sclass LineCompReader {
  new LS literals;
  new LPair<Int> pairs;
  new LinkedHashMap<S, L<Int>> versions;

  // takes .filecomp (text) or .filecomp.gz (gzipped)
  *(File f) {
    temp BufferedReader reader = rawByteReader_possiblyGZipped(f);
    load(reader);
  }
  
  *(BufferedReader reader) { load(reader); }
  
  void load(BufferedReader reader) ctex {
    S s = reader.readLine();
    new Matches m;
    if (!startsWith(s, "LINECOMP ", m)) fail("Not a LINECOMP file");
    int nLiterals = parseInt(m.rest());
    for i to nLiterals:
      literals.add(assertNotNull(reader.readLine()));
    while licensed {
      s = reader.readLine();
      if (s == null || contains(s, "=")) break;
      pairs.add(assertNotNull(listToPair(parseInts(splitAtSpace(s)))));
    }
    while (contains(s, "=")) {
      int i = indexOf(s, '=');
      versions.put(takeFirst(s, i), parseInts(splitAtSpace(substring(s, i+1))));
      s = reader.readLine();
    }
  }
  
  Set<S> versions() { ret keys(versions); }
  
  S getText(S version) { ret textForVersion(version); }
  S textForVersion(S version) {
    L<Int> encoded = versions.get(version);
    if (encoded == null) null;
    new LS buf;
    for (int idx : encoded)
      decode(idx, buf);
    ret myFromLines(buf);
  }
  
  S myFromLines(LS l) { ret fromLines_rtrim(l); }
  
  void decode(int idx, LS buf) {
    if (idx < l(literals))
      buf.add(literals.get(idx));
    else {
      Pair<Int> p = pairs.get(idx-l(literals));
      decode(p.a, buf);
      decode(p.b, buf);
    }
  }
}