package com.badlogic.gdx.graphics.g3d.particles;

import java.util.Arrays;

import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.GdxRuntimeException;
import com.badlogic.gdx.utils.reflect.ArrayReflection;

/** This class represents an group of elements like an array, but the properties of the elements are stored as separate arrays.
 *  These arrays are called {@link Channel} and are represented by {@link ChannelDescriptor}.
 *  It's not necessary to store primitive types in the channels but doing so will "exploit" data locality 
 *  in the JVM, which is ensured for primitive types.
 *  Use {@link FloatChannel}, {@link IntChannel}, {@link ObjectChannel} to store the data. 
 *  @author inferno */
public class ParallelArray {
	
	/** This class describes the content of a {@link Channel}*/
	public static class ChannelDescriptor{
		public int id;
		public Class<?> type;
		public int count;
		public ChannelDescriptor(int id, Class<?> type, int count){
			this.id = id;
			this.type = type;
			this.count = count;
		}
	}
	
	/** This class represents a container of values for all the elements for a given property*/
	public abstract class Channel{
		public int id;
		public Object data;
		public int strideSize;
		public Channel(int id, Object data, int strideSize){
			this.id = id;
			this.strideSize = strideSize;
			this.data = data;
		}
		public abstract void add(int index, Object...objects);
		public abstract void swap(int i, int k);
		protected abstract void setCapacity (int requiredCapacity);
	}
	
	/** This interface is used to provide custom initialization of the {@link Channel} data */
	public static interface ChannelInitializer<T extends Channel>{
		public void init(T channel);
	}
	
	public class FloatChannel extends Channel{
		public float[] data;
		public FloatChannel (int id, int strideSize, int size) {
			super(id, new float[size*strideSize], strideSize);
			this.data = (float[])super.data;
		}

		@Override
		public void add (int index, Object...objects) {
			for(int i=strideSize*size, c = i+strideSize, k=0; i < c; ++i, ++k){
				data[i] = (Float)objects[k];
			}
		}

		@Override
		public void swap (int i, int k) {
			float t;
			i=strideSize*i; 
			k =strideSize*k;
			for(int c = i+strideSize; i < c; ++i, ++k){
				t = data[i];
				data[i] = data[k];
				data[k] = t;
			}
		}

		@Override
		public void setCapacity (int requiredCapacity) {
			super.data = data = Arrays.copyOf(data, strideSize * requiredCapacity);
		}
	}
	
	public class IntChannel extends Channel{
		public int[] data;
		public IntChannel (int id, int strideSize, int size) {
			super(id, new int[size*strideSize], strideSize);
			this.data = (int[])super.data;
		}

		@Override
		public void add (int index, Object...objects) {
			for(int i=strideSize*size, c = i+strideSize, k=0; i < c; ++i, ++k){
				data[i] = (Integer)objects[k];
			}
		}

		@Override
		public void swap (int i, int k) {
			int t;
			i=strideSize*i; 
			k =strideSize*k;
			for(int c = i+strideSize; i < c; ++i, ++k){
				t = data[i];
				data[i] = data[k];
				data[k] = t;
			}
		}
		
		@Override
		public void setCapacity (int requiredCapacity) {
			super.data = data = Arrays.copyOf(data, strideSize * requiredCapacity);
		}
	}
	
	@SuppressWarnings("unchecked")
	public class ObjectChannel<T> extends Channel{
		public T[] data;
		public ObjectChannel (int id, int strideSize, int size, Class<T> type) {
			super(id, ArrayReflection.newInstance(type, size*strideSize), strideSize);
			this.data = (T[]) super.data;
		}

		@Override
		public void add (int index, Object...objects) {
			for(int i=strideSize*size, c = i+strideSize, k=0; i < c; ++i, ++k){
				this.data[i] = (T) objects[k];
			}
		}

		@Override
		public void swap (int i, int k) {
			T t;
			i=strideSize*i; 
			k =strideSize*k;
			for(int c = i+strideSize; i < c; ++i, ++k){
				t = data[i];
				data[i] = data[k];
				data[k] = t;
			}
		}
		
		@Override
		public void setCapacity (int requiredCapacity) {
			super.data = data = Arrays.copyOf(data, strideSize * requiredCapacity);
		}
	}
	
	/**the channels added to the array*/
	Array<Channel> arrays;
	/** the maximum amount of elements that this array can hold */
	public int capacity;
	/** the current amount of defined elements, do not change manually unless you know what you are doing.*/
	public int size;
	
	public ParallelArray(int capacity){
		arrays = new Array<Channel>(false, 2,  Channel.class);
		this.capacity = capacity;
		size = 0;
	}
	
	/** Adds and returns a channel described by the channel descriptor parameter.
	 *  If a channel with the same id already exists, no allocation is performed and that channel is returned. */
	public <T extends Channel> T addChannel(ChannelDescriptor channelDescriptor){
		return addChannel(channelDescriptor, null);
	}
	
	/** Adds and returns a channel described by the channel descriptor parameter.
	 *  If a channel with the same id already exists, no allocation is performed and that channel is returned.
	 *  Otherwise a new channel is allocated and initialized with the initializer. */
	public <T extends Channel> T addChannel(ChannelDescriptor channelDescriptor, ChannelInitializer<T> initializer){
		T channel = getChannel(channelDescriptor);
		if(channel == null){
			channel = allocateChannel(channelDescriptor);
			if(initializer != null)
				initializer.init(channel);
			arrays.add(channel);
		}
		return channel;
	}
	
	@SuppressWarnings({"unchecked", "rawtypes"})
	private <T extends Channel> T allocateChannel(ChannelDescriptor channelDescriptor){
		if(channelDescriptor.type == float.class){
			return (T)new FloatChannel(channelDescriptor.id, channelDescriptor.count, capacity);
		}
		else if(channelDescriptor.type == int.class){
			return (T)new IntChannel(channelDescriptor.id, channelDescriptor.count, capacity);
		}
		else {
			return (T)new ObjectChannel(channelDescriptor.id, channelDescriptor.count, capacity, channelDescriptor.type);
		}
	}
	
	/**Removes the channel with the given id*/
	public <T> void removeArray(int id){
		arrays.removeIndex(findIndex(id));
	}
	
	private int findIndex (int id) {
		for(int i=0; i < arrays.size;++i){
			Channel array = arrays.items[i];
			if(array.id == id)
				return i;
		}
		return -1;
	}
	
	/**Adds an element considering the values in the same order as the current channels in the array.
	 * The n_th value  must have the same type and stride of the given channel at position n*/
	public void addElement(Object...values){
		/*FIXME make it grow...*/
		if(size == capacity) 
			throw new GdxRuntimeException("Capacity reached, cannot add other elements");

		int k=0;
		for(Channel strideArray : arrays){
			strideArray.add(k, values);
			k+= strideArray.strideSize;
		}
		++size;
	}
	
	/**Removes the element at the given index and swaps it with the last available element */
	public void removeElement(int index){
		int last = size -1;
		//Swap
		for(Channel strideArray : arrays){
			strideArray.swap(index, last);
		}
		size = last;
	}
	
	/**@return the channel with the same id as the one in the descriptor */
	@SuppressWarnings("unchecked")
	public <T extends Channel> T getChannel (ChannelDescriptor descriptor) {
		for(Channel array : arrays){
			if(array.id == descriptor.id)
				return (T) array;
		}
		return null;
	}

	/** Removes all the channels and sets size to 0 */
	public void clear () {
		arrays.clear();
		size = 0;
	}

	/** Sets the capacity. 
	 * Each contained channel will be resized to match the required capacity and the current data will be preserved. */
	public void setCapacity (int requiredCapacity) {
		if(capacity != requiredCapacity){
			for(Channel channel : arrays){
				channel.setCapacity(requiredCapacity);
			}
			capacity = requiredCapacity;
		}
	}
	
}
