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

client.on('message', (receivedMessage) => {
    if (receivedMessage.author == client.user) { // Prevent bot from responding to its own messages
        return
    }

    if (receivedMessage.content.startsWith("!")) {
        processCommand(receivedMessage)
    }
})

function processCommand(receivedMessage) {
    let fullCommand = receivedMessage.content.substr(1) // Remove the leading exclamation mark
    let splitCommand = fullCommand.split(" ") // Split the message up in to pieces for each space
    let primaryCommand = splitCommand[0] // The first word directly after the exclamation is the command
    let arguments = splitCommand.slice(1) // All other words are arguments/parameters/options for the command

    console.log("Command received: " + primaryCommand)
    console.log("Arguments: " + arguments) // There may not be any arguments

    if (primaryCommand == "help") {
        helpCommand(arguments, receivedMessage)
    } else if (primaryCommand == "multiply") {
        multiplyCommand(arguments, receivedMessage)
    } else {
        receivedMessage.channel.send("I don't understand the command. Try `!help` or `!multiply`")
    }
}

function helpCommand(arguments, receivedMessage) {
    if (arguments.length > 0) {
        receivedMessage.channel.send("It looks like you might need help with " + arguments)
    } else {
        receivedMessage.channel.send("I'm not sure what you need help with. Try `!help [topic]`")
    }
}

function multiplyCommand(arguments, receivedMessage) {
    if (arguments.length < 2) {
        receivedMessage.channel.send("Not enough values to multiply. Try `!multiply 2 4 10` or `!multiply 5.2 7`")
        return
    }
    let product = 1
    arguments.forEach((value) => {
        product = product * parseFloat(value)
    })
    receivedMessage.channel.send("The product of " + arguments + " multiplied together is: " + product.toString())
}

client.login("token")