// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_LEVELDB_PROTO_PROTO_DATABASE_H_
#define COMPONENTS_LEVELDB_PROTO_PROTO_DATABASE_H_

#include <memory>
#include <string>
#include <utility>
#include <vector>

#include "base/callback.h"
#include "third_party/leveldatabase/env_chromium.h"

namespace base {
class FilePath;
}

namespace leveldb_proto {

// Interface for classes providing persistent storage of Protocol Buffer
// entries (T must be a Proto type extending MessageLite).
template <typename T>
class ProtoDatabase {
 public:
  using InitCallback = base::OnceCallback<void(bool success)>;
  using UpdateCallback = base::OnceCallback<void(bool success)>;
  using LoadCallback =
      base::OnceCallback<void(bool success, std::unique_ptr<std::vector<T>>)>;
  using LoadKeysCallback =
      base::OnceCallback<void(bool success,
                              std::unique_ptr<std::vector<std::string>>)>;
  using GetCallback =
      base::OnceCallback<void(bool success, std::unique_ptr<T>)>;
  using DestroyCallback = base::OnceCallback<void(bool success)>;

  // A list of key-value (string, T) tuples.
  using KeyEntryVector = std::vector<std::pair<std::string, T>>;

  virtual ~ProtoDatabase() {}

  // Asynchronously initializes the object with the specified |options|.
  // |callback| will be invoked on the calling thread when complete.
  virtual void Init(const char* client_name,
                    const base::FilePath& database_dir,
                    const leveldb_env::Options& options,
                    InitCallback callback) = 0;

  // Asynchronously saves |entries_to_save| and deletes entries from
  // |keys_to_remove| from the database. |callback| will be invoked on the
  // calling thread when complete.
  virtual void UpdateEntries(
      std::unique_ptr<KeyEntryVector> entries_to_save,
      std::unique_ptr<std::vector<std::string>> keys_to_remove,
      UpdateCallback callback) = 0;

  // Asynchronously loads all entries from the database and invokes |callback|
  // when complete.
  virtual void LoadEntries(LoadCallback callback) = 0;

  // Asynchronously loads all keys from the database and invokes |callback| with
  // those keys when complete.
  virtual void LoadKeys(LoadKeysCallback callback) = 0;

  // Asynchronously loads a single entry, identified by |key|, from the database
  // and invokes |callback| when complete. If no entry with |key| is found,
  // a nullptr is passed to the callback, but the success flag is still true.
  virtual void GetEntry(const std::string& key, GetCallback callback) = 0;

  // Asynchronously destroys the database.
  virtual void Destroy(DestroyCallback callback) = 0;
};

// Return a new instance of Options, but with two additions:
// 1) create_if_missing = true
// 2) max_open_files = 0
leveldb_env::Options CreateSimpleOptions();

}  // namespace leveldb_proto

#endif  // COMPONENTS_LEVELDB_PROTO_PROTO_DATABASE_H_