// Copyright (c) StellaOps. Licensed under the BUSL-1.1.

using System.Net.Http.Json;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace StellaOps.Audit.Emission;

/// <summary>
/// Sends audit events to the Timeline service's <c>POST /api/v1/audit/ingest</c> endpoint.
/// Failures are logged but never propagated -- audit emission must not block the calling service.
/// </summary>
public sealed class HttpAuditEventEmitter : IAuditEventEmitter
{
    /// <summary>
    /// Named HTTP client identifier used for DI registration.
    /// </summary>
    public const string HttpClientName = "StellaOps.AuditEmission";

    private static readonly JsonSerializerOptions SerializerOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
        WriteIndented = false
    };

    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IOptions<AuditEmissionOptions> _options;
    private readonly ILogger<HttpAuditEventEmitter> _logger;

    public HttpAuditEventEmitter(
        IHttpClientFactory httpClientFactory,
        IOptions<AuditEmissionOptions> options,
        ILogger<HttpAuditEventEmitter> logger)
    {
        _httpClientFactory = httpClientFactory;
        _options = options;
        _logger = logger;
    }

    public async Task EmitAsync(AuditEventPayload auditEvent, CancellationToken cancellationToken)
    {
        var options = _options.Value;
        if (!options.Enabled)
        {
            _logger.LogDebug("Audit emission is disabled; skipping event {EventId}", auditEvent.Id);
            return;
        }

        try
        {
            var client = _httpClientFactory.CreateClient(HttpClientName);
            var uri = new Uri(new Uri(options.TimelineBaseUrl), "/api/v1/audit/ingest");

            using var response = await client.PostAsJsonAsync(
                    uri,
                    auditEvent,
                    SerializerOptions,
                    cancellationToken)
                .ConfigureAwait(false);

            if (!response.IsSuccessStatusCode)
            {
                _logger.LogWarning(
                    "Audit ingest returned HTTP {StatusCode} for event {EventId}",
                    (int)response.StatusCode,
                    auditEvent.Id);
            }
            else
            {
                _logger.LogDebug(
                    "Audit event {EventId} emitted successfully ({Module}.{Action})",
                    auditEvent.Id,
                    auditEvent.Module,
                    auditEvent.Action);
            }
        }
        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
        {
            _logger.LogWarning("Audit emission timed out for event {EventId}", auditEvent.Id);
        }
        catch (Exception ex) when (ex is HttpRequestException or JsonException)
        {
            _logger.LogWarning(ex, "Audit emission failed for event {EventId}", auditEvent.Id);
        }
    }
}