package org.apache.fop.render.ps;

import java.io.FilterOutputStream;
import java.io.OutputStream;
import java.io.IOException;


/**
 * This class applies a RunLengthEncodeOutputStream filter to the stream. 
 *
 *
 * @author <a href="mailto:smwolke@geistig.com">Stephen Wolke</a>
 * 
 */

public class RunLengthEncodeOutputStream extends FilterOutputStream implements Finalizable{

    private static final int MAX_SEQUENCE_COUNT = 127;
    private static final int END_OF_DATA = 128;
    private static final int BYTE_MAX = 256;

    private static final int NOT_IDENTIFY_SEQUENCE = 0;
    private static final int START_SEQUENCE = 1;
    private static final int IN_SEQUENCE = 2;
    private static final int NOT_IN_SEQUENCE = 3;

    private int runCount = 0;
    private int isSequence = NOT_IDENTIFY_SEQUENCE;
    private byte[] runBuffer = new byte[MAX_SEQUENCE_COUNT + 1];



    public RunLengthEncodeOutputStream(OutputStream out){
        super(out);
    }



    public void write(byte b) throws java.io.IOException {
        runBuffer[runCount] = b;

        switch (runCount){
        case 0:
            runCount = 0;
            isSequence = NOT_IDENTIFY_SEQUENCE;
            runCount++;
            break;
        case 1:
            if (runBuffer[runCount] != runBuffer[runCount-1])
                isSequence = NOT_IN_SEQUENCE;
            runCount++;
            break;
        case 2:
            if (runBuffer[runCount] != runBuffer[runCount-1])
                isSequence = NOT_IN_SEQUENCE;
            else
                if (isSequence == NOT_IN_SEQUENCE)
                    isSequence = START_SEQUENCE;
                else
                    isSequence = IN_SEQUENCE;
            runCount++;
            break;
        case MAX_SEQUENCE_COUNT:
            if(isSequence == IN_SEQUENCE){
                out.write(BYTE_MAX-(MAX_SEQUENCE_COUNT - 1));
                out.write(runBuffer[runCount-1]);
                runBuffer[0] = runBuffer[runCount];
                runCount = 1;
            }
            else{
                out.write(MAX_SEQUENCE_COUNT);
                out.write(runBuffer,0,runCount+1);
                runCount = 0;
            }
            isSequence = NOT_IDENTIFY_SEQUENCE;
            break;
        default:
            switch(isSequence){
            case IN_SEQUENCE:
                if (runBuffer[runCount] != runBuffer[runCount-1]){
                    out.write(BYTE_MAX-(runCount - 1));
                    out.write(runBuffer[runCount-1]);
                    runBuffer[0] = runBuffer[runCount];
                    runCount = 1;
                    isSequence = NOT_IDENTIFY_SEQUENCE;
                    break;
                }
                runCount++;
                break;
            case NOT_IN_SEQUENCE:
                if (runBuffer[runCount] == runBuffer[runCount-1])
                    isSequence = START_SEQUENCE;
                runCount++;
                break;

            case START_SEQUENCE:
                if (runBuffer[runCount] == runBuffer[runCount-1]){
                    out.write(runCount-3);
                    out.write(runBuffer,0,runCount-2);
                    runBuffer[0] = runBuffer[runCount];
                    runBuffer[1] = runBuffer[runCount];
                    runBuffer[2] = runBuffer[runCount];
                    runCount = 3;
                    isSequence = IN_SEQUENCE;
                    break;
                }
                else{
                    isSequence =  NOT_IN_SEQUENCE;
                    runCount++;
                    break;
                }
            }
        }
    }

    public  void write(byte[] b)throws IOException{
        int i;

        for(i=0;i < b.length;i++){
            this.write(b[i]);
        }
    }

    public  void write(byte[] b, int off, int len)throws IOException{
        int i;

        for(i=0;i < len;i++){
            this.write(b[off + i]);
        }
    }

    public void finalizeStream()throws IOException {
        switch (isSequence){
        case IN_SEQUENCE:
            out.write(BYTE_MAX-(runCount - 1));
            out.write(runBuffer[runCount-1]);
            break;
        default:
            out.write(runCount-1);
            out.write(runBuffer,0,runCount);
        }

        out.write(END_OF_DATA);

        flush();
        if (out instanceof Finalizable) {
            ((Finalizable)out).finalizeStream();
        }
    }


    public void close() throws IOException {
        finalizeStream();
        super.close();
    }

}