package appeng.client.render;

import java.util.Random;

import net.minecraft.client.Minecraft;
import net.minecraft.client.multiplayer.WorldClient;
import net.minecraft.client.renderer.GLAllocation;
import net.minecraft.client.renderer.OpenGlHelper;
import net.minecraft.client.renderer.RenderHelper;
import net.minecraft.client.renderer.Tessellator;
import net.minecraftforge.client.IRenderHandler;

import org.lwjgl.opengl.GL11;

public class SpatialSkyRender extends IRenderHandler
{

	private static SpatialSkyRender instance = new SpatialSkyRender();

	private Random random = new Random();
	private long cycle = 0;
	private int dspList;

	public SpatialSkyRender() {
		dspList = GLAllocation.generateDisplayLists( 1 );
	}

	@Override
	public void render(float partialTicks, WorldClient world, Minecraft mc)
	{
		long now = System.currentTimeMillis();
		if ( now - cycle > 2000 )
		{
			cycle = now;
			GL11.glNewList( dspList, GL11.GL_COMPILE );
			renderTwinkles();
			GL11.glEndList();
		}

		float fade = now - cycle;
		fade /= 1000;
		fade = 0.15f * (1.0f - Math.abs( (fade - 1.0f) * (fade - 1.0f) ));

		if ( fade > 0.0f )
		{
			GL11.glPushAttrib( GL11.GL_ALL_ATTRIB_BITS );

			GL11.glDisable( GL11.GL_FOG );
			GL11.glDisable( GL11.GL_ALPHA_TEST );
			GL11.glEnable( GL11.GL_BLEND );
			GL11.glDepthMask( false );
			GL11.glEnable( GL11.GL_FOG );
			GL11.glDisable( GL11.GL_FOG );
			GL11.glDisable( GL11.GL_ALPHA_TEST );
			GL11.glEnable( GL11.GL_BLEND );
			GL11.glDisable( GL11.GL_TEXTURE_2D );
			OpenGlHelper.glBlendFunc( 770, 771, 1, 0 );
			RenderHelper.disableStandardItemLighting();
			GL11.glDepthMask( false );

			GL11.glColor4f( fade, fade, fade, 1.0f );
			GL11.glCallList( dspList );
			GL11.glPopAttrib();
		}

	}

	private void renderTwinkles()
	{
		Tessellator tessellator = Tessellator.instance;
		tessellator.startDrawingQuads();

		for (int i = 0; i < 50; ++i)
		{
			double iX = (double) (random.nextFloat() * 2.0F - 1.0F);
			double iY = (double) (random.nextFloat() * 2.0F - 1.0F);
			double iZ = (double) (random.nextFloat() * 2.0F - 1.0F);
			double d3 = (double) (0.05F + random.nextFloat() * 0.1F);
			double dist = iX * iX + iY * iY + iZ * iZ;

			if ( dist < 1.0D && dist > 0.01D )
			{
				dist = 1.0D / Math.sqrt( dist );
				iX *= dist;
				iY *= dist;
				iZ *= dist;
				double x = iX * 100.0D;
				double y = iY * 100.0D;
				double z = iZ * 100.0D;
				double d8 = Math.atan2( iX, iZ );
				double d9 = Math.sin( d8 );
				double d10 = Math.cos( d8 );
				double d11 = Math.atan2( Math.sqrt( iX * iX + iZ * iZ ), iY );
				double d12 = Math.sin( d11 );
				double d13 = Math.cos( d11 );
				double d14 = random.nextDouble() * Math.PI * 2.0D;
				double d15 = Math.sin( d14 );
				double d16 = Math.cos( d14 );

				for (int j = 0; j < 4; ++j)
				{
					double d17 = 0.0D;
					double d18 = (double) ((j & 2) - 1) * d3;
					double d19 = (double) ((j + 1 & 2) - 1) * d3;
					double d20 = d18 * d16 - d19 * d15;
					double d21 = d19 * d16 + d18 * d15;
					double d22 = d20 * d12 + d17 * d13;
					double d23 = d17 * d12 - d20 * d13;
					double d24 = d23 * d9 - d21 * d10;
					double d25 = d21 * d9 + d23 * d10;
					tessellator.addVertex( x + d24, y + d22, z + d25 );
				}
			}
		}

		tessellator.draw();
	}

	public static IRenderHandler getInstance()
	{
		return instance;
	}

}