text: // 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 DEVICE_BLUETOOTH_DBUS_BLUETOOTH_GATT_CHARACTERISTIC_CLIENT_H_
  #define DEVICE_BLUETOOTH_DBUS_BLUETOOTH_GATT_CHARACTERISTIC_CLIENT_H_
  
  #include <stdint.h>
  
  #include <string>
  #include <vector>
  
  #include "base/callback.h"
  #include "base/macros.h"
  #include "dbus/object_path.h"
  #include "dbus/property.h"
  #include "device/bluetooth/bluetooth_export.h"
  #include "device/bluetooth/bluetooth_gatt_characteristic.h"
  #include "device/bluetooth/dbus/bluez_dbus_client.h"
  
  namespace bluez {
  
  // BluetoothGattCharacteristicClient is used to communicate with remote GATT
  // characteristic objects exposed by the Bluetooth daemon.
  class DEVICE_BLUETOOTH_EXPORT BluetoothGattCharacteristicClient
      : public BluezDBusClient {
   public:
    // Structure of properties associated with GATT characteristics.
    struct Properties : public dbus::PropertySet {
      // The 128-bit characteristic UUID. [read-only]
      dbus::Property<std::string> uuid;
  
      // Object path of the GATT service the characteristic belongs to.
      // [read-only]
      dbus::Property<dbus::ObjectPath> service;
  
      // The cached value of the characteristic. This property gets updated only
      // after a successful read request and when a notification or indication is
      // received. [read-only]
      dbus::Property<std::vector<uint8_t>> value;
  
      // Whether or not this characteristic is currently sending ValueUpdated
      // signals. [read-only]
      dbus::Property<bool> notifying;
  
      // List of flags representing the GATT "Characteristic Properties bit field"
      // and properties read from the GATT "Characteristic Extended Properties"
      // descriptor bit field. [read-only, optional]
      dbus::Property<std::vector<std::string>> flags;
  
      Properties(dbus::ObjectProxy* object_proxy,
                 const std::string& interface_name,
                 const PropertyChangedCallback& callback);
      ~Properties() override;
    };
  
    // Interface for observing changes from a remote GATT characteristic.
    class Observer {
     public:
      virtual ~Observer() {}
  
      // Called when the GATT characteristic with object path |object_path| is
      // added to the system.
      virtual void GattCharacteristicAdded(const dbus::ObjectPath& object_path) {}
  
      // Called when the GATT characteristic with object path |object_path| is
      // removed from the system.
      virtual void GattCharacteristicRemoved(
          const dbus::ObjectPath& object_path) {}
  
      // Called when the GATT characteristic with object path |object_path| has a
      // change in the value of the property named |property_name|.
      virtual void GattCharacteristicPropertyChanged(
          const dbus::ObjectPath& object_path,
          const std::string& property_name) {}
    };
  
    // Callbacks used to report the result of asynchronous methods.
    using ErrorCallback =
        base::OnceCallback<void(const std::string& error_name,
                                const std::string& error_message)>;
    using ValueCallback =
        base::OnceCallback<void(const std::vector<uint8_t>& value)>;
  
    ~BluetoothGattCharacteristicClient() override;
  
    // Adds and removes observers for events on all remote GATT characteristics.
    // Check the |object_path| parameter of observer methods to determine which
    // GATT characteristic is issuing the event.
    virtual void AddObserver(Observer* observer) = 0;
    virtual void RemoveObserver(Observer* observer) = 0;
  
    // Returns the list of GATT characteristic object paths known to the system.
    virtual std::vector<dbus::ObjectPath> GetCharacteristics() = 0;
  
    // Obtain the properties for the GATT characteristic with object path
    // |object_path|. Values should be copied if needed.
    virtual Properties* GetProperties(const dbus::ObjectPath& object_path) = 0;
  
    // Issues a request to read the value of GATT characteristic with object path
    // |object_path| and returns the value in |callback| on success. On error,
    // invokes |error_callback|.
    virtual void ReadValue(const dbus::ObjectPath& object_path,
                           ValueCallback callback,
                           ErrorCallback error_callback) = 0;
  
    // Issues a request to write the value of GATT characteristic with object path
    // |object_path| with value |value|. Invokes |callback| on success and
    // |error_callback| on failure.
    virtual void WriteValue(const dbus::ObjectPath& object_path,
                            const std::vector<uint8_t>& value,
                            base::OnceClosure callback,
                            ErrorCallback error_callback) = 0;
  
    // Issues a request to prepare write the value of GATT characteristic with
    // object path |object_path| with value |value|.
    // Invokes |callback| on success and |error_callback| on failure.
    virtual void PrepareWriteValue(const dbus::ObjectPath& object_path,
                                   const std::vector<uint8_t>& value,
                                   base::OnceClosure callback,
                                   ErrorCallback error_callback) = 0;
  
    // Starts a notification session from this characteristic with object path
    // |object_path| if it supports value notifications or indications. Invokes
    // |callback| on success and |error_callback| on failure.
  #if defined(OS_CHROMEOS)
    virtual void StartNotify(
        const dbus::ObjectPath& object_path,
        device::BluetoothGattCharacteristic::NotificationType notification_type,
        base::OnceClosure callback,
        ErrorCallback error_callback) = 0;
  #else
    virtual void StartNotify(const dbus::ObjectPath& object_path,
                             base::OnceClosure callback,
                             ErrorCallback error_callback) = 0;
  #endif
  
    // Cancels any previous StartNotify transaction for characteristic with
    // object path |object_path|. Invokes |callback| on success and
    // |error_callback| on failure.
    virtual void StopNotify(const dbus::ObjectPath& object_path,
                            base::OnceClosure callback,
                            ErrorCallback error_callback) = 0;
  
    // Creates the instance.
    static BluetoothGattCharacteristicClient* Create();
  
    // Constants used to indicate exceptional error conditions.
    static const char kNoResponseError[];
    static const char kUnknownCharacteristicError[];
  
   protected:
    BluetoothGattCharacteristicClient();
  
   private:
    DISALLOW_COPY_AND_ASSIGN(BluetoothGattCharacteristicClient);
  };
  
  }  // namespace bluez
  
  #endif  // DEVICE_BLUETOOTH_DBUS_BLUETOOTH_GATT_CHARACTERISTIC_CLIENT_H_
  