// Copyright (C) 2011, 2012  Strahinja Val Markovic  <val@markovic.io>
//
// This file is part of YouCompleteMe.
//
// YouCompleteMe is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// YouCompleteMe is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with YouCompleteMe.  If not, see <http://www.gnu.org/licenses/>.

#include "ClangCompleter.h"
#include "exceptions.h"
#include "Result.h"
#include "Candidate.h"
#include "TranslationUnit.h"
#include "standard.h"
#include "CandidateRepository.h"
#include "CompletionData.h"
#include "ConcurrentLatestValue.h"
#include "Utils.h"
#include "ClangUtils.h"

#include <clang-c/Index.h>
#include <boost/make_shared.hpp>

using boost::bind;
using boost::cref;
using boost::function;
using boost::lock_guard;
using boost::make_shared;
using boost::mutex;
using boost::packaged_task;
using boost::ref;
using boost::shared_lock;
using boost::shared_mutex;
using boost::shared_ptr;
using boost::thread;
using boost::thread_interrupted;
using boost::try_to_lock_t;
using boost::unique_future;
using boost::unique_lock;
using boost::unordered_map;

namespace YouCompleteMe {

extern const unsigned int MAX_ASYNC_THREADS;
extern const unsigned int MIN_ASYNC_THREADS;

namespace {

struct CompletionDataAndResult {
  CompletionDataAndResult( const CompletionData *completion_data,
                           const Result &result )
    : completion_data_( completion_data ), result_( result ) {}

  bool operator< ( const CompletionDataAndResult &other ) const {
    return result_ < other.result_;
  }

  const CompletionData *completion_data_;
  Result result_;
};


} // unnamed namespace


ClangCompleter::ClangCompleter()
  : candidate_repository_( CandidateRepository::Instance() ),
    threading_enabled_( false ),
    time_to_die_( false ),
    clang_data_ready_( false ) {
  clang_index_ = clang_createIndex( 0, 0 );
}


ClangCompleter::~ClangCompleter() {
  // We need to clear this before calling clang_disposeIndex because the
  // translation units need to be destroyed before the index is destroyed.
  filename_to_translation_unit_.clear();
  clang_disposeIndex( clang_index_ );

  {
    unique_lock< shared_mutex > lock( time_to_die_mutex_ );
    time_to_die_ = true;
  }

  sorting_threads_.interrupt_all();
  sorting_threads_.join_all();

  clang_thread_.interrupt();
  clang_thread_.join();
}


// We need this mostly so that we can not use it in tests. Apparently the
// GoogleTest framework goes apeshit on us (on some platforms, in some
// occasions) if we enable threads by default.
void ClangCompleter::EnableThreading() {
  threading_enabled_ = true;
  InitThreads();
}


std::vector< Diagnostic > ClangCompleter::DiagnosticsForFile(
  const std::string &filename ) {
  shared_ptr< TranslationUnit > unit;
  {
    lock_guard< mutex > lock( filename_to_translation_unit_mutex_ );
    unit = FindWithDefault(
             filename_to_translation_unit_,
             filename,
             shared_ptr< TranslationUnit >() );
  }

  if ( !unit )
    return std::vector< Diagnostic >();

  return unit->LatestDiagnostics();
}


bool ClangCompleter::UpdatingTranslationUnit( const std::string &filename ) {
  shared_ptr< TranslationUnit > unit;
  {
    lock_guard< mutex > lock( filename_to_translation_unit_mutex_ );
    unit = FindWithDefault(
             filename_to_translation_unit_,
             filename,
             shared_ptr< TranslationUnit >() );
  }

  if ( !unit )
    return false;

  return unit->IsCurrentlyUpdating();
}


void ClangCompleter::UpdateTranslationUnit(
  const std::string &filename,
  const std::vector< UnsavedFile > &unsaved_files,
  const std::vector< std::string > &flags ) {
  bool translation_unit_created;
  shared_ptr< TranslationUnit > unit = GetTranslationUnitForFile(
                                         filename,
                                         unsaved_files,
                                         flags,
                                         translation_unit_created );

  if ( !unit )
    return;

  try {
    // There's no point in reparsing a TU that was just created, it was just
    // parsed in the TU constructor
    if ( !translation_unit_created )
      unit->Reparse( unsaved_files );
  }

  catch ( ClangParseError & ) {
    lock_guard< mutex > lock( filename_to_translation_unit_mutex_ );

    // If unit->Reparse fails, then the underlying TranslationUnit object is not
    // valid anymore and needs to be destroyed and removed from the filename ->
    // TU map.
    Erase( filename_to_translation_unit_, filename );
  }
}


Future< void > ClangCompleter::UpdateTranslationUnitAsync(
  std::string filename,
  std::vector< UnsavedFile > unsaved_files,
  std::vector< std::string > flags ) {
  function< void() > functor =
    bind( &ClangCompleter::UpdateTranslationUnit,
          boost::ref( *this ),
          boost::move( filename ),
          boost::move( unsaved_files ),
          boost::move( flags ) );

  shared_ptr< ClangPackagedTask > clang_packaged_task =
    make_shared< ClangPackagedTask >();

  clang_packaged_task->parsing_task_ = packaged_task< void >( functor );
  unique_future< void > future =
    clang_packaged_task->parsing_task_.get_future();
  clang_task_.Set( clang_packaged_task );

  return Future< void >( boost::move( future ) );
}


std::vector< CompletionData >
ClangCompleter::CandidatesForLocationInFile(
  const std::string &filename,
  int line,
  int column,
  const std::vector< UnsavedFile > &unsaved_files,
  const std::vector< std::string > &flags ) {
  shared_ptr< TranslationUnit > unit = GetTranslationUnitForFile( filename,
                                                                  unsaved_files,
                                                                  flags );

  if ( !unit )
    return std::vector< CompletionData >();

  return unit->CandidatesForLocation( line,
                                      column,
                                      unsaved_files );
}


Future< AsyncCompletions >
ClangCompleter::CandidatesForQueryAndLocationInFileAsync(
  const std::string &query,
  const std::string &filename,
  int line,
  int column,
  const std::vector< UnsavedFile > &unsaved_files,
  const std::vector< std::string > &flags ) {
  // TODO: throw exception when threading is not enabled and this is called
  if ( !threading_enabled_ )
    return Future< AsyncCompletions >();

  bool skip_clang_result_cache = ShouldSkipClangResultCache( query,
                                                             line,
                                                             column );

  if ( skip_clang_result_cache ) {
    // The clang thread is busy, return nothing
    if ( UpdatingTranslationUnit( filename ) )
      return Future< AsyncCompletions >();

    {
      lock_guard< mutex > lock( clang_data_ready_mutex_ );
      clang_data_ready_ = false;
    }

    // Needed to "reset" the sorting threads to the start of their loop. This
    // way any threads blocking on a read in sorting_task_.Get() are reset to
    // wait on the clang_data_ready_condition_variable_.
    sorting_threads_.interrupt_all();
  }

  // the sorting task needs to be set before the clang task (if any) just in
  // case the clang task finishes (and therefore notifies a sorting thread to
  // consume a sorting task) before the sorting task is set
  unique_future< AsyncCompletions > future;
  CreateSortingTask( query, future );

  if ( skip_clang_result_cache ) {
    CreateClangTask( filename, line, column, unsaved_files, flags );
  }

  return Future< AsyncCompletions >( boost::move( future ) );
}


bool ClangCompleter::ShouldSkipClangResultCache( const std::string &query,
                                                 int line,
                                                 int column ) {
  // We need query.empty() in addition to the second check because if we don't
  // have it, then we have a problem in the following situation:
  // The user has a variable 'foo' of type 'A' and a variable 'bar' of type 'B'.
  // He then types in 'foo.' and we store the clang results and also return
  // them. The user then deletes that code and types in 'bar.'. Without the
  // query.empty() check we would return the results from the cache here (it's
  // the same line and column!) which would be incorrect.
  return query.empty() || latest_clang_results_
         .NewPositionDifferentFromStoredPosition( line, column );
}


// Copy-ctor for unique_future is private in C++03 mode so we need to take it as
// an out param
void ClangCompleter::CreateSortingTask(
  const std::string &query,
  unique_future< AsyncCompletions > &future ) {
  // Careful! The code in this function may burn your eyes.

  function< CompletionDatas( const CompletionDatas & ) >
  sort_candidates_for_query_functor =
    bind( &ClangCompleter::SortCandidatesForQuery,
          boost::ref( *this ),
          query,
          _1 );

  function< CompletionDatas() > operate_on_completion_data_functor =
    bind( &ClangResultsCache::OperateOnCompletionDatas< CompletionDatas >,
          boost::cref( latest_clang_results_ ),
          boost::move( sort_candidates_for_query_functor ) );

  shared_ptr< packaged_task< AsyncCompletions > > task =
    make_shared< packaged_task< AsyncCompletions > >(
      bind( ReturnValueAsShared< std::vector< CompletionData > >,
            boost::move( operate_on_completion_data_functor ) ) );

  future = task->get_future();
  sorting_task_.Set( task );
}


void ClangCompleter::CreateClangTask(
  std::string filename,
  int line,
  int column,
  std::vector< UnsavedFile > unsaved_files,
  std::vector< std::string > flags ) {
  latest_clang_results_.ResetWithNewLineAndColumn( line, column );

  function< CompletionDatas() > candidates_for_location_functor =
    bind( &ClangCompleter::CandidatesForLocationInFile,
          boost::ref( *this ),
          boost::move( filename ),
          line,
          column,
          boost::move( unsaved_files ),
          boost::move( flags ) );

  shared_ptr< ClangPackagedTask > clang_packaged_task =
    make_shared< ClangPackagedTask >();

  clang_packaged_task->completions_task_ =
    packaged_task< AsyncCompletions >(
      bind( ReturnValueAsShared< std::vector< CompletionData > >,
            candidates_for_location_functor ) );

  clang_task_.Set( clang_packaged_task );
}


boost::shared_ptr< TranslationUnit > ClangCompleter::GetTranslationUnitForFile(
  const std::string &filename,
  const std::vector< UnsavedFile > &unsaved_files,
  const std::vector< std::string > &flags ) {
  bool dont_care;
  return GetTranslationUnitForFile( filename, unsaved_files, flags, dont_care );
}


// WARNING: It should not be possible to call this function from two separate
// threads at the same time. Currently only one thread (the clang thread) ever
// calls this function so there is no need for a mutex, but if that changes in
// the future a mutex will be needed to make sure that two threads don't try to
// create the same translation unit.
shared_ptr< TranslationUnit > ClangCompleter::GetTranslationUnitForFile(
  const std::string &filename,
  const std::vector< UnsavedFile > &unsaved_files,
  const std::vector< std::string > &flags,
  bool &translation_unit_created ) {
  {
    lock_guard< mutex > lock( filename_to_translation_unit_mutex_ );
    TranslationUnitForFilename::iterator it =
      filename_to_translation_unit_.find( filename );

    if ( it != filename_to_translation_unit_.end() ) {
      translation_unit_created = false;
      return it->second;
    }
  }

  shared_ptr< TranslationUnit > unit;

  try {
    unit = make_shared< TranslationUnit >(
             filename, unsaved_files, flags, clang_index_ );
  }

  catch ( ClangParseError & ) {
    return unit;
  }

  {
    lock_guard< mutex > lock( filename_to_translation_unit_mutex_ );
    filename_to_translation_unit_[ filename ] = unit;
  }

  translation_unit_created = true;
  return unit;
}


std::vector< CompletionData > ClangCompleter::SortCandidatesForQuery(
  const std::string &query,
  const std::vector< CompletionData > &completion_datas ) {
  Bitset query_bitset = LetterBitsetFromString( query );

  std::vector< const Candidate * > repository_candidates =
    candidate_repository_.GetCandidatesForStrings( completion_datas );

  std::vector< CompletionDataAndResult > data_and_results;

  for ( uint i = 0; i < repository_candidates.size(); ++i ) {
    const Candidate *candidate = repository_candidates[ i ];

    if ( !candidate->MatchesQueryBitset( query_bitset ) )
      continue;

    Result result = candidate->QueryMatchResult( query );

    if ( result.IsSubsequence() ) {
      CompletionDataAndResult data_and_result( &completion_datas[ i ], result );
      data_and_results.push_back( data_and_result );
    }
  }

  std::sort( data_and_results.begin(), data_and_results.end() );

  std::vector< CompletionData > sorted_completion_datas;
  sorted_completion_datas.reserve( data_and_results.size() );

  foreach ( const CompletionDataAndResult & data_and_result, data_and_results ) {
    sorted_completion_datas.push_back( *data_and_result.completion_data_ );
  }

  return sorted_completion_datas;
}


void ClangCompleter::InitThreads() {
  int threads_to_create =
    std::max( MIN_ASYNC_THREADS,
              std::min( MAX_ASYNC_THREADS, thread::hardware_concurrency() ) );

  for ( int i = 0; i < threads_to_create; ++i ) {
    sorting_threads_.create_thread( bind( &ClangCompleter::SortingThreadMain,
                                          boost::ref( *this ) ) );
  }

  clang_thread_ = thread( &ClangCompleter::ClangThreadMain,
                          boost::ref( *this ) );
}


void ClangCompleter::ClangThreadMain() {
  while ( true ) {
    try {
      shared_ptr< ClangPackagedTask > task = clang_task_.Get();

      bool has_completions_task = task->completions_task_.valid();

      if ( has_completions_task )
        task->completions_task_();
      else
        task->parsing_task_();

      if ( !has_completions_task )
        continue;

      unique_future< AsyncCompletions > future =
        task->completions_task_.get_future();
      latest_clang_results_.SetCompletionDatas( *future.get() );

      {
        lock_guard< mutex > lock( clang_data_ready_mutex_ );
        clang_data_ready_ = true;
      }

      clang_data_ready_condition_variable_.notify_all();
    }

    catch ( thread_interrupted & ) {
      shared_lock< shared_mutex > lock( time_to_die_mutex_ );

      if ( time_to_die_ )
        return;

      // else do nothing and re-enter the loop
    }
  }
}


void ClangCompleter::SortingThreadMain() {
  while ( true ) {
    try {
      {
        unique_lock< mutex > lock( clang_data_ready_mutex_ );

        while ( !clang_data_ready_ ) {
          clang_data_ready_condition_variable_.wait( lock );
        }
      }

      shared_ptr< packaged_task< AsyncCompletions > > task =
        sorting_task_.Get();

      ( *task )();
    }

    catch ( thread_interrupted & ) {
      shared_lock< shared_mutex > lock( time_to_die_mutex_ );

      if ( time_to_die_ )
        return;

      // else do nothing and re-enter the loop
    }
  }
}


} // namespace YouCompleteMe