// 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 EXTENSIONS_BROWSER_VALUE_STORE_LEVELDB_VALUE_STORE_H_
#define EXTENSIONS_BROWSER_VALUE_STORE_LEVELDB_VALUE_STORE_H_

#include <string>
#include <vector>

#include "base/compiler_specific.h"
#include "base/files/file_path.h"
#include "base/memory/scoped_ptr.h"
#include "extensions/browser/value_store/value_store.h"
#include "third_party/leveldatabase/src/include/leveldb/db.h"

// Value store area, backed by a leveldb database.
// All methods must be run on the FILE thread.
class LeveldbValueStore : public ValueStore {
 public:
  // Creates a database bound to |path|. The underlying database won't be
  // opened (i.e. may not be created) until one of the get/set/etc methods are
  // called - this is because opening the database may fail, and extensions
  // need to be notified of that, but we don't want to permanently give up.
  //
  // Must be created on the FILE thread.
  explicit LeveldbValueStore(const base::FilePath& path);

  // Must be deleted on the FILE thread.
  ~LeveldbValueStore() override;

  // ValueStore implementation.
  size_t GetBytesInUse(const std::string& key) override;
  size_t GetBytesInUse(const std::vector<std::string>& keys) override;
  size_t GetBytesInUse() override;
  ReadResult Get(const std::string& key) override;
  ReadResult Get(const std::vector<std::string>& keys) override;
  ReadResult Get() override;
  WriteResult Set(WriteOptions options,
                  const std::string& key,
                  const base::Value& value) override;
  WriteResult Set(WriteOptions options,
                  const base::DictionaryValue& values) override;
  WriteResult Remove(const std::string& key) override;
  WriteResult Remove(const std::vector<std::string>& keys) override;
  WriteResult Clear() override;
  bool Restore() override;
  bool RestoreKey(const std::string& key) override;

  // Write directly to the backing levelDB. Only used for testing to cause
  // corruption in the database.
  bool WriteToDbForTest(leveldb::WriteBatch* batch);

 private:
  // Tries to open the database if it hasn't been opened already.
  scoped_ptr<ValueStore::Error> EnsureDbIsOpen();

  // Reads a setting from the database.
  scoped_ptr<ValueStore::Error> ReadFromDb(
      leveldb::ReadOptions options,
      const std::string& key,
      // Will be reset() with the result, if any.
      scoped_ptr<base::Value>* setting);

  // Adds a setting to a WriteBatch, and logs the change in |changes|. For use
  // with WriteToDb.
  scoped_ptr<ValueStore::Error> AddToBatch(ValueStore::WriteOptions options,
                                           const std::string& key,
                                           const base::Value& value,
                                           leveldb::WriteBatch* batch,
                                           ValueStoreChangeList* changes);

  // Commits the changes in |batch| to the database.
  scoped_ptr<ValueStore::Error> WriteToDb(leveldb::WriteBatch* batch);

  // Converts an error leveldb::Status to a ValueStore::Error. Returns a
  // scoped_ptr for convenience; the result will always be non-empty.
  scoped_ptr<ValueStore::Error> ToValueStoreError(
      const leveldb::Status& status,
      scoped_ptr<std::string> key);

  // Removes the on-disk database at |db_path_|. Any file system locks should
  // be released before calling this method.
  void DeleteDbFile();

  // Returns whether the database is empty.
  bool IsEmpty();

  // The location of the leveldb backend.
  const base::FilePath db_path_;

  // leveldb backend.
  scoped_ptr<leveldb::DB> db_;

  DISALLOW_COPY_AND_ASSIGN(LeveldbValueStore);
};

#endif  // EXTENSIONS_BROWSER_VALUE_STORE_LEVELDB_VALUE_STORE_H_