Shazam.cs

using System;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using NAudio.CoreAudioApi;
using NAudio.Wave;
using Shozom.Magic;

namespace Shozom {

	internal static class Shazam {

		private static readonly MMDeviceEnumerator Enumerator = new();
		private static readonly HttpClient Http = new() { Timeout = TimeSpan.FromSeconds(3) };

		private static readonly string DeviceId = Guid.NewGuid().ToString();

		public static async Task<ShozomMatch> IdentifyAsync(string deviceId, CancellationToken cancel) {
			var device = Enumerator.GetDevice(deviceId);
			if (device == null || device.State != DeviceState.Active) throw new ArgumentException("Selected device not available");

			var capture = device.DataFlow switch {
				DataFlow.Capture => new WasapiCapture(device),
				DataFlow.Render => new WasapiLoopbackCapture(device)
			};

			var buffer = new BufferedWaveProvider(capture.WaveFormat) { ReadFully = false, DiscardOnBufferOverflow = true };
			using var resampler = new MediaFoundationResampler(buffer, new WaveFormat(16000, 16, 1));
			var samples = resampler.ToSampleProvider();

			capture.DataAvailable += (_, e) => { buffer.AddSamples(e.Buffer, 0, e.BytesRecorded); };
			capture.StartRecording();

			var analyser = new Analyser();
			var landmarker = new Landmarker(analyser);

			var retryMs = 3000;

			while (true) {
				if (cancel.IsCancellationRequested) {
					capture.StopRecording();
					throw new OperationCanceledException();
				}

				if (buffer.BufferedDuration.TotalSeconds < 1) {
					Thread.Sleep(100);
					continue;
				}

				analyser.ReadChunk(samples);

				if (analyser.StripeCount > 2 * Landmarker.RADIUS_TIME) landmarker.Find(analyser.StripeCount - Landmarker.RADIUS_TIME - 1);
				if (analyser.ProcessedMs < retryMs) continue;

				var body = new ShazamRequest {
					Signature = new ShazamSignature {
						Uri = "data:audio/vnd.shazam.sig;base64," + Convert.ToBase64String(Signature.Create(Analyser.SAMPLE_RATE, analyser.ProcessedSamples, landmarker)),
						SampleMs = analyser.ProcessedMs
					}
				};

				using var res = await Http.PostAsync($"https://amp.shazam.com/discovery/v5/en/US/android/-/tag/{DeviceId}/{Guid.NewGuid()}", new StringContent(JsonSerializer.Serialize(body), Encoding.UTF8, "application/json"), cancel);
				var data = JsonSerializer.Deserialize<ShazamResponse>(await res.Content.ReadAsStringAsync(cancel));

				if (data.RetryMs > 0) {
					retryMs = (int) data.RetryMs;
					continue;
				}

				capture.StopRecording();
				if (data.Track == null) return null;
				return new ShozomMatch {
					Title = data.Track.Title,
					Artist = data.Track.Subtitle,
					Link = data.Track.Share.Link,
					Cover = data.Track?.Images?.CoverHQ ?? data.Track?.Images?.Cover ?? data.Track.Share.Image
				};
			}
		}

	}

}