import java.io.*;

/**
 * The class which performs the encoding process.
 * 
 * @author Amanda Askew & Dane Barney
 * @version 2003.09.11
 */
public class Encoder extends Endec {
    public BitWriter out;
    public int encodedBytes;

    /**
     * Initializes the output stream, creates a new arithmetic coder, initializes
     * all the contexts, and writes the file header (which precedes the actual encoded
     * data).
     * 
     * @param compressedFile the file to decode
     */
    public Encoder(Image inputImage, String outputFile, Coords[] contextCoords) throws IOException {
        out = new BitWriter(new DataOutputStream(new FileOutputStream(outputFile)));
        im = inputImage;
        ar = new ArithmeticCoder();
        this.contextCoords = contextCoords;

        // create all the possible contexts and store them in an array
        createContextArray();

        // write image header to file
        writeImgHeader();

        // write context coordinates to file
        writeContextCoords();
    }
    
    /**
     * Writes the image header data, which is the first thing stored
     * in the compressed file.
     */
    public void writeImgHeader() throws IOException {
        out.writeByte((byte)im.type); // first send the type of image
        // now send the header byte-by-byte
        for(int i=0; i < im.header.length; i++)
            out.writeByte(im.header[i]);
        // finally, write the dominant color in this image
        out.write4Bytes(im.dominantColor);
    }
    
    /**
     * Writes the pixel coordinates in the context used to encode this file
     * (so the decoder knows).
     */
    public void writeContextCoords() throws IOException {
        out.writeByte((byte)contextCoords.length); // first write total number of context coordinates to write
        for(int i=0; i < contextCoords.length; i++) {
            out.writeByte((byte)contextCoords[i].x); // 1st byte = x coord
            out.writeByte((byte)contextCoords[i].y); // 2nd byte = y coord
        }
    }
    
    /**
     * Encodes pixels from the image and writes to the output stream.
     */
    public void encode() throws IOException {
        int startingBytes = out.bytesWritten;

        // iterate through all the pixels in the pixel matrix
        for(int j=0; j < im.height; j++) {
            for(int i=0; i < im.width; i++) {
                int currentPixel = im.pixels[i][j];
                // locate the correct context for this particular pixel
                Context context = findContext(i,j);
                
                // send this pixel to the arithmetic coder
                ar.encodeValue(currentPixel, context, out);
            }
        }
  	ar.finishEncode(out);
	out.finish();
        encodedBytes = out.bytesWritten - startingBytes;
        
        out.close();
    }
    
}