Discord-History-Tracker/app/Server/Endpoints/TrackMessagesEndpoint.cs

using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Net;
using System.Text.Json;
using System.Threading.Tasks;
using DHT.Server.Data;
using DHT.Server.Data.Filters;
using DHT.Server.Database;
using DHT.Server.Download;
using DHT.Utils.Collections;
using DHT.Utils.Http;
using Microsoft.AspNetCore.Http;

namespace DHT.Server.Endpoints;

sealed class TrackMessagesEndpoint : BaseEndpoint {
	private const string HasNewMessages = "1";
	private const string NoNewMessages = "0";

	public TrackMessagesEndpoint(IDatabaseFile db) : base(db) {}

	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
		var root = await ReadJson(ctx);

		if (root.ValueKind != JsonValueKind.Array) {
			throw new HttpException(HttpStatusCode.BadRequest, "Expected root element to be an array.");
		}

		var addedMessageIds = new HashSet<ulong>();
		var messages = new Message[root.GetArrayLength()];

		int i = 0;
		foreach (JsonElement ele in root.EnumerateArray()) {
			var message = ReadMessage(ele, "message");
			messages[i++] = message;
			addedMessageIds.Add(message.Id);
		}

		var addedMessageFilter = new MessageFilter { MessageIds = addedMessageIds };
		bool anyNewMessages = await Db.Messages.Count(addedMessageFilter) < addedMessageIds.Count;

		await Db.Messages.Add(messages);

		return new HttpOutput.Text(anyNewMessages ? HasNewMessages : NoNewMessages);
	}

	private static Message ReadMessage(JsonElement json, string path) => new () {
		Id = json.RequireSnowflake("id", path),
		Sender = json.RequireSnowflake("sender", path),
		Channel = json.RequireSnowflake("channel", path),
		Text = json.RequireString("text", path),
		Timestamp = json.RequireLong("timestamp", path),
		EditTimestamp = json.HasKey("editTimestamp") ? json.RequireLong("editTimestamp", path) : null,
		RepliedToId = json.HasKey("repliedToId") ? json.RequireSnowflake("repliedToId", path) : null,
		Attachments = json.HasKey("attachments") ? ReadAttachments(json.RequireArray("attachments", path + ".attachments"), path + ".attachments[]").ToImmutableList() : ImmutableList<Attachment>.Empty,
		Embeds = json.HasKey("embeds") ? ReadEmbeds(json.RequireArray("embeds", path + ".embeds"), path + ".embeds[]").ToImmutableList() : ImmutableList<Embed>.Empty,
		Reactions = json.HasKey("reactions") ? ReadReactions(json.RequireArray("reactions", path + ".reactions"), path + ".reactions[]").ToImmutableList() : ImmutableList<Reaction>.Empty,
	};

	[SuppressMessage("ReSharper", "ConvertToLambdaExpression")]
	private static IEnumerable<Attachment> ReadAttachments(JsonElement.ArrayEnumerator array, string path) => array.Select(ele => {
		var downloadUrl = ele.RequireString("url", path);
		return new Attachment {
			Id = ele.RequireSnowflake("id", path),
			Name = ele.RequireString("name", path),
			Type = ele.HasKey("type") ? ele.RequireString("type", path) : null,
			NormalizedUrl = DiscordCdn.NormalizeUrl(downloadUrl),
			DownloadUrl = downloadUrl,
			Size = (ulong) ele.RequireLong("size", path),
			Width = ele.HasKey("width") ? ele.RequireInt("width", path) : null,
			Height = ele.HasKey("height") ? ele.RequireInt("height", path) : null,
		};
	}).DistinctByKeyStable(static attachment => {
		// Some Discord messages have duplicate attachments with the same id for unknown reasons.
		return attachment.Id;
	});

	private static IEnumerable<Embed> ReadEmbeds(JsonElement.ArrayEnumerator array, string path) => array.Select(ele => new Embed {
		Json = ele.ValueKind == JsonValueKind.String ? ele.ToString() : throw new HttpException(HttpStatusCode.BadRequest, "Expected key '" + path + "' to be a string.")
	});

	private static IEnumerable<Reaction> ReadReactions(JsonElement.ArrayEnumerator array, string path) => array.Select(ele => {
		var reaction = new Reaction {
			EmojiId = ele.HasKey("id") ? ele.RequireSnowflake("id", path) : null,
			EmojiName = ele.HasKey("name") ? ele.RequireString("name", path) : null,
			EmojiFlags = ReadEmojiFlag(ele, "isAnimated", path, EmojiFlags.Animated),
			Count = ele.RequireInt("count", path),
		};

		if (reaction.EmojiId == null && reaction.EmojiName == null) {
			throw new HttpException(HttpStatusCode.BadRequest, "Expected key '" + path + ".id' and/or '" + path + ".name' to be present.");
		}

		return reaction;
	});

	private static EmojiFlags ReadEmojiFlag(JsonElement ele, string key, string path, EmojiFlags flag) {
		return ele.HasKey(key) && ele.RequireBool(key, path) ? flag : EmojiFlags.None;
	}
}