using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using CodeHollow.FeedReader;
using Serilog;
using SharpRss.Models;

namespace SharpRss.Services
{
    /// <summary>
    /// Managing RSS feeds and groups.
    /// </summary>
    public class RssService : IDisposable
    {
        public RssService()
        {
            SetupTestGroupsAndFeedsAsync();
        }
        private readonly DatabaseService _dbService = new DatabaseService();

        public async Task<HashSet<object>> GetGroupsFeedsAsync()
        {
            HashSet<object> items = new HashSet<object>();
            items.UnionWith(await GetGroupsAsync());
            items.UnionWith(await GetUngroupedFeedsAsync());
            return items;
        }
        public async Task<bool> CreateGroupAsync(GroupModel group) => await _dbService.SetGroupAsync(group);
		public async Task<HashSet<GroupModel>> GetGroupsAsync() => await _dbService.GetGroupsAsync();
        
        //TODO: Need to rework this implementation!!!
        /*public async Task<bool> FetchFeeds(string[]? rssUrls, GroupModel? group = null)
        {
            bool result = false;
            if (rssUrls == null) return result;
            HashSet<Feed> fetchedFeeds = new HashSet<Feed>();
            foreach (var rssUrl in rssUrls)
            {
                fetchedFeeds.Add(await FetchFeed(rssUrl));
            }
            Feed fetched = await FetchFeed(rssUrl);
            
            if (fetched == null)
                return result;
			FeedModel feedModel = new FeedModel(rssUrl)
            {
                Title = fetched.Title,
                GroupId = group?.Id ?? string.Empty,
                FeedType = fetched.Type.ToString(),
                Description = fetched.Description,
                Language = fetched.Language,
                Copyright = fetched.Copyright,
                DateAdded = DateTimeOffset.Now,
                LastUpdated = DateTimeOffset.Now,
                ImageUrl = fetched.ImageUrl,
                OriginalDocument = fetched.OriginalDocument
            };
            FeedModel? dbFeed = await _dbService.SetFeedAsync(feedModel);
            result = dbFeed != null;
            if (dbFeed == null)
                return result;
            if (await AddFeedItems(fetched.Items, dbFeed) == 0)
                Log.Warning("No feed items added to feed: {FeedUrl}", dbFeed.Url);
			return result;
        }*/
        public async Task<HashSet<FeedModel>> GetFeedsAsync(string? groupId = null) => await _dbService.GetFeedsAsync(groupId);
        public async Task<HashSet<FeedModel>> GetUngroupedFeedsAsync() => await _dbService.GetFeedsAsync("");

        public async Task<HashSet<FeedItemModel>> GetFeedItemsAsync(string feedId, string? groupId = null) => await GetFeedItemsFromFeedsAsync(new[] { feedId }, groupId);
        public async Task<HashSet<FeedItemModel>> GetFeedItemsFromFeedsAsync(string[] feedIds, string? groupId = null)
        {
            var items =  await _dbService.GetFeedItemsAsync(feedIds);
            return items;
        }

        private async Task<int> AddFeedItems(IList<FeedItem> items, FeedModel feedModel)
		{
            int result = 0;
            if (!items.Any())
                return result;
            HashSet<FeedItemModel> itemModels = new HashSet<FeedItemModel>();
            foreach (FeedItem item in items)
            {
                itemModels.Add(new FeedItemModel()
                {
                    Id = item.Id,
                    FeedId = feedModel.Id,
                    Title = item.Title,
                    Description = item.Description,
                    Link = item.Link,
                    LastUpdated = DateTimeOffset.Now,
                    PublishingDate = item.PublishingDate != null ? new DateTimeOffset((DateTime)item.PublishingDate) : null,
                    Author = item.Author,
                    Categories = item.Categories.ToArray(),
                    Content = item.Content
                });
            }
            result = await _dbService.SetFeedItemsAsync(itemModels);
			return result;
		}
		private async Task<Feed> FetchFeed(string url)
        {
            Log.Verbose("Fetching feed: {FeedUrl}", url);
            var urls = await FeedReader.ParseFeedUrlsAsStringAsync(url);
            string feedUrl = url;
            if (urls.Any())
                feedUrl = urls.First();
            return await FeedReader.ReadAsync(feedUrl);
        }
        private async void SetupTestGroupsAndFeedsAsync()
        {
            //TODO: Make multiple adding of feed to a transaction, now throws an exception.
            /*var groupRes = await CreateGroupAsync(new GroupModel() { Name = "Test" });
            groupRes = await CreateGroupAsync(new GroupModel() { Name = "News" });
            groupRes = await CreateGroupAsync(new GroupModel() { Name = "Tech" });
            groupRes = await CreateGroupAsync(new GroupModel() { Name = "Science" });*/
            /*Log.Verbose("Fetching feeds...");
            var groups = await GetGroupsAsync();
            GroupModel testGroup = groups.Single(x => x.Name == "Test");
            try
            {
                var res = await AddFeed("http://fedoramagazine.org/feed/", testGroup);
                res = await AddFeed("https://www.nasa.gov/rss/dyn/breaking_news.rss", testGroup);
                res = await AddFeed("https://journals.plos.org/plosone/feed/atom", testGroup);
                res = await AddFeed("https://itsfoss.com/feed", testGroup);
                res = await AddFeed("https://advisories.ncsc.nl/rss/advisories", testGroup);
            }
            catch (Exception e)
            {
                Log.Error(e, "Error fetching feeds!");
                throw;
            }*/
        }

		public void Dispose()
		{
			_dbService.Dispose();
		}
	}
}