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

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

namespace ClassicalSharp.Particles {
	
	public partial class ParticleManager : IDisposable {
		
		void BreakBlockEffect(object sender, BlockChangedEventArgs e) {
			if (e.Block != 0) return;
			Vector3I position = e.Coords;
			BlockID block = e.OldBlock;
			
			Vector3 worldPos = new Vector3(position.X, position.Y, position.Z);
			int texLoc = game.BlockInfo.GetTextureLoc(block, Side.Left), texIndex = 0;
			TextureRec baseRec = game.TerrainAtlas1D.GetTexRec(texLoc, 1, out texIndex);
			float uScale = (1/16f), vScale = (1/16f) * game.TerrainAtlas1D.invElementSize;
			
			Vector3 minBB = game.BlockInfo.MinBB[block];
			Vector3 maxBB = game.BlockInfo.MaxBB[block];
			int minU = Math.Min((int)(minBB.X * 16), (int)(minBB.Z * 16));
			int maxU = Math.Min((int)(maxBB.X * 16), (int)(maxBB.Z * 16));
			int minV = (int)(16 - maxBB.Y * 16), maxV = (int)(16 - minBB.Y * 16);
			int maxUsedU = maxU, maxUsedV = maxV;
			// This way we can avoid creating particles which outside the bounds and need to be clamped
			if (minU < 12 && maxU > 12) maxUsedU = 12;
			if (minV < 12 && maxV > 12) maxUsedV = 12;
			
			const int gridSize = 4;
			// gridOffset gives the centre of the cell on a grid
			const float cellCentre = (1f / gridSize) * 0.5f;
			
			for (int x = 0; x < gridSize; x++)
				for (int y = 0; y < gridSize; y++)
					for (int z = 0; z < gridSize; z++)
			{
				float cellX = (float)x / gridSize, cellY = (float)y / gridSize, cellZ = (float)z / gridSize;
				Vector3 cell = new Vector3(cellCentre + cellX, cellCentre / 2 + cellY, cellCentre + cellZ);
				if (cell.X < minBB.X || cell.X > maxBB.X || cell.Y < minBB.Y
				    || cell.Y > maxBB.Y || cell.Z < minBB.Z || cell.Z > maxBB.Z) continue;
				
				double velX = cellCentre + (cellX - 0.5f) + (rnd.NextDouble() * 0.4 - 0.2); // centre random offset around [-0.2, 0.2]
				double velY = cellCentre + (cellY - 0.0f) + (rnd.NextDouble() * 0.4 - 0.2);
				double velZ = cellCentre + (cellZ - 0.5f) + (rnd.NextDouble() * 0.4 - 0.2);
				Vector3 velocity = new Vector3((float)velX, (float)velY, (float)velZ);
				
				TextureRec rec = baseRec;
				rec.U1 = baseRec.U1 + rnd.Next(minU, maxUsedU) * uScale;
				rec.V1 = baseRec.V1 + rnd.Next(minV, maxUsedV) * vScale;
				rec.U2 = Math.Min(baseRec.U1 + maxU * uScale, rec.U1 + 4 * uScale) - 0.01f * uScale;
				rec.V2 = Math.Min(baseRec.V1 + maxV * vScale, rec.V1 + 4 * vScale) - 0.01f * vScale;
				double life = 0.3 + rnd.NextDouble() * 1.2;
				
				TerrainParticle p = AddParticle(terrainParticles, ref terrainCount, false);
				p.ResetState(worldPos + cell, velocity, life);
				p.rec = rec;
				
				p.texLoc = (byte)texLoc;
				p.block = block;
			}
		}
		
		public void AddRainParticle(Vector3 pos) {
			Vector3 startPos = pos;
			for (int i = 0; i < 2; i++) {
				double velX = rnd.NextDouble() * 0.8 - 0.4; // [-0.4, 0.4]
				double velZ = rnd.NextDouble() * 0.8 - 0.4;
				double velY = rnd.NextDouble() + 0.4;
				Vector3 velocity = new Vector3((float)velX, (float)velY, (float)velZ);
				
				double xOffset = rnd.NextDouble() - 0.5; // [-0.5, 0.5]
				double yOffset = rnd.NextDouble() * 0.1 + 0.01;
				double zOffset = rnd.NextDouble() - 0.5;
				pos = startPos + new Vector3(0.5f + (float)xOffset,
				                             (float)yOffset, 0.5f + (float)zOffset);
				double life = 40;
				RainParticle p = AddParticle(rainParticles, ref rainCount, true);
				p.ResetState(pos, velocity, life);
				p.Big = rnd.Next(0, 20) >= 18;
				p.Tiny = rnd.Next(0, 30) >= 28;
			}
		}
		
		T AddParticle<T>(T[] particles, ref int count, bool rain) where T : Particle, new() {
			if (count == maxParticles)
				RemoveAt(0, particles, ref count);
			count++;
			
			T old = particles[count - 1];
			if (old != null) return old;
			
			T newT = rain ? (T)(object)new RainParticle() : (T)(object)new TerrainParticle();
			particles[count - 1] = newT;
			return newT;
		}
	}
}