using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using FinlyticCore.Dtos.News;
using FinlyticCore.Services;
using FinlyticNews.Database;
using FinlyticNews.Entities;
using FinlyticNews.Util;
using Microsoft.EntityFrameworkCore;

namespace FinlyticNews.Services;

/// <summary>
/// Defines database persistence operations for news articles and sources following the FinlyticNews lifecycle pipeline.
/// </summary>
public interface INewsDbService
{
    Task<List<ArticleSourceEntity>> GetSourcesAsync();
    Task<bool> IsUrlDuplicateAsync(string url);

    /// <summary>
    /// Phase 1: Discovers and locks a new article URL by setting its status to "Pending".
    /// </summary>
    Task<NewsArticleEntity> CreatePendingArticleAsync(
        string url,
        List<string>? discoveredIsins = null,
        string? title = null,
        string? summary = null,
        DateTime? publishedAt = null,
        string? language = null);

    /// <summary>
    /// Transitions the lifecycle state of an article (e.g. Pending -> Processing -> Scraping / Failed / Completed / Analyzed).
    /// </summary>
    Task UpdateArticleStatusAsync(Guid id, string status);

    /// <summary>
    /// Updates the target URL of an article if a redirect is resolved during the Processing phase.
    /// </summary>
    Task UpdateArticleUrlAsync(Guid id, string resolvedUrl);

    /// <summary>
    /// Phase 4: Saves AI classification from n8n and sets the lifecycle status to "Completed".
    /// </summary>
    Task<NewsArticleEntity?> SaveArticleClassificationAsync(Guid id, N8nResponsePayload payload, List<MatchedAssetEntity> matchedAssets);

    Task<List<NewsArticleEntity>> GetArticlesByStatusAsync(string status);

    Task<List<NewsArticleEntity>> GetFilteredNewsAsync(
        int limit,
        int offset,
        string? isin = null,
        DateTime? date = null,
        string? status = null,
        string? searchQuery = null);

    Task<NewsArticleEntity?> GetArticleByIdAsync(Guid id);
}

/// <inheritdoc />
public class NewsDbService : INewsDbService
{
    private readonly NewsDbContext _context;
    private readonly IFinlyticLogger<NewsDbService> _finlyticLogger;

    public NewsDbService(NewsDbContext context, IFinlyticLogger<NewsDbService> finlyticLogger)
    {
        _context = context;
        _finlyticLogger = finlyticLogger;
    }

    /// <inheritdoc />
    public async Task<List<ArticleSourceEntity>> GetSourcesAsync()
    {
        return await _context.ArticleSources.AsNoTracking().ToListAsync();
    }

    /// <inheritdoc />
    public async Task<NewsArticleEntity?> GetArticleByIdAsync(Guid id)
    {
        return await _context.NewsArticles
            .Include(a => a.MatchedAssets)
            .AsNoTracking()
            .FirstOrDefaultAsync(a => a.Id == id);
    }

    /// <inheritdoc />
    public async Task<bool> IsUrlDuplicateAsync(string url)
    {
        var trimmedUrl = url.Trim();
        return await _context.NewsArticles
            .AsNoTracking()
            .AnyAsync(a => a.SourceUrl == trimmedUrl);
    }

    /// <inheritdoc />
    public async Task<NewsArticleEntity> CreatePendingArticleAsync(
        string url,
        List<string>? discoveredIsins = null,
        string? title = null,
        string? summary = null,
        DateTime? publishedAt = null,
        string? language = null)
    {
        var trimmedUrl = url.Trim();
        var cleanUrl = trimmedUrl.TrimEnd('.', '/');

        var existingArticle = await _context.NewsArticles
            .FirstOrDefaultAsync(a => a.SourceUrl == trimmedUrl || a.SourceUrl == cleanUrl || a.SourceUrl.StartsWith(cleanUrl));

        if (existingArticle != null)
        {
            await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[Lifecycle] Article URL already exists (Duplicate hit): {Url}", trimmedUrl);
            return existingArticle;
        }

        var finalPublishedAt = publishedAt.HasValue
            ? (publishedAt.Value.Kind == DateTimeKind.Unspecified
                ? DateTime.SpecifyKind(publishedAt.Value, DateTimeKind.Utc)
                : publishedAt.Value.ToUniversalTime())
            : DateTime.UtcNow;

        if (finalPublishedAt > DateTime.UtcNow)
        {
            finalPublishedAt = DateTime.UtcNow;
        }

        var article = new NewsArticleEntity
        {
            Id = Guid.NewGuid(),
            Title = !string.IsNullOrWhiteSpace(title) ? title : "Pending Discovery",
            Summary = !string.IsNullOrWhiteSpace(summary) ? summary : "Extraction in progress...",
            ContentRaw = "Extraction in progress...",
            SourceUrl = trimmedUrl,
            Language = language,
            ScrapedAt = DateTime.UtcNow,
            PublishedAt = finalPublishedAt,
            Status = "Pending"
        };

        if (discoveredIsins != null && discoveredIsins.Count > 0)
        {
            foreach (var isin in discoveredIsins)
            {
                article.MatchedAssets.Add(new MatchedAssetEntity
                {
                    Id = Guid.NewGuid(),
                    NewsArticleId = article.Id,
                    Isin = isin,
                    Name = isin
                });
            }
        }

        try
        {
            _context.NewsArticles.Add(article);
            await _context.SaveChangesAsync();
            await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[Lifecycle] Registered new article with status 'Pending'. ID: {Id}, Url: {Url}", article.Id, trimmedUrl);
        }
        catch (DbUpdateException ex)
        {
            _context.ChangeTracker.Clear();
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsChannel] Unique constraint or concurrency hit during insert for URL: {Url}. Fetching existing fallback. ({Message})", trimmedUrl, ex.InnerException?.Message ?? ex.Message);
            var existing = await _context.NewsArticles.AsNoTracking().FirstOrDefaultAsync(a => a.SourceUrl == trimmedUrl || a.SourceUrl == cleanUrl || a.SourceUrl.StartsWith(cleanUrl));
            if (existing != null)
            {
                return existing;
            }
            return article;
        }

        return article;
    }

    /// <inheritdoc />
    public async Task UpdateArticleStatusAsync(Guid id, string status)
    {
        var rowsAffected = await _context.NewsArticles
            .Where(a => a.Id == id)
            .ExecuteUpdateAsync(s => s.SetProperty(a => a.Status, status));

        if (rowsAffected == 0)
        {
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsChannel] Attempted status transition for non-existing article. ID: {Id}", id);
        }
        else
        {
            await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[Lifecycle] Transitioned article {Id} to status '{Status}'", id, status);
        }
    }

    /// <inheritdoc />
    public async Task UpdateArticleUrlAsync(Guid id, string resolvedUrl)
    {
        var rowsAffected = await _context.NewsArticles
            .Where(a => a.Id == id)
            .ExecuteUpdateAsync(s => s.SetProperty(a => a.SourceUrl, resolvedUrl));

        if (rowsAffected == 0)
        {
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsChannel] Attempted URL update for non-existing article. ID: {Id}", id);
        }
        else
        {
            await _finlyticLogger.LogDebugAsync(SettingKeys.NewsChannel, "[Lifecycle] Resolved redirect for article {Id} -> New URL: {Url}", id, resolvedUrl);
        }
    }

    /// <inheritdoc />
    public async Task<NewsArticleEntity?> SaveArticleClassificationAsync(Guid id, N8nResponsePayload payload, List<MatchedAssetEntity> matchedAssets)
    {
        var article = await _context.NewsArticles
            .FirstOrDefaultAsync(a => a.Id == id);

        if (article == null)
        {
            await _finlyticLogger.LogWarningAsync(SettingKeys.NewsChannel, "[NewsChannel] Article with ID {Id} not found for classification update.", id);
            return null;
        }

        article.Title = payload.Title;
        article.Author = payload.Author;
        article.Summary = payload.Summary;
        article.ContentRaw = payload.ContentRaw;
        article.Language = payload.Language;
        article.Status = "Completed";

        if (DateTime.TryParse(payload.PublishedAt, out var publishedDate))
        {
            article.PublishedAt = publishedDate.Kind == DateTimeKind.Unspecified
                ? DateTime.SpecifyKind(publishedDate, DateTimeKind.Utc)
                : publishedDate.ToUniversalTime();
        }

        if (DateTime.TryParse(payload.ScrapedAt, out var scrapedDate))
        {
            article.ScrapedAt = scrapedDate.ToUniversalTime();
        }

        await _context.MatchedAssets.Where(m => m.NewsArticleId == id).ExecuteDeleteAsync();

        article.MatchedAssets = new List<MatchedAssetEntity>();
        foreach (var asset in matchedAssets)
        {
            if (asset.Id == Guid.Empty)
            {
                asset.Id = Guid.NewGuid();
            }

            _context.MatchedAssets.Add(asset);
            article.MatchedAssets.Add(asset);
        }

        await _context.SaveChangesAsync();
        await _finlyticLogger.LogInfoAsync(SettingKeys.NewsChannel, "[Lifecycle] Article {Id} successfully classified and marked 'Completed'. Title: '{Title}'", article.Id, article.Title);

        return article;
    }

    /// <inheritdoc />
    public async Task<List<NewsArticleEntity>> GetArticlesByStatusAsync(string status)
    {
        return await _context.NewsArticles
            .Include(a => a.MatchedAssets)
            .Where(a => a.Status == status)
            .OrderByDescending(a => a.PublishedAt)
            .AsNoTracking()
            .ToListAsync();
    }

    /// <inheritdoc />
    public async Task<List<NewsArticleEntity>> GetFilteredNewsAsync(
        int limit,
        int offset,
        string? isin = null,
        DateTime? date = null,
        string? status = null,
        string? searchQuery = null)
    {
        var query = _context.NewsArticles
            .Include(a => a.MatchedAssets)
            .AsNoTracking()
            .AsQueryable();

        if (!string.IsNullOrWhiteSpace(isin))
        {
            var cleanIsin = isin.Trim();
            query = query.Where(a => a.MatchedAssets.Any(m => m.Isin == cleanIsin));
        }

        if (date.HasValue)
        {
            var startUtc = date.Value.Date.ToUniversalTime();
            var endUtc = startUtc.AddDays(1);
            query = query.Where(a => a.PublishedAt >= startUtc && a.PublishedAt < endUtc);
        }

        if (!string.IsNullOrWhiteSpace(status))
        {
            query = query.Where(a => a.Status == status);
        }

        if (!string.IsNullOrWhiteSpace(searchQuery))
        {
            var cleanSearch = searchQuery.Trim().ToLower();
            query = query.Where(a =>
                a.Title.ToLower().Contains(cleanSearch) ||
                a.Summary.ToLower().Contains(cleanSearch) ||
                a.MatchedAssets.Any(m => m.Name.ToLower().Contains(cleanSearch)));
        }

        return await query
            .OrderByDescending(a => a.PublishedAt)
            .Skip(offset)
            .Take(limit)
            .ToListAsync();
    }
}