package cn.org.matrix.gmatrix.gameLab.util.pak;

import java.io.*;
import java.util.Vector;
/**
 * Pak工具類
 * 功能：
 * 從Pak文件中取出png圖片，構(gòu)造byte數(shù)組（可以用來構(gòu)造Image對(duì)象）
 * @author cleverpig
 *
 */
public class PakUtil {
	
	public PakUtil(){
	}
	
	/**
	 * 計(jì)算文件位移的起始點(diǎn)
	 * @return 文件位移的起始點(diǎn)
	 */
	private long workOutOffsetStart(PakHeader header){
		//計(jì)算出文件頭+文件table的長(zhǎng)度
		return PakHeader.size()+header.getNumFileTableEntries()*PakFileTable.size();
	}
	
	/**
	 * 從DataInputStream讀取char數(shù)組
	 * @param dis DataInputStream
	 * @param readLength 讀取長(zhǎng)度
	 * @return char數(shù)組
	 * @throws Exception
	 */
	private char[] readCharArray(DataInputStream dis,int readLength) throws Exception{
		char[] readCharArray=new char[readLength];
		
		for(int i=0;i<readLength;i++){
			readCharArray[i]=dis.readChar();
		}
		return readCharArray;
	}
	
	/**
	 * 從PAK文件中讀取文件頭
	 * @param dis DataInputStream
	 * @return PakHeader
	 * @throws Exception
	 */
	private PakHeader readHeader(DataInputStream dis) throws Exception{
		PakHeader header=new PakHeader();
		char[] signature=readCharArray(dis,PakHeader.SIGNATURE_LENGTH);
		header.setSignature(signature);
		header.setVersion(dis.readFloat());
		header.setNumFileTableEntries(dis.readLong());
		header.setCipherAction(dis.readByte());
		header.setCipherValue(dis.readByte());
		char[] uniqueID=readCharArray(dis,PakHeader.UNIQUEID_LENGTH);
		header.setUniqueID(uniqueID);
		header.setReserved(dis.readLong());
		return header;
	}
	
	/**
	 * 讀取所有的文件table
	 * @param dis DataInputStream
	 * @param fileTableNumber 文件表總數(shù)
	 * @return 文件table數(shù)組
	 * @throws Exception
	 */
	private PakFileTable[] readFileTable(DataInputStream dis,int fileTableNumber) throws Exception{
		PakFileTable[] fileTable=new PakFileTable[fileTableNumber];
		for(int i=0;i<fileTableNumber;i++){
			PakFileTable ft=new PakFileTable();
			ft.setFileName(readCharArray(dis,PakFileTable.FILENAME_LENGTH));
			ft.setFileSize(dis.readLong());
			ft.setOffSet(dis.readLong());
			fileTable[i]=ft;
		}
		return fileTable;
	}
	
	/**
	 * 從pak文件讀取文件到byte數(shù)組
	 * @param dis DataInputStream
	 * @param fileTable PakFileTable
	 * @return byte數(shù)組
	 * @throws Exception
	 */
	private byte[] readFileFromPak(DataInputStream dis,PakHeader header,PakFileTable fileTable) throws Exception{
		dis.skip(fileTable.getOffSet()-workOutOffsetStart(header));
		//
		int fileLength=(int)fileTable.getFileSize();
		byte[] fileBuff=new byte[fileLength];
		int readLength=dis.read(fileBuff,0,fileLength);
		if (readLength<fileLength){
			System.out.println("讀取數(shù)據(jù)長(zhǎng)度不正確");
			return null;
		}
		else{
			decryptBuff(fileBuff,readLength,header);
		}
		return fileBuff;
	}
	
	/**
	 * 使用文件頭中的密碼對(duì)數(shù)據(jù)進(jìn)行解密
	 * @param buff 被解密的數(shù)據(jù)
	 * @param buffLength 數(shù)據(jù)的長(zhǎng)度
	 * @param header 文件頭
	 */
	private void decryptBuff(byte[] buff,int buffLength,PakHeader header){
		for(int i=0;i<buffLength;i++){
			switch(header.getCipherAction()){
			case PakHeader.ADDITION_CIPHERACTION:
				buff[i]-=header.getCipherValue();
				break;
			case PakHeader.SUBTRACT_CIHOERACTION:
				buff[i]+=header.getCipherValue();
				break;
			}
		}
	}
	
	/**
	 * 從pak文件中取出指定的文件到byte數(shù)組
	 * @param pakResourceURL  pak文件的資源路徑
	 * @param extractResourceName pak文件中將要被取出的文件名
	 * @return byte數(shù)組
	 * @throws Exception
	 */
	public byte[] extractResourceFromPak(String pakResourceURL
			,String extractResourceName) throws Exception{
		InputStream is=this.getClass().getResourceAsStream(pakResourceURL);
		DataInputStream dis=new DataInputStream(is);
		PakHeader header=readHeader(dis);
//		System.out.println("文件頭:");
//		System.out.println(header);
		PakFileTable[] fileTable=readFileTable(dis,(int)header.getNumFileTableEntries());
//		for(int i=0;i<fileTable.length;i++){
//			System.out.println("文件table["+i+"]:");
//			System.out.println(fileTable[i]);
//		}
		boolean find=false;
		int fileIndex=0;
		for(int i=0;i<fileTable.length;i++){
			String fileName=new String(fileTable[i].getFileName()).trim();
			if (fileName.equals(extractResourceName)){
				find=true;
				fileIndex=i;
				break;
			}
		}
		if (find==false){
			System.out.println("沒有找到指定的文件");
			return null;
		}
		else{
			byte[] buff=readFileFromPak(dis,header,fileTable[fileIndex]);
			return buff;
		}
	}
	
	
	/**
	 * 從pak文件中取出指定的Pak文件的信息
	 * @param pakResourcePath  pak文件資源路徑
	 * @return 裝載文件頭和文件table數(shù)組的Vector
	 * @throws Exception
	 */
	public Vector showPakFileInfo(String pakResourcePath) throws Exception{
		InputStream is=this.getClass().getResourceAsStream(pakResourcePath);
		DataInputStream dis=new DataInputStream(is);
		
		PakHeader header=readHeader(dis);
		PakFileTable[] fileTable=readFileTable(dis,(int)header.getNumFileTableEntries());

		Vector result=new Vector();
		result.addElement(header);
		result.addElement(fileTable);
		return result;
	}
	
	public static void main(String[] argv) throws Exception{
		PakUtil pu=new PakUtil();
		String extractResourcePath="/test.pak";
		//從Pak文件中取出所有的圖片文件
		Vector pakInfo=pu.showPakFileInfo(extractResourcePath);
		PakHeader header=(PakHeader)pakInfo.elementAt(0);
		System.out.println("Pak文件信息:");
		System.out.println("文件頭:");
		System.out.println(header);
		
		PakFileTable[] fileTable=(PakFileTable[])pakInfo.elementAt(1);
		for(int i=0;i<fileTable.length;i++){
			System.out.println("文件table["+i+"]:");
			System.out.println(fileTable[i]);
		}
		
		String restoreFileName=null;
		byte[] fileBuff=null;
		for(int i=0;i<fileTable.length;i++){
			restoreFileName=new String(fileTable[i].getFileName()).trim();
			System.out.println("從Pak文件中取出"+restoreFileName+"文件數(shù)據(jù)...");
			fileBuff=pu.extractResourceFromPak(extractResourcePath,restoreFileName);
			System.out.println("從Pak文件中取出"+restoreFileName+"文件數(shù)據(jù)完成");
		}
	}
}