using Xunit;
using System.Collections.Immutable;
using Microsoft.Extensions.Options;
using StellaOps.Policy;
using StellaOps.Policy.Engine.Compilation;
using StellaOps.Policy.Engine.Domain;
using StellaOps.Policy.Engine.Options;
using StellaOps.Policy.Engine.Services;
using StellaOps.PolicyDsl;

namespace StellaOps.Policy.Engine.Tests;

public sealed class PolicyBundleServiceTests
{
    private const string BaselineDsl = """
        policy "Baseline Production Policy" syntax "stella-dsl@1" {
          rule r1 { when true then status := "ok" because "baseline" }
        }
        """;

    [Fact]
    public async Task CompileAndStoreAsync_SucceedsAndStoresBundle()
    {
        var services = CreateServices();
        var request = new PolicyBundleRequest(new PolicyDslPayload("stella-dsl@1", BaselineDsl), SigningKeyId: "test-key");

        var response = await services.BundleService.CompileAndStoreAsync("pack-1", 1, request, CancellationToken.None);

        Assert.True(response.Success);
        Assert.NotNull(response.Digest);
        Assert.StartsWith("sig:sha256:", response.Signature);
        Assert.True(response.SizeBytes > 0);
    }

    [Fact]
    public async Task CompileAndStoreAsync_FailsWithBadSyntax()
    {
        var services = CreateServices();
        var request = new PolicyBundleRequest(new PolicyDslPayload("unknown", "policy bad"), SigningKeyId: null);

        var response = await services.BundleService.CompileAndStoreAsync("pack-1", 1, request, CancellationToken.None);

        Assert.False(response.Success);
        Assert.Null(response.Digest);
        Assert.NotEmpty(response.Diagnostics);
    }

    [Fact]
    public async Task CompileAndStoreAsync_ReturnsAocMetadata()
    {
        var services = CreateServices();
        var request = new PolicyBundleRequest(new PolicyDslPayload("stella-dsl@1", BaselineDsl), SigningKeyId: "test-key");

        var response = await services.BundleService.CompileAndStoreAsync("pack-1", 1, request, CancellationToken.None);

        Assert.True(response.Success);
        Assert.NotNull(response.AocMetadata);
        Assert.StartsWith("comp-", response.AocMetadata!.CompilationId);
        Assert.Equal("stella-dsl@1", response.AocMetadata.CompilerVersion);
        Assert.StartsWith("sha256:", response.AocMetadata.SourceDigest);
        Assert.StartsWith("sha256:", response.AocMetadata.ArtifactDigest);
        Assert.True(response.AocMetadata.RuleCount >= 1);
        Assert.True(response.AocMetadata.ComplexityScore >= 0);
    }

    [Fact]
    public async Task CompileAndStoreAsync_IncludesProvenanceWhenProvided()
    {
        var services = CreateServices();
        var provenance = new PolicyProvenanceInput(
            SourceType: "git",
            SourceUrl: "https://github.com/test/policies",
            Submitter: "test-user",
            CommitSha: "abc123",
            Branch: "main");
        var request = new PolicyBundleRequest(
            new PolicyDslPayload("stella-dsl@1", BaselineDsl),
            SigningKeyId: "test-key",
            Provenance: provenance);

        var response = await services.BundleService.CompileAndStoreAsync("pack-1", 1, request, CancellationToken.None);

        Assert.True(response.Success);
        Assert.NotNull(response.AocMetadata);

        // Verify bundle record has provenance stored
        var bundle = await services.Repository.GetBundleAsync("pack-1", 1, CancellationToken.None);
        Assert.NotNull(bundle);
        Assert.NotNull(bundle!.AocMetadata);
        Assert.NotNull(bundle.AocMetadata!.Provenance);
        Assert.Equal("git", bundle.AocMetadata.Provenance!.SourceType);
        Assert.Equal("https://github.com/test/policies", bundle.AocMetadata.Provenance.SourceUrl);
        Assert.Equal("test-user", bundle.AocMetadata.Provenance.Submitter);
        Assert.Equal("abc123", bundle.AocMetadata.Provenance.CommitSha);
        Assert.Equal("main", bundle.AocMetadata.Provenance.Branch);
    }

    [Fact]
    public async Task CompileAndStoreAsync_NullAocMetadataOnFailure()
    {
        var services = CreateServices();
        var request = new PolicyBundleRequest(new PolicyDslPayload("unknown", "policy bad"), SigningKeyId: null);

        var response = await services.BundleService.CompileAndStoreAsync("pack-1", 1, request, CancellationToken.None);

        Assert.False(response.Success);
        Assert.Null(response.AocMetadata);
    }

    [Fact]
    public async Task CompileAndStoreAsync_SourceDigestIsDeterministic()
    {
        var services = CreateServices();
        var request1 = new PolicyBundleRequest(new PolicyDslPayload("stella-dsl@1", BaselineDsl), SigningKeyId: "test-key");
        var request2 = new PolicyBundleRequest(new PolicyDslPayload("stella-dsl@1", BaselineDsl), SigningKeyId: "test-key");

        var response1 = await services.BundleService.CompileAndStoreAsync("pack-1", 1, request1, CancellationToken.None);
        var response2 = await services.BundleService.CompileAndStoreAsync("pack-2", 1, request2, CancellationToken.None);

        Assert.NotNull(response1.AocMetadata);
        Assert.NotNull(response2.AocMetadata);
        Assert.Equal(response1.AocMetadata!.SourceDigest, response2.AocMetadata!.SourceDigest);
        Assert.Equal(response1.AocMetadata.ArtifactDigest, response2.AocMetadata.ArtifactDigest);
    }

    private static ServiceHarness CreateServices()
    {
        var compiler = new PolicyCompiler();
        var complexity = new PolicyComplexityAnalyzer();
        var options = Microsoft.Extensions.Options.Options.Create(new PolicyEngineOptions());
        var metadataExtractor = new PolicyMetadataExtractor();
        var compilationService = new PolicyCompilationService(compiler, complexity, metadataExtractor, new StaticOptionsMonitor(options.Value), TimeProvider.System);
        var repo = new InMemoryPolicyPackRepository();
        return new ServiceHarness(
            new PolicyBundleService(compilationService, repo, TimeProvider.System),
            repo);
    }

    private sealed record ServiceHarness(PolicyBundleService BundleService, InMemoryPolicyPackRepository Repository);

    private sealed class StaticOptionsMonitor : IOptionsMonitor<PolicyEngineOptions>
    {
        private readonly PolicyEngineOptions _value;

        public StaticOptionsMonitor(PolicyEngineOptions value) => _value = value;

        public PolicyEngineOptions CurrentValue => _value;

        public PolicyEngineOptions Get(string? name) => _value;

        public IDisposable OnChange(Action<PolicyEngineOptions, string> listener) => NullDisposable.Instance;

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