using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using FinlyticCore.Dtos.News;
using FinlyticCore.Services;
using FinlyticNews.Adapters.Discovery;
using FinlyticNews.Util;

namespace FinlyticNews.Services;

public interface IArticleDiscoveryService
{
    Task<List<DiscoveredArticle>?> DiscoverLinksAsync(string url, string adapterType, CancellationToken ct = default);
}

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

    public ArticleDiscoveryService(
        IEnumerable<ArticleDiscoveryAdapter> adapters,
        IFinlyticLogger<ArticleDiscoveryService> finlyticLogger,
        HttpClient httpClient)
    {
        _adapters = adapters;
        _finlyticLogger = finlyticLogger;
        _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))
        {
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[ArticleDiscoveryService] Invalid source URL passed for discovery: {Url}", url);
            return null;
        }

        try
        {
            await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[ArticleDiscoveryService] Fetching content from discovery source: {Url}", uri);
            var content = await _httpClient.GetStringAsync(uri, ct);

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

            var trimmedContent = content.TrimStart();

            var adapter = _adapters.FirstOrDefault(a => 
                a.Name.Equals(adapterType, StringComparison.OrdinalIgnoreCase) || 
                uri.Host.Contains(a.Name, StringComparison.OrdinalIgnoreCase));

            if (adapter != null)
            {
                await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[ArticleDiscoveryService] Using specialized adapter {AdapterName} for source: {Url}", adapter.Name, url);
                return adapter.ExtractUrls(content, url);
            }

            if (adapterType.Equals("rss", StringComparison.OrdinalIgnoreCase) || 
                trimmedContent.StartsWith("<?xml", StringComparison.OrdinalIgnoreCase) ||
                trimmedContent.StartsWith("<rss", StringComparison.OrdinalIgnoreCase) ||
                trimmedContent.StartsWith("<feed", StringComparison.OrdinalIgnoreCase))
            {
                await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[ArticleDiscoveryService] Syndication (RSS) format detected for source: {Url}", url);
                
                var rssAdapter = _adapters.FirstOrDefault(a => a.Name.Equals("rss", StringComparison.OrdinalIgnoreCase)) 
                                 ?? new RssDiscoveryAdapter();

                return rssAdapter.ExtractUrls(content, url);
            }

            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[ArticleDiscoveryService] No suitable discovery adapter found for type '{Type}' and URL: {Url}", adapterType, url);
            return [];
        }
        catch (Exception ex)
        {
            await _finlyticLogger.LogErrorAsync(SettingKeys.NewsChannel, ex, "[ArticleDiscoveryService] Failed to run article discovery on URL: {Url}", url);
            return [];
        }
    }
}