Minecraft-Phantom-Panel/Server/Phantom.Server.Minecraft/MinecraftVersionApi.cs

using System.Collections.Immutable;
using System.Net.Http.Json;
using System.Text.Json;
using Phantom.Common.Data.Minecraft;
using Phantom.Common.Logging;
using Phantom.Utils.Cryptography;
using Phantom.Utils.IO;
using Phantom.Utils.Runtime;
using Serilog;

namespace Phantom.Server.Minecraft;

sealed class MinecraftVersionApi : IDisposable {
	private static readonly ILogger Logger = PhantomLogger.Create<MinecraftVersionApi>();
	
	private const string VersionManifestUrl = "https://launchermeta.mojang.com/mc/game/version_manifest.json";
	
	private readonly HttpClient http = new ();

	public void Dispose() {
		http.Dispose();
	}

	public async Task<ImmutableArray<MinecraftVersion>> GetVersions(CancellationToken cancellationToken) {
		return await FetchVersions(cancellationToken) ?? ImmutableArray<MinecraftVersion>.Empty;
	}
	
	private async Task<ImmutableArray<MinecraftVersion>?> FetchVersions(CancellationToken cancellationToken) {
		return await FetchOrFailSilently(async () => {
			var versionManifest = await FetchJson(VersionManifestUrl, "version manifest", cancellationToken);
			return GetVersionsFromManifest(versionManifest);
		});
	}
	
	public async Task<FileDownloadInfo?> GetServerExecutableInfo(ImmutableArray<MinecraftVersion> versions, string version, CancellationToken cancellationToken) {
		var versionObject = versions.FirstOrDefault(v => v.Id == version);
		if (versionObject == null) {
			Logger.Error("Version {Version} was not found in version manifest.", version);
			return null;
		}
		
		return await FetchOrFailSilently(async () => {
			var versionMetadata = await FetchJson(versionObject.MetadataUrl, "version metadata", cancellationToken);
			return GetServerExecutableInfoFromMetadata(versionMetadata);
		});
	}

	private static async Task<T?> FetchOrFailSilently<T>(Func<Task<T?>> task) {
		try {
			return await task();
		} catch (StopProcedureException) {
			return default;
		} catch (Exception e) {
			Logger.Error(e, "An unexpected error occurred.");
			return default;
		}
	}

	private async Task<JsonElement> FetchJson(string url, string description, CancellationToken cancellationToken) {
		Logger.Debug("Fetching {Description} JSON from: {Url}", description, url);

		try {
			return await http.GetFromJsonAsync<JsonElement>(url, cancellationToken);
		} catch (HttpRequestException e) {
			Logger.Error(e, "Unable to download {Description}.", description);
			throw StopProcedureException.Instance;
		} catch (Exception e) {
			Logger.Error(e, "Unable to parse {Description} as JSON.", description);
			throw StopProcedureException.Instance;
		}
	}

	private static ImmutableArray<MinecraftVersion> GetVersionsFromManifest(JsonElement versionManifest) {
		JsonElement versionsElement = GetJsonPropertyOrThrow(versionManifest, "versions", JsonValueKind.Array, "version manifest");
		var foundVersions = ImmutableArray.CreateBuilder<MinecraftVersion>(versionsElement.GetArrayLength());

		foreach (var versionElement in versionsElement.EnumerateArray()) {
			try {
				foundVersions.Add(GetVersionFromManifestEntry(versionElement));
			} catch (StopProcedureException) {}
		}

		return foundVersions.MoveToImmutable();
	}

	private static MinecraftVersion GetVersionFromManifestEntry(JsonElement versionElement) {
		JsonElement idElement = GetJsonPropertyOrThrow(versionElement, "id", JsonValueKind.String, "version entry in version manifest");
		string id = idElement.GetString() ?? throw new InvalidOperationException();

		JsonElement typeElement = GetJsonPropertyOrThrow(versionElement, "type", JsonValueKind.String, "version entry in version manifest");
		string? typeString = typeElement.GetString();

		var type = MinecraftVersionTypes.FromString(typeString);
		if (type == MinecraftVersionType.Other) {
			Logger.Warning("Unknown version type: {Type} ({Version})", typeString, id);
		}

		JsonElement urlElement = GetJsonPropertyOrThrow(versionElement, "url", JsonValueKind.String, "version entry in version manifest");
		string? url = urlElement.GetString();

		if (!Uri.TryCreate(url, UriKind.Absolute, out var uri)) {
			Logger.Error("The \"url\" key in version entry in version manifest does not contain a valid URL: {Url}", url);
			throw StopProcedureException.Instance;
		}

		if (uri.Scheme != "https" || !uri.AbsolutePath.EndsWith(".json", StringComparison.OrdinalIgnoreCase)) {
			Logger.Error("The \"url\" key in version entry in version manifest does not contain an accepted URL: {Url}", url);
			throw StopProcedureException.Instance;
		}

		return new MinecraftVersion(id, type, url);
	}

	private static FileDownloadInfo GetServerExecutableInfoFromMetadata(JsonElement versionMetadata) {
		JsonElement downloadsElement = GetJsonPropertyOrThrow(versionMetadata, "downloads", JsonValueKind.Object, "version metadata");
		JsonElement serverElement = GetJsonPropertyOrThrow(downloadsElement, "server", JsonValueKind.Object, "downloads object in version metadata");
		JsonElement urlElement = GetJsonPropertyOrThrow(serverElement, "url", JsonValueKind.String, "downloads.server object in version metadata");
		string? url = urlElement.GetString();

		if (!Uri.TryCreate(url, UriKind.Absolute, out var uri)) {
			Logger.Error("The \"url\" key in downloads.server object in version metadata does not contain a valid URL: {Url}", url);
			throw StopProcedureException.Instance;
		}

		if (uri.Scheme != "https" || !uri.AbsolutePath.EndsWith(".jar", StringComparison.OrdinalIgnoreCase)) {
			Logger.Error("The \"url\" key in downloads.server object in version metadata does not contain a accepted URL: {Url}", url);
			throw StopProcedureException.Instance;
		}

		JsonElement sizeElement = GetJsonPropertyOrThrow(serverElement, "size", JsonValueKind.Number, "downloads.server object in version metadata");
		ulong size;
		try {
			size = sizeElement.GetUInt64();
		} catch (FormatException) {
			Logger.Error("The \"size\" key in downloads.server object in version metadata contains an invalid file size: {Size}", sizeElement);
			throw StopProcedureException.Instance;
		}

		JsonElement sha1Element = GetJsonPropertyOrThrow(serverElement, "sha1", JsonValueKind.String, "downloads.server object in version metadata");
		Sha1String hash;
		try {
			hash = Sha1String.FromString(sha1Element.GetString());
		} catch (Exception) {
			Logger.Error("The \"sha1\" key in downloads.server object in version metadata does not contain a valid SHA-1 hash: {Sha1}", sha1Element.GetString());
			throw StopProcedureException.Instance;
		}

		return new FileDownloadInfo(url, hash, new FileSize(size));
	}

	private static JsonElement GetJsonPropertyOrThrow(JsonElement parentElement, string propertyKey, JsonValueKind expectedKind, string location) {
		if (!parentElement.TryGetProperty(propertyKey, out var valueElement)) {
			Logger.Error("Missing \"{Property}\" key in " + location + ".", propertyKey);
			throw StopProcedureException.Instance;
		}

		if (valueElement.ValueKind != expectedKind) {
			Logger.Error("The \"{Property}\" key in " + location + " does not contain a JSON {ExpectedType}. Actual type: {ActualType}", propertyKey, expectedKind, valueElement.ValueKind);
			throw StopProcedureException.Instance;
		}

		return valueElement;
	}
}