using FinlyticCore.Dtos.News;
using FinlyticNews.Adapters.Discovery;
using Microsoft.Extensions.Logging;

namespace FinlyticNews.Services;

/// <summary>
/// Defines operations for discovering article links from various news feeds and web pages.
/// </summary>
public interface IArticleDiscoveryService
{
    /// <summary>
    /// Discovers article links from a given source URL using configured adapters.
    /// </summary>
    /// <param name="url">The URL of the source news page or feed.</param>
    /// <param name="adapterType">The type identifier of the adapter to use (e.g. "rss", "html").</param>
    /// <param name="ct">The token to monitor for cancellation requests.</param>
    /// <returns>A list of discovered absolute article URLs (optionally carrying ISINs), or null if the URL was invalid.</returns>
    Task<List<DiscoveredArticle>?> DiscoverLinksAsync(string url, string adapterType, CancellationToken ct = default);
}

/// <inheritdoc />
public class ArticleDiscoveryService : IArticleDiscoveryService
{
    private readonly IEnumerable<ArticleDiscoveryAdapter> _adapters;
    private readonly ILogger<ArticleDiscoveryService> _logger;
    private readonly HttpClient _httpClient;

    /// <summary>
    /// Initializes a new instance of the <see cref="ArticleDiscoveryService"/> class.
    /// </summary>
    /// <param name="adapters">Registered list of specialized adapters.</param>
    /// <param name="logger">The application logging channel.</param>
    /// <param name="httpClient">The HTTP client to fetch feeds.</param>
    public ArticleDiscoveryService(
        IEnumerable<ArticleDiscoveryAdapter> adapters,
        ILogger<ArticleDiscoveryService> logger,
        HttpClient httpClient)
    {
        _adapters = adapters;
        _logger = logger;
        _httpClient = httpClient;
    }

    /// <inheritdoc />
    public async Task<List<DiscoveredArticle>?> DiscoverLinksAsync(string url, string adapterType, CancellationToken ct = default)
    {
        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
        {
            _logger.LogWarning("[{Channel}] Invalid source URL passed for discovery: {Url}", "NewsChannel", url);
            return null;
        }

        try
        {
            _logger.LogDebug("Fetching content from discovery source: {Url}", uri);
            var content = await _httpClient.GetStringAsync(uri, ct);

            if (string.IsNullOrWhiteSpace(content)) return [];

            var trimmedContent = content.TrimStart();

            // 1. Zuerst gezielt nach registriertem Adapter suchen (z. B. finanznachrichten_rss)
            var adapter = _adapters.FirstOrDefault(a => 
                a.Name.Equals(adapterType, StringComparison.OrdinalIgnoreCase) || 
                uri.Host.Contains(a.Name, StringComparison.OrdinalIgnoreCase));

            if (adapter != null)
            {
                _logger.LogInformation("[{Channel}] Using specialized adapter {AdapterName} for source: {Url}", "NewsChannel", adapter.Name, url);
                return adapter.ExtractUrls(content, url);
            }

            // 2. Fallback: Automatische Erkennung für generische RSS/Atom-Feeds
            if (adapterType.Equals("rss", StringComparison.OrdinalIgnoreCase) || 
                trimmedContent.StartsWith("<?xml", StringComparison.OrdinalIgnoreCase) ||
                trimmedContent.StartsWith("<rss", StringComparison.OrdinalIgnoreCase) ||
                trimmedContent.StartsWith("<feed", StringComparison.OrdinalIgnoreCase))
            {
                _logger.LogInformation("[{Channel}] Syndication (RSS) format detected for source: {Url}", "NewsChannel", url);
                
                var rssAdapter = _adapters.FirstOrDefault(a => a.Name.Equals("rss", StringComparison.OrdinalIgnoreCase)) 
                                 ?? new RssDiscoveryAdapter();

                return rssAdapter.ExtractUrls(content, url);
            }

            _logger.LogWarning("[{Channel}] No suitable discovery adapter found for type '{Type}' and URL: {Url}", "NewsChannel", adapterType, url);
            return [];
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "[{Channel}] Failed to run article discovery on URL: {Url}", "NewsChannel", url);
            return [];
        }
    }
}