Iceshrimp.NET/Iceshrimp.Backend/Core/Services/InstanceService.cs

using AngleSharp.Html.Parser;
using AsyncKeyedLock;
using Iceshrimp.Backend.Core.Database;
using Iceshrimp.Backend.Core.Database.Tables;
using Iceshrimp.Backend.Core.Extensions;
using Iceshrimp.Backend.Core.Federation.WebFinger;
using Iceshrimp.Backend.Core.Helpers;
using Microsoft.EntityFrameworkCore;

namespace Iceshrimp.Backend.Core.Services;

public class InstanceService(
	DatabaseContext db,
	HttpClient httpClient,
	ILogger<InstanceService> logger,
	MetaService meta
) : IScopedService
{
	private static readonly AsyncKeyedLocker<string> KeyedLocker = new(o =>
	{
		o.PoolSize        = 100;
		o.PoolInitialFill = 5;
	});

	private async Task<Instance> GetUpdatedInstanceMetadataAsync(string host, string webDomain)
	{
		if (host == webDomain)
			logger.LogDebug("Updating instance metadata for {host}", host);
		else
			logger.LogDebug("Updating instance metadata for {host} ({domain})", host, webDomain);

		host = host.ToPunycodeLower();
		var instance = await db.Instances.FirstOrDefaultAsync(p => p.Host == host);
		if (instance == null)
		{
			if (!KeyedLocker.IsInUse(host))
			{
				using (await KeyedLocker.LockAsync(host))
				{
					instance = new Instance
					{
						Id                 = IdHelpers.GenerateSnowflakeId(),
						Host               = host,
						CaughtAt           = DateTime.UtcNow,
						LastCommunicatedAt = DateTime.UtcNow
					};
					await db.AddAsync(instance);
					await db.SaveChangesAsync();
				}
			}
			else
			{
				using (await KeyedLocker.LockAsync(host))
				{
					instance = await db.Instances.FirstOrDefaultAsync(p => p.Host == host);
				}

				if (instance == null) throw new Exception("Failed to get instance metadata for {host}");
			}
		}

		if (instance.NeedsUpdate && !KeyedLocker.IsInUse(host))
		{
			using (await KeyedLocker.LockAsync(host))
			{
				instance.InfoUpdatedAt = DateTime.UtcNow;
				var nodeinfo = await GetNodeInfoAsync(webDomain);
				var icons    = await GetIconsAsync(webDomain);
				if (nodeinfo != null)
				{
					instance.Name        = nodeinfo.Metadata?.NodeName;
					instance.Description = nodeinfo.Metadata?.NodeDescription;
					instance.FaviconUrl  = icons.FaviconUrl;
					//instance.FollowersCount = TODO,
					//instance.FollowingCount = TODO,
					instance.IconUrl           = icons.IconUrl;
					instance.MaintainerName    = nodeinfo.Metadata?.Maintainer?.Name;
					instance.MaintainerEmail   = nodeinfo.Metadata?.Maintainer?.Email;
					instance.OpenRegistrations = nodeinfo.OpenRegistrations;
					instance.SoftwareName      = nodeinfo.Software?.Name;
					instance.SoftwareVersion   = nodeinfo.Software?.Version;
					instance.ThemeColor        = nodeinfo.Metadata?.ThemeColor;
				}

				await db.SaveChangesAsync();
			}
		}

		return instance;
	}

	public async Task<Instance> GetUpdatedInstanceMetadataAsync(User user)
	{
		if (user.Host == null || user.Uri == null) throw new Exception("Can't fetch instance metadata for local user");
		return await GetUpdatedInstanceMetadataAsync(user.Host, new Uri(user.Uri).Host);
	}

	private async Task<(string? FaviconUrl, string? IconUrl)> GetIconsAsync(string webDomain)
	{
		try
		{
			const int maxLength = 1_000_000;
			var       res = await httpClient.GetAsync($"https://{webDomain}", HttpCompletionOption.ResponseHeadersRead);

			if (res is not
			    {
				    IsSuccessStatusCode: true,
				    Content.Headers: { ContentType.MediaType: "text/html", ContentLength: null or <= maxLength }
			    })
				return (null, null);

			var contentLength = res.Content.Headers.ContentLength;
			var stream = await res.Content.ReadAsStreamAsync()
			                      .ContinueWithResult(p => p.GetSafeStreamOrNullAsync(maxLength, contentLength));

			if (stream == Stream.Null) return (null, null);

			var document = await new HtmlParser().ParseDocumentAsync(stream);

			var faviconUrl = document.Head?.Children.Last(e => e.NodeName.ToLower() == "link"
			                                                   && (e.GetAttribute("rel")
			                                                        ?.Contains("icon")
			                                                       ?? false))
			                         .GetAttribute("href");

			if (faviconUrl == null)
			{
				var favicon = await httpClient.GetAsync($"https://{webDomain}/favicon.ico");
				if (favicon.IsSuccessStatusCode) faviconUrl = $"https://{webDomain}/favicon.ico";
			}

			var iconUrl = document.Head?.Children.Last(e => e.NodeName.ToLower() == "link"
			                                                && (e.GetAttribute("rel")
			                                                     ?.Contains("apple-touch-icon-precomposed")
			                                                    ?? false)
			                                                || (e.GetAttribute("rel")
			                                                     ?.Contains("apple-touch-icon")
			                                                    ?? false)
			                                                || (e.GetAttribute("rel")
			                                                     ?.Contains("icon")
			                                                    ?? false))
			                      .GetAttribute("href");

			var baseUri = new Uri($"https://{webDomain}");

			return (
				faviconUrl != null ? new Uri(baseUri, faviconUrl).ToString() : null,
				iconUrl != null ? new Uri(baseUri, iconUrl).ToString() : null
			);
		}
		catch
		{
			return (null, null);
		}
	}

	private async Task<NodeInfoResponse?> GetNodeInfoAsync(string webDomain)
	{
		try
		{
			var res =
				await httpClient.GetFromJsonAsync<NodeInfoIndexResponse>($"https://{webDomain}/.well-known/nodeinfo");

			var url = res?.Links.FirstOrDefault(p => p.Rel == "http://nodeinfo.diaspora.software/ns/schema/2.1") ??
			          res?.Links.FirstOrDefault(p => p.Rel == "http://nodeinfo.diaspora.software/ns/schema/2.0");

			if (url == null) return null;

			return await httpClient.GetFromJsonAsync<NodeInfoResponse>(url.Href);
		}
		catch
		{
			return null;
		}
	}

	public async Task UpdateInstanceStatusAsync(string host, string webDomain)
	{
		var instance = await GetUpdatedInstanceMetadataAsync(host, webDomain);

		instance.LastCommunicatedAt      = DateTime.UtcNow;
		instance.LatestRequestReceivedAt = DateTime.UtcNow;

		await db.SaveChangesAsync();
	}

	public async Task UpdateInstanceStatusAsync(string host, string webDomain, int statusCode, bool notResponding)
	{
		var instance = await GetUpdatedInstanceMetadataAsync(host, webDomain);

		instance.LatestStatus        = statusCode;
		instance.LatestRequestSentAt = DateTime.UtcNow;

		if (notResponding)
		{
			instance.IsNotResponding = true;
		}
		else
		{
			instance.IsNotResponding    = false;
			instance.LastCommunicatedAt = DateTime.UtcNow;
		}

		await db.SaveChangesAsync();
	}

	public async Task MarkInstanceAsUnresponsiveAsync(string host, string webDomain)
	{
		var instance = await GetUpdatedInstanceMetadataAsync(host, webDomain);
		instance.LatestRequestSentAt = DateTime.UtcNow;
		instance.IsNotResponding     = true;
		await db.SaveChangesAsync();
	}

	public async Task<List<Rule>> GetRulesAsync()
	{
		return await db.Rules.OrderBy(p => p.Order).ThenBy(p => p.Id).ToListAsync();
	}

	public async Task<Rule> CreateRuleAsync(string text, string? description)
	{
		var count = await db.Rules.CountAsync();

		var rule = new Rule
		{
			Id          = IdHelpers.GenerateSnowflakeId(),
			Order       = count + 1,
			Text        = text,
			Description = description
		};

		db.Add(rule);
		await db.SaveChangesAsync();

		return rule;
	}

	public async Task<Rule> UpdateRuleAsync(Rule rule, int order, string text, string? description)
	{
		var count = await db.Rules.CountAsync();
		
		if (order > 0 && order != rule.Order && count != 1)
		{
			order = Math.Min(order, count);
			
			if (order > rule.Order)
			{
				var rules = await db.Rules
				                    .Where(p => rule.Order < p.Order && p.Order <= order)
				                    .ToListAsync();

				foreach (var r in rules)
					r.Order -= 1;

				db.UpdateRange(rules);
			}
			else
			{
				var rules = await db.Rules
				                    .Where(p => order <= p.Order && p.Order < rule.Order)
				                    .ToListAsync();

				foreach (var r in rules)
					r.Order += 1;

				db.UpdateRange(rules);
			}
			
			rule.Order = order;
		}

		rule.Text        = text;
		rule.Description = description;

		await db.SaveChangesAsync();

		return rule;
	}

	public async Task<(string?, string?)> GetInstanceImageAsync()
	{
		var (iconId, bannerId) = await meta.GetManyAsync(MetaEntity.IconFileId, MetaEntity.BannerFileId);
		return (await db.DriveFiles.Where(p => p.Id == iconId).Select(p => p.RawAccessUrl).FirstOrDefaultAsync(),
		        await db.DriveFiles.Where(p => p.Id == bannerId).Select(p => p.RawAccessUrl).FirstOrDefaultAsync());
	}
}