using System.Collections.Generic;
using System.Net;
using System.Net.Http;
using System.Linq;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using StellaOps.Signals.Models;
using StellaOps.Signals.Options;
using StellaOps.Signals.Services;
using Xunit;

namespace StellaOps.Signals.Tests;

public class RouterEventsPublisherTests
{
    [Fact]
    public async Task PublishFactUpdatedAsync_SendsEnvelopeToRouter()
    {
        var options = CreateOptions();
        var handler = new StubHandler(HttpStatusCode.Accepted);
        using var httpClient = new HttpClient(handler) { BaseAddress = new Uri(options.Events.Router.BaseUrl) };
        var logger = new ListLogger<RouterEventsPublisher>();
        var builder = new ReachabilityFactEventBuilder(options, TimeProvider.System);
        var publisher = new RouterEventsPublisher(builder, options, httpClient, logger);

        await publisher.PublishFactUpdatedAsync(CreateFact(), CancellationToken.None);

        var request = Assert.Single(handler.Requests);
        Assert.Equal(options.Events.Router.Path, request.Uri!.PathAndQuery);
        Assert.Equal("application/json", request.ContentType);
        Assert.Contains(options.Events.Router.ApiKeyHeader, request.Headers.Keys);

        using var doc = JsonDocument.Parse(request.Body ?? "{}");
        Assert.Equal(options.Events.Stream, doc.RootElement.GetProperty("topic").GetString());
        Assert.Equal("signals.fact.updated@v1", doc.RootElement.GetProperty("version").GetString());
        Assert.Contains(logger.Messages, m => m.Contains("Router publish succeeded"));
    }

    [Fact]
    public async Task PublishFactUpdatedAsync_LogsFailure()
    {
        var options = CreateOptions();
        var handler = new StubHandler(HttpStatusCode.InternalServerError, "boom");
        using var httpClient = new HttpClient(handler) { BaseAddress = new Uri(options.Events.Router.BaseUrl) };
        var logger = new ListLogger<RouterEventsPublisher>();
        var builder = new ReachabilityFactEventBuilder(options, TimeProvider.System);
        var publisher = new RouterEventsPublisher(builder, options, httpClient, logger);

        await publisher.PublishFactUpdatedAsync(CreateFact(), CancellationToken.None);

        Assert.Contains(logger.Messages, m => m.Contains("Router publish failed"));
    }

    private static SignalsOptions CreateOptions()
    {
        var options = new SignalsOptions();
        options.Events.Driver = "router";
        options.Events.Stream = "signals.fact.updated.v1";
        options.Events.Router.BaseUrl = "https://router.test";
        options.Events.Router.Path = "/router/events/signals.fact.updated";
        options.Events.Router.ApiKeyHeader = "X-Test-Key";
        options.Events.Router.ApiKey = "secret";
        return options;
    }

    private static ReachabilityFactDocument CreateFact()
    {
        return new ReachabilityFactDocument
        {
            SubjectKey = "tenant:image@sha256:abc",
            CallgraphId = "cg-123",
            ComputedAt = DateTimeOffset.Parse("2025-12-10T00:00:00Z"),
            States = new List<ReachabilityStateDocument>
            {
                new()
                {
                    Target = "pkg:pypi/django",
                    Reachable = true,
                    Confidence = 0.9,
                    Bucket = "runtime",
                    Weight = 0.45
                }
            }
        };
    }

    private sealed class StubHandler : HttpMessageHandler
    {
        private readonly HttpStatusCode statusCode;
        private readonly string? responseBody;

        public List<CapturedRequest> Requests { get; } = new();

        public StubHandler(HttpStatusCode statusCode, string? responseBody = null)
        {
            this.statusCode = statusCode;
            this.responseBody = responseBody;
        }

        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            var body = request.Content is null
                ? null
                : await request.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);

            Requests.Add(new CapturedRequest
            {
                Uri = request.RequestUri,
                ContentType = request.Content?.Headers.ContentType?.MediaType,
                Headers = request.Headers.ToDictionary(h => h.Key, h => h.Value.ToArray()),
                Body = body
            });

            var response = new HttpResponseMessage(statusCode);
            if (!string.IsNullOrEmpty(responseBody))
            {
                response.Content = new StringContent(responseBody);
            }

            return response;
        }
    }

    private sealed record CapturedRequest
    {
        public Uri? Uri { get; init; }
        public string? ContentType { get; init; }
        public Dictionary<string, string[]> Headers { get; init; } = new(StringComparer.OrdinalIgnoreCase);
        public string? Body { get; init; }
    }

    private sealed class ListLogger<T> : ILogger<T>
    {
        public List<string> Messages { get; } = new();

        public IDisposable BeginScope<TState>(TState state) where TState : notnull => NullScope.Instance;

        public bool IsEnabled(LogLevel logLevel) => true;

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
        {
            Messages.Add(formatter(state, exception));
        }

        private sealed class NullScope : IDisposable
        {
            public static readonly NullScope Instance = new();
            public void Dispose() { }
        }
    }
}