using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Text.RegularExpressions;
using Xunit;
using ytLive.Models;
using ytLive.Services;

namespace ytLive.Tests;

public class YouTubeAuthServiceTests
{
    private sealed class FakeHandler : HttpMessageHandler
    {
        private readonly string _tokenResponse;
        private readonly string _channelResponse;

        public FakeHandler(string tokenResponse, string channelResponse)
        {
            _tokenResponse = tokenResponse;
            _channelResponse = channelResponse;
        }

        protected override Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request, CancellationToken cancellationToken)
        {
            var isToken = request.RequestUri!.PathAndQuery.Contains("/token");
            var body = isToken ? _tokenResponse : _channelResponse;
            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent(body, Encoding.UTF8, "application/json"),
            });
        }
    }

    private static YouTubeAuthService CreateService(string tokenResponse, string channelResponse) =>
        new("test-id", "test-secret", new HttpClient(new FakeHandler(tokenResponse, channelResponse)));

    [Fact]
    public async Task ExchangeCodeForToken_MockServer_ParsesChannel()
    {
        var service = CreateService(
            """{"access_token":"acc-123","refresh_token":"ref-123","expires_in":3600}""",
            """{"items":[{"id":"UC123","snippet":{"title":"Test Channel","thumbnails":{"default":{"url":"http://example/thumb.jpg"}}}}]}""");

        var channel = await service.ExchangeCodeForToken("auth-code", "http://localhost:8765/oauth2/callback");

        Assert.NotNull(channel);
        Assert.Equal("UC123", channel!.ChannelId);
        Assert.Equal("Test Channel", channel.DisplayName);
        Assert.Equal("http://example/thumb.jpg", channel.ProfileImageUrl);
        Assert.Equal("acc-123", channel.AccessToken);
        Assert.Equal("ref-123", channel.RefreshToken);
        Assert.InRange(channel.TokenExpiry, DateTime.UtcNow.AddSeconds(3590), DateTime.UtcNow.AddSeconds(3610));
    }

    [Fact]
    public async Task RefreshToken_MockServer_UpdatesAccessTokenAndExpiry()
    {
        var service = CreateService(
            """{"access_token":"new-acc","expires_in":3600}""",
            """{"items":[]}""");
        service.SetSession(new YouTubeChannel
        {
            RefreshToken = "ref-123",
            TokenExpiry = DateTime.UtcNow.AddMinutes(-5),
        });

        var ok = await service.RefreshToken();

        Assert.True(ok);
        Assert.Equal("new-acc", service.CurrentChannel!.AccessToken);
        Assert.InRange(service.CurrentChannel.TokenExpiry,
            DateTime.UtcNow.AddSeconds(3590), DateTime.UtcNow.AddSeconds(3610));
    }

    [Fact]
    public void ClearSession_DropsCurrentChannel()
    {
        var service = CreateService("""{"access_token":"a","refresh_token":"r","expires_in":3600}""",
            """{"items":[]}""");
        service.SetSession(new YouTubeChannel { DisplayName = "Test Channel" });

        service.ClearSession();

        Assert.Null(service.CurrentChannel);
    }

    /// <summary>Creator report 2026-09-27: clicking "Change Account", cancelling in the
    /// Google account chooser, then clicking again failed with "cannot sign-in because
    /// the callback url was not released". Abandoning the browser gives the app no
    /// signal, so the first attempt sat on the loopback callback port for its full
    /// 5-minute timeout and the second attempt could not bind.
    /// <para>Requires nothing else to be listening on port 8765 — close a running
    /// LlamaCasty that happens to be mid-sign-in, or this test sees a genuine
    /// "address already in use" from the host.</para></summary>
    [Fact]
    public async Task RetryingAfterAnAbandonedAttempt_ReleasesTheCallbackPort()
    {
        var service = new YouTubeAuthService(
            "test-id", "test-secret",
            new HttpClient(new FakeHandler("{}", "{}")),
            openBrowser: _ => { });   // never shell out to a real browser from a test

        var first = service.AuthenticateAsync();

        // The creator gives up on the chooser and clicks "Change Account" again.
        var second = service.AuthenticateAsync();

        // The abandoned attempt must be released promptly rather than left holding the
        // port for its whole 5-minute timeout. If it weren't, this await would time out.
        Assert.Null(await first.WaitAsync(TimeSpan.FromSeconds(15)));

        // Taking over again proves `second` really did bind the port: had it not,
        // awaiting it would throw HttpListenerException ("address already in use").
        _ = service.AuthenticateAsync();
        Assert.Null(await second.WaitAsync(TimeSpan.FromSeconds(15)));

        // The last attempt is deliberately left pending — nothing can cancel it and the
        // test host exits before its 5-minute timer fires.
    }

    /// <summary>
    /// The app requests exactly ONE scope, and it is the broad one. 2026-09-28:
    /// `auth/youtube.force-ssl` was dropped as redundant — its grant ("see, edit, and
    /// permanently delete your videos, ratings, comments and captions") is a strict subset of
    /// `auth/youtube` ("Manage your YouTube account"), which is also the only scope that can
    /// cover live broadcast create/transition, so it was never avoidable.
    ///
    /// Asserted from source because the const is private and the auth flow cannot be exercised
    /// without a browser. What is worth locking in is the DECISION — that the redundant scope
    /// does not come back — not merely today's string.
    ///
    /// The assertion reads the const's <b>value</b> out of the source rather than scanning the
    /// file. A file-wide `DoesNotContain("force-ssl")` fails on this very file's doc comment,
    /// which names force-ssl precisely to explain why it went. A test that fails on the prose
    /// documenting the guarantee gets deleted instead of obeyed.
    /// </summary>
    [Fact]
    public void ExactlyOneScopeIsRequested_AndItIsTheBroadOne()
    {
        var source = File.ReadAllText(RepoFile("Services", "YouTubeAuthService.cs"));

        var match = Regex.Match(source, @"private const string Scope = ""([^""]*)"";");
        Assert.True(match.Success, "could not find the Scope const in YouTubeAuthService.cs");

        var scopes = match.Groups[1].Value.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        Assert.Equal(new[] { "https://www.googleapis.com/auth/youtube" }, scopes);
    }

    private static string RepoFile(params string[] parts)
    {
        var dir = new DirectoryInfo(AppContext.BaseDirectory);
        while (dir != null)
        {
            var candidate = Path.Combine(new[] { dir.FullName }.Concat(parts).ToArray());
            if (File.Exists(candidate)) return candidate;
            dir = dir.Parent;
        }
        throw new FileNotFoundException(
            $"could not locate {Path.Combine(parts)} above {AppContext.BaseDirectory}");
    }
}