module Telegram
  module Bot
    class Api
      ENDPOINTS = %w(
        getUpdates setWebhook getMe sendMessage forwardMessage sendPhoto
        sendAudio sendDocument sendSticker sendVideo sendVoice sendLocation
        sendVenue sendContact sendChatAction getUserProfilePhotos getFile
        kickChatMember unbanChatMember answerCallbackQuery editMessageText
        editMessageCaption editMessageReplyMarkup answerInlineQuery
      ).freeze
      REPLY_MARKUP_TYPES = [
        Telegram::Bot::Types::ReplyKeyboardMarkup,
        Telegram::Bot::Types::ReplyKeyboardHide,
        Telegram::Bot::Types::ForceReply,
        Telegram::Bot::Types::InlineKeyboardMarkup
      ].freeze
      INLINE_QUERY_RESULT_TYPES = [
        Telegram::Bot::Types::InlineQueryResultArticle,
        Telegram::Bot::Types::InlineQueryResultPhoto,
        Telegram::Bot::Types::InlineQueryResultGif,
        Telegram::Bot::Types::InlineQueryResultMpeg4Gif,
        Telegram::Bot::Types::InlineQueryResultVideo,
        Telegram::Bot::Types::InlineQueryResultAudio,
        Telegram::Bot::Types::InlineQueryResultVoice,
        Telegram::Bot::Types::InlineQueryResultDocument,
        Telegram::Bot::Types::InlineQueryResultLocation,
        Telegram::Bot::Types::InlineQueryResultVenue,
        Telegram::Bot::Types::InlineQueryResultContact,
        Telegram::Bot::Types::InlineQueryResultCachedPhoto,
        Telegram::Bot::Types::InlineQueryResultCachedGif,
        Telegram::Bot::Types::InlineQueryResultCachedMpeg4Gif,
        Telegram::Bot::Types::InlineQueryResultCachedSticker,
        Telegram::Bot::Types::InlineQueryResultCachedDocument,
        Telegram::Bot::Types::InlineQueryResultCachedVideo,
        Telegram::Bot::Types::InlineQueryResultCachedVoice,
        Telegram::Bot::Types::InlineQueryResultCachedAudio
      ].freeze

      attr_reader :token

      def initialize(token)
        @token = token
      end

      def method_missing(method_name, *args, &block)
        endpoint = method_name.to_s
        endpoint = camelize(endpoint) if endpoint.include?('_')

        ENDPOINTS.include?(endpoint) ? call(endpoint, *args) : super
      end

      def respond_to_missing?(*args)
        method_name = args[0].to_s
        method_name = camelize(method_name) if method_name.include?('_')

        ENDPOINTS.include?(method_name) || super
      end

      def call(endpoint, raw_params = {})
        params = build_params(raw_params)
        response = conn.post("/bot#{token}/#{endpoint}", params)
        if response.status == 200
          JSON.parse(response.body)
        else
          raise Exceptions::ResponseError.new(response),
                'Telegram API has returned the error.'
        end
      end

      private

      def build_params(h)
        h.each_with_object({}) do |(key, value), params|
          params[key] = sanitize_value(value)
        end
      end

      def sanitize_value(value)
        jsonify_inline_query_results(jsonify_reply_markup(value))
      end

      def jsonify_reply_markup(value)
        return value unless REPLY_MARKUP_TYPES.include?(value.class)
        value.to_h.to_json
      end

      def jsonify_inline_query_results(value)
        return value unless value.is_a?(Array) && value.all? { |i| INLINE_QUERY_RESULT_TYPES.include?(i.class) }
        value.map { |i| i.to_h.select { |_, v| v } }.to_json
      end

      def camelize(method_name)
        words = method_name.split('_')
        words.drop(1).map(&:capitalize!)
        words.join
      end

      def conn
        @conn ||= Faraday.new(url: 'https://api.telegram.org') do |faraday|
          faraday.request :multipart
          faraday.request :url_encoded
          faraday.adapter Telegram::Bot.configuration.adapter
        end
      end
    end
  end
end