// Copyright 2014-2017 ClassicalSharp | Licensed under BSD-3
using System;
using ClassicalSharp.GraphicsAPI;
using ClassicalSharp.Map;
using OpenTK;

#if USE16_BIT
using BlockID = System.UInt16;
#else
using BlockID = System.Byte;
#endif

namespace ClassicalSharp.Particles {

	public abstract class Particle {
		
		public Vector3 Position;
		public Vector3 Velocity;
		public float Lifetime;
		protected Vector3 lastPos, nextPos;

		public abstract int Get1DBatch(Game game);
		
		public abstract void Render(Game game, double delta, float t,
		                            VertexP3fT2fC4b[] vertices, ref int index);
		
		protected void DoRender(Game game, ref Vector2 size, ref TextureRec rec,
		                        int col, VertexP3fT2fC4b[] vertices, ref int index) {
			Vector3 p111, p121, p212, p222;
			Utils.CalcBillboardPoints(size, Position, ref game.View,
			                          out p111, out p121, out p212, out p222);

			vertices[index++] = new VertexP3fT2fC4b(ref p111, rec.U1, rec.V2, col);
			vertices[index++] = new VertexP3fT2fC4b(ref p121, rec.U1, rec.V1, col);
			vertices[index++] = new VertexP3fT2fC4b(ref p222, rec.U2, rec.V1, col);
			vertices[index++] = new VertexP3fT2fC4b(ref p212, rec.U2, rec.V2, col);
		}
		
		public virtual bool Tick(Game game, double delta) {
			Lifetime -= (float)delta;
			return Lifetime < 0;
		}
	}
	
	public sealed class RainParticle : CollidableParticle {
		
		static Vector2 bigSize = new Vector2(1/16f, 1/16f);
		static Vector2 smallSize = new Vector2(0.75f/16f, 0.75f/16f);
		static Vector2 tinySize = new Vector2(0.5f/16f, 0.5f/16f);
		static TextureRec rec = new TextureRec(2/128f, 14/128f, 3/128f, 2/128f);
		
		public RainParticle() { throughLiquids = false; }
		
		public bool Big, Tiny;
		
		public override bool Tick(Game game, double delta) {
			bool dies = Tick(game, 3.5f, delta);
			return hitTerrain ? true : dies;
		}
		
		public override int Get1DBatch(Game game) { return 0; }
		
		public override void Render(Game game, double delta, float t,
		                            VertexP3fT2fC4b[] vertices, ref int index) {
			Position = Vector3.Lerp(lastPos, nextPos, t);
			Vector2 size = Big ? bigSize : (Tiny ? tinySize : smallSize);
			
			Vector3I P = Vector3I.Floor(Position);
			int col = game.World.IsValidPos(P) ?
				game.Lighting.LightCol(P.X, P.Y, P.Z) : game.Lighting.Outside;
			DoRender(game, ref size, ref rec, col, vertices, ref index);
		}
	}
	
	public sealed class TerrainParticle : CollidableParticle {
		
		static Vector2 terrainSize = new Vector2(1/8f, 1/8f);
		internal TextureRec rec;
		internal byte texLoc;
		internal BlockID block;
		
		public override bool Tick(Game game, double delta) {
			return Tick(game, 5.4f, delta);
		}
		
		public override int Get1DBatch(Game game) {
			return game.TerrainAtlas1D.Get1DIndex(texLoc);
		}
		
		public override void Render(Game game, double delta, float t,
		                            VertexP3fT2fC4b[] vertices, ref int index) {
			Position = Vector3.Lerp(lastPos, nextPos, t);
			
			int col = FastColour.WhitePacked;
			if (!game.BlockInfo.FullBright[block]) {
				Vector3I P = Vector3I.Floor(Position);
				col = game.World.IsValidPos(P) ?
					game.Lighting.LightCol_ZSide(P.X, P.Y, P.Z) : game.Lighting.OutsideZSide;
			}
			
			if (game.BlockInfo.Tinted[block]) {
				FastColour fogCol = game.BlockInfo.FogColour[block];
				FastColour newCol = FastColour.Unpack(col);
				newCol *= fogCol;
				col = newCol.Pack();
			}
			DoRender(game, ref terrainSize, ref rec, col, vertices, ref index);
		}
	}
}