android/pandora/server/src/GattServerManager.kt

/*
 * Copyright (C) 2022 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 com.android.pandora

import android.bluetooth.BluetoothDevice
import android.bluetooth.BluetoothGatt
import android.bluetooth.BluetoothGattCharacteristic
import android.bluetooth.BluetoothGattServer
import android.bluetooth.BluetoothGattServerCallback
import android.bluetooth.BluetoothGattService
import android.bluetooth.BluetoothManager
import android.content.Context
import android.util.Log
import java.util.UUID
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.flow.MutableSharedFlow

class GattServerManager(
    bluetoothManager: BluetoothManager,
    context: Context,
    globalScope: CoroutineScope
) {
    val TAG = "PandoraGattServerManager"

    val services = mutableMapOf<UUID, BluetoothGattService>()
    val newServiceFlow = MutableSharedFlow<BluetoothGattService>(extraBufferCapacity = 8)
    var negociatedMtu = -1

    val callback =
        object : BluetoothGattServerCallback() {
            override fun onServiceAdded(status: Int, service: BluetoothGattService) {
                Log.i(TAG, "onServiceAdded status=$status")
                check(status == BluetoothGatt.GATT_SUCCESS)
                check(newServiceFlow.tryEmit(service))
            }
            override fun onMtuChanged(device: BluetoothDevice, mtu: Int) {
                Log.i(TAG, "onMtuChanged mtu=$mtu")
                negociatedMtu = mtu
            }

            override fun onCharacteristicReadRequest(
                device: BluetoothDevice,
                requestId: Int,
                offset: Int,
                characteristic: BluetoothGattCharacteristic
            ) {
                Log.i(TAG, "onCharacteristicReadRequest requestId=$requestId")
                if (negociatedMtu != -1) {
                    server.sendResponse(
                        device,
                        requestId,
                        BluetoothGatt.GATT_SUCCESS,
                        offset,
                        ByteArray(negociatedMtu)
                    )
                } else {
                    server.sendResponse(
                        device,
                        requestId,
                        BluetoothGatt.GATT_SUCCESS,
                        offset,
                        ByteArray(512 - offset)
                    )
                }
            }

            override fun onCharacteristicWriteRequest(
                device: BluetoothDevice,
                requestId: Int,
                characteristic: BluetoothGattCharacteristic,
                preparedWrite: Boolean,
                responseNeeded: Boolean,
                offset: Int,
                value: ByteArray
            ) {
                Log.i(TAG, "onCharacteristicWriteRequest requestId=$requestId")
            }

            override fun onExecuteWrite(device: BluetoothDevice, requestId: Int, execute: Boolean) {
                Log.i(TAG, "onExecuteWrite requestId=$requestId")
            }
        }

    val server: BluetoothGattServer = bluetoothManager.openGattServer(context, callback)
}