using System;
using System.Collections.Generic;
using System.Diagnostics.Metrics;
using System.Net;
using System.Net.Http;
using System.Security.Claims;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using Microsoft.Extensions.Hosting;
using Microsoft.IdentityModel.Tokens;
using StellaOps.Auth.Client;
using StellaOps.Policy.Gateway.Clients;
using StellaOps.Policy.Gateway.Contracts;
using StellaOps.Policy.Gateway.Options;
using StellaOps.Policy.Gateway.Services;
using Xunit;


using StellaOps.TestKit;
namespace StellaOps.Policy.Gateway.Tests;

public class PolicyEngineClientTests
{
    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public async Task ActivateRevision_UsesServiceTokenWhenForwardingContextMissing()
    {
        var options = CreateGatewayOptions();
        options.PolicyEngine.ClientCredentials.Enabled = true;
        options.PolicyEngine.ClientCredentials.ClientId = "policy-gateway";
        options.PolicyEngine.ClientCredentials.ClientSecret = "secret";
        options.PolicyEngine.ClientCredentials.Scopes.Clear();
        options.PolicyEngine.ClientCredentials.Scopes.Add("policy:activate");
        options.PolicyEngine.BaseAddress = "https://policy-engine.test/";

        var optionsMonitor = new TestOptionsMonitor(options);
        var tokenClient = new StubTokenClient();
        var dpopGenerator = new PolicyGatewayDpopProofGenerator(new StubHostEnvironment(), optionsMonitor, TimeProvider.System, NullLogger<PolicyGatewayDpopProofGenerator>.Instance);
        var tokenProvider = new PolicyEngineTokenProvider(tokenClient, optionsMonitor, dpopGenerator, TimeProvider.System, NullLogger<PolicyEngineTokenProvider>.Instance);

        using var recordingHandler = new RecordingHandler();
        using var httpClient = new HttpClient(recordingHandler)
        {
            BaseAddress = new Uri(options.PolicyEngine.BaseAddress)
        };

        var client = new PolicyEngineClient(httpClient, Microsoft.Extensions.Options.Options.Create(options), tokenProvider, NullLogger<PolicyEngineClient>.Instance);

        var request = new ActivatePolicyRevisionRequest("comment");
        var result = await client.ActivatePolicyRevisionAsync(null, "pack-123", 7, request, CancellationToken.None);

        Assert.True(result.IsSuccess);
        Assert.NotNull(recordingHandler.LastRequest);
        var authorization = recordingHandler.LastRequest!.Headers.Authorization;
        Assert.NotNull(authorization);
        Assert.Equal("Bearer", authorization!.Scheme);
        Assert.Equal("service-token", authorization.Parameter);
        Assert.Equal(1, tokenClient.RequestCount);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void Metrics_RecordActivation_EmitsExpectedTags()
    {
        using var metrics = new PolicyGatewayMetrics();
        using var listener = new MeterListener();
using StellaOps.TestKit;
        var measurements = new List<(long Value, string Outcome, string Source)>();
        var latencies = new List<(double Value, string Outcome, string Source)>();

        listener.InstrumentPublished += (instrument, meterListener) =>
        {
            if (!string.Equals(instrument.Meter.Name, "StellaOps.Policy.Gateway", StringComparison.Ordinal))
            {
                return;
            }

            meterListener.EnableMeasurementEvents(instrument);
        };

        listener.SetMeasurementEventCallback<long>((instrument, value, tags, state) =>
        {
            if (instrument.Name != "policy_gateway_activation_requests_total")
            {
                return;
            }

            measurements.Add((value, GetTag(tags, "outcome"), GetTag(tags, "source")));
        });

        listener.SetMeasurementEventCallback<double>((instrument, value, tags, state) =>
        {
            if (instrument.Name != "policy_gateway_activation_latency_ms")
            {
                return;
            }

            latencies.Add((value, GetTag(tags, "outcome"), GetTag(tags, "source")));
        });

        listener.Start();

        metrics.RecordActivation("activated", "service", 42.5);

        listener.Dispose();

        Assert.Contains(measurements, entry => entry.Value == 1 && entry.Outcome == "activated" && entry.Source == "service");
        Assert.Contains(latencies, entry => entry.Outcome == "activated" && entry.Source == "service" && entry.Value == 42.5);
    }

    private static string GetTag(ReadOnlySpan<KeyValuePair<string, object?>> tags, string key)
    {
        foreach (var tag in tags)
        {
            if (string.Equals(tag.Key, key, StringComparison.Ordinal))
            {
                return tag.Value?.ToString() ?? string.Empty;
            }
        }

        return string.Empty;
    }

    private static PolicyGatewayOptions CreateGatewayOptions()
    {
        return new PolicyGatewayOptions
        {
            PolicyEngine =
            {
                BaseAddress = "https://policy-engine.test/"
            }
        };
    }

    private sealed class TestOptionsMonitor : IOptionsMonitor<PolicyGatewayOptions>
    {
        public TestOptionsMonitor(PolicyGatewayOptions current)
        {
            CurrentValue = current;
        }

        public PolicyGatewayOptions CurrentValue { get; }

        public PolicyGatewayOptions Get(string? name) => CurrentValue;

        public IDisposable OnChange(Action<PolicyGatewayOptions, string?> listener) => EmptyDisposable.Instance;

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

    private sealed class StubTokenClient : IStellaOpsTokenClient
    {
        public int RequestCount { get; private set; }

        public IReadOnlyDictionary<string, string>? LastAdditionalParameters { get; private set; }

        public Task<StellaOpsTokenResult> RequestClientCredentialsTokenAsync(string? scope = null, IReadOnlyDictionary<string, string>? additionalParameters = null, CancellationToken cancellationToken = default)
        {
            RequestCount++;
            LastAdditionalParameters = additionalParameters;
            return Task.FromResult(new StellaOpsTokenResult("service-token", "Bearer", DateTimeOffset.UtcNow.AddMinutes(5), Array.Empty<string>()));
        }

        public Task<StellaOpsTokenResult> RequestPasswordTokenAsync(string username, string password, string? scope = null, IReadOnlyDictionary<string, string>? additionalParameters = null, CancellationToken cancellationToken = default)
            => throw new NotSupportedException();

        public Task<JsonWebKeySet> GetJsonWebKeySetAsync(CancellationToken cancellationToken = default)
            => throw new NotSupportedException();

        public ValueTask<StellaOpsTokenCacheEntry?> GetCachedTokenAsync(string key, CancellationToken cancellationToken = default)
            => ValueTask.FromResult<StellaOpsTokenCacheEntry?>(null);

        public ValueTask CacheTokenAsync(string key, StellaOpsTokenCacheEntry entry, CancellationToken cancellationToken = default)
            => ValueTask.CompletedTask;

        public ValueTask ClearCachedTokenAsync(string key, CancellationToken cancellationToken = default)
            => ValueTask.CompletedTask;
    }

    private sealed class RecordingHandler : HttpMessageHandler
    {
        public HttpRequestMessage? LastRequest { get; private set; }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            LastRequest = request;

            var payload = JsonSerializer.Serialize(new PolicyRevisionActivationDto("activated", new PolicyRevisionDto(7, "Activated", false, DateTimeOffset.UtcNow, DateTimeOffset.UtcNow, Array.Empty<PolicyActivationApprovalDto>())));
            var response = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent(payload, Encoding.UTF8, "application/json")
            };

            return Task.FromResult(response);
        }
    }

    private sealed class StubHostEnvironment : IHostEnvironment
    {
        public string EnvironmentName { get; set; } = "Development";
        public string ApplicationName { get; set; } = "PolicyGatewayTests";
        public string ContentRootPath { get; set; } = AppContext.BaseDirectory;
        public IFileProvider ContentRootFileProvider { get; set; } = new NullFileProvider();
    }
}