// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// llil4tkh2.cc
// A tkrzw::HashDBM demonstration.
// https://www.perlmonks.com/?node_id=11149643
//
// April 25, 2024
//    Based on llil3m.cpp  https://perlmonks.com/?node_id=11149482
//    Original challenge   https://perlmonks.com/?node_id=11147822
//         and summary     https://perlmonks.com/?node_id=11150293
//    Other demonstrations https://perlmonks.com/?node_id=11149907
//
// Authors
//    Mario Roy - C++ demonstration with parallel capabilities
//    eyepopslikeamosquito - Co-author, learning C++ at PerlMonks.com
//
// See also, memory efficient variant
//    https://gist.github.com/marioroy/d02881b96b20fa1adde4388b3e216163
//
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// OpenMP Little Book - https://nanxiao.gitbooks.io/openmp-little-book
//
// On macOS, use g++-12 from https://brew.sh (installation: brew install gcc@12).
//
// This demonstration requires the Tkrzw C++ library.
//  - homepage       https://dbmx.net/tkrzw/
//  - C++ source     https://dbmx.net/tkrzw/pkg/
//  - documentation  https://dbmx.net/tkrzw/api/
//  - GitHub page    https://github.com/estraier/tkrzw
//  - installation:
//    on Linux: ./configure
//    on macOS: CC=gcc-12 CXX=g++-12 ./configure
//    make
//    make install  # Note: you may need to use "sudo"
//
// The Tkrzw bundled command "tkrzw_build_util" is useful to know the include and LDFLAGS.
//    tkrzw_build_util config -i
//    tkrzw_build_util config -l
//
// Compile on Linux (clang++ or g++):
//    clang++ -o llil4tkh2 -std=c++20 -fopenmp -Wall -O3 llil4tkh2.cc -I/usr/local/include -L/usr/local/lib -ltkrzw -lstdc++ -lrt -latomic -lpthread -lm -lc
//
// Compile on macOS (g++-12):
//    g++-12 -o llil4tkh2 -std=c++20 -fopenmp -Wall -O3 llil4tkh2.cc -I/usr/local/include -L/usr/local/lib -ltkrzw -lstdc++ -latomic -lpthread -lm -lc
//
// Obtain gen-llil.pl and gen-long-llil.pl from https://perlmonks.com/?node_id=11148681
//    perl gen-llil.pl big1.txt 200 3 1
//    perl gen-llil.pl big2.txt 200 3 1
//    perl gen-llil.pl big3.txt 200 3 1
//
// To make random input, obtain shuffle.pl from https://perlmonks.com/?node_id=11149800
//    perl shuffle.pl big1.txt >tmp && mv tmp big1.txt
//    perl shuffle.pl big2.txt >tmp && mv tmp big2.txt
//    perl shuffle.pl big3.txt >tmp && mv tmp big3.txt
//
// Example run:  llil4tkh2 big1.txt big2.txt big3.txt >out.txt
// TMPDIR=/dev/shm NUM_THREADS=8 NUM_MAPS=32 llil4tkh2 ...
// TMPDIR=/dev/shm NUM_THREADS=max NUM_MAPS=max llil4tkh2 ...
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <cassert>
#include <cstdio>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <compare>
#include <chrono>

#include <string>
#include <string_view>

#include <array>
#include <vector>

#include <thread>
#include <execution>
#include <atomic>

#include <iomanip>
#include <iostream>
#include <fstream>

#include <unistd.h>
#include <filesystem>
namespace fs = std::filesystem;

#include <tkrzw_dbm_common_impl.h>
#include <tkrzw_dbm_hash.h>
#include <tkrzw_str_util.h>

static_assert(sizeof(size_t) == sizeof(int64_t), "size_t too small, need a 64-bit compile");

// Specify 0/1 to use boost's parallel sorting algorithm; faster than __gnu_parallel::sort.
// https://www.boost.org/doc/libs/1_85_0/libs/sort/doc/html/sort/parallel.html
// https://www.boost.org/doc/libs/1_85_0/libs/sort/doc/papers/block_indirect_sort_en.pdf
// This requires the boost header files: e.g. devpkg-boost bundle on Clear Linux.
// Note: Another option is downloading and unpacking Boost locally.
// (no need to build it because the bits we use are header file only)
#define USE_BOOST_PARALLEL_SORT 1

#if USE_BOOST_PARALLEL_SORT
   #ifdef __clang__
      #pragma clang diagnostic push
      #pragma clang diagnostic ignored "-Wunused-parameter"
      #pragma clang diagnostic ignored "-Wshadow"
      #include <boost/sort/sort.hpp>
      #pragma clang diagnostic pop
   #else
      #include <boost/sort/sort.hpp>
   #endif
#endif

#ifdef _OPENMP
   #include <omp.h>
#endif

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

typedef int64_t int_type;

// All words in big1.txt, big2.txt, big3.txt are <= 6 chars in length.
// big.txt  max word length is 6
// long.txt max word length is 208
//
// Based on rough benchmarking, the short fixed string hack below is only
// worth trying for MAX_STR_LEN_L up to about 30.
// See also https://backlinko.com/google-keyword-study
//
// To use (limited length) fixed length strings uncomment the next line.
#define MAX_STR_LEN_L (size_t) 12

#ifdef MAX_STR_LEN_L
struct str_type : std::array<char, MAX_STR_LEN_L> {
   bool operator==( const str_type& o ) const {
      return ::memcmp(this->data(), o.data(), MAX_STR_LEN_L) == 0;
   }
   bool operator<( const str_type& o ) const {
      return ::memcmp(this->data(), o.data(), MAX_STR_LEN_L) < 0;
   }
};
#else
using str_type = std::basic_string<char>;
#endif

using str_int_type     = std::pair<str_type, int_type>;
using vec_str_int_type = std::vector<str_int_type>;

// Mimic the Perl get_properties subroutine ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// convert positive number from string to uint32_t
inline uint32_t fast_atoll64(const char* str)
{
   uint32_t val = 0;
   uint8_t digit;
   while ((digit = uint8_t(*str++ - '0')) <= 9)
      val = val * 10 + digit;
   return val;
}

// Helper function to find a character.
inline char* find_char(char* first, char* last, char c)
{
   while (first != last) {
      if (*first == c) break;
      ++first;
   }
   return first;
}

// Limit line length and chunk size.
inline constexpr size_t MAX_LINE_LEN = 255;
inline constexpr size_t CHUNK_SIZE   = 32768;
inline constexpr int    MAX_NUM_MAPS = 255;

static int64_t get_properties(
   const char*        fname,     // in   : the input file name
   const int          nthds,     // in   : the number of threads
   const int          nmaps,     // in   : the number of maps (or shards)
   auto&              dbm_ret)   // inout: the dbm to be updated
{
   int64_t num_lines = 0;
   std::ifstream fin(fname, std::ifstream::binary);
   if (!fin.is_open()) {
      std::cerr << "Error opening '" << fname << "' : " << strerror(errno) << '\n';
      return num_lines;
   }

   #pragma omp parallel reduction(+:num_lines)
   {
      std::string buf;
      buf.resize(CHUNK_SIZE + MAX_LINE_LEN + 1, '\0');

      while (fin.good()) {
         size_t len = 0;

         // Read the next chunk serially.
         #pragma omp critical
         {
            fin.read(&buf[0], CHUNK_SIZE);
            if ((len = fin.gcount()) > 0) {
               if (buf[len - 1] != '\n' && fin.getline(&buf[len], MAX_LINE_LEN)) {
                  // Getline discards the newline char and appends null char.
                  // Therefore, change '\0' to '\n'.
                  len += fin.gcount();
                  buf[len - 1] = '\n';
               }
            }
         }

         if (!len)
            break;

         buf[len]    = '\0';
         char *first = &buf[0];
         char *last  = &buf[len];

         // Process max Nthreads chunks concurrently.
         while (first < last) {
            char* beg_ptr{first};
            char* end_ptr{find_char(first, last, '\n')};
            char* found = find_char(beg_ptr, end_ptr, '\t');

            first = end_ptr + 1;
            if (found == end_ptr)
               continue;

            assert(*found == '\t');
            int_type count = fast_atoll64(found + 1);
#ifdef MAX_STR_LEN_L
            size_t klen = std::min(MAX_STR_LEN_L, (size_t)(found - beg_ptr));
#else
            size_t klen = found - beg_ptr;
#endif

            std::basic_string_view<char> key {
               reinterpret_cast<const char*>(beg_ptr), klen };

            size_t idx = tkrzw::SecondaryHash(key, nmaps);
            dbm_ret[idx].IncrementSimple(key, count);

            ++num_lines;
         }
      }
   }

   fin.close();
   // std::cerr << "getprops done\n";
   return num_lines;
}

// Output subroutine ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

size_t divide_up(size_t dividend, size_t divisor)
{
   if (dividend % divisor)
      return (size_t)(dividend / divisor) + 1;
   else
      return (size_t)(dividend / divisor);
}

static void out_properties(
   const int          nthds,     // in   : the number of threads
   vec_str_int_type&  vec)       // in   : the vector to output
{
   size_t num_chunks = divide_up(vec.size(), CHUNK_SIZE);
   int nthds_out = 1;
#ifdef _OPENMP
   nthds_out = std::min(nthds, 32);
#endif

   #pragma omp parallel for ordered schedule(static, 1) num_threads(nthds_out)
   for (size_t chunk_id = 1; chunk_id <= num_chunks; ++chunk_id) {
      std::string str(""); str.reserve(2048 * 1024);
      auto it  = vec.begin() + (chunk_id - 1) * CHUNK_SIZE;
      auto it2 = vec.begin() + std::min(vec.size(), chunk_id * CHUNK_SIZE);

      for (; it != it2; ++it) {
#ifdef MAX_STR_LEN_L
         str.append(it->first.data());
#else
         str.append(it->first.data(), it->first.size());
#endif
         str.append("\t", 1);
         str.append(std::to_string(it->second));
         str.append("\n", 1);
      }

      #pragma omp ordered
      std::cout << str << std::flush;
   }
}

typedef std::chrono::high_resolution_clock high_resolution_clock;
typedef std::chrono::high_resolution_clock::time_point time_point;
typedef std::chrono::milliseconds milliseconds;

double elaspe_time(time_point cend, time_point cstart) {
   return double (
      std::chrono::duration_cast<milliseconds>(cend - cstart).count()
   ) * 1e-3;
}

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

int main(int argc, char* argv[])
{
   if (argc < 2) {
      if (argc > 0)
         std::cerr << "usage: llil4tkh2 file1 file2 ... >out.txt\n";
      return 1;
   }

   // Determine the temp dir to use.
   fs::path tmpdir = fs::temp_directory_path();
   const char* env_tmpdir = std::getenv("TMPDIR");
   if (env_tmpdir && strlen(env_tmpdir))
      tmpdir.assign(env_tmpdir);
   else if (fs::is_directory("/dev/shm") && !access("/dev/shm", W_OK))
      tmpdir.assign("/dev/shm");

#ifdef _OPENMP
   // Determine the number of maps (or shards).
   const char* env_nmaps = std::getenv("NUM_MAPS");
   int nmaps = (env_nmaps && strlen(env_nmaps))
      ? (::strcmp(env_nmaps, "max") == 0) ? MAX_NUM_MAPS : ::atoi(env_nmaps)
      : 32;
   if (nmaps <= 0) nmaps = 32;
   if (nmaps > MAX_NUM_MAPS) nmaps = MAX_NUM_MAPS;

   // Determine the number of threads.
   const char* env_nthds = std::getenv("NUM_THREADS");
   int ncpus = std::thread::hardware_concurrency();
   int nthds = (env_nthds && strlen(env_nthds))
      ? (::strcmp(env_nthds, "max") == 0) ? ncpus : ::atoi(env_nthds)
      : ncpus;
   if (nthds <= 0) nthds = ncpus;

   omp_set_dynamic(false);
   omp_set_num_threads(nthds);
#else
   int nmaps = 1;
   int nthds = 1;
#endif

   std::cerr << std::setprecision(3) << std::setiosflags(std::ios::fixed);
#ifdef MAX_STR_LEN_L
   std::cerr << "llil4tkh (fixed string length=" << MAX_STR_LEN_L; 
#else
   std::cerr << "llil4tkh (fixed string length=unlimited";
#endif
   std::cerr << ", threads=" << nthds << ", maps=" << nmaps << ") start\n";
   std::cerr << "sharding managed by the application\n";
#ifdef _OPENMP
   std::cerr << "use OpenMP\n";
#else
   std::cerr << "don't use OpenMP\n";
#endif
#if USE_BOOST_PARALLEL_SORT == 0
   std::cerr << "don't use boost sort\n";
#else
   std::cerr << "use boost sort\n";
#endif
   time_point cstart1, cend1, cstart2, cend2, cstart3, cend3s, cend3;
   cstart1 = high_resolution_clock::now();

   // Get the list of input files from the command line.
   int    nfiles = argc - 1;
   char** fname  = &argv[1];
   char   path[255];

   // Sharding is managed by the application.
   std::array<tkrzw::HashDBM, MAX_NUM_MAPS> dbm;

   for (int i = 0; i < nmaps; ++i) {
      std::sprintf(path, "%s/llil.tkh-%05d-of-%05d", tmpdir.c_str(), i, nmaps);
      dbm[i].Open(
         path, true,
         tkrzw::File::OPEN_DEFAULT | tkrzw::File::OPEN_TRUNCATE
      ).OrDie();
   }

   // Load properties into the DB.
   int64_t num_lines = 0;
   for (int i = 0; i < nfiles; ++i)
      num_lines += get_properties(fname[i], nthds, nmaps, dbm);

   int64_t num_keys = 0;
   for (int i = 0; i < nmaps; ++i)
      num_keys += dbm[i].CountSimple();

   cend1 = high_resolution_clock::now();
   double ctaken1 = elaspe_time(cend1, cstart1);
   std::cerr << "get properties      " << std::setw(8) << ctaken1 << " secs\n";

   if (num_keys <= 0) {
      std::cerr << "No work, exiting...\n";
      return 1;
   }

   cstart2 = high_resolution_clock::now();

   // Store the properties into a vector
   vec_str_int_type propvec; propvec.reserve(num_keys);

   #pragma omp parallel for schedule(static, 1)
   for (int i = 0; i < nmaps; ++i) {
      int64_t num_keys = dbm[i].CountSimple();

      if (num_keys > 0) {
         vec_str_int_type locvec; locvec.reserve(num_keys);

#ifdef MAX_STR_LEN_L
         str_type str;
#endif
         std::string key, value;
         std::unique_ptr<tkrzw::DBM::Iterator> iter = dbm[i].MakeIterator();
         iter->First();

         while (iter->Get(&key, &value) == tkrzw::Status::SUCCESS) {
#ifdef MAX_STR_LEN_L
            ::memset(str.data(), '\0', str.size());
            ::memcpy(str.data(), key.data(), key.size());
            locvec.emplace_back(str, tkrzw::StrToIntBigEndian(value));
#else
            locvec.emplace_back(key, tkrzw::StrToIntBigEndian(value));
#endif
            iter->Next();
         }

         #pragma omp critical
         propvec.insert(
            // Append local vector to propvec
            propvec.end(), 
            std::make_move_iterator(locvec.begin()),
            std::make_move_iterator(locvec.end())
         );
      }

      dbm[i].Close();
   }

   // Remove the temp DB files.
   for (int i = 0; i < nmaps; ++i) {
      std::sprintf(path, "%s/llil.tkh-%05d-of-%05d", tmpdir.c_str(), i, nmaps);
      fs::remove(path);
   }

   cend2 = high_resolution_clock::now();
   double ctaken2 = elaspe_time(cend2, cstart2);
   std::cerr << "hashDBMs to vector  " << std::setw(8) << ctaken2 << " secs\n";

   cstart3 = high_resolution_clock::now();

   // Sort the vector by (count) in reverse order, (name) in lexical order
   auto reverse_order = [](const str_int_type& left, const str_int_type& right) {
      return left.second != right.second
         ? left.second > right.second
         : left.first  < right.first;
   };
#if USE_BOOST_PARALLEL_SORT == 0
   // Standard sort
   std::sort(propvec.begin(), propvec.end(), reverse_order);
#else
   // Parallel sort
   boost::sort::block_indirect_sort(
      propvec.begin(), propvec.end(), reverse_order,
   #ifdef __NVCOMPILER_LLVM__
      std::min(nthds, 32)
   #else
      nthds
   #endif
   );
#endif

   cend3s = high_resolution_clock::now();

   // Output the sorted vector
   out_properties(nthds, propvec);
   cend3 = high_resolution_clock::now();

   double ctaken   = elaspe_time(cend3, cstart1);
   double ctaken3s = elaspe_time(cend3s, cstart3);
   double ctaken3o = elaspe_time(cend3, cend3s);

   std::cerr << "vector stable sort  " << std::setw(8) << ctaken3s << " secs\n";
   std::cerr << "write stdout        " << std::setw(8) << ctaken3o << " secs\n";
   std::cerr << "total time          " << std::setw(8) << ctaken   << " secs\n";
   std::cerr << "    count lines     " << num_lines << "\n";
   std::cerr << "    count unique    " << num_keys << "\n";

   // Hack to see Private Bytes in Windows Task Manager
   // (uncomment next line so process doesn't exit too quickly)
   // std::this_thread::sleep_for(milliseconds(9000));

   return 0;
}