/**
 * Manage rd5 diff-file creation
 *
 * @author ab
 */
package btools.mapaccess;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

final public class Rd5DiffManager {
  public static void main(String[] args) throws Exception {
    calcDiffs(new File(args[0]), new File(args[1]));
  }

  /**
   * Compute diffs for all RD5 files
   */
  public static void calcDiffs(File oldDir, File newDir) throws Exception {
    File oldDiffDir = new File(oldDir, "diff");
    File newDiffDir = new File(newDir, "diff");

    File[] filesNew = newDir.listFiles();

    for (File fn : filesNew) {
      String name = fn.getName();
      if (!name.endsWith(".rd5")) {
        continue;
      }
      if (fn.length() < 1024 * 1024) {
        continue; // exclude very small files from diffing
      }
      String basename = name.substring(0, name.length() - 4);
      File fo = new File(oldDir, name);
      if (!fo.isFile()) {
        continue;
      }

      // calculate MD5 of old file
      String md5 = getMD5(fo);

      String md5New = getMD5(fn);

      System.out.println("name=" + name + " md5=" + md5);

      File specificNewDiffs = new File(newDiffDir, basename);
      specificNewDiffs.mkdirs();

      String diffFileName = md5 + ".df5";
      File diffFile = new File(specificNewDiffs, diffFileName);

      String dummyDiffFileName = md5New + ".df5";
      File dummyDiffFile = new File(specificNewDiffs, dummyDiffFileName);
      dummyDiffFile.createNewFile();

      // calc the new diff
      Rd5DiffTool.diff2files(fo, fn, diffFile);

      // ... and add that to old diff files
      File specificOldDiffs = new File(oldDiffDir, basename);
      if (specificOldDiffs.isDirectory()) {
        File[] oldDiffs = specificOldDiffs.listFiles();
        for (File od : oldDiffs) {
          if (!od.getName().endsWith(".df5")) {
            continue;
          }
          if (System.currentTimeMillis() - od.lastModified() > 9 * 86400000L) {
            continue; // limit diff history to 9 days
          }

          File updatedDiff = new File(specificNewDiffs, od.getName());
          if (!updatedDiff.exists()) {
            Rd5DiffTool.addDeltas(od, diffFile, updatedDiff);
            updatedDiff.setLastModified(od.lastModified());
          }
        }
      }
    }
  }

  public static String getMD5(File f) throws IOException {
    try {
      MessageDigest md = MessageDigest.getInstance("MD5");
      BufferedInputStream bis = new BufferedInputStream(new FileInputStream(f));
      DigestInputStream dis = new DigestInputStream(bis, md);
      byte[] buf = new byte[8192];
      for (; ; ) {
        int len = dis.read(buf);
        if (len <= 0) {
          break;
        }
      }
      dis.close();
      byte[] bytes = md.digest();

      StringBuilder sb = new StringBuilder();
      for (int j = 0; j < bytes.length; j++) {
        int v = bytes[j] & 0xff;
        sb.append(hexChar(v >>> 4)).append(hexChar(v & 0xf));
      }
      return sb.toString();
    } catch (NoSuchAlgorithmException e) {
      throw new IOException("MD5 algorithm not available", e);
    }
  }

  private static char hexChar(int v) {
    return (char) (v > 9 ? 'a' + (v - 10) : '0' + v);
  }
}