feat: public endpoint to list links on a reddit post id

Resolves #33

Author: kyleratti

ApplicationData/DataReaderExtensions.cs

@@ -0,0 +1,17 @@
+using System.Data;
+using System.Data.Common;
+
+namespace ApplicationData;
+
+public static class DataReaderExtensions
+{
+	public static async IAsyncEnumerable<T> SelectAsync<T>(this DbDataReader reader, Func<IDataReader, T> mapper)
+	{
+		await using var scopedReader = reader; // auto-dispose
+
+		while (await scopedReader.ReadAsync())
+		{
+			yield return await Task.FromResult(mapper(scopedReader));
+		}
+	}
+}

ApplicationData/Services/LinkProvider.cs

@@ -79,6 +79,27 @@ FROM app.links l
 		);
 	}
 
+	public async Task<IReadOnlyCollection<Link>> FindAllLinksByPostId(string redditPostId)
+	{
+		 var links = (await _db.ExecuteReaderAsync(
+			$@"SELECT l.link_id, l.reddit_post_id, l.link_url, l.link_type, l.created_at, l.owner
+				FROM app.links l
+				WHERE
+					l.reddit_post_id = @redditPostId
+					AND l.is_deleted = false",
+			new NpgsqlParameter[] { new("@redditPostId", redditPostId) }))
+			.SelectAsync(reader => new Link(
+				linkId: reader.GetInt32(0),
+				redditPostId: reader.GetString(1),
+				linkUrl: reader.GetString(2),
+				linkType: ParseRawLinkType(reader.GetInt16(3)),
+				createdAt: reader.GetDateTime(4),
+				ownerId: reader.GetInt32(5)
+			));
+
+		 return await links.ToArrayAsync();
+	}
+
 	public async Task DeleteLinkById(int linkId)
 	{
 		await using var tx = await _db.CreateTransactionAsync(System.Data.IsolationLevel.Serializable);

WebApi/AuthHandlers/ApiKeyAuthHandler.cs

@@ -5,6 +5,7 @@
 using System.Text.RegularExpressions;
 using ApplicationData.Services;
 using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authorization;
 using Microsoft.Extensions.Options;
 using WebApi.Middleware;
 using WebApi.Util;
@@ -40,6 +41,10 @@ UserCache userCache
 	protected override async Task<AuthenticateResult> HandleAuthenticateAsync() =>
 		await JsonExceptionMiddleware.InvokeWithExceptionHandler(Request.HttpContext, async () =>
 		{
+			// For endpoints with IAllowAnonymous, skip the authentication check.
+			if (Context.GetEndpoint()?.Metadata.GetMetadata<IAllowAnonymous>() != null)
+				return AuthenticateResult.NoResult();
+
 			if (!Request.Headers.TryGetValue("Authorization", out var authorization))
 				return AuthenticateResult.Fail("No authorization key provided");
 

WebApi/Controllers/PublicController.cs

@@ -0,0 +1,61 @@
+using System.Net;
+using ApplicationData.Services;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Newtonsoft.Json;
+using Swashbuckle.AspNetCore.Annotations;
+using WebApi.Models;
+using WebApi.Util;
+
+namespace WebApi.Controllers;
+
+/// <summary>
+/// PublicController
+/// </summary>
+[ApiController]
+[Route("v1/[controller]")]
+[AllowAnonymous]
+public class PublicController : ApiController
+{
+	private readonly LinkProvider _linkProvider;
+	private readonly UserCache _userCache;
+
+	/// <summary>
+	/// C'tor
+	/// </summary>
+	public PublicController(IServiceProvider serviceProvider, LinkProvider linkProvider, UserCache userCache)
+		: base(serviceProvider)
+	{
+		_linkProvider = linkProvider;
+		_userCache = userCache;
+	}
+
+	/// <summary>
+	/// Find links available for the specified reddit post ID.
+	/// </summary>
+	/// <param name="redditPostId">The unique reddit post ID. For example, use "sf8kp8" from the permalink "https://www.reddit.com/r/aww/comments/sf8kp8/treats_you_say/".</param>
+	[HttpGet]
+	[Route("Link/By-Reddit-Post-Id/{redditPostId}")]
+	[SwaggerResponse((int)HttpStatusCode.OK,
+		description: "OK. A list of links available for this reddit post ID.",
+		type: typeof(IReadOnlyCollection<PublicLinkListingResult>))]
+	public async Task<IReadOnlyCollection<PublicLinkListingResult>> FindLinksByPostId(string redditPostId)
+	{
+		var linksByPostId = await _linkProvider.FindAllLinksByPostId(redditPostId);
+		return await linksByPostId.ToAsyncEnumerable()
+			.SelectAwait(async link => new PublicLinkListingResult(
+				link.LinkUrl,
+				LinkTypeHelpers.ParseToSerializableLinkType(link.LinkType.RawValue),
+				ProviderUsername: (await _userCache.FindUser(link.OwnerId)).Map(x => x.DisplayUsername).Value))
+			.ToArrayAsync();
+	}
+
+	/// <summary>
+	/// A link listing result accessible to the public.
+	/// </summary>
+	public record PublicLinkListingResult(
+		[JsonProperty("linkUrl")] string LinkUrl,
+		[JsonProperty("linkType")] SerializableLinkType LinkType,
+		[JsonProperty("providerUsername")] string ProviderUsername
+	);
+}