using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using BotFramework.Attributes;
using BotFramework.Enums;
using Kruzya.TelegramBot.Core.Extensions;
using Kruzya.TelegramBot.RichSiteSummary.Data;
using Microsoft.EntityFrameworkCore;
using Telegram.Bot;
using Telegram.Bot.Types;
using Telegram.Bot.Types.Enums;
using Telegram.Bot.Types.ReplyMarkups;

namespace Kruzya.TelegramBot.RichSiteSummary.Handler
{
    public class FeedList : AbstractHandler
    {
        public FeedList(RichSiteSummaryContext dbContext) : base(dbContext)
        {
        }
        
        [ParametrizedCommand("rss_show")]
        public async Task ShowFeed(Feed feed) => await ShowFeed(feed, Chat, From);

        public async Task ShowFeed(Guid feedId, Chat chat, User from)
        {
            var feed = await _dbContext.FindAsync<Feed>(feedId);
            if (feed == null)
            {
                return;
            }

            await ShowFeed(feed, chat, from);
        }

        public async Task ShowFeed(Feed feed, Chat chat, User from, Message message = null)
        {
            var textBuilder = new StringBuilder();
            textBuilder.Append(feed.Representation(ParseMode.Html));
            textBuilder.Append("\n");
            textBuilder.Append($"<b>Posts at this moment</b>: {feed.Posts.Count}\n");
            textBuilder.Append($"<b>RSS feed</b>: <code>{feed.Url}</code>\n");
            textBuilder.Append($"<b>Home page</b>: <code>{feed.HomePage}</code>\n");
            textBuilder.Append($"<b>Last synchronization</b>: <code>{feed.UpdatedAt}</code>");

            var text = textBuilder.ToString();

            var buttons = new List<InlineKeyboardButton>();
            var callbackData = $"feed|{from.Id}|do|{feed.FeedId}";
            if (await _dbContext.Subscriptions.HasSubscription(chat, feed))
            {
                buttons.Add(new InlineKeyboardButton("Unsubscribe")
                {
                    CallbackData = callbackData,
                });
            }
            else
            {
                buttons.Add(new InlineKeyboardButton("Subscribe")
                {
                    CallbackData = callbackData,
                });
            }
            buttons.Add(new InlineKeyboardButton("Last 10 posts")
            {
                CallbackData = $"feed|{from.Id}|last|{feed.FeedId}",
            });

            var inlineButtons = new InlineKeyboardMarkup(buttons);
            if (message == null)
            {
                await Bot.SendTextMessageAsync(new ChatId(chat.Id), text, 0, ParseMode.Html, null, true, true, false, 0, replyMarkup: inlineButtons);
            }
            else
            {
                await Bot.EditMessageTextAsync(chat, message.MessageId, text, ParseMode.Html, null, true, replyMarkup: inlineButtons);
            }
        }
        
        [ParametrizedCommand("rss_list")]
        public async Task List() => await GenerateMenu();

        [ParametrizedCommand("rss_search")]
        public async Task Search(string query)
        {
            if (!(await GenerateMenu(query)))
            {
                await Bot.SendTextMessageAsync(Chat, $"No one feed match by search pattern (<code>{query}</code>).", 0, ParseMode.Html, null, true);
            }
        }

        [Command("rss_subscriptions")]
        public async Task Subscriptions()
        {
            if (!(await GenerateMenu(":sub")))
            {
                await Bot.SendTextMessageAsync(Chat,
                    "There are no one subscription. Add new with /feed_list or /feed_search.");
            }
        }

        #region Message generator
        
        protected async Task<bool> GenerateMenu() =>
            await GenerateMenu(string.Empty);

        protected async Task<bool> GenerateMenu(string query) =>
            await GenerateMenu(query, 0);

        protected async Task<bool> GenerateMenu(string query, UInt16 page, Message editableMessage = null)
        {
            var chat = editableMessage != null ? (editableMessage.Chat) : Chat;
            var elementsOnPage = 9;
            var startIndex = page * elementsOnPage;
            var dbQuery = _dbContext.Feeds.AsQueryable()
                .Where(f => !f.IsPrivate);

            if (!string.IsNullOrWhiteSpace(query))
            {
                var searchQuery = query.ToLower();
                if (query.EndsWith(":sub"))
                {
                    var chatList = await _dbContext.Subscriptions.AllSubscriptions(chat).Select(chat => chat.Feed.FeedId).ToArrayAsync();
                    dbQuery = dbQuery.Where(sub => chatList.Contains(sub.FeedId));

                    searchQuery = searchQuery.Remove(searchQuery.Length - 4, 4);
                }
                
                dbQuery = dbQuery.Where(feed => feed.Title.ToLower().Contains(searchQuery) || feed.Url.ToLower().Contains(searchQuery) || feed.HomePage.ToLower().Contains(searchQuery));
            }

            var totalCount = await dbQuery.CountAsync();
            if (totalCount == 0)
            {
                return false;
            }

            if (totalCount == 1)
            {
                await ShowFeed((await dbQuery.FirstOrDefaultAsync()), Chat, From);
                return true;
            }
            
            var result = await dbQuery.Take(elementsOnPage * (page + 1)).Skip(startIndex)
                .ToArrayAsync();
            
            var backButton = (page > 0);
            var nextButton = totalCount >= (startIndex + elementsOnPage);

            var buttons = new List<List<InlineKeyboardButton>>();
            List<InlineKeyboardButton> row;
            foreach (var feed in result)
            {
                row = new List<InlineKeyboardButton>();
                row.Add(new InlineKeyboardButton(feed.Title)
                {
                    CallbackData = $"feed|{From.Id}|show|{feed.FeedId.ToString()}",
                });

                buttons.Add(row);
            }
            
            if (backButton || nextButton)
            {
                row = new List<InlineKeyboardButton>();
                if (backButton)
                {
                    row.Add(new InlineKeyboardButton("⬅️")
                    {
                        CallbackData = $"feed|{From.Id}|page|{query}|{page - 1}",
                    });
                }
                
                row.Add(new InlineKeyboardButton($"{page + 1}/{(totalCount / elementsOnPage) + 1}")
                {
                    CallbackData = $"feed|{From.Id}|donothing",
                });

                if (nextButton)
                {
                    row.Add(new InlineKeyboardButton("➡️")
                    {
                        CallbackData = $"feed|{From.Id}|page|{query}|{page + 1}",
                    });
                }
                
                buttons.Add(row);
            }
            
            if (editableMessage == null)
            {
                await Bot.SendTextMessageAsync(Chat, "Select the feed for viewing details", 0, null,
                    null, true, true, false, 0, replyMarkup: new InlineKeyboardMarkup(buttons));
            }
            else
            {
                await Bot.EditMessageTextAsync(editableMessage.Chat, editableMessage.MessageId, "Select the feed for viewing details", null, null, false,
                    new InlineKeyboardMarkup(buttons));
            }

            return true;
        }
        
        #endregion

        #region Message handler

        [Update(UpdateFlag.CallbackQuery)]
        public async Task HandleAction()
        {
            if (!RawUpdate.CallbackQuery.Data.StartsWith("feed|"))
            {
                return;
            }

            var data = RawUpdate.CallbackQuery.Data.Split('|');
            var fromId = Int64.Parse(data[1]);
            if (fromId != From.Id)
            {
                await Bot.AnswerCallbackQueryAsync(RawUpdate.CallbackQuery.Id,
                    "You can't perform this action: command called by another user.", true);
                return;
            }

            // Check action.
            switch (data[2])
            {
                case "page":
                    await GenerateMenu(data[3], UInt16.Parse(data[4]), RawUpdate.CallbackQuery.Message);
                    break;
                
                case "show":
                    await ShowFeed(Guid.Parse(data[3]), RawUpdate.CallbackQuery.Message.Chat, RawUpdate.CallbackQuery.From);
                    break;
                
                case "do":
                    if (RawUpdate.CallbackQuery.From.Id != RawUpdate.CallbackQuery.Message.Chat.Id)
                    {
                        var userStatus = (await Bot.GetChatMemberAsync(RawUpdate.CallbackQuery.Message.Chat, RawUpdate.CallbackQuery.From.Id)).Status;
                        var allowedUserStatuses = new ChatMemberStatus[]
                            {ChatMemberStatus.Administrator, ChatMemberStatus.Creator};

                        if (!allowedUserStatuses.Contains(userStatus))
                        {
                            await Bot.AnswerCallbackQueryAsync(RawUpdate.CallbackQuery.Id,
                                "You can't perform this action: you don't have administrator permissions.", true);
                            return;
                        }
                    }

                    await ChangeFeedSubscription(Guid.Parse(data[3]), RawUpdate.CallbackQuery.Message.Chat, RawUpdate.CallbackQuery.From, RawUpdate.CallbackQuery.Message);
                    break;
                
                case "last":
                    var feed = await _dbContext.FindAsync<Feed>(Guid.Parse(data[3]));
                    var posts = feed.Posts.OrderByDescending(p => p.ReceivedAt).Take(10).ToList();
                    
                    var messageTextBuilder = new StringBuilder();
                    messageTextBuilder.Append($"Last 10 posts from {feed.Representation(ParseMode.Html)}\n");
                    messageTextBuilder.Append("\n");

                    var idx = 1;
                    foreach (var post in posts)
                    {
                        messageTextBuilder.Append($"{idx}. {post}\n");
                        idx++;
                    }

                    await Bot.SendTextMessageAsync(RawUpdate.CallbackQuery.Message.Chat, messageTextBuilder.ToString(),
                        0, ParseMode.Html, null, true);
                    break;
            }
            
            await Bot.AnswerCallbackQueryAsync(RawUpdate.CallbackQuery.Id);
        }

        protected async Task ChangeFeedSubscription(Guid feedId, Chat chat, User from, Message message)
        {
            var feed = await _dbContext.FindAsync<Feed>(feedId);
            if (feed == null)
            {
                return;
            }

            var subscriptionState = await _dbContext.Subscriptions.HasSubscription(chat, feed);
            if (subscriptionState)
            {
                var subId = await _dbContext.Subscriptions
                    .Where(subscriber => subscriber.Feed == feed && subscriber.SubscriberId == chat.Id)
                    .Select(subscriber => subscriber.SubscriptionId).FirstAsync();
                
                _dbContext.Remove(_dbContext.Find<Subscriber>(subId));
            }
            else
            {
                var subscription = _dbContext.Subscriptions.Create();
                subscription.Feed = feed;
                subscription.SubscriberId = chat.Id;
                
                _dbContext.Add(subscription);
            }

            await _dbContext.SaveChangesAsync();
            await ShowFeed(feed, chat, from, message);
        }
        
        #endregion
    }
}