import java.io.*;
import java.nio.ByteOrder;
import java.util.*;
import libcore.io.BufferIterator;
import libcore.util.ZoneInfo;

// usage: java ZoneCompiler <setup file> <data directory> <output directory> <tzdata version>
//
// Compile a set of tzfile-formatted files into a single file containing an index.
//
// The compilation is controlled by a setup file, which is provided as a
// command-line argument.  The setup file has the form:
//
// Link <toName> <fromName>
// ...
// <zone filename>
// ...
//
// Note that the links must be declared prior to the zone names.
// A zone name is a filename relative to the source directory such as
// 'GMT', 'Africa/Dakar', or 'America/Argentina/Jujuy'.
//
// Use the 'zic' command-line tool to convert from flat files
// (such as 'africa' or 'northamerica') to a directory
// hierarchy suitable for this tool (containing files such as 'data/Africa/Abidjan').
//

public class ZoneCompactor {
  public static class ByteArrayBufferIteratorBE extends BufferIterator {
    private final byte[] bytes;
    private int offset = 0;

    public ByteArrayBufferIteratorBE(byte[] bytes) {
      this.bytes = bytes;
      this.offset = 0;
    }

    public void seek(int offset) {
      this.offset = offset;
    }

    public void skip(int byteCount) {
      this.offset += byteCount;
    }

    public void readByteArray(byte[] dst, int dstOffset, int byteCount) {
      System.arraycopy(bytes, offset, dst, dstOffset, byteCount);
      offset += byteCount;
    }

    public byte readByte() {
      return bytes[offset++];
    }

    public int readInt() {
      return ((readByte() & 0xff) << 24) | ((readByte() & 0xff) << 16) | ((readByte() & 0xff) << 8) | (readByte() & 0xff);
    }

    public void readIntArray(int[] dst, int dstOffset, int intCount) {
      for (int i = 0; i < intCount; ++i) {
        dst[dstOffset++] = readInt();
      }
    }

    public short readShort() {
      throw new UnsupportedOperationException();
    }
  }

  // Maximum number of characters in a zone name, including '\0' terminator
  private static final int MAXNAME = 40;

  // Zone name synonyms
  private Map<String,String> links = new HashMap<String,String>();

  // File starting bytes by zone name
  private Map<String,Integer> starts = new HashMap<String,Integer>();

  // File lengths by zone name
  private Map<String,Integer> lengths = new HashMap<String,Integer>();

  // Raw GMT offsets by zone name
  private Map<String,Integer> offsets = new HashMap<String,Integer>();
  private int start = 0;

  // Concatenate the contents of 'inFile' onto 'out'
  // and return the contents as a byte array.
  private static byte[] copyFile(File inFile, OutputStream out) throws Exception {
    byte[] ret = new byte[0];

    InputStream in = new FileInputStream(inFile);
    byte[] buf = new byte[8192];
    while (true) {
      int nbytes = in.read(buf);
      if (nbytes == -1) {
        break;
      }
      out.write(buf, 0, nbytes);

      byte[] nret = new byte[ret.length + nbytes];
      System.arraycopy(ret, 0, nret, 0, ret.length);
      System.arraycopy(buf, 0, nret, ret.length, nbytes);
      ret = nret;
    }
    out.flush();
    return ret;
  }

  public ZoneCompactor(String setupFile, String dataDirectory, String outputDirectory, String version) throws Exception {
    // Read the setup file, and concatenate all the data.
    ByteArrayOutputStream allData = new ByteArrayOutputStream();
    BufferedReader reader = new BufferedReader(new FileReader(setupFile));
    String s;
    while ((s = reader.readLine()) != null) {
      s = s.trim();
      if (s.startsWith("Link")) {
        StringTokenizer st = new StringTokenizer(s);
        st.nextToken();
        String to = st.nextToken();
        String from = st.nextToken();
        links.put(from, to);
      } else {
        String link = links.get(s);
        if (link == null) {
          File sourceFile = new File(dataDirectory, s);
          long length = sourceFile.length();
          starts.put(s, start);
          lengths.put(s, (int) length);

          start += length;
          byte[] data = copyFile(sourceFile, allData);

          BufferIterator it = new ByteArrayBufferIteratorBE(data);
          TimeZone tz = ZoneInfo.makeTimeZone(s, it);
          int gmtOffset = tz.getRawOffset();
          offsets.put(s, gmtOffset);
        }
      }
    }

    // Fill in fields for links.
    Iterator<String> it = links.keySet().iterator();
    while (it.hasNext()) {
      String from = it.next();
      String to = links.get(from);

      starts.put(from, starts.get(to));
      lengths.put(from, lengths.get(to));
      offsets.put(from, offsets.get(to));
    }

    // Create/truncate the destination file.
    RandomAccessFile f = new RandomAccessFile(new File(outputDirectory, "tzdata"), "rw");
    f.setLength(0);

    // Write the header.

    // byte[12] tzdata_version          -- 'tzdata2012f\0'
    // int file_format_version          -- probably won't need this, but just in case
    // int index_offset                 -- likewise
    // int data_offset
    // int zonetab_offset

    // tzdata_version
    f.write(toAscii(new byte[12], version));

    // file_format_version
    f.writeInt(1);

    // Write dummy values for the three offsets, and remember where we need to seek back to later
    // when we have the real values.
    int index_offset_offset = (int) f.getFilePointer();
    f.writeInt(0);
    int data_offset_offset = (int) f.getFilePointer();
    f.writeInt(0);
    int zonetab_offset_offset = (int) f.getFilePointer();
    f.writeInt(0);

    int index_offset = (int) f.getFilePointer();

    // Write the index.
    ArrayList<String> sortedOlsonIds = new ArrayList<String>();
    sortedOlsonIds.addAll(starts.keySet());
    Collections.sort(sortedOlsonIds);
    it = sortedOlsonIds.iterator();
    while (it.hasNext()) {
      String zoneName = it.next();
      if (zoneName.length() >= MAXNAME) {
        throw new RuntimeException("zone filename too long: " + zoneName.length());
      }

      f.write(toAscii(new byte[MAXNAME], zoneName));
      f.writeInt(starts.get(zoneName));
      f.writeInt(lengths.get(zoneName));
      f.writeInt(offsets.get(zoneName));
    }

    int data_offset = (int) f.getFilePointer();

    // Write the data.
    f.write(allData.toByteArray());

    // TODO: append the zonetab.
    int zonetab_offset = 0;

    // Go back and fix up the offsets in the header.
    f.seek(index_offset_offset);
    f.writeInt(index_offset);
    f.seek(data_offset_offset);
    f.writeInt(data_offset);
    f.seek(zonetab_offset_offset);
    f.writeInt(zonetab_offset);

    f.close();
  }

  private static byte[] toAscii(byte[] dst, String src) {
    for (int i = 0; i < src.length(); ++i) {
      if (src.charAt(i) > '~') {
        throw new RuntimeException("non-ASCII string: " + src);
      }
      dst[i] = (byte) src.charAt(i);
    }
    return dst;
  }

  public static void main(String[] args) throws Exception {
    if (args.length != 4) {
      System.err.println("usage: java ZoneCompactor <setup file> <data directory> <output directory> <tzdata version>");
      System.exit(0);
    }
    new ZoneCompactor(args[0], args[1], args[2], args[3]);
  }
}