// Copyright 2014 Google Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

#ifndef MEDIA_BASE_WIDEVINE_ENCRYPTION_KEY_SOURCE_H_
#define MEDIA_BASE_WIDEVINE_ENCRYPTION_KEY_SOURCE_H_

#include <map>

#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "media/base/closure_thread.h"
#include "media/base/encryption_key_source.h"
#include "media/base/producer_consumer_queue.h"

namespace media {
/// A negative crypto period index disables key rotation.
static const int kDisableKeyRotation = -1;

class HttpFetcher;
class RequestSigner;

/// WidevineEncryptionKeySource talks to the Widevine encryption service to
/// acquire the encryption keys.
class WidevineEncryptionKeySource : public EncryptionKeySource {
 public:
  /// @param server_url is the Widevine common encryption server url.
  /// @param content_id the unique id identify the content to be encrypted.
  /// @param policy specifies the DRM content rights.
  /// @param signer signs the request message. It should not be NULL.
  /// @param first_crypto_period_index indicates the starting crypto period
  ///        index. Set it to kDisableKeyRotation to disable key rotation.
  WidevineEncryptionKeySource(const std::string& server_url,
                              const std::string& content_id,
                              const std::string& policy,
                              scoped_ptr<RequestSigner> signer,
                              int first_crypto_period_index);
  virtual ~WidevineEncryptionKeySource();

  /// Initialize the key source. Must be called before calling GetKey or
  /// GetCryptoPeriodKey.
  /// @return OK on success, an error status otherwise.
  Status Initialize();

  /// @name EncryptionKeySource implementation overrides.
  /// @{
  virtual Status GetKey(TrackType track_type, EncryptionKey* key) OVERRIDE;
  virtual Status GetCryptoPeriodKey(uint32 crypto_period_index,
                                    TrackType track_type,
                                    EncryptionKey* key) OVERRIDE;
  /// @}

  /// Inject an @b HttpFetcher object, mainly used for testing.
  /// @param http_fetcher points to the @b HttpFetcher object to be injected.
  void set_http_fetcher(scoped_ptr<HttpFetcher> http_fetcher);

 private:
  typedef std::map<TrackType, EncryptionKey*> EncryptionKeyMap;
  class RefCountedEncryptionKeyMap;

  // Internal routine for getting keys.
  Status GetKeyInternal(uint32 crypto_period_index,
                        TrackType track_type,
                        EncryptionKey* key);

  // The closure task to fetch keys repeatedly.
  void FetchKeysTask();

  // Fetch keys from server.
  Status FetchKeys(uint32 first_crypto_period_index);

  // Fill |request| with necessary fields for Widevine encryption request.
  // |request| should not be NULL.
  void FillRequest(const std::string& content_id,
                   uint32 first_crypto_period_index,
                   std::string* request);
  // Sign and properly format |request|.
  // |signed_request| should not be NULL. Return OK on success.
  Status SignRequest(const std::string& request, std::string* signed_request);
  // Decode |response| from JSON formatted |raw_response|.
  // |response| should not be NULL.
  bool DecodeResponse(const std::string& raw_response, std::string* response);
  // Extract encryption key from |response|, which is expected to be properly
  // formatted. |transient_error| will be set to true if it fails and the
  // failure is because of a transient error from the server. |transient_error|
  // should not be NULL.
  bool ExtractEncryptionKey(const std::string& response, bool* transient_error);
  // Push the keys to the key pool.
  bool PushToKeyPool(EncryptionKeyMap* encryption_key_map);

  // The fetcher object used to fetch HTTP response from server.
  // It is initialized to a default fetcher on class initialization.
  // Can be overridden using set_http_fetcher for testing or other purposes.
  scoped_ptr<HttpFetcher> http_fetcher_;
  std::string server_url_;
  std::string content_id_;
  std::string policy_;
  scoped_ptr<RequestSigner> signer_;

  const bool key_rotation_enabled_;
  const uint32 crypto_period_count_;
  uint32 first_crypto_period_index_;
  ClosureThread key_production_thread_;
  ProducerConsumerQueue<scoped_refptr<RefCountedEncryptionKeyMap> > key_pool_;
  Status common_encryption_request_status_;

  DISALLOW_COPY_AND_ASSIGN(WidevineEncryptionKeySource);
};

}  // namespace media

#endif  // MEDIA_BASE_WIDEVINE_ENCRYPTION_KEY_SOURCE_H_