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

namespace ClassicalSharp.Renderers {

	public sealed class SkyboxRenderer : IGameComponent {
		
		int tex, vb = -1;
		Game game;
		const int count = 6 * 4;
		
		public bool ShouldRender {
			get { return tex > 0 && !(game.EnvRenderer is MinimalEnvRenderer); }
		}
		
		public void Init(Game game) {
			this.game = game;
			game.Events.TextureChanged += TextureChanged;
			game.Events.TexturePackChanged += TexturePackChanged;
			game.WorldEvents.EnvVariableChanged += EnvVariableChanged;
			game.WorldEvents.OnNewMap += OnNewMap;
			game.Graphics.ContextLost += ContextLost;
			game.Graphics.ContextRecreated += ContextRecreated;
			ContextRecreated();
		}
		
		public void Reset(Game game) { game.Graphics.DeleteTexture(ref tex); }
		public void Ready(Game game) { }
		public void OnNewMap(Game game) { }
		public void OnNewMapLoaded(Game game) { }
		
		public void Dispose() {
			game.Graphics.DeleteTexture(ref tex);
			ContextLost();
			
			game.Events.TextureChanged -= TextureChanged;
			game.Events.TexturePackChanged -= TexturePackChanged;
			game.WorldEvents.EnvVariableChanged -= EnvVariableChanged;
			game.WorldEvents.OnNewMap -= OnNewMap;
			game.Graphics.ContextLost -= ContextLost;
			game.Graphics.ContextRecreated -= ContextRecreated;			
		}

		void OnNewMap(object sender, EventArgs e) { MakeVb(); }
		
		void EnvVariableChanged(object sender, EnvVarEventArgs e) {
			if (e.Var != EnvVar.CloudsColour) return;
			MakeVb();
		}
		
		void TexturePackChanged(object sender, EventArgs e) {
			game.Graphics.DeleteTexture(ref tex);
		}
		
		void TextureChanged(object sender, TextureEventArgs e) {
			if (e.Name == "skybox.png")
				game.UpdateTexture(ref tex, e.Name, e.Data, false);
		}
		
		public void Render(double deltaTime) {
			if (vb == -1) return;
			game.Graphics.DepthWrite = false;
			game.Graphics.Texturing = true;
			game.Graphics.BindTexture(tex);
			game.Graphics.SetBatchFormat(VertexFormat.P3fT2fC4b);
			
			Vector3 pos = game.CurrentCameraPos;
			Matrix4 m = Matrix4.Identity;
			Vector2 rotation = game.Camera.GetCameraOrientation();
			m *= Matrix4.RotateY(rotation.X); // yaw
			m *= Matrix4.RotateX(rotation.Y); // pitch
			m = m * game.Camera.tiltM;
			game.Graphics.LoadMatrix(ref m);
			
			game.Graphics.BindVb(vb);
			game.Graphics.DrawIndexedVb(DrawMode.Triangles, count * 6 / 4, 0);
			
			game.Graphics.Texturing = false;
			game.Graphics.LoadMatrix(ref game.View);
			game.Graphics.DepthWrite = true;
		}
		
		void ContextLost() { game.Graphics.DeleteVb(ref vb); }	
		void ContextRecreated() { MakeVb(); }
		
		
		unsafe void MakeVb() {
			if (game.Graphics.LostContext) return;
			game.Graphics.DeleteVb(ref vb);			
			VertexP3fT2fC4b* vertices = stackalloc VertexP3fT2fC4b[count];
			IntPtr start = (IntPtr)vertices;
			const float pos = 0.5f;
			TextureRec rec;
			int col = game.World.Env.CloudsCol.Pack();
			
			// Render the front quad
			rec = new TextureRec(1/4f, 1/2f, 1/4f, 1/2f);
			*vertices = new VertexP3fT2fC4b( pos, -pos, -pos, rec.U1, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos, -pos, -pos, rec.U2, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos,  pos, -pos, rec.U2, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos,  pos, -pos, rec.U1, rec.V1, col); vertices++;
			// Render the left quad
			rec = new TextureRec(0/4f, 1/2f, 1/4f, 1/2f);
			*vertices = new VertexP3fT2fC4b( pos, -pos,  pos, rec.U1, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos, -pos, -pos, rec.U2, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos,  pos, -pos, rec.U2, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos,  pos,  pos, rec.U1, rec.V1, col); vertices++;
			// Render the back quad
			rec = new TextureRec(3/4f, 1/2f, 1/4f, 1/2f);
			*vertices = new VertexP3fT2fC4b(-pos, -pos,  pos, rec.U1, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos, -pos,  pos, rec.U2, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos,  pos,  pos, rec.U2, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos,  pos,  pos, rec.U1, rec.V1, col); vertices++;
			// Render the right quad
			rec = new TextureRec(2/4f, 1/2f, 1/4f, 1/2f);
			*vertices = new VertexP3fT2fC4b(-pos, -pos, -pos, rec.U1, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos, -pos,  pos, rec.U2, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos,  pos,  pos, rec.U2, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos,  pos, -pos, rec.U1, rec.V1, col); vertices++;
			// Render the top quad
			rec = new TextureRec(1/4f, 0/2f, 1/4f, 1/2f);
			*vertices = new VertexP3fT2fC4b(-pos,  pos, -pos, rec.U2, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos,  pos,  pos, rec.U2, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos,  pos,  pos, rec.U1, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos,  pos, -pos, rec.U1, rec.V2, col); vertices++;
			// Render the bottom quad
			rec = new TextureRec(2/4f, 0/2f, 1/4f, 1/2f);
			*vertices = new VertexP3fT2fC4b(-pos, -pos, -pos, rec.U2, rec.V2, col); vertices++;
			*vertices = new VertexP3fT2fC4b(-pos, -pos,  pos, rec.U2, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos, -pos,  pos, rec.U1, rec.V1, col); vertices++;
			*vertices = new VertexP3fT2fC4b( pos, -pos, -pos, rec.U1, rec.V2, col); vertices++;
			vb = game.Graphics.CreateVb(start, VertexFormat.P3fT2fC4b, count);
		}
	}
}