using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.Json;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using FinlyticAssets.Models;
using FinlyticAssets.Util;
using FinlyticCore.Dtos.News;
using FinlyticCore.Services;
using FinlyticCore.Util;
using FinlyticNews.Entities;
using FinlyticNews.Util;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace FinlyticNews.Services;

/// <summary>
/// A background worker service that orchestrates link discovery, Playwright scraping,
/// pre-filtering, n8n AI enrichment, database persistence, and MQTT broadcasts.
/// </summary>
public class NewsScraperBackgroundService : BackgroundService
{
    private record CompiledAssetMatcher(
        AssetIndex Asset,
        string CoreName,
        Regex? WordRegex,
        Regex? CoreWordRegex
    );

    private readonly IServiceScopeFactory _scopeFactory;
    private readonly IFinlyticLogger<NewsScraperBackgroundService> _finlyticLogger;
    private readonly NewsMqttClient _mqttClient;
    private readonly string _indexPath;

    private List<CompiledAssetMatcher>? _cachedAssetMatchers;
    private DateTime _lastIndexLoadTime = DateTime.MinValue;

    public NewsScraperBackgroundService(
        IServiceScopeFactory scopeFactory,
        IFinlyticLogger<NewsScraperBackgroundService> finlyticLogger,
        NewsMqttClient mqttClient,
        IConfiguration configuration)
    {
        _scopeFactory = scopeFactory;
        _finlyticLogger = finlyticLogger;
        _mqttClient = mqttClient;
        _indexPath = Path.Combine(Volumes.IndexRelativePath, "index.json");
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] NewsScraperBackgroundService started.");

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await using var scope = _scopeFactory.CreateAsyncScope();
                var settings = scope.ServiceProvider.GetRequiredService<ISettingsService>();
                bool enabled = await settings.GetSettingAsync(SettingKeys.EnableAutoScraping, stoppingToken);

                if (enabled)
                {
                    await RunScrapingCycleAsync(stoppingToken);
                }
                else
                {
                    await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Auto-scraping is disabled via settings.");
                }
            }
            catch (Exception ex) when (ex is not OperationCanceledException)
            {
                await _finlyticLogger.LogErrorAsync(SettingKeys.NewsChannel, ex, "[NewsScraperBackgroundService] An unhandled exception occurred during news scraping cycle.");
            }

            int intervalMinutes = 15;
            try
            {
                await using var scope = _scopeFactory.CreateAsyncScope();
                var settings = scope.ServiceProvider.GetRequiredService<ISettingsService>();
                intervalMinutes = await settings.GetSettingAsync(SettingKeys.ScrapeIntervalMinutes, stoppingToken);
            }
            catch { }

            var jitterSeconds = Random.Shared.Next(0, 60);
            var nextRunDelay = TimeSpan.FromMinutes(intervalMinutes) + TimeSpan.FromSeconds(jitterSeconds);
            await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Scraping cycle completed. Next cycle in {Delay} (interval: {Minutes}m).", nextRunDelay, intervalMinutes);

            try
            {
                await Task.Delay(nextRunDelay, stoppingToken);
            }
            catch (OperationCanceledException)
            {
                break;
            }
        }

        await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] NewsScraperBackgroundService stopping.");
    }

    private async Task RunScrapingCycleAsync(CancellationToken stoppingToken)
    {
        await using var scope = _scopeFactory.CreateAsyncScope();
        var dbService = scope.ServiceProvider.GetRequiredService<INewsDbService>();
        var discoveryService = scope.ServiceProvider.GetRequiredService<IArticleDiscoveryService>();
        var scraperService = scope.ServiceProvider.GetRequiredService<IPlaywrightScraperService>();
        var n8nService = scope.ServiceProvider.GetRequiredService<IN8nService>();
        var settings = scope.ServiceProvider.GetRequiredService<ISettingsService>();

        var maxArticlesPerFeed = await settings.GetSettingAsync(SettingKeys.MaxArticlesPerFeed, stoppingToken);

        var assetMatchers = await GetOrLoadAssetMatchersAsync();
        await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Loaded {Count} asset index items for text pre-filtering.", assetMatchers.Count);

        var failedArticles = await dbService.GetArticlesByStatusAsync("Scraping");
        if (failedArticles.Count > 0)
        {
            await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Found {Count} articles in status 'Scraping' that failed to scrape previously. Retrying...", failedArticles.Count);
            foreach (var article in failedArticles)
            {
                if (stoppingToken.IsCancellationRequested) return;
                await ProcessSingleArticleAsync(article, scraperService, n8nService, dbService, assetMatchers, stoppingToken);
            }
        }

        var sources = await dbService.GetSourcesAsync();
        if (sources.Count == 0)
        {
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] No article sources configured in database. Skipping cycle.");
            return;
        }

        foreach (var source in sources)
        {
            if (stoppingToken.IsCancellationRequested) break;

            await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Starting article link discovery for source: {SourceName} ({Url})", source.Name, source.Source);
            var discoveredArticles = await discoveryService.DiscoverLinksAsync(source.Source, source.Type, stoppingToken);

            if (discoveredArticles == null || discoveredArticles.Count == 0)
            {
                await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] No links discovered from source: {SourceName}", source.Name);
                continue;
            }

            await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Discovered {Count} potential article links from {SourceName}.", discoveredArticles.Count, source.Name);

            var toProcess = discoveredArticles.Take(maxArticlesPerFeed > 0 ? maxArticlesPerFeed : 20);

            foreach (var discovered in toProcess)
            {
                if (stoppingToken.IsCancellationRequested) break;

                if (await dbService.IsUrlDuplicateAsync(discovered.Url))
                {
                    await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Skipping duplicate article URL: {Url}", discovered.Url);
                    continue;
                }

                NewsArticleEntity article;
                try
                {
                    article = await dbService.CreatePendingArticleAsync(
                        discovered.Url,
                        discovered.Isins,
                        discovered.Title,
                        discovered.Summary,
                        discovered.PublishedAt,
                        discovered.Language
                    );
                }
                catch (Exception ex)
                {
                    await _finlyticLogger.LogErrorAsync(SettingKeys.NewsChannel, ex, "[NewsScraperBackgroundService] Failed to register initial pending state for URL: {Url}. Skipping.", discovered.Url);
                    continue;
                }

                if (article.Id == Guid.Empty)
                {
                    await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Created pending article has invalid/empty ID for URL: {Url}. Skipping.", discovered.Url);
                    continue;
                }

                await ProcessSingleArticleAsync(article, scraperService, n8nService, dbService, assetMatchers, stoppingToken);
            }
        }
    }

    private async Task ProcessSingleArticleAsync(
        NewsArticleEntity article,
        IPlaywrightScraperService scraperService,
        IN8nService n8nService,
        INewsDbService dbService,
        List<CompiledAssetMatcher> assetMatchers,
        CancellationToken stoppingToken)
    {
        try
        {
            await dbService.UpdateArticleStatusAsync(article.Id, "Processing");

            var (resolvedUrl, rawContent) = await scraperService.ScrapeArticleAsync(article.SourceUrl);

            if (!string.IsNullOrWhiteSpace(resolvedUrl) &&
                !resolvedUrl.Equals(article.SourceUrl, StringComparison.OrdinalIgnoreCase))
            {
                await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Redirect detected. Initial: {OldUrl} -> Resolved: {NewUrl}", article.SourceUrl, resolvedUrl);
                if (await dbService.IsUrlDuplicateAsync(resolvedUrl))
                {
                    await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Redirected URL {ResolvedUrl} is a duplicate. Terminating processing.", resolvedUrl);
                    await dbService.UpdateArticleStatusAsync(article.Id, "Failed");
                    return;
                }

                await dbService.UpdateArticleUrlAsync(article.Id, resolvedUrl);
                article.SourceUrl = resolvedUrl;
            }

            if (string.IsNullOrWhiteSpace(rawContent) || rawContent.Length < 60)
            {
                await dbService.UpdateArticleStatusAsync(article.Id, "Failed");
                return;
            }

            var discoveredIsins = article.MatchedAssets.Select(m => m.Isin).Where(i => !string.IsNullOrEmpty(i)).ToList();
            var preFilteredAssets = PreFilterAssets(rawContent, article.Title, assetMatchers, discoveredIsins);

            if (preFilteredAssets.Count == 0)
            {
                await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Pre-filtering: Article {Id} does not reference any known assets. Terminating pipeline.", article.Id);
                await dbService.UpdateArticleStatusAsync(article.Id, "Failed");
                return;
            }

            await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Pre-filtering matched {Count} assets for article {Id}.", preFilteredAssets.Count, article.Id);

            var n8nResponse = await n8nService.AnalyzeArticleAsync(rawContent, preFilteredAssets, stoppingToken);
            if (n8nResponse == null)
            {
                await dbService.UpdateArticleStatusAsync(article.Id, "Failed");
                return;
            }

            var matchedEntities = new List<MatchedAssetEntity>();
            if (n8nResponse.MatchedAssets != null && n8nResponse.MatchedAssets.Count > 0)
            {
                foreach (var asset in n8nResponse.MatchedAssets)
                {
                    var preMatch = preFilteredAssets.FirstOrDefault(p => p.Name.Equals(asset.Name, StringComparison.OrdinalIgnoreCase));
                    var isin = preMatch?.Isin ?? asset.Ticker ?? "";
                    if (string.IsNullOrWhiteSpace(isin)) continue;

                    matchedEntities.Add(new MatchedAssetEntity
                    {
                        Id = Guid.NewGuid(),
                        NewsArticleId = article.Id,
                        Isin = isin.Trim().ToUpperInvariant(),
                        Name = !string.IsNullOrWhiteSpace(asset.Name) ? asset.Name.Trim() : isin.Trim().ToUpperInvariant()
                    });
                }
            }

            if (matchedEntities.Count == 0)
            {
                foreach (var preMatch in preFilteredAssets)
                {
                    matchedEntities.Add(new MatchedAssetEntity
                    {
                        Id = Guid.NewGuid(),
                        NewsArticleId = article.Id,
                        Isin = preMatch.Isin,
                        Name = preMatch.Name
                    });
                }
            }

            var updatedArticle = await dbService.SaveArticleClassificationAsync(article.Id, n8nResponse, matchedEntities);

            if (updatedArticle != null)
            {
                var dto = new NewsArticleDto
                {
                    Id = updatedArticle.Id,
                    Title = updatedArticle.Title,
                    Author = updatedArticle.Author,
                    Summary = updatedArticle.Summary,
                    ContentRaw = updatedArticle.ContentRaw,
                    Language = updatedArticle.Language,
                    SourceUrl = updatedArticle.SourceUrl,
                    ScrapedAt = updatedArticle.ScrapedAt,
                    PublishedAt = updatedArticle.PublishedAt,
                    Status = updatedArticle.Status,
                    MatchedAssets = updatedArticle.MatchedAssets.Select(m => new MatchedAssetDto
                    {
                        Name = m.Name,
                        Isin = m.Isin
                    }).ToList()
                };

                await _mqttClient.BroadcastArticleAsync(dto);
            }
        }
        catch (Exception ex)
        {
            await _finlyticLogger.LogErrorAsync(SettingKeys.NewsChannel, ex, "[NewsScraperBackgroundService] Failed to complete processing pipeline for article: {Url}. Transitioning to 'Scraping' for next cycle retry.", article.SourceUrl);
            await dbService.UpdateArticleStatusAsync(article.Id, "Scraping");
        }
    }

    private List<FilteredAssetPayload> PreFilterAssets(
        string content,
        string? title,
        List<CompiledAssetMatcher> assetMatchers,
        List<string>? priorityIsins = null)
    {
        if (assetMatchers.Count == 0) return new List<FilteredAssetPayload>();

        var fullText = (title != null ? title + " " + content : content);
        var matched = new Dictionary<string, FilteredAssetPayload>(StringComparer.OrdinalIgnoreCase);

        if (priorityIsins != null && priorityIsins.Count > 0)
        {
            foreach (var isin in priorityIsins)
            {
                var match = assetMatchers.FirstOrDefault(m => string.Equals(m.Asset.Isin, isin, StringComparison.OrdinalIgnoreCase));
                if (match != null && !matched.ContainsKey(match.Asset.Isin))
                {
                    matched[match.Asset.Isin] = new FilteredAssetPayload(match.Asset.Name, match.Asset.Isin);
                }
            }
        }

        foreach (var m in assetMatchers)
        {
            if (matched.ContainsKey(m.Asset.Isin)) continue;

            if (fullText.Contains(m.Asset.Isin, StringComparison.OrdinalIgnoreCase))
            {
                matched[m.Asset.Isin] = new FilteredAssetPayload(m.Asset.Name, m.Asset.Isin);
                continue;
            }

            if (m.WordRegex != null && m.WordRegex.IsMatch(fullText))
            {
                matched[m.Asset.Isin] = new FilteredAssetPayload(m.Asset.Name, m.Asset.Isin);
                continue;
            }

            if (m.CoreWordRegex != null && m.CoreWordRegex.IsMatch(fullText))
            {
                matched[m.Asset.Isin] = new FilteredAssetPayload(m.Asset.Name, m.Asset.Isin);
            }
        }

        return matched.Values.ToList();
    }

    private async Task<List<CompiledAssetMatcher>> GetOrLoadAssetMatchersAsync()
    {
        if (_cachedAssetMatchers != null && (DateTime.UtcNow - _lastIndexLoadTime).TotalMinutes < 60)
        {
            return _cachedAssetMatchers;
        }

        if (!File.Exists(_indexPath))
        {
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsScraperBackgroundService] Asset index file not found at: {Path}. Pre-filtering will match 0 assets.", _indexPath);
            return new List<CompiledAssetMatcher>();
        }

        try
        {
            using var stream = File.OpenRead(_indexPath);
            var indexList = await JsonSerializer.DeserializeAsync<List<AssetIndex>>(stream);

            if (indexList == null || indexList.Count == 0)
            {
                return new List<CompiledAssetMatcher>();
            }

            var compiled = new List<CompiledAssetMatcher>(indexList.Count);
            foreach (var asset in indexList)
            {
                if (string.IsNullOrWhiteSpace(asset.Name) || string.IsNullOrWhiteSpace(asset.Isin))
                    continue;

                var rawName = asset.Name.Trim();
                var coreName = ExtractCoreName(rawName);

                Regex? wordRegex = null;
                if (rawName.Length >= 4)
                {
                    wordRegex = new Regex($@"\b{Regex.Escape(rawName)}\b", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.Compiled);
                }

                Regex? coreWordRegex = null;
                if (!string.IsNullOrWhiteSpace(coreName) && coreName.Length >= 4 && !coreName.Equals(rawName, StringComparison.OrdinalIgnoreCase))
                {
                    coreWordRegex = new Regex($@"\b{Regex.Escape(coreName)}\b", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.Compiled);
                }

                compiled.Add(new CompiledAssetMatcher(asset, coreName, wordRegex, coreWordRegex));
            }

            _cachedAssetMatchers = compiled;
            _lastIndexLoadTime = DateTime.UtcNow;
            return _cachedAssetMatchers;
        }
        catch (Exception ex)
        {
            await _finlyticLogger.LogErrorAsync(SettingKeys.NewsChannel, ex, "[NewsScraperBackgroundService] Failed to read or parse asset index file from {Path}.", _indexPath);
            return _cachedAssetMatchers ?? new List<CompiledAssetMatcher>();
        }
    }

    private static string ExtractCoreName(string rawName)
    {
        var cleaned = Regex.Replace(rawName, @"\b(AG|SE|SA|NV|PLC|INC|CORP|LLC|GMBH|CO|KG|HOLDING|GROUP|CLASS\s+[A-Z])\b", "", RegexOptions.IgnoreCase);
        return cleaned.Trim(' ', '.', ',', '-');
    }
}