using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;

namespace StellaOps.Scanner.Surface.Secrets.Providers;

/// <summary>
/// Wraps a secret provider with audit logging. Each secret access is logged with tenant, component,
/// secret type, and provider metadata for observability and compliance.
/// </summary>
internal sealed class AuditingSurfaceSecretProvider : ISurfaceSecretProvider
{
    private readonly ISurfaceSecretProvider _inner;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger _logger;
    private readonly string _componentName;

    public AuditingSurfaceSecretProvider(
        ISurfaceSecretProvider inner,
        TimeProvider timeProvider,
        ILogger logger,
        string componentName)
    {
        _inner = inner ?? throw new ArgumentNullException(nameof(inner));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _componentName = componentName ?? throw new ArgumentNullException(nameof(componentName));
    }

    public SurfaceSecretHandle Get(SurfaceSecretRequest request)
    {
        var startTime = _timeProvider.GetUtcNow();

        try
        {
            var handle = _inner.Get(request);

            var elapsed = _timeProvider.GetUtcNow() - startTime;
            LogAuditEvent(
                request,
                handle.Metadata,
                success: true,
                elapsed,
                error: null);

            return handle;
        }
        catch (SurfaceSecretNotFoundException)
        {
            var elapsed = _timeProvider.GetUtcNow() - startTime;
            LogAuditEvent(
                request,
                metadata: null,
                success: false,
                elapsed,
                error: "NotFound");

            throw;
        }
        catch (Exception ex)
        {
            var elapsed = _timeProvider.GetUtcNow() - startTime;
            LogAuditEvent(
                request,
                metadata: null,
                success: false,
                elapsed,
                error: ex.GetType().Name);

            throw;
        }
    }

    public async ValueTask<SurfaceSecretHandle> GetAsync(
        SurfaceSecretRequest request,
        CancellationToken cancellationToken = default)
    {
        var startTime = _timeProvider.GetUtcNow();

        try
        {
            var handle = await _inner.GetAsync(request, cancellationToken).ConfigureAwait(false);

            var elapsed = _timeProvider.GetUtcNow() - startTime;
            LogAuditEvent(
                request,
                handle.Metadata,
                success: true,
                elapsed,
                error: null);

            return handle;
        }
        catch (SurfaceSecretNotFoundException)
        {
            var elapsed = _timeProvider.GetUtcNow() - startTime;
            LogAuditEvent(
                request,
                metadata: null,
                success: false,
                elapsed,
                error: "NotFound");

            throw;
        }
        catch (Exception ex)
        {
            var elapsed = _timeProvider.GetUtcNow() - startTime;
            LogAuditEvent(
                request,
                metadata: null,
                success: false,
                elapsed,
                error: ex.GetType().Name);

            throw;
        }
    }

    private void LogAuditEvent(
        SurfaceSecretRequest request,
        IReadOnlyDictionary<string, string>? metadata,
        bool success,
        TimeSpan elapsed,
        string? error)
    {
        // Structured log entry for audit trail. NEVER log secret contents.
        _logger.Log(
            success ? LogLevel.Information : LogLevel.Warning,
            "Surface secret access: " +
            "Component={Component}, " +
            "Tenant={Tenant}, " +
            "RequestComponent={RequestComponent}, " +
            "SecretType={SecretType}, " +
            "Name={Name}, " +
            "Success={Success}, " +
            "ElapsedMs={ElapsedMs}, " +
            "Provider={Provider}, " +
            "Error={Error}",
            _componentName,
            request.Tenant,
            request.Component,
            request.SecretType,
            request.Name ?? "default",
            success,
            elapsed.TotalMilliseconds,
            metadata?.GetValueOrDefault("source") ?? "unknown",
            error ?? "(none)");
    }
}