feat: begin adding subscription to YT notifications

src/src/StevesBot.Webhook/Program.cs

@@ -1,7 +1,18 @@
 var builder = WebApplication.CreateBuilder(args);
 
+builder.Services
+  .AddOptionsWithValidateOnStart<SubscriptionOptions>()
+  .BindConfiguration(nameof(SubscriptionOptions))
+  .ValidateDataAnnotations();
+
+builder.Services
+  .AddHttpClient<IPubSubClient, PubSubClient>()
+  .AddStandardResilienceHandler();
+
 builder.Services.AddOpenApi();
 
+builder.Services.AddHostedService<SubscriptionWorker>();
+
 var app = builder.Build();
 
 if (app.Environment.IsDevelopment())

src/src/StevesBot.Webhook/StevesBot.Webhook.csproj

@@ -8,6 +8,8 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" />
+    <PackageReference Include="Microsoft.Extensions.Http" />
+    <PackageReference Include="Microsoft.Extensions.Http.Resilience" />
   </ItemGroup>
 
 </Project>

src/src/StevesBot.Webhook/SubscriptionWorker.cs

@@ -0,0 +1,49 @@
+namespace StevesBot.Webhook;
+
+internal sealed class SubscriptionWorker(
+  ILogger<SubscriptionWorker> logger,
+  IOptions<SubscriptionOptions> options,
+  IPubSubClient pubSubClient
+) : IHostedLifecycleService
+{
+  private readonly ILogger<SubscriptionWorker> _logger = logger;
+  private readonly SubscriptionOptions _options = options.Value;
+  private readonly IPubSubClient _pubSubClient = pubSubClient;
+
+  public Task StartAsync(CancellationToken cancellationToken)
+  {
+    return Task.CompletedTask;
+  }
+
+  public Task StartingAsync(CancellationToken cancellationToken)
+  {
+    return Task.CompletedTask;
+  }
+
+  public async Task StartedAsync(CancellationToken cancellationToken)
+  {
+    _logger.LogInformation("Subscribing to notifications");
+
+    await _pubSubClient.SubscribeAsync(
+      _options.CallbackBaseUrl,
+      _options.TopicUrl,
+      cancellationToken
+    );
+  }
+
+
+  public Task StopAsync(CancellationToken cancellationToken)
+  {
+    return Task.CompletedTask;
+  }
+
+  public Task StoppingAsync(CancellationToken cancellationToken)
+  {
+    return Task.CompletedTask;
+  }
+
+  public Task StoppedAsync(CancellationToken cancellationToken)
+  {
+    return Task.CompletedTask;
+  }
+}

src/src/StevesBot.Webhook/Usings.cs

@@ -0,0 +1,6 @@
+global using System.ComponentModel.DataAnnotations;
+
+global using Microsoft.Extensions.Options;
+
+global using StevesBot.Webhook;
+global using StevesBot.Webhook.YouTube;

src/src/StevesBot.Webhook/YouTube/IPubSubClient.cs

@@ -0,0 +1,16 @@
+namespace StevesBot.Webhook.YouTube;
+
+internal interface IPubSubClient
+{
+  Task SubscribeAsync(
+    string callbackUrl,
+    string topicUrl,
+    CancellationToken cancellationToken = default
+  );
+
+  Task UnsubscribeAsync(
+    string callbackUrl,
+    string topicUrl,
+    CancellationToken cancellationToken = default
+  );
+}

src/src/StevesBot.Webhook/YouTube/PubSubClient.cs

@@ -0,0 +1,32 @@
+
+namespace StevesBot.Webhook.YouTube;
+
+internal sealed class PubSubClient(HttpClient httpClient) : IPubSubClient
+{
+  private const string SubscribeEndpoint = "subscribe";
+  private readonly HttpClient _httpClient = httpClient;
+
+  public async Task SubscribeAsync(string callbackUrl, string topicUrl, CancellationToken cancellationToken = default)
+  {
+    var uri = new Uri(SubscribeEndpoint, UriKind.Relative);
+    var formFields = new Dictionary<string, string>()
+    {
+      { "hub.callback", callbackUrl },
+      { "hub.topic", topicUrl },
+      { "hub.verify", "async" },
+      { "hub.mode", "subscribe" }
+    };
+    using var form = new FormUrlEncodedContent(formFields);
+    var response = await _httpClient.PostAsync(uri, form, cancellationToken);
+
+    if (response.IsSuccessStatusCode is false)
+    {
+      throw new PubSubClientException("Failed to subscribe");
+    }
+  }
+
+  public Task UnsubscribeAsync(string callbackUrl, string topicUrl, CancellationToken cancellationToken = default)
+  {
+    throw new NotImplementedException();
+  }
+}

src/src/StevesBot.Webhook/YouTube/PubSubClientException.cs

@@ -0,0 +1,16 @@
+namespace StevesBot.Webhook.YouTube;
+
+internal sealed class PubSubClientException : Exception
+{
+  public PubSubClientException()
+  {
+  }
+
+  public PubSubClientException(string message) : base(message)
+  {
+  }
+
+  public PubSubClientException(string message, Exception innerException) : base(message, innerException)
+  {
+  }
+}

src/src/StevesBot.Webhook/YouTube/SubscriptionOptions.cs

@@ -0,0 +1,10 @@
+namespace StevesBot.Webhook.YouTube;
+
+internal sealed record SubscriptionOptions
+{
+  [Required]
+  public string CallbackBaseUrl { get; init; } = string.Empty;
+
+  [Required]
+  public string TopicUrl { get; init; } = string.Empty;
+}

src/src/StevesBot.Webhook/appsettings.Example.json

@@ -0,0 +1,6 @@
+{
+  "SubscriptionOptions": {
+    "CallbackUrl": "CallbackUrl",
+    "TopicUrl": "TopicUrl"
+  }
+}