package at.gv.egiz.asic.impl;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Created by afitzek on 6/15/16.
 */
public class ZipCommentReaderStream extends InputStream {

    private InputStream inputStream;

    private int[] tempBuffer = new int[22];

    private int[] commentBuffer = null;

    private int commentBufferContentLen = 0;
    private int commentBufferContentOff = 0;

    private int tempBufferContentLen = 0;
    private int tempBufferContentOff = 0;

    private String fileComment = null;

    private static final byte[] directoryRecord = new byte[] { (byte)0x50, (byte)0x4b, 0x05, 0x06  };

    public ZipCommentReaderStream(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    private int readIntIntoBuffer() throws IOException {
        int tValue = this.inputStream.read();

        if(this.tempBuffer.length <= tempBufferContentOff) {
            throw new IOException("Temp Buffer is out of space! @ " + tempBufferContentOff);
        }

        this.tempBuffer[tempBufferContentOff] = tValue;
        tempBufferContentOff++;
        tempBufferContentLen++;

        return tValue;
    }

    private int readIntIntoCommentBuffer() throws IOException {
        int tValue = this.inputStream.read();

        if(this.commentBuffer.length <= commentBufferContentOff) {
            throw new IOException("Comment Buffer is out of space! @ " + commentBufferContentOff);
        }

        this.commentBuffer[commentBufferContentOff] = tValue;
        commentBufferContentOff++;
        commentBufferContentLen++;

        return tValue;
    }

    private void checkMagicBytes() throws IOException {
        boolean foundMagic = true;
        tempBufferContentOff = 0;
        tempBufferContentLen = 0;
        for(int i = 1; i < directoryRecord.length; i++) {
            int tValue = readIntIntoBuffer();
            if(tValue != directoryRecord[i]) {
                foundMagic = false;
                break;
            }
            if(tValue < 0) {
                // Found EOF
                return;
            }
        }

        if(foundMagic) {
            // read input stream until comment length
            for(int i = 0; i < 16; i++) {
                int tValue = readIntIntoBuffer();

                if(tValue < 0) {
                    // Found EOF
                    return;
                }
            }

            int commentlengthHigh = readIntIntoBuffer();

            if(commentlengthHigh < 0) {
                // Found EOF
                return;
            }

            int commentlengthLow = readIntIntoBuffer();

            if(commentlengthLow < 0) {
                // Found EOF
                return;
            }

            int commentLength = commentlengthLow * 255 + commentlengthHigh;

            if(commentLength == 0) {
                return;
            }

            this.commentBuffer = new int[commentLength];

            commentBufferContentOff = 0;
            commentBufferContentLen = 0;

            // read comment buffer string
            for(int i = 0; i < commentLength; i++) {
                int tValue = readIntIntoCommentBuffer();

                if(tValue < 0) {
                    // Found EOF
                    return;
                }
            }

            byte[] stringBuffer = new byte[this.commentBuffer.length];

            for(int i = 0; i < stringBuffer.length; i++) {
                stringBuffer[i] = (byte)this.commentBuffer[i];
            }

            this.fileComment = new String(stringBuffer);
        }
    }

    @Override
    public int read() throws IOException {
        int value = -1;
        if(tempBufferContentLen > 0) {
            value = this.tempBuffer[tempBufferContentOff];
            tempBufferContentOff++;

            // reset temp buffer
            if(tempBufferContentOff >= tempBufferContentLen) {
                tempBufferContentOff = 0;
                tempBufferContentLen = 0;
            }

            return value;
        }

        if(this.commentBuffer != null) {
            value = this.commentBuffer[commentBufferContentOff];

            commentBufferContentOff++;

            // reset comment buffer
            if(commentBufferContentOff >= commentBufferContentLen) {
                commentBufferContentOff = 0;
                commentBufferContentLen = 0;
                this.commentBuffer = null;
            }

            return value;
        }

        value = this.inputStream.read();

        if(value == directoryRecord[0] && this.fileComment == null) {
            // might have found start of magic bytes
            checkMagicBytes();
            // reset buffer offsets
            tempBufferContentOff = 0;
            commentBufferContentOff = 0;
        }

        return value;
    }

    public String getFileComment() {
        return this.fileComment;
    }
}