// Copyright 2017-2018 ccls Authors
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "clang_tu.h"
#include "lru_cache.h"
#include "lsp_completion.h"
#include "lsp_diagnostic.h"
#include "project.h"
#include "threaded_queue.h"
#include "working_files.h"

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

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

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

struct PreambleData {
  PreambleData(clang::PrecompiledPreamble P, std::vector<Diag> diags)
      : Preamble(std::move(P)), diags(std::move(diags)) {}
  clang::PrecompiledPreamble Preamble;
  std::vector<Diag> diags;
};

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

  Project::Entry file;
  WorkingFiles *wfiles;

  // TODO share
  llvm::IntrusiveRefCntPtr<clang::vfs::FileSystem> FS =
      clang::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();
  void BuildPreamble(clang::CompilerInvocation &CI);
};
}

struct CompletionManager {
  using OnDiagnostic = std::function<void(
      std::string path, std::vector<lsDiagnostic> diagnostics)>;
  using OnComplete = std::function<void(
      const std::vector<lsCompletionItem> &results, bool is_cached_result)>;
  using OnDropped = std::function<void(lsRequestId request_id)>;

  struct PreloadRequest {
    PreloadRequest(const std::string &path)
        : request_time(std::chrono::high_resolution_clock::now()), path(path) {}

    std::chrono::time_point<std::chrono::high_resolution_clock> request_time;
    std::string path;
  };
  struct CompletionRequest {
    CompletionRequest(const lsRequestId &id,
                      const lsTextDocumentIdentifier &document,
                      const lsPosition &position, const OnComplete &on_complete)
        : id(id), document(document), position(position),
          on_complete(on_complete) {}

    lsRequestId id;
    lsTextDocumentIdentifier document;
    lsPosition position;
    OnComplete on_complete;
  };
  struct DiagnosticRequest {
    lsTextDocumentIdentifier document;
  };

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

  // Start a code completion at the given location. |on_complete| will run when
  // completion results are available. |on_complete| may run on any thread.
  void CodeComplete(const lsRequestId &request_id,
                    const lsTextDocumentPositionParams &completion_location,
                    const OnComplete &on_complete);
  // Request a diagnostics update.
  void DiagnosticsUpdate(const lsTextDocumentIdentifier &document);

  // 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 NotifyClose(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 mark_as_completion,
                bool create_if_needed);

  // Flushes all saved sessions with the supplied filename
  void FlushSession(const std::string &path);
  // Flushes all saved sessions
  void FlushAllSessions(void);

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

  // Global state.
  Project *project_;
  WorkingFiles *working_files_;
  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 preloaded_sessions_;
  // 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 completion_sessions_;
  // Mutex which protects |view_sessions_| and |edit_sessions_|.
  std::mutex sessions_lock_;

  // 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.
struct CodeCompleteCache {
  // NOTE: Make sure to access these variables under |WithLock|.
  std::optional<std::string> cached_path_;
  std::optional<lsPosition> cached_completion_position_;
  std::vector<lsCompletionItem> cached_results_;

  std::mutex mutex_;

  void WithLock(std::function<void()> action);
  bool IsCacheValid(lsTextDocumentPositionParams position);
};