/**
 * @author Aleksey Terzi
 *
 */

package com.encrox.instancedregions.chunkmap;

import java.io.IOException;
import java.util.Arrays;

import com.encrox.instancedregions.types.BlockState;

public class ChunkMapManager {
    private static final ThreadLocal<ChunkMapBuffer> _buffer = new ThreadLocal<ChunkMapBuffer>() {
    	@Override
        protected ChunkMapBuffer initialValue() {
            return new ChunkMapBuffer();
        }
    };
    
    private ChunkMapBuffer buffer;
    private ChunkData chunkData;
    private ChunkReader reader;
    private int sectionCount;
    private int sectionIndex;
    private int y;
    private int minX;
    private int maxX;
    private int minZ;
    private int maxZ;
    private int blockIndex;
    
    public int getSectionCount() {
    	return this.sectionCount;
    }
    
    public int getY() {
    	return this.y;
    }
    
    public ChunkData getChunkData() {
    	return this.chunkData;
    }

    public ChunkMapManager(ChunkData chunkData) {
    	this.buffer = _buffer.get();
    	this.chunkData = chunkData;
    }
    
    public void init() throws IOException {
    	this.reader = new ChunkReader(this.chunkData.data);
    	this.sectionCount = 0;
    	this.sectionIndex = -1;
    	this.minX = this.chunkData.chunkX << 4;
    	this.maxX = this.minX + 15;
    	this.minZ = this.chunkData.chunkZ << 4;
    	this.maxZ = this.minZ + 15;
    	
		this.buffer.lightArrayLength = 2048;
		
		if(this.chunkData.isOverworld) {
			this.buffer.lightArrayLength <<= 1;
		}
    	
    	this.buffer.writer.init();
    	
    	int mask = this.chunkData.primaryBitMask;
    	
    	while(mask != 0) {
    		if((mask & 0x1) != 0) {
    			this.sectionCount++;
    		}
    		
    		mask >>>= 1;
    	}
    	
    	this.buffer.clearLayers();

    	moveToNextLayer();
    }
    
    public boolean inputHasNonAirBlock() {
    	return this.buffer.paletteLength > 1 || this.buffer.palette[0] != 0;
    }
    
    public static void blockDataToState(int blockData, BlockState blockState) {
    	blockState.id = blockData >>> 4;
    	blockState.meta = blockData & 0xf;
    }
    
    public static int getBlockIdFromData(int blockData) {
    	return blockData >>> 4;
    }

    public static int getBlockMetaFromData(int blockData) {
    	return blockData & 0xf;
    }

    public static int blockStateToData(BlockState blockState) {
    	return (blockState.id << 4) | blockState.meta; 
    }
    
    public static int getBlockDataFromId(int id) {
    	return id << 4;
    }

    public boolean initOutputPalette() {
    	if(this.buffer.paletteLength == 0 || this.buffer.paletteLength == 255) {
    		this.buffer.outputPaletteLength = 0;
    		return false;
    	}
    	
    	Arrays.fill(this.buffer.outputPaletteMap, (byte)-1);
    	
    	this.buffer.outputPaletteLength = this.buffer.paletteLength;
    	
    	for(int i = 0; i < this.buffer.paletteLength; i++) {
    		int blockData = this.buffer.palette[i];
    		    		
    		this.buffer.outputPalette[i] = blockData;
    		
    		if(blockData >= 0) {
    			this.buffer.outputPaletteMap[blockData] = (byte)i;
    		}
    	}
    	
    	return true;
    }
    
    public boolean addToOutputPalette(int blockData) {
    	if(this.buffer.outputPaletteMap[blockData] >= 0) return true;
    	
    	//255 (-1 for byte) is special code in my algorithm
    	if(this.buffer.outputPaletteLength == 254) {
    		this.buffer.outputPaletteLength = 0;
    		return false;
    	}
    	
    	this.buffer.outputPalette[this.buffer.outputPaletteLength] = blockData;
    	this.buffer.outputPaletteMap[blockData] = (byte)this.buffer.outputPaletteLength;
    	
    	this.buffer.outputPaletteLength++;
    	
    	return true;
    }
    
    public void initOutputSection() throws IOException {
    	calcOutputBitsPerBlock();
    	
    	this.buffer.writer.setBitsPerBlock(this.buffer.outputBitsPerBlock);
    	
    	//Bits Per Block
    	this.buffer.writer.writeByte((byte)this.buffer.outputBitsPerBlock);
    	
    	//Palette Length
    	this.buffer.writer.writeVarInt(this.buffer.outputPaletteLength);
    	
    	//Palette
    	for(int i = 0; i < this.buffer.outputPaletteLength; i++) {
    		this.buffer.writer.writeVarInt(this.buffer.outputPalette[i]);
    	}
    	
    	int dataArrayLengthInBits = this.buffer.outputBitsPerBlock << 12;// multiply by 4096
    	int outputDataArrayLength = dataArrayLengthInBits >>> 6;//divide by 64
    	
    	if((dataArrayLengthInBits & 0x3f) != 0) {
    		outputDataArrayLength++;
    	}
    	
    	//Data Array Length
    	this.buffer.writer.writeVarInt(outputDataArrayLength);
    	
    	//Copy Block Light and Sky Light arrays
    	int lightArrayStartIndex = this.buffer.dataArrayStartIndex + (this.buffer.dataArrayLength << 3);
    	int outputLightArrayStartIndex = this.buffer.writer.getByteIndex() + (outputDataArrayLength << 3);
    	
    	System.arraycopy(
    			this.chunkData.data,
    			lightArrayStartIndex,
    			this.buffer.output,
    			outputLightArrayStartIndex,
    			this.buffer.lightArrayLength
    			);
    }
    
    public void writeOutputBlock(int blockData) throws IOException {
    	if(this.buffer.outputPaletteLength > 0) {
    		long paletteIndex = this.buffer.outputPaletteMap[blockData] & 0xffL;
    		
    		if(paletteIndex == 255) {
    			BlockState blockState = new BlockState();
    			blockDataToState(blockData, blockState);
    			throw new IllegalArgumentException("Block " + blockState.id + ":" + blockState.meta + " is absent in output palette.");
    		}
    		
    		this.buffer.writer.writeBlockBits(paletteIndex);
    	} else {
    		this.buffer.writer.writeBlockBits(blockData);
    	}
    }
    
    public void finalizeOutput() throws IOException {
    	if(this.buffer.writer.getByteIndex() == 0) return;
    	
    	this.buffer.writer.save();
    	this.buffer.writer.skip(this.buffer.lightArrayLength);
    }
    
    public byte[] createOutput() {
    	int readerByteIndex = this.reader.getByteIndex();
    	int writerByteIndex = this.buffer.writer.getByteIndex();
    	int biomesSize = this.chunkData.data.length - readerByteIndex;
    	byte[] output = new byte[writerByteIndex + biomesSize];
    	
    	System.arraycopy(this.buffer.output, 0, output, 0, writerByteIndex);
    	
    	if(biomesSize > 0) {
	    	System.arraycopy(
	    			this.chunkData.data,
	    			readerByteIndex,
	    			output,
	    			writerByteIndex,
	    			biomesSize
	    			);
    	}
    	
    	return output;
    }
    
    private void calcOutputBitsPerBlock() {
    	if(this.buffer.outputPaletteLength == 0) {
    		this.buffer.outputBitsPerBlock = 13;
    	} else {
    		byte mask = (byte)this.buffer.outputPaletteLength;
    		int index = 0;
    		
    		while((mask & 0x80) == 0) {
    			index++;
    			mask <<= 1;
    		}
    		
    		this.buffer.outputBitsPerBlock = 8 - index;
  			
  			if(this.buffer.outputBitsPerBlock < 4) {
  				this.buffer.outputBitsPerBlock = 4;
  			}
    	}
    }
    
    public int readNextBlock() throws IOException {
    	if(this.blockIndex == 16 * 16) {
    		if(!moveToNextLayer()) return -1;
    	}
    	
    	return this.buffer.curLayer.map[this.blockIndex++];
    }
    
    public int get(int x, int y, int z) throws IOException {
    	if(x < minX || x > maxX
    			|| z < minZ || z > maxZ
    			|| y > 255 || y < this.y - 1 || y > this.y + 1
    			) {
    		return -1;
    	}
    	
    	ChunkLayer layer;
    	
    	if(y == this.y) layer = this.buffer.curLayer;
    	else if(y == this.y - 1) layer = this.buffer.prevLayer;
    	else layer = this.buffer.nextLayer;
    	
    	if(!layer.hasData) return -1;
    	
    	int blockIndex = ((z - this.minZ) << 4) | (x - this.minX);

    	return layer.map[blockIndex];
    }
        
    private boolean moveToNextLayer() throws IOException {
    	if(!increaseY()) return false;
		
		shiftLayersDown();
		
		if(!this.buffer.curLayer.hasData) {
			readLayer(this.buffer.curLayer);
		}

		if(((this.y + 1) >>> 4) > this.sectionIndex) {
			int oldSectionIndex = this.sectionIndex;
			
			moveToNextSection();
			
			if(this.sectionIndex < 16 && oldSectionIndex + 1 == this.sectionIndex) {
				readLayer(this.buffer.nextLayer);
			}
		} else {
			readLayer(this.buffer.nextLayer);
		}
		
		this.blockIndex = 0;
		
		return true;
    }
    
    private boolean increaseY() throws IOException {
		if(this.sectionIndex < 0) {
			if(!moveToNextSection()) return false;
			
			this.y = this.sectionIndex << 4;
		}
		else {
			this.y++;
			
			if((this.y & 0xf) == 0) {
				if(this.sectionIndex > 15) return false;

	    		if((this.y >>> 4) != this.sectionIndex) {
					this.buffer.clearLayers();
		    		this.y = this.sectionIndex << 4;
	    		}
			}
		}
		
		return true;
	}
    
    private void shiftLayersDown() {
		ChunkLayer temp = this.buffer.prevLayer;
		
		this.buffer.prevLayer = this.buffer.curLayer;
		this.buffer.curLayer = this.buffer.nextLayer;
		this.buffer.nextLayer = temp;
		this.buffer.nextLayer.hasData = false;
	}
    
    private boolean moveToNextSection() throws IOException {
    	if(this.sectionIndex >= 0) {
    		this.reader.skip(this.buffer.lightArrayLength);
    	}
    	
		do {
			this.sectionIndex++;
		} while(this.sectionIndex < 16 && (this.chunkData.primaryBitMask & (1 << this.sectionIndex)) == 0);
		
		if(this.sectionIndex >= 16) return false;
		
		readSectionHeader();
    	    	
    	return true;
    }
    
    private void readLayer(ChunkLayer layer) throws IOException {
    	for(int i = 0; i < 16 * 16; i++) {
    		int blockData = this.reader.readBlockBits();
    		
        	if(this.buffer.paletteLength > 0) {
        		blockData = blockData >= 0 && blockData < this.buffer.paletteLength
        				? this.buffer.palette[blockData]
        				: 0;
        	}

        	layer.map[i] = blockData;
    	}
    	
    	layer.hasData = true;
    }
    
    private void readSectionHeader() throws IOException {
    	this.buffer.bitsPerBlock = this.reader.readByte();
    	this.buffer.paletteLength = this.reader.readVarInt();
    	
    	for(int i = 0; i < this.buffer.paletteLength; i++) {
    		int paletteData = this.reader.readVarInt();
    		
    		this.buffer.palette[i] = paletteData;
    	}
    	
    	this.buffer.dataArrayLength = this.reader.readVarInt();
    	
    	this.buffer.dataArrayStartIndex = this.reader.getByteIndex();
    	
    	this.reader.setBitsPerBlock(this.buffer.bitsPerBlock);
    }
}