using System.Net;
using System.Net.Http;
using System.Text.Json.Nodes;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using StellaOps.Findings.Ledger.Domain;
using StellaOps.Findings.Ledger.Infrastructure.Policy;
using StellaOps.Findings.Ledger.Options;
using Xunit;

namespace StellaOps.Findings.Ledger.Tests;

public sealed class PolicyEngineEvaluationServiceTests
{
    private const string TenantId = "tenant-1";
    private static readonly DateTimeOffset Now = DateTimeOffset.UtcNow;

    [Fact]
    public async Task EvaluateAsync_UsesPolicyEngineAndCachesResult()
    {
        var handler = new StubHttpHandler(_ => new HttpResponseMessage(HttpStatusCode.OK)
        {
            Content = new StringContent(
                """
                {
                  "items": [
                    {
                      "findingId": "finding-1",
                      "status": "affected",
                      "severity": 7.5,
                      "labels": { "exposure": "runtime" },
                      "explainRef": "policy://explain/123",
                      "rationale": ["policy://explain/123"]
                    }
                  ]
                }
                """,
                System.Text.Encoding.UTF8,
                "application/json")
        });

        var factory = new TestHttpClientFactory(handler);
        var options = CreateOptions(new Uri("https://policy.example/"));
        using var cache = new PolicyEvaluationCache(options.PolicyEngine, NullLogger<PolicyEvaluationCache>.Instance);
        var inline = new InlinePolicyEvaluationService(NullLogger<InlinePolicyEvaluationService>.Instance);
        var service = new PolicyEngineEvaluationService(factory, inline, cache, Microsoft.Extensions.Options.Options.Create(options), NullLogger<PolicyEngineEvaluationService>.Instance);

        var record = CreateRecord();

        var first = await service.EvaluateAsync(record, existingProjection: null, CancellationToken.None);
        var second = await service.EvaluateAsync(record, existingProjection: null, CancellationToken.None);

        Assert.Equal("affected", first.Status);
        Assert.Equal(7.5m, first.Severity);
        Assert.Equal("policy://explain/123", first.ExplainRef);
        Assert.Equal("runtime", first.Labels?["exposure"]?.GetValue<string>());
        Assert.Equal(1, handler.CallCount); // cached second call
        Assert.Equal("affected", second.Status);
        Assert.Equal("policy://explain/123", second.Rationale[0]?.GetValue<string>());
    }

    [Fact]
    public async Task EvaluateAsync_FallsBackToInlineWhenRequestFails()
    {
        var handler = new StubHttpHandler(_ => new HttpResponseMessage(HttpStatusCode.InternalServerError));
        var factory = new TestHttpClientFactory(handler);
        var options = CreateOptions(new Uri("https://policy.example/"));
        using var cache = new PolicyEvaluationCache(options.PolicyEngine, NullLogger<PolicyEvaluationCache>.Instance);
        var inline = new InlinePolicyEvaluationService(NullLogger<InlinePolicyEvaluationService>.Instance);
        var service = new PolicyEngineEvaluationService(factory, inline, cache, Microsoft.Extensions.Options.Options.Create(options), NullLogger<PolicyEngineEvaluationService>.Instance);

        var record = CreateRecord(payloadStatus: "investigating", payloadSeverity: 4.2m);

        var result = await service.EvaluateAsync(record, existingProjection: null, CancellationToken.None);

        Assert.Equal("investigating", result.Status);
        Assert.Equal(4.2m, result.Severity);
        Assert.Equal(1, handler.CallCount);
    }

    [Fact]
    public async Task EvaluateAsync_UsesInlineWhenNoBaseAddressConfigured()
    {
        var handler = new StubHttpHandler(_ => throw new InvalidOperationException("Handler should not be invoked."));
        var factory = new TestHttpClientFactory(handler);
        var options = CreateOptions(baseAddress: null);
        using var cache = new PolicyEvaluationCache(options.PolicyEngine, NullLogger<PolicyEvaluationCache>.Instance);
        var inline = new InlinePolicyEvaluationService(NullLogger<InlinePolicyEvaluationService>.Instance);
        var service = new PolicyEngineEvaluationService(factory, inline, cache, Microsoft.Extensions.Options.Options.Create(options), NullLogger<PolicyEngineEvaluationService>.Instance);

        var record = CreateRecord(payloadStatus: "accepted_risk", payloadSeverity: 1.0m);

        var result = await service.EvaluateAsync(record, existingProjection: null, CancellationToken.None);

        Assert.Equal("accepted_risk", result.Status);
        Assert.Equal(1.0m, result.Severity);
        Assert.Equal(0, handler.CallCount);
    }

    private static LedgerServiceOptions CreateOptions(Uri? baseAddress)
    {
        return new LedgerServiceOptions
        {
            PolicyEngine = new LedgerServiceOptions.PolicyEngineOptions
            {
                BaseAddress = baseAddress,
                Cache = new LedgerServiceOptions.PolicyEngineCacheOptions
                {
                    SizeLimit = 16,
                    EntryLifetime = TimeSpan.FromMinutes(5)
                }
            }
        };
    }

    private static LedgerEventRecord CreateRecord(string payloadStatus = "affected", decimal? payloadSeverity = 5.0m)
    {
        var payload = new JsonObject
        {
            ["status"] = payloadStatus,
            ["severity"] = payloadSeverity,
            ["labels"] = new JsonObject { ["source"] = "policy" }
        };

        var envelope = new JsonObject
        {
            ["event"] = new JsonObject
            {
                ["payload"] = payload
            }
        };

        return new LedgerEventRecord(
            TenantId,
            Guid.NewGuid(),
            1,
            Guid.NewGuid(),
            LedgerEventConstants.EventFindingStatusChanged,
            "policy/v1",
            "finding-1",
            "artifact-1",
            null,
            "actor",
            "service",
            Now,
            Now,
            envelope,
            "hash",
            "prev",
            "leaf",
            envelope.ToJsonString());
    }

    private sealed class StubHttpHandler : HttpMessageHandler
    {
        private readonly Func<HttpRequestMessage, HttpResponseMessage> _handler;

        public StubHttpHandler(Func<HttpRequestMessage, HttpResponseMessage> handler)
        {
            _handler = handler ?? throw new ArgumentNullException(nameof(handler));
        }

        public int CallCount { get; private set; }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            CallCount++;
            return Task.FromResult(_handler(request));
        }
    }

    private sealed class TestHttpClientFactory : IHttpClientFactory
    {
        private readonly HttpMessageHandler _handler;

        public TestHttpClientFactory(HttpMessageHandler handler)
        {
            _handler = handler;
        }

        public HttpClient CreateClient(string name)
        {
            return new HttpClient(_handler, disposeHandler: false);
        }
    }
}