using FluentAssertions;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Xunit;

namespace StellaOps.FeatureFlags.Tests;

[Trait("Category", "Unit")]
public class FeatureFlagServiceCollectionExtensionsTests
{
    [Fact]
    public void AddFeatureFlags_RegistersFeatureFlagService()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        // Act
        services.AddFeatureFlags();
        var provider = services.BuildServiceProvider();

        // Assert
        var service = provider.GetService<IFeatureFlagService>();
        service.Should().NotBeNull();
        service.Should().BeOfType<CompositeFeatureFlagService>();
    }

    [Fact]
    public void AddFeatureFlags_WithOptions_ConfiguresOptions()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        // Act
        services.AddFeatureFlags(options =>
        {
            options.EnableCaching = true;
            options.CacheDuration = TimeSpan.FromMinutes(5);
            options.DefaultValue = true;
        });

        var provider = services.BuildServiceProvider();
        var options = provider.GetRequiredService<Microsoft.Extensions.Options.IOptions<FeatureFlagOptions>>();

        // Assert
        options.Value.EnableCaching.Should().BeTrue();
        options.Value.CacheDuration.Should().Be(TimeSpan.FromMinutes(5));
        options.Value.DefaultValue.Should().BeTrue();
    }

    [Fact]
    public void AddConfigurationFeatureFlags_RegistersConfigurationProvider()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        var configData = new Dictionary<string, string?>
        {
            { "FeatureFlags:TestFlag", "true" }
        };
        var configuration = new ConfigurationBuilder()
            .AddInMemoryCollection(configData)
            .Build();

        services.AddSingleton<IConfiguration>(configuration);
        services.AddFeatureFlags();
        services.AddConfigurationFeatureFlags();

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagProviders = provider.GetServices<IFeatureFlagProvider>().ToList();

        // Assert
        featureFlagProviders.Should().ContainSingle();
        featureFlagProviders[0].Name.Should().Be("Configuration");
    }

    [Fact]
    public void AddConfigurationFeatureFlags_WithCustomSectionName_UsesCorrectSection()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        var configData = new Dictionary<string, string?>
        {
            { "CustomFlags:MyFlag", "true" }
        };
        var configuration = new ConfigurationBuilder()
            .AddInMemoryCollection(configData)
            .Build();

        services.AddSingleton<IConfiguration>(configuration);
        services.AddFeatureFlags();
        services.AddConfigurationFeatureFlags(sectionName: "CustomFlags");

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagService = provider.GetRequiredService<IFeatureFlagService>();
        var result = featureFlagService.IsEnabledAsync("MyFlag").Result;

        // Assert
        result.Should().BeTrue();
    }

    [Fact]
    public void AddInMemoryFeatureFlags_RegistersInMemoryProvider()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        var flags = new Dictionary<string, bool>
        {
            { "InMemoryFlag", true }
        };

        services.AddFeatureFlags();
        services.AddInMemoryFeatureFlags(flags);

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagService = provider.GetRequiredService<IFeatureFlagService>();
        var result = featureFlagService.IsEnabledAsync("InMemoryFlag").Result;

        // Assert
        result.Should().BeTrue();
    }

    [Fact]
    public void AddInMemoryFeatureFlags_WithPriority_SetsCorrectPriority()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        services.AddFeatureFlags();
        services.AddInMemoryFeatureFlags(new Dictionary<string, bool> { { "Flag", true } }, priority: 5);

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagProviders = provider.GetServices<IFeatureFlagProvider>().ToList();

        // Assert
        featureFlagProviders.Single().Priority.Should().Be(5);
    }

    [Fact]
    public void AddFeatureFlagProvider_RegistersCustomProvider()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        services.AddFeatureFlags();
        services.AddFeatureFlagProvider<TestFeatureFlagProvider>();

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagProviders = provider.GetServices<IFeatureFlagProvider>().ToList();

        // Assert
        featureFlagProviders.Should().ContainSingle();
        featureFlagProviders[0].Should().BeOfType<TestFeatureFlagProvider>();
    }

    [Fact]
    public void AddFeatureFlagProvider_WithFactory_RegistersCustomProvider()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        services.AddFeatureFlags();
        services.AddFeatureFlagProvider(_ => new TestFeatureFlagProvider());

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagProviders = provider.GetServices<IFeatureFlagProvider>().ToList();

        // Assert
        featureFlagProviders.Should().ContainSingle();
        featureFlagProviders[0].Should().BeOfType<TestFeatureFlagProvider>();
    }

    [Fact]
    public void MultipleProviders_AreRegisteredInPriorityOrder()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();

        var configData = new Dictionary<string, string?>
        {
            { "FeatureFlags:SharedFlag", "false" }
        };
        var configuration = new ConfigurationBuilder()
            .AddInMemoryCollection(configData)
            .Build();

        services.AddSingleton<IConfiguration>(configuration);
        services.AddFeatureFlags();
        services.AddConfigurationFeatureFlags(priority: 50);
        services.AddInMemoryFeatureFlags(new Dictionary<string, bool> { { "SharedFlag", true } }, priority: 10);

        // Act
        var provider = services.BuildServiceProvider();
        var featureFlagService = provider.GetRequiredService<IFeatureFlagService>();
        var result = featureFlagService.IsEnabledAsync("SharedFlag").Result;

        // Assert - InMemory has lower priority number (higher precedence), so it wins
        result.Should().BeTrue();
    }

    private class TestFeatureFlagProvider : FeatureFlagProviderBase
    {
        public override string Name => "Test";

        public override Task<FeatureFlagResult?> TryGetFlagAsync(
            string flagKey,
            FeatureFlagEvaluationContext context,
            CancellationToken ct = default)
        {
            return Task.FromResult<FeatureFlagResult?>(
                new FeatureFlagResult(flagKey, true, null, "Test", Name));
        }
    }
}