import Event from "../core/event";
import Command from "../core/command";
import $ from "../core/lib";
import {Message, Permissions, Collection} from "discord.js";
import {Config, Storage} from "../core/structures";
import {loadCommands} from "../core/command";

// It's a rather hacky solution, but since there's no top-level await, I just have to make the loading conditional.
let commands: Collection<string, Command>|null = null;

export default new Event({
	async on(message: Message)
	{
		// Load commands if it hasn't already done so. Luckily, it's called once at most.
		if(!commands)
			commands = await loadCommands();
		
		// Message Setup //
		if(message.author.bot)
			return;
		
		const prefix = Storage.getGuild(message.guild?.id || "N/A").prefix || Config.prefix;
		
		if(!message.content.startsWith(prefix))
			return;
		
		const [header, ...args] = message.content.substring(prefix.length).split(/ +/);
		
		if(!commands.has(header))
			return;
		if(message.channel.type === "text" && !message.channel.permissionsFor(message.client.user || "")?.has(Permissions.FLAGS.SEND_MESSAGES))
		{
			let status;
			
			if(message.member?.hasPermission(Permissions.FLAGS.ADMINISTRATOR))
				status = "Because you're a server admin, you have the ability to change that channel's permissions to match if that's what you intended.";
			else
				status = "Try using a different channel or contacting a server admin to change permissions of that channel if you think something's wrong.";
			
			return message.author.send(`I don't have permission to send messages in ${message.channel.toString()}. ${status}`);
		}
		
		$.log(`${message.author.username}#${message.author.discriminator} executed the command "${header}" with arguments "${args}".`);
		
		// Subcommand Recursion //
		let command = commands.get(header);
		if(!command) return $.warn(`Command "${header}" was called but for some reason it's still undefined!`);
		const params: any[] = [];
		let isEndpoint = false;
		
		for(let param of args)
		{
			if(command.endpoint)
			{
				if(command.subcommands || command.user || command.number || command.any)
					$.warn(`An endpoint cannot have subcommands! Check ${prefix}${header} again.`);
				isEndpoint = true;
				break;
			}
			
			const type = command.resolve(param);
			command = command.get(param);
			
			if(type === Command.TYPES.USER)
			{
				const id = param.match(/\d+/g)![0];
				try {params.push(await message.client.users.fetch(id))}
				catch(error) {return message.channel.send(`No user found by the ID \`${id}\`!`)}
			}
			else if(type === Command.TYPES.NUMBER)
				params.push(Number(param));
			else if(type !== Command.TYPES.SUBCOMMAND)
				params.push(param);
		}
		
		if(isEndpoint)
			return message.channel.send("Too many arguments!");
		
		// Execute with dynamic library attached. //
		// The purpose of using $.bind($) is to clone the function so as to not modify the original $.
		// The cloned function doesn't copy the properties, so Object.assign() is used.
		// Object.assign() modifies the first element and returns that, the second element applies its properties and the third element applies its own overriding the second one.
		command.execute(Object.assign($.bind($), {
			args: params,
			author: message.author,
			channel: message.channel,
			client: message.client,
			guild: message.guild,
			member: message.member,
			message: message
		}, $));
	}
});