using BotPages.Core;
using BotPages.Core.Abstractions;
using BotPages.Core.Context;
using BotPages.Core.Logging;
using BotPages.Core.Messaging;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Telegram.Bot;
using Telegram.Bot.Types;
using Telegram.Bot.Types.Enums;
using Telegram.Bot.Types.ReplyMarkups;

namespace BotPages.Telegram;


/// <summary>
/// Адаптер для Telegram на базе Telegram.Bot.
/// Реализует отправку текста, кнопок, файлов, альбомов и прогресса.
/// </summary>
public sealed class TelegramAdapter : IMessengerAdapterSetup
{
    internal static readonly string AdapterType = typeof(TelegramAdapter).FullName;

    private readonly ILogger _logger;
    private TelegramBotClient? _client;
    private string _token;
    private readonly TelegramOptions _options;
    private static Capabilities _capabilities = new()
    {
        SupportsInlineButtons = true,
        SupportsReplyButtons = true,
        SupportsAlbums = true,
        SupportsFormattingMarkdown = true,
        SupportsFormattingHtml = true,
        MaxMessageLength = 4096,
    };

    /// <summary>Создать адаптер Telegram.</summary>
    public TelegramAdapter(ILogger logger, string token, TelegramOptions? options = null)
    {
        _logger = logger;
        _token = token;
        _options = options ?? new TelegramOptions();
    }

    /// <summary>
    ///Идентификатор мессенджера / адаптера
    /// </summary>
    public string MessengerType { get; set; } = "Telegram: " + Guid.NewGuid().ToString();

    /// <summary>
    /// Доступные возможности адаптера.
    /// </summary>
    public Capabilities Capabilities => _capabilities;

    /// <summary>
    /// Запустить polling для приема обновлений от Telegram.
    /// </summary>
    public async Task StartAdapterAsync(Func<UpdateContext, Task> onUpdate, List<BotPages.Core.Routing.Command> commands, CancellationToken ct)
    {
        _client = new TelegramBotClient(_token);

        _client.StartReceiving(
            updateHandler: async (_, update, ct2) =>
            {
                var mapped = TelegramUpdateMapper.Map(MessengerType, update, _client);
                if (mapped is not null)
                    await onUpdate(mapped);
                if (update.CallbackQuery is not null)
                {
                    await _.AnswerCallbackQuery(update.CallbackQuery.Id);
                }
            },

            errorHandler: async (_, ex, ct2) =>
            {
                _logger.Log(LogLevel.Warn, $"{MessengerType} error.", ex);
                await Task.CompletedTask;
            },

            cancellationToken: ct
        );


        await _client.SetMyCommands(commands.Where(t => t.Publish).Select(t => new BotCommand(t.Name, t.Description ?? t.Name.TrimStart('/'))), cancellationToken: ct);

        var me = await _client.GetMe();
        _logger.Log(LogLevel.Info, $"{MessengerType} started: @{me.Username}");

        return;
    }

    /// <summary>
    /// Универсальный внутренний метод отправки — определяет, нужно ли отправлять текст или файл по параметрам.
    /// Возвращает id сообщения (или null).
    /// </summary>
    public async Task<string?> SendAsync(SendRequest req, CancellationToken ct)
    {
        if (_client is null)
        {
            _logger.Log(LogLevel.Critical, $"{MessengerType} client is not initialized.");
            return null;
        }

        // Определите параметры адаптера (TelegramOptions) из папки или используйте параметры адаптера по умолчанию.
        TelegramOptions telegramOptions = _options;
        if (req.AdapterOptions is AdapterOptionsBag bag && bag.TryGet(AdapterType, out TelegramOptions? opt) && opt is not null)
        {
            telegramOptions = opt;
        }
        var disableNotification = !telegramOptions.NotifyOnSend;

        // Build markup
        var inlineMarkup = BuildInlineMarkup(req.Inline);
        ReplyMarkup? markup = BuildReplyMarkup(req.Reply);

        // Файлы: сейчас поддерживается один файл через SendRequest.File.
        // При необходимости для нескольких файлов следует использовать альбомы (CreateAlbumBuilder)
        if (req.File is not null)
        {
            if (inlineMarkup is not null) markup = inlineMarkup;

            var sent = await SendFileAsync(req.File, req.ChatId, markup, disableNotification, req.Caption, req.CaptionFormat, ct);
            return sent?.MessageId.ToString();
        }

        // Текст
        if (!string.IsNullOrWhiteSpace(req.Text))
        {
            return await SendTextAsync(req, inlineMarkup, markup, disableNotification, ct);
        }

        return null;
    }

    // --- Helpers ---

    private InlineKeyboardMarkup? BuildInlineMarkup(IEnumerable<IEnumerable<InlineButton>>? inline)
    {
        if (inline is null || !inline.Any()) return null;
        return new InlineKeyboardMarkup(
            inline.Select(row => row.Select(b => new InlineKeyboardButton(b.Label, b.Value)).ToArray()).ToArray()
        );
    }

    private ReplyMarkup? BuildReplyMarkup(IEnumerable<IEnumerable<ReplyButton>>? reply)
    {
        if (reply is null) return null;

        if (reply.Any())
        {
            return new ReplyKeyboardMarkup(reply.Select(row => row.Select(b => new KeyboardButton(b.Label)).ToArray()).ToArray())
            {
                ResizeKeyboard = true
            };
        }
        else
        {
            return new ReplyKeyboardRemove();
        }
    }

    private static ParseMode GetParseMode(MessageFormat? format)
    {
        return format switch
        {
            MessageFormat.Html => ParseMode.Html,
            MessageFormat.Markdown => ParseMode.MarkdownV2,
            _ => ParseMode.None,
        };
    }

    private async Task<InputFile> CreateInputFileAsync(FileDescriptor file, CancellationToken ct)
    {
        Stream? stream = null;
        if (file.GetStreamAsync is not null)
        {
            stream = await file.GetStreamAsync(ct);
            if (stream is not null) stream.Position = 0;
        }

        if (stream is not null && stream != Stream.Null)
        {
            return new InputFileStream(stream, file.Name);
        }
        else if (file.Id.StartsWith("http://") || file.Id.StartsWith("https://"))
        {
            return new InputFileUrl(file.Id);
        }
        else
        {
            return new InputFileId(file.Id);
        }
    }

    private async Task<Message?> SendFileAsync(FileDescriptor file, string chatId, ReplyMarkup? markup, bool disableNotification, string? caption, MessageFormat? captionFormat, CancellationToken ct)
    {
        var inputFile = await CreateInputFileAsync(file, ct);
        var parseMode = GetParseMode(captionFormat);

        return file.Kind switch
        {
            FileKind.Photo => await _client.SendPhoto(long.Parse(chatId), inputFile, caption ?? "", parseMode, replyMarkup: markup, disableNotification: disableNotification, cancellationToken: ct),
            FileKind.Video => await _client.SendVideo(long.Parse(chatId), inputFile, caption: caption ?? "", parseMode, replyMarkup: markup, disableNotification: disableNotification, cancellationToken: ct),
            FileKind.Audio => await _client.SendAudio(long.Parse(chatId), inputFile, caption ?? "", parseMode, replyMarkup: markup, disableNotification: disableNotification, cancellationToken: ct),
            _ => await _client.SendDocument(long.Parse(chatId), inputFile, caption ?? "", parseMode, replyMarkup: markup, disableNotification: disableNotification, cancellationToken: ct),
        };
    }

    private async Task<string?> SendTextAsync(SendRequest req, InlineKeyboardMarkup? inlineMarkup, ReplyMarkup? markup, bool disableNotification, CancellationToken ct)
    {
        var format = req.TextFormat ?? MessageFormat.Plain;
        var parseMode = GetParseMode(format);

        var text = req.Text!;
        if (text.Length > Capabilities.MaxMessageLength)
        {
            _logger.Log(LogLevel.Warn, $"Message too long ({text.Length}). Truncated to {Capabilities.MaxMessageLength}.");
            text = text.Substring(0, Capabilities.MaxMessageLength);
        }

        if (!string.IsNullOrWhiteSpace(req.MessageId))
        {
            await _client.EditMessageText(
                messageId: int.Parse(req.MessageId),
                chatId: long.Parse(req.ChatId),
                text: text,
                parseMode: parseMode,
                replyMarkup: inlineMarkup,
                cancellationToken: ct
            );

            return req.MessageId;
        }
        else
        {
            if (inlineMarkup is not null) markup = inlineMarkup;

            var message = await _client.SendMessage(
                chatId: long.Parse(req.ChatId),
                text: text,
                parseMode: parseMode,
                replyMarkup: markup,
                disableNotification: disableNotification,
                cancellationToken: ct
            );

            return message.MessageId.ToString();
        }
    }

    /// <inheritdoc />
    public IAlbumBuilder CreateAlbumBuilder(PageContext ctx) => new TelegramAlbumBuilder(this, ctx, _logger, _client);

    /// <inheritdoc />
    public Task OnLeaveAsync(PageContext ctx, CancellationToken ct) => Task.CompletedTask;
}