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using System.Collections.Concurrent;
using System.Diagnostics;
using System.Net.Http.Json;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Text.Json.Serialization;
using ArcaneLibs.Collections;
using ArcaneLibs.Extensions;
using LibMatrix.Extensions;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
namespace LibMatrix.Services;
public class HomeserverResolverService {
private readonly MatrixHttpClient _httpClient = new() {
Timeout = TimeSpan.FromMilliseconds(10000)
};
private static readonly SemaphoreCache<WellKnownUris> WellKnownCache = new();
private readonly ILogger<HomeserverResolverService> _logger;
public HomeserverResolverService(ILogger<HomeserverResolverService> logger) {
_logger = logger;
if (logger is NullLogger<HomeserverResolverService>) {
var stackFrame = new StackTrace(true).GetFrame(1);
Console.WriteLine(
$"WARN | Null logger provided to HomeserverResolverService!\n{stackFrame.GetMethod().DeclaringType} at {stackFrame.GetFileName()}:{stackFrame.GetFileLineNumber()}");
}
}
private static SemaphoreSlim _wellKnownSemaphore = new(1, 1);
public async Task<WellKnownUris> ResolveHomeserverFromWellKnown(string homeserver) {
ArgumentNullException.ThrowIfNull(homeserver);
return await WellKnownCache.GetOrAdd(homeserver, async () => {
await _wellKnownSemaphore.WaitAsync();
_logger.LogTrace($"Resolving homeserver well-knowns: {homeserver}");
var client = _tryResolveClientEndpoint(homeserver);
var res = new WellKnownUris();
// try {
res.Client = await client ?? throw new Exception("Could not resolve client URL.");
// }
// catch (Exception e) {
// _logger.LogError(e, "Error resolving client well-known for {hs}", homeserver);
// }
var server = _tryResolveServerEndpoint(homeserver);
// try {
res.Server = await server ?? throw new Exception("Could not resolve server URL.");
// }
// catch (Exception e) {
// _logger.LogError(e, "Error resolving server well-known for {hs}", homeserver);
// }
_logger.LogInformation("Resolved well-knowns for {hs}: {json}", homeserver, res.ToJson(indent: false));
_wellKnownSemaphore.Release();
return res;
});
}
private async Task<string?> _tryResolveClientEndpoint(string homeserver) {
ArgumentNullException.ThrowIfNull(homeserver);
_logger.LogTrace("Resolving client well-known: {homeserver}", homeserver);
ClientWellKnown? clientWellKnown = null;
// check if homeserver has a client well-known
if (homeserver.StartsWith("https://")) {
clientWellKnown = await _httpClient.TryGetFromJsonAsync<ClientWellKnown>($"{homeserver}/.well-known/matrix/client");
}
else if (homeserver.StartsWith("http://")) {
clientWellKnown = await _httpClient.TryGetFromJsonAsync<ClientWellKnown>($"{homeserver}/.well-known/matrix/client");
}
else {
clientWellKnown ??= await _httpClient.TryGetFromJsonAsync<ClientWellKnown>($"https://{homeserver}/.well-known/matrix/client");
clientWellKnown ??= await _httpClient.TryGetFromJsonAsync<ClientWellKnown>($"http://{homeserver}/.well-known/matrix/client");
if (clientWellKnown is null) {
if (await _httpClient.CheckSuccessStatus($"https://{homeserver}/_matrix/client/versions"))
return $"https://{homeserver}";
if (await _httpClient.CheckSuccessStatus($"http://{homeserver}/_matrix/client/versions"))
return $"http://{homeserver}";
}
}
if (!string.IsNullOrWhiteSpace(clientWellKnown?.Homeserver.BaseUrl))
return clientWellKnown.Homeserver.BaseUrl;
_logger.LogInformation("No client well-known...");
return null;
}
private async Task<string?> _tryResolveServerEndpoint(string homeserver) {
// TODO: implement SRV delegation via DoH: https://developers.google.com/speed/public-dns/docs/doh/json
ArgumentNullException.ThrowIfNull(homeserver);
_logger.LogTrace($"Resolving server well-known: {homeserver}");
ServerWellKnown? serverWellKnown = null;
// check if homeserver has a server well-known
if (homeserver.StartsWith("https://")) {
serverWellKnown = await _httpClient.TryGetFromJsonAsync<ServerWellKnown>($"{homeserver}/.well-known/matrix/server");
}
else if (homeserver.StartsWith("http://")) {
serverWellKnown = await _httpClient.TryGetFromJsonAsync<ServerWellKnown>($"{homeserver}/.well-known/matrix/server");
}
else {
serverWellKnown ??= await _httpClient.TryGetFromJsonAsync<ServerWellKnown>($"https://{homeserver}/.well-known/matrix/server");
serverWellKnown ??= await _httpClient.TryGetFromJsonAsync<ServerWellKnown>($"http://{homeserver}/.well-known/matrix/server");
}
_logger.LogInformation("Server well-known for {hs}: {json}", homeserver, serverWellKnown?.ToJson() ?? "null");
if (!string.IsNullOrWhiteSpace(serverWellKnown?.Homeserver)) {
var resolved = serverWellKnown.Homeserver;
if (resolved.StartsWith("https://") || resolved.StartsWith("http://"))
return resolved;
if (await _httpClient.CheckSuccessStatus($"https://{resolved}/_matrix/federation/v1/version"))
return $"https://{resolved}";
if (await _httpClient.CheckSuccessStatus($"http://{resolved}/_matrix/federation/v1/version"))
return $"http://{resolved}";
_logger.LogWarning("Server well-known points to invalid server: {resolved}", resolved);
}
// fallback: most servers host C2S and S2S on the same domain
var clientUrl = await _tryResolveClientEndpoint(homeserver);
if (clientUrl is not null && await _httpClient.CheckSuccessStatus($"{clientUrl}/_matrix/federation/v1/version"))
return clientUrl;
_logger.LogInformation("No server well-known...");
return null;
}
public async Task<string?> ResolveMediaUri(string homeserver, string mxc) {
if (homeserver is null) throw new ArgumentNullException(nameof(homeserver));
if (mxc is null) throw new ArgumentNullException(nameof(mxc));
if (!mxc.StartsWith("mxc://")) throw new InvalidDataException("mxc must start with mxc://");
homeserver = (await ResolveHomeserverFromWellKnown(homeserver)).Client;
return mxc.Replace("mxc://", $"{homeserver}/_matrix/media/v3/download/");
}
public class WellKnownUris {
public string? Client { get; set; }
public string? Server { get; set; }
}
public class ClientWellKnown {
[JsonPropertyName("m.homeserver")]
public WellKnownHomeserver Homeserver { get; set; }
public class WellKnownHomeserver {
[JsonPropertyName("base_url")]
public string BaseUrl { get; set; }
}
}
public class ServerWellKnown {
[JsonPropertyName("m.server")]
public string Homeserver { get; set; }
}
}
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