/*************************************************************************
 *  YOU DO NOT NEED TO MODIFY THIS FILE
 *
 *  Compilation:  javac Stitcher.java
 *  Execution:    java Stitcher img1.png img2.png xoffset yoffset [ ref.img ]
 *  Dependencies: ImageSeam.java CostMatrix.java Picture.java
 *
 *  Stitch img1 and img2 together using a dynamic program to compute
 *  the optimal seam between them.  Display the result, or show where
 *  it differs from a reference image if one is specified.
 *
 *  % java Stitcher sea1.png sea2.png 318 -7
 *  % java Stitcher sea1.png sea2.png 318 -7 sea-stitched.png
 *
 *************************************************************************/

import java.awt.Color;

public class Stitcher {
  public static void main(String[] args) {
    Picture img1 = new Picture(args[0]);
    int w1 = img1.width();
    int h1 = img1.height();

    Picture img2 = new Picture(args[1]);
    int w2 = img2.width();
    int h2 = img2.height();

    int offsetx = 0, offsety = 0;
    if (args.length > 3) {
      offsetx = Integer.parseInt(args[2]);
      offsety = Integer.parseInt(args[3]);
    }

    int x1 = 0, x2 = 0, y1 = 0, y2 = 0, w = 0, h = 0;

    if (offsetx >= 0) {
      x1 = offsetx;
      w = Math.min(w1 - offsetx, w2);
    } else {
      x2 = -offsetx;
      w = Math.min(w1, w2 + offsetx);
    }

    if (offsety >= 0) {
      y1 = offsety;
      h = Math.min(h1 - offsety, h2);
    } else {
      y2 = -offsety;
      h = Math.min(h1, h2 + offsety);
    }

    Picture a = new Picture(w, h);
    Picture b = new Picture(w, h);

    for (int row = 0; row < h; row++) {
      for (int col = 0; col < w; col++) {
        a.set(col, row, img1.get(col + x1, row + y1));
        b.set(col, row, img2.get(col + x2, row + y2));
      }
    }

    if (offsetx >= 0) {
      flipHorizontal(a);
      flipHorizontal(b);
    }

    if (offsety <= 0) {
      flipVertical(a);
      flipVertical(b);
    }

    ImageSeam seam = new ImageSeam(b, a);
    Path p = CostMatrix.costIterative(seam);
    System.out.println("Stitching cost is " + p.cost);
    seam.showSeam(p);
    Picture stitched = seam.getStitchedPicture(p);

    if (offsetx >= 0) {
      flipHorizontal(a);
      flipHorizontal(b);
      flipHorizontal(stitched);
    }

    if (offsety <= 0) {
      flipVertical(a);
      flipVertical(b);
      flipVertical(stitched);
    }

    int out_w = w1 + w2 - w;
    int out_h = h1 + h2 - h;
    Picture out = new Picture(out_w, out_h);

    for (int row = 0; row < h1; row++)
      for (int col = 0; col < w1; col++)
        out.set(col + x2, row + y2, img1.get(col, row));

    for (int row = 0; row < h2; row++)
      for (int col = 0; col < w2; col++)
        out.set(col + x1, row + y1, img2.get(col, row));

    for (int row = 0; row < h; row++)
      for (int col = 0; col < w; col++)
        out.set(col + x1 + x2, row + y1 + y2, stitched.get(col, row));

    if (args.length > 4) {
      Picture ground_truth = new Picture(args[4]);
      if (ground_truth.height() != out_h || ground_truth.width() != out_w) {
        System.out.println("The stitched image's dimensions (" + out_w + " x " + out_h +
                           ") differ from the ground truth image " + args[4] + "'s dimensions (" +
                           ground_truth.width() + " x " + ground_truth.height() + ").");
        for (int row = 0; row < out_h; row++)
          for (int col = 0; col < out_w; col++)
            out.set(col, row, Color.RED);
      } else {
        for (int row = 0; row < out_h; row++)
          for (int col = 0; col < out_w; col++)
            if (out.get(col, row).equals(ground_truth.get(col, row)))
              out.set(col, row, Color.WHITE);
            else out.set(col, row, Color.BLACK);
      }
    }

    out.show();
  }

  private static void flipHorizontal(Picture img) {
    int w = img.width();
    for (int row = 0; row < img.height(); row++) {
      for (int col = 0; col < w / 2; col++) {
        Color c = img.get(col, row);
        img.set(col, row, img.get(w - col - 1, row));
        img.set(w - col - 1, row, c);
      }
    }
  }

  private static void flipVertical(Picture img) {
    int h = img.height();
    for (int row = 0; row < h / 2; row++) {
      for (int col = 0; col < img.width(); col++) {
        Color c = img.get(col, row);
        img.set(col, row, img.get(col, h - row - 1));
        img.set(col, h - row - 1, c);
      }
    }
  }
}