using MaxMind.Db;

using Microsoft.Extensions.Logging.Abstractions;

using PrivaPub.Infrastructure.Geo;
using PrivaPub.Infrastructure.Statistics;
using PrivaPub.Tests.Support;

using System.IO.Compression;

namespace PrivaPub.Tests.Infrastructure
{
	public sealed class GeoUpdaterTests : IAsyncLifetime
	{
		static readonly DateTime Now = new(2026, 10, 4, 12, 0, 0, DateTimeKind.Utc);
		static readonly DateTime LastMonth = new(2026, 9, 2, 0, 0, 0, DateTimeKind.Utc);

		readonly string _directory = Path.Combine(Path.GetTempPath(), $"privapub-geo-{Guid.NewGuid():N}");
		Peer _peer;
		GeoUpdater _updater;
		DbIpLocator _locator;

		public async ValueTask InitializeAsync()
		{
			_peer = await Peer.Start();
			var options = new StaticOptions<StatisticsOptions>(new StatisticsOptions
			{
				GeoDirectory = _directory,
				Geo = new GeoOptions { DownloadBase = $"{_peer.A}/free" }
			});
			_locator = new DbIpLocator(options, NullLogger<DbIpLocator>.Instance);
			_updater = new GeoUpdater(new Clients(), options, _locator, NullLogger<GeoUpdater>.Instance);
		}

		public async ValueTask DisposeAsync()
		{
			_locator?.Dispose();
			await _peer.DisposeAsync();
			if (Directory.Exists(_directory))
				Directory.Delete(_directory, recursive: true);
		}

		sealed class Clients : IHttpClientFactory
		{
			public HttpClient CreateClient(string name) => new();
		}

		static byte[] Gzip(byte[] bytes)
		{
			using var output = new MemoryStream();
			using (var gzip = new GZipStream(output, CompressionLevel.Fastest))
				gzip.Write(bytes);
			return output.ToArray();
		}

		void Publish(string kind, DateTime month, byte[] database) =>
			_peer.ServeFile($"/free/dbip-{kind}-lite-{month:yyyy-MM}.mmdb.gz", Gzip(database), "application/gzip");

		static byte[] City(DateTime built) => MiniMmdb.Build("DBIP-City-Lite", built);
		static byte[] Asn(DateTime built) => MiniMmdb.Build("DBIP-ASN-Lite (compat=GeoLite2-ASN)", built);

		DateTime Built(string kind)
		{
			using var reader = new Reader(Path.Combine(_directory, GeoUpdater.FileOf(kind)));
			return reader.Metadata.BuildDate;
		}

		[Fact]
		public async Task Missing_databases_are_fetched_checked_and_read_at_once()
		{
			Publish("city", Now, City(Now));
			Publish("asn", Now, Asn(Now));

			Assert.Equal(2, await _updater.Update(Now, TestContext.Current.CancellationToken));

			Assert.Equal(Now.Date, Built("city").Date);
			Assert.Equal(Now.Date, Built("asn").Date);
			Assert.Equal("DB-IP Lite 2026-10", _locator.Source);
			Assert.Empty(Directory.GetFiles(_directory).Where(f => f.EndsWith(".part") || f.EndsWith(".new")));
		}

		[Fact]
		public async Task Early_in_the_month_last_months_database_is_used_and_not_fetched_again()
		{
			Publish("city", LastMonth, City(LastMonth));
			Publish("asn", LastMonth, Asn(LastMonth));

			Assert.Equal(2, await _updater.Update(Now, TestContext.Current.CancellationToken));
			var asked = _peer.Requests.Count;
			Assert.Equal(0, await _updater.Update(Now, TestContext.Current.CancellationToken));

			Assert.Equal(LastMonth.Date, Built("city").Date);
			Assert.DoesNotContain(_peer.Requests.Skip(asked), r => r.Path.Contains("2026-09"));
		}

		[Fact]
		public async Task A_current_database_asks_nothing()
		{
			Publish("city", Now, City(Now));
			Publish("asn", Now, Asn(Now));
			await _updater.Update(Now, TestContext.Current.CancellationToken);
			var asked = _peer.Requests.Count;

			Assert.Equal(0, await _updater.Update(Now.AddDays(1), TestContext.Current.CancellationToken));

			Assert.Equal(asked, _peer.Requests.Count);
		}

		[Fact]
		public async Task A_broken_or_wrong_database_is_refused_and_the_old_one_kept()
		{
			Publish("city", LastMonth, City(LastMonth));
			Publish("asn", LastMonth, Asn(LastMonth));
			await _updater.Update(LastMonth.AddDays(1), TestContext.Current.CancellationToken);
			Publish("city", Now, "not a database at all"u8.ToArray());
			Publish("asn", Now, City(Now));

			Assert.Equal(0, await _updater.Update(Now, TestContext.Current.CancellationToken));

			Assert.Equal(LastMonth.Date, Built("city").Date);
			Assert.Equal(LastMonth.Date, Built("asn").Date);
			Assert.Empty(Directory.GetFiles(_directory).Where(f => f.EndsWith(".part") || f.EndsWith(".new")));
		}
	}
}