using System.Diagnostics;
using System.Diagnostics.Metrics;

namespace StellaOps.Cryptography;

/// <summary>
/// Telemetry diagnostics for crypto compliance operations.
/// </summary>
public sealed class CryptoComplianceDiagnostics : IDisposable
{
    /// <summary>
    /// Activity source name for distributed tracing.
    /// </summary>
    public const string ActivitySourceName = "StellaOps.Crypto.Compliance";

    /// <summary>
    /// Meter name for metrics.
    /// </summary>
    public const string MeterName = "StellaOps.Crypto.Compliance";

    private readonly ActivitySource _activitySource;
    private readonly Meter _meter;

    // Counters
    private readonly Counter<long> _hashOperations;
    private readonly Counter<long> _complianceViolations;
    private readonly Histogram<double> _hashDurationMs;

    public CryptoComplianceDiagnostics()
    {
        _activitySource = new ActivitySource(ActivitySourceName, "1.0.0");
        _meter = new Meter(MeterName, "1.0.0");

        _hashOperations = _meter.CreateCounter<long>(
            name: "crypto.hash.operations",
            unit: "{operation}",
            description: "Total number of hash operations performed.");

        _complianceViolations = _meter.CreateCounter<long>(
            name: "crypto.compliance.violations",
            unit: "{violation}",
            description: "Number of compliance violations detected.");

        _hashDurationMs = _meter.CreateHistogram<double>(
            name: "crypto.hash.duration",
            unit: "ms",
            description: "Duration of hash operations in milliseconds.");
    }

    /// <summary>
    /// Starts an activity for a hash operation.
    /// </summary>
    public Activity? StartHashOperation(string purpose, string algorithm, string profile)
    {
        var activity = _activitySource.StartActivity("crypto.hash", ActivityKind.Internal);
        if (activity is not null)
        {
            activity.SetTag("crypto.purpose", purpose);
            activity.SetTag("crypto.algorithm", algorithm);
            activity.SetTag("crypto.profile", profile);
        }
        return activity;
    }

    /// <summary>
    /// Records a completed hash operation.
    /// </summary>
    public void RecordHashOperation(
        string profile,
        string purpose,
        string algorithm,
        TimeSpan duration,
        bool success = true)
    {
        var tags = new TagList
        {
            { "profile", profile },
            { "purpose", purpose },
            { "algorithm", algorithm },
            { "success", success.ToString().ToLowerInvariant() }
        };

        _hashOperations.Add(1, tags);
        _hashDurationMs.Record(duration.TotalMilliseconds, tags);
    }

    /// <summary>
    /// Records a compliance violation.
    /// </summary>
    public void RecordComplianceViolation(
        string profile,
        string purpose,
        string requestedAlgorithm,
        string expectedAlgorithm,
        bool wasBlocked)
    {
        var tags = new TagList
        {
            { "profile", profile },
            { "purpose", purpose },
            { "requested_algorithm", requestedAlgorithm },
            { "expected_algorithm", expectedAlgorithm },
            { "blocked", wasBlocked.ToString().ToLowerInvariant() }
        };

        _complianceViolations.Add(1, tags);
    }

    /// <summary>
    /// Disposes of the diagnostics resources.
    /// </summary>
    public void Dispose()
    {
        _activitySource.Dispose();
        _meter.Dispose();
    }
}