import discord, {
  MessageReaction, PartialMessageReaction,
  User, PartialUser,
} from 'discord.js';
import {HydratedDocument} from 'mongoose';

import {logger} from '../logger';
import {config} from '../config';
import {Guild, guildModel} from '../models/Guild';
import {GiveawayMsg, giveawayMsgModel} from '../models/GiveawayMsg';

function isMessageReaction(reaction: MessageReaction | PartialMessageReaction): reaction is MessageReaction{
  return reaction.partial === false;
}

function isUser(user: User | PartialUser): user is User{
  return user.partial === false;
}

export async function handleGiveaway(
  reaction: MessageReaction | PartialMessageReaction, 
  user: User | PartialUser
): Promise<void>{
  try{
    // fetch data
    if(config.clientId === user.id) return;
    if(reaction.partial){
      reaction = await reaction.fetch();
      logger.debug('reaction in handleRole has fetched');
    }
    if(user.partial){
      user = await user.fetch();
      logger.debug('user in handleRole has fetched');
    }
    if(!isMessageReaction(reaction))
      throw Error('type mismatch: reaction.partial');
    if(!isUser(user))
      throw Error('type mismatch: user.partial');
    if(!reaction.emoji)
      throw Error('reaction.emoji not exist');
    if(reaction.emoji.toString() !== config.giveaway.emoji) return;
    let dbGiveawayMsg: HydratedDocument<GiveawayMsg> | null = 
      await giveawayMsgModel.findOne(
        {messageId: reaction.message.id}
      );
    if(!dbGiveawayMsg) return;
    if(dbGiveawayMsg.userIds.includes(user.id)){
      logger.info(`${user} has already in giveaway userIds`);
      return;
    }
    const dbGuild: HydratedDocument<Guild> | null = 
      await guildModel.findById(dbGiveawayMsg.guild._id);
    if(!dbGuild) 
      throw Error('dbGuild not exist');
    const guild: discord.Guild = await reaction.client.guilds.resolve(dbGuild.id);
    if(!guild) 
      throw Error('guild not exist');

    // record
    dbGiveawayMsg = await giveawayMsgModel.findOneAndUpdate(
      {messageId: dbGiveawayMsg.messageId}, 
      {$push: {userIds: user.id}}, {new: true}
    );
    if(!dbGiveawayMsg) 
      throw Error('dbGiveawayMsg not exist');

    // notify
    logger.log(`${user} has been reacted to giveaway, id: ${dbGiveawayMsg.messageId}.`);
    if(!dbGuild.giveawayLogChannelId){
      const author: discord.User | null = 
        await reaction.client.users.fetch(dbGiveawayMsg.authorId);
      if(!author)
        throw Error(`author ${author} not exist`);
      await author.send({content: `user ${user} has reacted to giveaway, id: ${dbGiveawayMsg.messageId}`});
    }else{
      const logChannel: discord.Channel | null = 
        await guild.channels.resolve(dbGuild.giveawayLogChannelId);
      if(!logChannel || !logChannel.isTextBased()) 
        throw Error('logChannel not exist or logChannel isn\'t text based');
      await logChannel.send({content: `user ${user} has reacted to giveaway, id: ${dbGiveawayMsg.messageId}`});
    }
  }catch(err: unknown){
    let message;
    if(err instanceof Error) message = err.message;
    else message = String(message);
    logger.error(`While executing "handleGiveaway", ${message}`);
  }
}