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

namespace ClassicalSharp.Particles {
	
	public partial class ParticleManager : IGameComponent {
		
		public int ParticlesTexId;
		TerrainParticle[] terrainParticles = new TerrainParticle[maxParticles];
		RainParticle[] rainParticles = new RainParticle[maxParticles];
		int terrainCount, rainCount;
		int[] terrain1DCount, terrain1DIndices;
		
		Game game;
		Random rnd = new Random();
		int vb;
		const int maxParticles = 600;
		
		public void Init(Game game) {
			this.game = game;
			game.Events.TerrainAtlasChanged += TerrainAtlasChanged;
			game.UserEvents.BlockChanged += BreakBlockEffect;
			game.Events.TextureChanged += TextureChanged;
			
			ContextRecreated();
			game.Graphics.ContextLost += ContextLost;
			game.Graphics.ContextRecreated += ContextRecreated;
		}
		
		public void Ready(Game game) { }
		public void Reset(Game game) { rainCount = 0; terrainCount = 0; }
		public void OnNewMap(Game game) { rainCount = 0; terrainCount = 0; }
		public void OnNewMapLoaded(Game game) { }

		void TerrainAtlasChanged(object sender, EventArgs e) {
			terrain1DCount = new int[game.TerrainAtlas1D.TexIds.Length];
			terrain1DIndices = new int[game.TerrainAtlas1D.TexIds.Length];
		}
		
		void TextureChanged(object sender, TextureEventArgs e) {
			if (e.Name == "particles.png")
				game.UpdateTexture(ref ParticlesTexId, e.Name, e.Data, false);
		}
		
		VertexP3fT2fC4b[] vertices = new VertexP3fT2fC4b[0];
		public void Render(double delta, float t) {
			if (terrainCount == 0 && rainCount == 0) return;
			if (game.Graphics.LostContext) return;
			
			IGraphicsApi gfx = game.Graphics;
			gfx.Texturing = true;
			gfx.AlphaTest = true;
			gfx.SetBatchFormat(VertexFormat.P3fT2fC4b);
			
			RenderTerrainParticles(gfx, terrainParticles, terrainCount, delta, t);
			RenderRainParticles(gfx, rainParticles, rainCount, delta, t);
			
			gfx.AlphaTest = false;
			gfx.Texturing = false;
		}
		
		void RenderTerrainParticles(IGraphicsApi gfx, Particle[] particles, int elems, double delta, float t) {
			int count = elems * 4;
			if (count > vertices.Length)
				vertices = new VertexP3fT2fC4b[count];

			Update1DCounts(particles, elems);
			for (int i = 0; i < elems; i++) {
				int index = particles[i].Get1DBatch(game);
				particles[i].Render(game, delta, t, vertices, ref terrain1DIndices[index]);
			}
			int drawCount = Math.Min(count, maxParticles * 4);
			if (drawCount == 0) return;
			
			gfx.SetDynamicVbData(vb, vertices, drawCount);
			int offset = 0;
			for (int i = 0; i < terrain1DCount.Length; i++) {
				int partCount = terrain1DCount[i];
				if (partCount == 0) continue;
				
				gfx.BindTexture(game.TerrainAtlas1D.TexIds[i]);
				gfx.DrawIndexedVb(DrawMode.Triangles, partCount * 6 / 4, offset * 6 / 4);
				offset += partCount;
			}
		}
		
		void Update1DCounts(Particle[] particles, int elems) {
			for (int i = 0; i < terrain1DCount.Length; i++) {
				terrain1DCount[i] = 0;
				terrain1DIndices[i] = 0;
			}
			for (int i = 0; i < elems; i++) {
				int index = particles[i].Get1DBatch(game);
				terrain1DCount[index] += 4;
			}
			for (int i = 1; i < terrain1DCount.Length; i++)
				terrain1DIndices[i] = terrain1DIndices[i - 1] + terrain1DCount[i - 1];
		}
		
		void RenderRainParticles(IGraphicsApi gfx, Particle[] particles, int elems, double delta, float t) {
			int count = elems * 4;
			if (count > vertices.Length)
				vertices = new VertexP3fT2fC4b[count];
			
			int index = 0;
			for (int i = 0; i < elems; i++)
				particles[i].Render(game, delta, t, vertices, ref index);
			
			int drawCount = Math.Min(count, maxParticles * 4);
			if (drawCount == 0) return;
			gfx.BindTexture(ParticlesTexId);
			gfx.UpdateDynamicIndexedVb(DrawMode.Triangles, vb, vertices, drawCount);
		}
		
		public void Tick(ScheduledTask task) {
			TickParticles(terrainParticles, ref terrainCount, task.Interval);
			TickParticles(rainParticles, ref rainCount, task.Interval);
		}
		
		void TickParticles(Particle[] particles, ref int count, double delta) {
			for (int i = 0; i < count; i++) {
				Particle particle = particles[i];
				if (particle.Tick(game, delta)) {
					RemoveAt(i, particles, ref count);
					i--;
				}
			}
		}
		
		public void Dispose() {
			game.Graphics.DeleteTexture(ref ParticlesTexId);
			game.UserEvents.BlockChanged -= BreakBlockEffect;
			game.Events.TerrainAtlasChanged -= TerrainAtlasChanged;
			game.Events.TextureChanged -= TextureChanged;
			
			ContextLost();
			game.Graphics.ContextLost -= ContextLost;
			game.Graphics.ContextRecreated -= ContextRecreated;
		}
		
		void RemoveAt<T>(int index, T[] particles, ref int count) where T : Particle {
			T removed = particles[index];
			for (int i = index; i < count - 1; i++) {
				particles[i] = particles[i + 1];
			}
			
			particles[count - 1] = removed;
			count--;
		}
		
		void ContextLost() { game.Graphics.DeleteVb(ref vb); }
		
		void ContextRecreated() {
			vb = game.Graphics.CreateDynamicVb(VertexFormat.P3fT2fC4b, maxParticles * 4);
		}
	}
}