const Discord = require('discord.js');
const client = new Discord.Client();

client.on('message', interpretMessage);

secretToken = "Nice try Kyle";
client.login(secretToken).catch(console.log);

function interpretMessage(receivedMessage)
{
    try
    {
        content = receivedMessage.content;
        if (receivedMessage.author != client.user && content.includes("@"))
        {
            console.log(`Interpreting message "${content}"`);
            potentialPings = content.match(/@[^@#:]*(?=\s+|$)/g);
            console.log(potentialPings);
            guildMembers = receivedMessage.guild.members.array();
            originalMentionedUsers = receivedMessage.mentions;

            usersToMention = [];
            messageToPost = "";
            for (let ping of potentialPings)
            {
                for (let member of guildMembers)
                {
                    regexPattern = getRegExpFromNickname(member.displayName)

                    if(regexPattern)
                    {
                        pingWithoutAtSymbol = ping.substring(1)
                        execResults = regexPattern.exec(pingWithoutAtSymbol)
                        if(execResults && execResults[0] == pingWithoutAtSymbol && !(member.user in originalMentionedUsers) && !(member in usersToMention))
                        {
                            usersToMention.push(member);
                        }
                    }
                }
            }

            messageToPost = usersToMention.join(" ");
            console.log(`Posting "${messageToPost}"`);
            if(messageToPost)
            {
                receivedMessage.channel.send(messageToPost);
            }
            else
            {
                console.log("Empty message");
            }
        }
    }
    catch(e)
    {
        console.log(e);
    }
}
    // //Returns a RegExp object of nickname if it can be represented as a regex, otherwise, returns null.
function getRegExpFromNickname(nickname)
{
    //Found on stackoverflow. Apparently javascript doesn't have a .count() method.
    slashesCount = (nickname.match(/\//g) || []).length;
    if (nickname[0] == "/" && slashesCount >= 2) //We can't just check the front and back of the name, because there might be flags included
    {
        lastSlashIndex = nickname.lastIndexOf("/");

        regexString = nickname.substring(1, lastSlashIndex);

        flags = "";
        if (lastSlashIndex != nickname.length - 1)
        {
            flags = nickname.substring(lastSlashIndex + 1);
        }

        regexPattern = null;
        try
        {
            regexPattern = new RegExp(regexString, flags); //Attempts to build a regex. If it succeeds, the name must be a regex.
            return regexPattern;
        }
        catch (e)
        {
            return null;
        }
    }

    return null;
}