using StellaOps.Doctor.Models;
using StellaOps.Doctor.Plugins;
using StellaOps.Doctor.Plugins.Builders;
using StellaOps.Doctor.Plugins.Verification.Configuration;
using System.Diagnostics;

namespace StellaOps.Doctor.Plugins.Verification.Checks;

/// <summary>
/// Verifies ability to pull a test artifact by digest.
/// </summary>
public sealed class TestArtifactPullCheck : VerificationCheckBase
{
    private const string RunbookUrlValue = "docs/doctor/articles/verification/verification-artifact-pull.md";

    /// <inheritdoc />
    public override string CheckId => "check.verification.artifact.pull";

    /// <inheritdoc />
    public override string Name => "Test Artifact Pull";

    /// <inheritdoc />
    public override string Description => "Verifies ability to pull a test artifact by digest from the configured registry";

    /// <inheritdoc />
    public override IReadOnlyList<string> Tags => ["verification", "artifact", "registry", "connectivity"];

    /// <inheritdoc />
    public override TimeSpan EstimatedDuration => TimeSpan.FromSeconds(15);

    /// <inheritdoc />
    protected override string RunbookUrl => RunbookUrlValue;

    /// <inheritdoc />
    public override bool CanRun(DoctorPluginContext context)
    {
        if (!base.CanRun(context))
            return false;

        var options = VerificationPlugin.GetOptions(context);
        return HasTestArtifactConfigured(options);
    }

    /// <inheritdoc />
    protected override async Task<DoctorCheckResult> ExecuteCheckAsync(
        DoctorPluginContext context,
        VerificationPluginOptions options,
        CheckResultBuilder result,
        CancellationToken ct)
    {
        if (!HasTestArtifactConfigured(options))
        {
            return GetNoTestArtifactConfiguredResult(result, CheckId);
        }

        // Check offline bundle first if configured
        if (!string.IsNullOrEmpty(options.TestArtifact.OfflineBundlePath))
        {
            return await CheckOfflineBundle(options, result, ct);
        }

        // Online artifact pull
        return await CheckOnlineArtifact(options, result, ct);
    }

    private static Task<DoctorCheckResult> CheckOfflineBundle(
        VerificationPluginOptions options,
        CheckResultBuilder result,
        CancellationToken ct)
    {
        var bundlePath = options.TestArtifact.OfflineBundlePath!;

        if (!File.Exists(bundlePath))
        {
            return Task.FromResult(result
                .Fail($"Offline test artifact bundle not found: {bundlePath}")
                .WithEvidence("Bundle", e => e
                    .Add("BundlePath", bundlePath)
                    .Add("FileExists", "false"))
                .WithCauses(
                    "Bundle file was deleted or moved",
                    "Path is incorrect")
                .WithRemediation(r => r
                    .AddShellStep(1, "Verify file exists", $"ls -la {bundlePath}")
                    .AddShellStep(2, "Export bundle from online system", "stella verification bundle export --output " + bundlePath)
                    .WithRunbookUrl(RunbookUrlValue))
                .WithVerification($"stella doctor --check check.verification.artifact.pull")
                .Build());
        }

        var fileInfo = new FileInfo(bundlePath);

        return Task.FromResult(result
            .Pass($"Offline test artifact bundle available ({FormatFileSize(fileInfo.Length)})")
            .WithEvidence("Bundle", e => e
                .Add("BundlePath", bundlePath)
                .Add("FileSize", FormatFileSize(fileInfo.Length))
                .Add("Mode", "Offline"))
            .Build());
    }

    private static async Task<DoctorCheckResult> CheckOnlineArtifact(
        VerificationPluginOptions options,
        CheckResultBuilder result,
        CancellationToken ct)
    {
        var reference = options.TestArtifact.Reference!;

        // Parse OCI reference
        var (registry, repository, digest) = ParseOciReference(reference);

        if (string.IsNullOrEmpty(registry) || string.IsNullOrEmpty(repository))
        {
            return result
                .Fail($"Invalid OCI reference: {reference}")
                .WithEvidence("Reference", e => e
                    .Add("Reference", reference)
                    .Add("Error", "Could not parse registry and repository"))
                .WithCauses("Reference format is incorrect")
                .WithRemediation(r => r
                    .AddManualStep(1, "Fix reference format", "Use format: oci://registry/repository@sha256:digest or registry/repository@sha256:digest")
                    .WithRunbookUrl(RunbookUrlValue))
                .WithVerification($"stella doctor --check check.verification.artifact.pull")
                .Build();
        }

        // Check if we can resolve the manifest (metadata only, no full pull)
        using var httpClient = CreateHttpClient(options);

        // Build registry API URL
        var manifestUrl = $"https://{registry}/v2/{repository}/manifests/{digest ?? "latest"}";

        var sw = Stopwatch.StartNew();

        try
        {
            using var request = new HttpRequestMessage(HttpMethod.Head, manifestUrl);
            request.Headers.Add("Accept", "application/vnd.oci.image.manifest.v1+json, application/vnd.docker.distribution.manifest.v2+json");

            var response = await httpClient.SendAsync(request, ct);
            sw.Stop();

            if (!response.IsSuccessStatusCode)
            {
                return result
                    .Fail($"Cannot access test artifact: {(int)response.StatusCode} {response.ReasonPhrase}")
                    .WithEvidence("Artifact", e => e
                        .Add("Reference", reference)
                        .Add("Registry", registry)
                        .Add("Repository", repository)
                        .Add("StatusCode", ((int)response.StatusCode).ToString())
                        .Add("ResponseTime", $"{sw.ElapsedMilliseconds}ms"))
                    .WithCauses(
                        "Artifact does not exist",
                        "Authentication required",
                        "Insufficient permissions")
                    .WithRemediation(r => r
                        .AddShellStep(1, "Test with crane", $"crane manifest {reference}")
                        .AddManualStep(2, "Check registry credentials", "Ensure registry credentials are configured")
                        .AddManualStep(3, "Verify artifact exists", "Confirm the test artifact has been pushed to the registry")
                        .WithRunbookUrl(RunbookUrlValue))
                    .WithVerification($"stella doctor --check check.verification.artifact.pull")
                    .Build();
            }

            // Extract digest from response if available
            var responseDigest = response.Headers.TryGetValues("Docker-Content-Digest", out var digestValues)
                ? digestValues.FirstOrDefault()
                : null;

            // Verify digest matches expected if configured
            if (!string.IsNullOrEmpty(options.TestArtifact.ExpectedDigest)
                && !string.IsNullOrEmpty(responseDigest)
                && !responseDigest.Equals(options.TestArtifact.ExpectedDigest, StringComparison.OrdinalIgnoreCase))
            {
                return result
                    .Warn("Test artifact digest mismatch")
                    .WithEvidence("Artifact", e => e
                        .Add("Reference", reference)
                        .Add("ExpectedDigest", options.TestArtifact.ExpectedDigest)
                        .Add("ActualDigest", responseDigest)
                        .Add("ResponseTime", $"{sw.ElapsedMilliseconds}ms"))
                    .WithCauses(
                        "Test artifact was updated",
                        "Wrong artifact tag being pulled")
                    .WithRemediation(r => r
                        .AddManualStep(1, "Update expected digest", $"Set Doctor:Plugins:Verification:TestArtifact:ExpectedDigest to {responseDigest}")
                        .AddManualStep(2, "Or use digest in reference", "Use @sha256:... in the reference instead of :tag")
                        .WithRunbookUrl(RunbookUrlValue))
                    .WithVerification($"stella doctor --check check.verification.artifact.pull")
                    .Build();
            }

            return result
                .Pass($"Test artifact accessible ({sw.ElapsedMilliseconds}ms)")
                .WithEvidence("Artifact", e => e
                    .Add("Reference", reference)
                    .Add("Registry", registry)
                    .Add("Repository", repository)
                    .Add("Digest", responseDigest ?? "(not provided)")
                    .Add("ResponseTime", $"{sw.ElapsedMilliseconds}ms"))
                .Build();
        }
        catch (HttpRequestException ex)
        {
            sw.Stop();
            return result
                .Fail($"Cannot reach registry: {ex.Message}")
                .WithEvidence("Artifact", e => e
                    .Add("Reference", reference)
                    .Add("Registry", registry)
                    .Add("Error", ex.Message))
                .WithCauses(
                    "Registry is unreachable",
                    "Network connectivity issue",
                    "DNS resolution failure")
                .WithRemediation(r => r
                    .AddShellStep(1, "Test registry connectivity", $"curl -I https://{registry}/v2/")
                    .AddManualStep(2, "Check network configuration", "Ensure HTTPS traffic to the registry is allowed")
                    .WithRunbookUrl(RunbookUrlValue))
                .WithVerification($"stella doctor --check check.verification.artifact.pull")
                .Build();
        }
    }

    private static (string? Registry, string? Repository, string? Digest) ParseOciReference(string reference)
    {
        // Remove oci:// prefix if present
        var cleanRef = reference;
        if (cleanRef.StartsWith("oci://", StringComparison.OrdinalIgnoreCase))
            cleanRef = cleanRef[6..];

        // Split by @ to get digest
        string? digest = null;
        var atIndex = cleanRef.IndexOf('@');
        if (atIndex > 0)
        {
            digest = cleanRef[(atIndex + 1)..];
            cleanRef = cleanRef[..atIndex];
        }

        // Split by : to remove tag (we prefer digest)
        var colonIndex = cleanRef.LastIndexOf(':');
        if (colonIndex > 0 && !cleanRef[..colonIndex].Contains('/'))
        {
            // This is a port, not a tag
        }
        else if (colonIndex > cleanRef.IndexOf('/'))
        {
            cleanRef = cleanRef[..colonIndex];
        }

        // First part is registry, rest is repository
        var slashIndex = cleanRef.IndexOf('/');
        if (slashIndex <= 0)
            return (null, null, null);

        var registry = cleanRef[..slashIndex];
        var repository = cleanRef[(slashIndex + 1)..];

        return (registry, repository, digest);
    }

    private static string FormatFileSize(long bytes)
    {
        return bytes switch
        {
            < 1024 => $"{bytes} B",
            < 1024 * 1024 => $"{bytes / 1024.0:F1} KB",
            < 1024 * 1024 * 1024 => $"{bytes / (1024.0 * 1024.0):F1} MB",
            _ => $"{bytes / (1024.0 * 1024.0 * 1024.0):F1} GB"
        };
    }
}