Height;
				b.Position = p;
				Bullets[i] = b;
			}

			for ( int i=0, n=Explosions.Count ; i<n ; ++i ) {
				var e = Explosions[i];
				var p = e.Position;
				p += dt*e.Velocity;
				if ( (p.X %= Width ) < 0 ) p.X += Width;
				if ( (p.Y %= Height) < 0 ) p.Y += Height;
				e.Position = p;
				e.AdvanceAnimation(dt);
				Explosions[i] = e;
			}
			Explosions.RemoveAll(e=>!e.IsAlive);

			foreach ( var s in Ships ) {
				var p = s.Position;
				p += dt*s.Velocity;
				if ( (p.X %= Width) < 0 ) p.X += Width;
				if ( (p.Y %= Height) < 0 ) p.Y += Height;
				s.Position = p;

				var rot_facing = Matrix.RotationZ(s.Facing);
				var acceleration = new Vector2( s.InputState.Strafe, s.InputState.Thrust );
				acceleration.X *= 30;
				acceleration.Y *= 60;
				acceleration = Vector2.TransformCoordinate(acceleration,rot_facing);
				s.Velocity += dt*acceleration;

				s.Facing += dt*3*s.InputState.Rotation;

				foreach ( var weapon in s.Weapons ) {
					weapon.Cooldown -= dt;
					if ( s.InputState.Firing ) while ( weapon.Cooldown < 0f ) {
						Bullets.Add( new Bullet() { Position = s.Position + Vector2.TransformCoordinate(weapon.Offset,rot_facing), Velocity = s.Velocity + Vector2.TransformCoordinate(weapon.InitialRelativeBulletVelocity,rot_facing) } );
						weapon.Cooldown += 1/weapon.RoF;
					} else if ( weapon.Cooldown < 0f ) {
						weapon.Cooldown = 0f;
					}
					//
					//Bullets.Add( new Bullet() { Position = s.Position, Velocity = s.Velocity } );
				}
			}
		}
	}
}