/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.bluetooth;

import java.util.UUID;

/**
 * Represents a Bluetooth GATT Descriptor
 *
 * <p> GATT Descriptors contain additional information and attributes of a GATT
 * characteristic, {@link BluetoothGattCharacteristic}. They can be used to describe
 * the characteristic's features or to control certain behaviours of the characteristic.
 */
public class BluetoothGattDescriptor {

    /**
     * Value used to enable notification for a client configuration descriptor
     */
    public static final byte[] ENABLE_NOTIFICATION_VALUE = {0x01, 0x00};

    /**
     * Value used to enable indication for a client configuration descriptor
     */
    public static final byte[] ENABLE_INDICATION_VALUE = {0x02, 0x00};

    /**
     * Value used to disable notifications or indicatinos
     */
    public static final byte[] DISABLE_NOTIFICATION_VALUE = {0x00, 0x00};

    /**
     * Descriptor read permission
     */
    public static final int PERMISSION_READ = 0x01;

    /**
     * Descriptor permission: Allow encrypted read operations
     */
    public static final int PERMISSION_READ_ENCRYPTED = 0x02;

    /**
     * Descriptor permission: Allow reading with man-in-the-middle protection
     */
    public static final int PERMISSION_READ_ENCRYPTED_MITM = 0x04;

    /**
     * Descriptor write permission
     */
    public static final int PERMISSION_WRITE = 0x10;

    /**
     * Descriptor permission: Allow encrypted writes
     */
    public static final int PERMISSION_WRITE_ENCRYPTED = 0x20;

    /**
     * Descriptor permission: Allow encrypted writes with man-in-the-middle
     * protection
     */
    public static final int PERMISSION_WRITE_ENCRYPTED_MITM = 0x40;

    /**
     * Descriptor permission: Allow signed write operations
     */
    public static final int PERMISSION_WRITE_SIGNED = 0x80;

    /**
     * Descriptor permission: Allow signed write operations with
     * man-in-the-middle protection
     */
    public static final int PERMISSION_WRITE_SIGNED_MITM = 0x100;

    /**
     * The UUID of this descriptor.
     * @hide
     */
    protected UUID mUuid;

    /**
     * Instance ID for this descriptor.
     * @hide
     */
    protected int mInstance;

    /**
     * Permissions for this descriptor
     * @hide
     */
    protected int mPermissions;

    /**
     * Back-reference to the characteristic this descriptor belongs to.
     * @hide
     */
    protected BluetoothGattCharacteristic mCharacteristic;

    /**
     * The value for this descriptor.
     * @hide
     */
    protected byte[] mValue;

    /**
     * Create a new BluetoothGattDescriptor.
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param uuid The UUID for this descriptor
     * @param permissions Permissions for this descriptor
     */
    public BluetoothGattDescriptor(UUID uuid, int permissions) {
        initDescriptor(null, uuid, 0, permissions);
    }

    /**
     * Create a new BluetoothGattDescriptor.
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @param characteristic The characteristic this descriptor belongs to
     * @param uuid The UUID for this descriptor
     * @param permissions Permissions for this descriptor
     */
    /*package*/ BluetoothGattDescriptor(BluetoothGattCharacteristic characteristic, UUID uuid,
                                    int instance, int permissions) {
        initDescriptor(characteristic, uuid, instance, permissions);
    }

    private void initDescriptor(BluetoothGattCharacteristic characteristic, UUID uuid,
                                int instance, int permissions) {
        mCharacteristic = characteristic;
        mUuid = uuid;
        mInstance = instance;
        mPermissions = permissions;
    }

    /**
     * Returns the characteristic this descriptor belongs to.
     * @return The characteristic.
     */
    public BluetoothGattCharacteristic getCharacteristic() {
        return mCharacteristic;
    }

    /**
     * Set the back-reference to the associated characteristic
     * @hide
     */
    /*package*/ void setCharacteristic(BluetoothGattCharacteristic characteristic) {
        mCharacteristic = characteristic;
    }

    /**
     * Returns the UUID of this descriptor.
     *
     * @return UUID of this descriptor
     */
    public UUID getUuid() {
        return mUuid;
    }

    /**
     * Returns the instance ID for this descriptor.
     *
     * <p>If a remote device offers multiple descriptors with the same UUID,
     * the instance ID is used to distuinguish between descriptors.
     *
     * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
     *
     * @return Instance ID of this descriptor
     * @hide
     */
    public int getInstanceId() {
        return mInstance;
    }

    /**
     * Returns the permissions for this descriptor.
     *
     * @return Permissions of this descriptor
     */
    public int getPermissions() {
        return mPermissions;
    }

    /**
     * Returns the stored value for this descriptor
     *
     * <p>This function returns the stored value for this descriptor as
     * retrieved by calling {@link BluetoothGatt#readDescriptor}. The cached
     * value of the descriptor is updated as a result of a descriptor read
     * operation.
     *
     * @return Cached value of the descriptor
     */
    public byte[] getValue() {
        return mValue;
    }

    /**
     * Updates the locally stored value of this descriptor.
     *
     * <p>This function modifies the locally stored cached value of this
     * descriptor. To send the value to the remote device, call
     * {@link BluetoothGatt#writeDescriptor} to send the value to the
     * remote device.
     *
     * @param value New value for this descriptor
     * @return true if the locally stored value has been set, false if the
     *              requested value could not be stored locally.
     */
    public boolean setValue(byte[] value) {
        mValue = value;
        return true;
    }
}
