// Copyright 2017 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 REMOTING_HOST_FILE_PROXY_WRAPPER_H_
#define REMOTING_HOST_FILE_PROXY_WRAPPER_H_

#include "base/callback.h"
#include "base/files/file_proxy.h"
#include "base/optional.h"
#include "remoting/proto/file_transfer.pb.h"

namespace remoting {

// FileProxyWrapper is an interface for implementing platform-specific file
// writers for file transfers. Each operation is posted to a separate file IO
// thread, and possibly a different process depending on the platform.
// TODO(jarhar): Create interfaces for reading and writing implemented by this
// interface to constrain the usage of this interface to reading or writing.
class FileProxyWrapper {
 public:
  enum State {
    // Created, but Init() has not been called yet.
    kUninitialized = 0,

    // Init() has been called.
    kInitialized = 1,

    // The file has been opened. WriteChunk(), ReadChunk(), and Close() can be
    // called.
    kReady = 2,

    // A file operation is currently being processed. WriteChunk(), ReadChunk(),
    // and Close() cannot be called until the state changes back to kReady.
    kBusy = 3,

    // Close() has been called and succeeded.
    kClosed = 4,

    // Cancel() has been called or an error occured.
    kFailed = 5,
  };

  // If writing the file fails, the status callback will be called with the
  // causal error. Otherwise, the callback will be called with a nullopt once
  // the file has been successfully written.
  typedef base::OnceCallback<void(base::Optional<protocol::FileTransfer_Error>)>
      ResultCallback;

  typedef base::OnceCallback<void(int64_t filesize)> OpenFileCallback;

  typedef base::OnceCallback<void(std::unique_ptr<std::vector<char>>)>
      ReadCallback;

  // Creates a platform-specific FileProxyWrapper.
  static std::unique_ptr<FileProxyWrapper> Create();

  FileProxyWrapper();
  virtual ~FileProxyWrapper();

  // |result_callback| is called either when FileProxyWrapper encounters an
  // error or when Close() has been called and the file has been written
  // successfully. |result_callback| must not immediately destroy this
  // FileProxyWrapper.
  virtual void Init(ResultCallback result_callback) = 0;
  // Creates a new file and opens it for writing.
  virtual void CreateFile(const base::FilePath& directory,
                          const std::string& filename) = 0;
  // Opens an existing file for reading.
  virtual void OpenFile(const base::FilePath& filepath,
                        OpenFileCallback open_callback) = 0;
  virtual void WriteChunk(std::string buffer) = 0;
  // |size| must not be greater than the remaining amount of bytes in the file
  // from the current read offset. After calling ReadChunk(), ReadChunk() cannot
  // be called again until |read_callback| is called and state() returns kReady.
  virtual void ReadChunk(uint64_t size, ReadCallback read_callback) = 0;
  virtual void Close() = 0;
  virtual void Cancel() = 0;
  virtual State state() = 0;
};

}  // namespace remoting

#endif  // REMOTING_HOST_FILE_PROXY_WRAPPER_H_