/* Copyright 2017-2018 ccls Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#pragma once

#include "clang_tu.hh"
#include "lsp.hh"
#include "project.hh"
#include "threaded_queue.hh"
#include "working_files.hh"

#include <clang/Frontend/CompilerInstance.h>
#include <clang/Frontend/FrontendActions.h>
#include <clang/Sema/CodeCompleteOptions.h>

#include <algorithm>
#include <functional>
#include <memory>
#include <mutex>
#include <string>
#include <vector>

namespace ccls {
struct PreambleData;

struct DiagBase {
  Range range;
  std::string message;
  std::string file;
  clang::DiagnosticsEngine::Level level = clang::DiagnosticsEngine::Note;
  unsigned category;
  bool concerned = false;
};
struct Note : DiagBase {};
struct Diag : DiagBase {
  std::vector<Note> notes;
  std::vector<TextEdit> edits;
};

TextEdit ToTextEdit(const clang::SourceManager &SM,
                      const clang::LangOptions &L,
                      const clang::FixItHint &FixIt);

template <typename K, typename V> struct LruCache {
  LruCache(int capacity) : capacity(capacity) {}

  std::shared_ptr<V> Get(const K &key) {
    for (auto it = items.begin(); it != items.end(); ++it)
      if (it->first == key) {
        auto x = std::move(*it);
        std::move_backward(items.begin(), it, it + 1);
        items[0] = std::move(x);
        return items[0].second;
      }
    return nullptr;
  }
  std::shared_ptr<V> Take(const K &key) {
    for (auto it = items.begin(); it != items.end(); ++it)
      if (it->first == key) {
        auto x = std::move(it->second);
        items.erase(it);
        return x;
      }
    return nullptr;
  }
  void Insert(const K &key, std::shared_ptr<V> value) {
    if ((int)items.size() >= capacity)
      items.pop_back();
    items.emplace(items.begin(), key, std::move(value));
  }
  void Clear() { items.clear(); }

private:
  std::vector<std::pair<K, std::shared_ptr<V>>> items;
  int capacity;
};

struct CompletionSession
    : public std::enable_shared_from_this<CompletionSession> {
  std::mutex mutex;
  std::shared_ptr<PreambleData> preamble;

  Project::Entry file;
  WorkingFiles *wfiles;
  bool inferred = false;

  // TODO share
  llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS =
      llvm::vfs::getRealFileSystem();
  std::shared_ptr<clang::PCHContainerOperations> PCH;

  CompletionSession(const Project::Entry &file, WorkingFiles *wfiles,
                    std::shared_ptr<clang::PCHContainerOperations> PCH)
      : file(file), wfiles(wfiles), PCH(PCH) {}

  std::shared_ptr<PreambleData> GetPreamble();
};

struct CompletionManager {
  using OnDiagnostic = std::function<void(
      std::string path, std::vector<Diagnostic> diagnostics)>;
  // If OptConsumer is nullptr, the request has been cancelled.
  using OnComplete =
      std::function<void(clang::CodeCompleteConsumer *OptConsumer)>;
  using OnDropped = std::function<void(RequestId request_id)>;

  struct PreloadRequest {
    std::string path;
  };
  struct CompletionRequest {
    CompletionRequest(const RequestId &id,
                      const TextDocumentIdentifier &document,
                      const Position &position,
                      std::unique_ptr<clang::CodeCompleteConsumer> Consumer,
                      clang::CodeCompleteOptions CCOpts,
                      const OnComplete &on_complete)
        : id(id), document(document), position(position),
          Consumer(std::move(Consumer)), CCOpts(CCOpts),
          on_complete(on_complete) {}

    RequestId id;
    TextDocumentIdentifier document;
    Position position;
    std::unique_ptr<clang::CodeCompleteConsumer> Consumer;
    clang::CodeCompleteOptions CCOpts;
    OnComplete on_complete;
  };
  struct DiagnosticRequest {
    std::string path;
    int64_t wait_until;
    int64_t debounce;
  };

  CompletionManager(Project *project, WorkingFiles *wfiles,
                    OnDiagnostic on_diagnostic, OnDropped on_dropped);

  // Request a diagnostics update.
  void DiagnosticsUpdate(const std::string &path, int debounce);

  // Notify the completion manager that |filename| has been viewed and we
  // should begin preloading completion data.
  void NotifyView(const std::string &path);
  // Notify the completion manager that |filename| has been saved. This
  // triggers a reparse.
  void NotifySave(const std::string &path);
  // Notify the completion manager that |filename| has been closed. Any existing
  // completion session will be dropped.
  void OnClose(const std::string &path);

  // Ensures there is a completion or preloaded session. Returns true if a new
  // session was created.
  bool EnsureCompletionOrCreatePreloadSession(const std::string &path);
  // Tries to find an edit session for |filename|. This will move the session
  // from view to edit.
  std::shared_ptr<ccls::CompletionSession>
  TryGetSession(const std::string &path, bool preload, bool *is_open = nullptr);

  // Flushes all saved sessions
  void FlushAllSessions(void);

  // TODO: make these configurable.
  const int kMaxPreloadedSessions = 10;
  const int kMaxCompletionSessions = 5;

  // Global state.
  Project *project_;
  WorkingFiles *wfiles_;
  OnDiagnostic on_diagnostic_;
  OnDropped on_dropped_;

  using LruSessionCache = LruCache<std::string, ccls::CompletionSession>;

  // CompletionSession instances which are preloaded, ie, files which the user
  // has viewed but not requested code completion for.
  LruSessionCache preloads;
  // CompletionSession instances which the user has actually performed
  // completion on. This is more rare so these instances tend to stay alive
  // much longer than the ones in |preloaded_sessions_|.
  LruSessionCache sessions;
  // Mutex which protects |view_sessions_| and |edit_sessions_|.
  std::mutex sessions_lock_;

  std::mutex diag_mutex;
  std::unordered_map<std::string, int64_t> next_diag;

  // Request a code completion at the given location.
  ThreadedQueue<std::unique_ptr<CompletionRequest>> completion_request_;
  ThreadedQueue<DiagnosticRequest> diagnostic_request_;
  // Parse requests. The path may already be parsed, in which case it should be
  // reparsed.
  ThreadedQueue<PreloadRequest> preload_requests_;

  std::shared_ptr<clang::PCHContainerOperations> PCH;
};

// Cached completion information, so we can give fast completion results when
// the user erases a character. vscode will resend the completion request if
// that happens.
template <typename T>
struct CompleteConsumerCache {
  // NOTE: Make sure to access these variables under |WithLock|.
  std::optional<std::string> path;
  std::optional<Position> position;
  T result;

  std::mutex mutex;

  void WithLock(std::function<void()> action) {
    std::lock_guard lock(mutex);
    action();
  }
  bool IsCacheValid(const std::string path, Position position) {
    std::lock_guard lock(mutex);
    return this->path == path && this->position == position;
  }
};
} // namespace ccls