// llil.cpp. C++ 11 version of Perl llil.pl.
// g++ compile on Linux:
//   g++ -o llil -std=c++11 -Wall -O3 llil.cpp
// This g++ command also works with mingw C++ compiler (https://sourceforge.net/projects/mingw-w64)
// that comes bundled with Strawberry Perl (C:\Strawberry\c\bin\g++.exe).
// Example run: llil tt1.txt tt2.txt >out.txt

// Uncomment next line to sort by creating a multimap (instead of via the sort function)
// #define LLIL_SORT_VIA_MULTIMAP_L 1

#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <ctime>
#include <cstdio>

#include <string>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>

#include <algorithm>
#include <utility>

#include <iostream>
#include <fstream>
#include <sstream>

// ------------------------------------------------------------

// Performance hacks to speed up IO.
// See https://www.reddit.com/r/rust/comments/9xedap/how_to_achieve_fast_stdinstdout_io_suitable_for/
// Avoid flush by using "\n" instead of std::endl (this made a big difference in this program!)
// This one made almost no difference in this program:
//   const auto io_speed_up =[](){
//      std::ios::sync_with_stdio(false);
//      std::cin.tie(nullptr);
//      return nullptr;
//   }();

// ------------------------------------------------------------

using str_int_type     = std::pair<std::string, int>;
using map_str_int_type = std::unordered_map<std::string, int>;
using vec_str_int_type = std::vector<str_int_type>;

// Mimic the Perl get_properties subroutine
static void get_properties(
   int                nfiles,     //  in: the number of input files
   char*              fname[],    //  in: the input file names
   map_str_int_type&  hash_ret)   // out: a hash of properties
{
   for (int i = 0; i < nfiles; ++i) {
      std::ifstream llfile(fname[i]);
      if (!llfile) {
         std::cerr << "Error opening '" << fname[i] << "'\n";
         return;
      }
      for (std::string line; std::getline(llfile, line); ) {
         std::string word, count;
         std::stringstream ssline(line);
         std::getline(ssline, word, '\t');
         std::getline(ssline, count);
         hash_ret[word] += std::stoi(count);
      }
   }
}

#ifdef LLIL_SORT_VIA_MULTIMAP_L

// Convert a std::unordered_map<key, value> to a std::multimap<value, key>
static std::multimap<int, std::string> invert_map(const std::unordered_map<std::string, int>& m)
{
   std::multimap<int, std::string> mm;
   for (std::unordered_map<std::string, int>::const_iterator it = m.begin(); it != m.end(); ++it) {
      mm.insert( std::make_pair(it->second, it->first) );
   }
   return mm;
}

#endif

int main(int argc, char* argv[])
{
   if (argc < 2) {
      std::cerr << "usage: llil file1 file2 ... >out.txt\n";
      return 1;
   }

#ifdef LLIL_SORT_VIA_MULTIMAP_L
   std::cerr << "llil start (multimap version)\n";
#else
   std::cerr << "llil start (sort version)\n";
#endif
   time_t tstart1 = ::time(NULL);

   // Create the hash of properties
   map_str_int_type hash_ret;
   get_properties(argc - 1, &argv[1], hash_ret);
   time_t tend1 = ::time(NULL);
   long taken1  = static_cast<long>(::difftime(tend1, tstart1) + 0.5);
   std::cerr << "get_properties : " << taken1 << " secs\n";

   // Sort descending by value, i.e. mimic this Perl code in C++:
   //   sort { $href->{$b} <=> $href->{$a} || $a cmp $b } keys %{$href}

   time_t tstart2 = ::time(NULL);

#ifdef LLIL_SORT_VIA_MULTIMAP_L

   std::multimap<int, std::string> newmap = invert_map(hash_ret);
   for (std::multimap<int, std::string>::reverse_iterator it = newmap.rbegin(); it != newmap.rend(); ++it) {
      std::cout << it->second << '\t' << it->first << "\n"; 
   }

#else

   vec_str_int_type v( hash_ret.begin(), hash_ret.end() );
   std::sort( v.begin(), v.end(),
      [](const str_int_type& left, const str_int_type& right) { return right.second != left.second ? right.second < left.second : left.first < right.first; }
   );
   for ( const std::pair<const std::string, int>& n : v ) {
       std::cout << n.first << '\t' << n.second << "\n";
   }

#endif

   time_t tend2 = ::time(NULL);
   long taken2  = static_cast<long>(::difftime(tend2, tstart2) + 0.5);
   long taken   = static_cast<long>(::difftime(tend2, tstart1) + 0.5);
   std::cerr << "sort + output  : " << taken2 << " secs\n";
   std::cerr << "total          : " << taken << " secs\n";

   return 0;
}