// This program takes gzipped sorted files and merges them in sorted order
// to stdout. Written by Ulrich Germann
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/shared_ptr.hpp>
#include <algorithm>
#include <string>
#include <vector>
#include "moses/TranslationModel/UG/generic/file_io/ug_stream.h"
using namespace std;
using namespace ugdiss;
using namespace boost::iostreams;

typedef boost::shared_ptr<filtering_istream> fptr;

class Part
{
  string       fname;
  fptr             f;
  string my_lines[2];
  size_t         ctr;
public:
  string const& line() const {
    static string empty_line;
    return f ? my_lines[ctr%2] : empty_line;
  }

  Part(string _fname) : ctr(0) {
    fname = _fname;
    f.reset(open_input_stream(fname));
    if (!getline(*f, my_lines[0])) f.reset();
  }

  bool next() {
    if (!f) return false;
    if (!getline(*f, my_lines[++ctr%2])) {
      f.reset();
      --ctr;
      return false;
    }
    assert(my_lines[(ctr-1)%2] <= my_lines[ctr%2]);
    return true;
  }

  bool operator <(Part const& other) const {
    return line() < other.line();
  }

  bool operator <=(Part const& other) const {
    return line() <= other.line();
  }

  bool operator >(Part const& other) const {
    return line() > other.line();
  }

  bool operator >=(Part const& other) const {
    return line() >= other.line();
  }

  bool go(ostream& out) {
    if (!f) return false;
#if 0
    if (ctr) {
      out << fname << "-" << ctr - 1 << "-";
      out << my_lines[(ctr - 1)%2] << endl;
    }
    do {
      out << fname << " " << ctr << " ";
      out << line() << "\n";
    } while (next() && my_lines[0] == my_lines[1]);
#else
    do    {
      out << line() << "\n";
    } while (next() && my_lines[0] == my_lines[1]);
    out.flush();
#endif
    return f != NULL;
  }

};


int main(int argc, char* argv[])
{
  vector<Part> parts;
  for (int i = 1; i < argc; ++i)
    parts.push_back(Part(argv[i]));
  make_heap(parts.begin(), parts.end(), greater<Part>());
  while (parts.size()) {
    pop_heap(parts.begin(), parts.end(), greater<Part>());
    if (parts.back().go(cout))
      push_heap(parts.begin(), parts.end(), greater<Part>());
    else parts.pop_back();
  }
}