Bluetooth APIs with TaskCompletionSource

Extensions.cs

using System;
using System.Threading.Tasks;
using System.Linq;
using System.Diagnostics;

namespace Robotics.Mobile.Core.Bluetooth.LE
{
	public static class Extensions
	{
		/// <summary>
		/// Create a full Guid from the Bluetooth "Assigned Number" (short version)
		/// </summary>
		/// <returns>a Guid of the form {00002A37-0000-1000-8000-00805f9b34fb}</returns>
		/// <param name="@partial">4 digit hex value, eg 0x2A37 (which is heart rate measurement)</param>
		public static Guid UuidFromPartial(this Int32 @partial) {
			//this sometimes returns only the significant bits, e.g.
			//180d or whatever. so we need to add the full string
			string id = @partial.ToString ("X").PadRight(4,'0');
			if (id.Length == 4) {
				id = "0000" + id + "-0000-1000-8000-00805f9b34fb";
			}
			return Guid.ParseExact (id, "d");
		}

		/// <summary>
		/// Extract the Bluetooth "Assigned Number" from a Uuid 
		/// </summary>
		/// <returns>4 digit hex value, eg 0x2A37 (which is heart rate measurement)</returns>
		/// <param name="uuid">a Guid of the form {00002A37-0000-1000-8000-00805f9b34fb}</param>
		public static string PartialFromUuid(this Guid uuid) {
			// opposite of the UuidFromPartial method
			string id = uuid.ToString ();
			if (id.Length > 8) {
				id = id.Substring (4, 4);
			}
			return "0x" + id;
		}

		/// <summary>
		/// Asynchronously gets the requested service
		/// </summary>
		public static Task<IDevice> ConnectAsync (this IAdapter adapter, IDevice device)
		{
			if (device.State == DeviceState.Connected)
				return Task.FromResult<IDevice> (null);

			var tcs = new TaskCompletionSource<IDevice> ();
			EventHandler<DeviceConnectionEventArgs> h = null;
			h = (sender, e) => {
				Debug.WriteLine ("CCC: " + e.Device.ID + " " + e.Device.State);
		        if (e.Device.ID == device.ID)
		        {
					adapter.DeviceConnected -= h;
          			tcs.SetResult (e.Device);
				}
			};
			adapter.DeviceConnected += h;

			adapter.ConnectToDevice (device);

			return tcs.Task;
		}

		/// <summary>
		/// Asynchronously gets the requested service
		/// </summary>
		public static Task<IService> GetServiceAsync (this IDevice device, Guid id)
		{
			if (device.Services.Count > 0) {
				return Task.FromResult (device.Services.First (x => x.ID == id));
			}

			var tcs = new TaskCompletionSource<IService> ();
			EventHandler h = null;
			h = (sender, e) => {
				device.ServicesDiscovered -= h;
				try {
					var s = device.Services.First (x => x.ID == id);
					tcs.SetResult (s);
				} catch (Exception ex) {
					tcs.SetException (ex);
				}
			};
			device.ServicesDiscovered += h;
			device.DiscoverServices ();

			return tcs.Task;
		}

		/// <summary>
		/// Asynchronously gets the requested characteristic
		/// </summary>
		public static Task<ICharacteristic> GetCharacteristicAsync (this IService service, Guid id)
		{
			if (service.Characteristics.Count > 0) {
				return Task.FromResult (service.Characteristics.First (x => x.ID == id));
			}

			var tcs = new TaskCompletionSource<ICharacteristic> ();
			EventHandler h = null;
			h = (sender, e) => {
				service.CharacteristicsDiscovered -= h;
				try {
					var s = service.Characteristics.First (x => x.ID == id);
					tcs.SetResult (s);
				} catch (Exception ex) {
					tcs.SetException (ex);
				}
			};
			service.CharacteristicsDiscovered += h;
			service.DiscoverCharacteristics ();

			return tcs.Task;
		}
	}
}