// Copyright (c) 2012 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 CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_STORE_H_
#define CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_STORE_H_

#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "chrome/browser/policy/cloud/cloud_policy_validator.h"
#include "chrome/browser/policy/proto/cloud/device_management_backend.pb.h"
#include "components/policy/core/common/policy_map.h"

namespace policy {

class CloudExternalDataManager;

// Defines the low-level interface used by the cloud policy code to:
//   1. Validate policy blobs that should be applied locally
//   2. Persist policy blobs
//   3. Decode policy blobs to PolicyMap representation
class CloudPolicyStore {
 public:
  // Status codes.
  enum Status {
    // Everything is in good order.
    STATUS_OK,
    // Loading policy from the underlying data store failed.
    STATUS_LOAD_ERROR,
    // Failed to store policy to the data store.
    STATUS_STORE_ERROR,
    // Failed to parse the policy read from the data store.
    STATUS_PARSE_ERROR,
    // Failed to serialize policy for storage.
    STATUS_SERIALIZE_ERROR,
    // Validation error.
    STATUS_VALIDATION_ERROR,
    // Store cannot accept policy (e.g. non-enterprise device).
    STATUS_BAD_STATE,
  };

  // Callbacks for policy store events. Most importantly, policy updates.
  class Observer {
   public:
    virtual ~Observer();

    // Called on changes to store->policy() and/or store->policy_map().
    virtual void OnStoreLoaded(CloudPolicyStore* store) = 0;

    // Called upon encountering errors.
    virtual void OnStoreError(CloudPolicyStore* store) = 0;
  };

  CloudPolicyStore();
  virtual ~CloudPolicyStore();

  // Indicates whether the store has been fully initialized. This is
  // accomplished by calling Load() after startup.
  bool is_initialized() const { return is_initialized_; }

  base::WeakPtr<CloudExternalDataManager> external_data_manager() const {
    return external_data_manager_;
  }

  const PolicyMap& policy_map() const { return policy_map_; }
  bool has_policy() const {
    return policy_.get() != NULL;
  }
  const enterprise_management::PolicyData* policy() const {
    return policy_.get();
  }
  bool is_managed() const {
    return policy_.get() &&
           policy_->state() == enterprise_management::PolicyData::ACTIVE;
  }
  Status status() const { return status_; }
  CloudPolicyValidatorBase::Status validation_status() const {
    return validation_status_;
  }

  // Store a new policy blob. Pending load/store operations will be canceled.
  // The store operation may proceed asynchronously and observers are notified
  // once the operation finishes. If successful, OnStoreLoaded() will be invoked
  // on the observers and the updated policy can be read through policy().
  // Errors generate OnStoreError() notifications.
  // |invalidation_version| is the invalidation version of the policy to be
  // stored.
  void Store(
      const enterprise_management::PolicyFetchResponse& policy,
      int64 invalidation_version);

  virtual void Store(
      const enterprise_management::PolicyFetchResponse& policy) = 0;

  // Load the current policy blob from persistent storage. Pending load/store
  // operations will be canceled. This may trigger asynchronous operations.
  // Upon success, OnStoreLoaded() will be called on the registered observers.
  // Otherwise, OnStoreError() reports the reason for failure.
  virtual void Load() = 0;

  // Registers an observer to be notified when policy changes.
  void AddObserver(Observer* observer);

  // Removes the specified observer.
  void RemoveObserver(Observer* observer);

  // The invalidation version of the last policy stored. This value can be read
  // by observers to determine which version of the policy is now available.
  int64 invalidation_version() {
    return invalidation_version_;
  }

  // Indicate that external data referenced by policies in this store is managed
  // by |external_data_manager|. The |external_data_manager| will be notified
  // about policy changes before any other observers.
  void SetExternalDataManager(
      base::WeakPtr<CloudExternalDataManager> external_data_manager);

  // Replaces |policy_map_| and calls the registered observers, simulating a
  // successful load of |policy_map| from persistent storage.
  // TODO(bartfab): This override is only needed because there are no policies
  // that reference external data and therefore, no ExternalDataFetchers in the
  // |policy_map_|. Once the first such policy is added, use that policy in
  // tests and remove the override.
  void SetPolicyMapForTesting(const PolicyMap& policy_map);

 protected:
  // Invokes the corresponding callback on all registered observers.
  void NotifyStoreLoaded();
  void NotifyStoreError();

  // Manages external data referenced by policies.
  base::WeakPtr<CloudExternalDataManager> external_data_manager_;

  // Decoded version of the currently effective policy.
  PolicyMap policy_map_;

  // Currently effective policy.
  scoped_ptr<enterprise_management::PolicyData> policy_;

  // Latest status code.
  Status status_;

  // Latest validation status.
  CloudPolicyValidatorBase::Status validation_status_;

  // The invalidation version of the last policy stored.
  int64 invalidation_version_;

 private:
  // Whether the store has completed asynchronous initialization, which is
  // triggered by calling Load().
  bool is_initialized_;

  ObserverList<Observer, true> observers_;

  DISALLOW_COPY_AND_ASSIGN(CloudPolicyStore);
};

}  // namespace policy

#endif  // CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_STORE_H_