export class ArgParser {
	/**
	 * Create a unix-like argument parser to extract flags from the argument list. Can also create help messages.
	 * @param opts - {examples: string[], arguments: {key: string, alias: string, type: string, optional: boolean, desc: string}[], desc: string}
	 */
	constructor(opts) {
		this.examples = opts.examples ?? [];
		this.arguments = opts.args ?? [];
		this.description = opts.desc;
	}

	/**
	 * Parse the list for arguments & create a dictionary.
	 * @param args {any[]} - Array of arguments
	 * @returns Dictionary of matched flags + unmatched args under 'extra'
	 */
	parse(args) {
		const req = this.arguments.filter(a => !a.optional);
		const queue = [...args];
		const parsed = {};
		for(let i = 0; i < queue.length; i++) {
			if(queue[i][0] != '-') continue;
			let value = null, parse = queue[i].slice(queue[i][1] == '-' ? 2 : 1);
			if(parse.indexOf('=')) {
				const split = parse.split('=');
				parse = split[0];
				value = split[1];
			}
			let arg = this.arguments.find(a => a.key == parse) ?? this.arguments.find(a => a.alias == parse);
			if(!arg) continue;
			if(!value) value = arg.type && arg.type != 'bool' ? queue.splice(i + 1, 1)[0] : true;
			parsed[arg.key] = value;
			queue.splice(i, 1);
		}
		req.forEach((a, i) => parsed[a.key] = queue[i]);
		queue.splice(0, req.length);
		if(queue.length) parsed.extra = queue;
		return parsed;
	}

	/**
	 * Create a help message of the expected paramters & usage.
	 * @param msg {String} - Optional message to display with help
	 */
	help(msg) {
		let message = '\n\n';
		message += msg ? msg : this.description;
		if(this.examples.length) message += '\n\nUsage:\t' + this.examples.join('\n\t');
		const required = this.arguments.filter(a => !a.optional);
		if(required.length) message += '\n\n\t' + required.map(a => {
			const padding = 3 - ~~(a.key.length / 8);
			return `${a.key}${Array(padding).fill('\t').join('')} ${a.desc}`;
		}).join('\n\t');
		const optional = this.arguments.filter(a => a.optional);
		if(optional.length) message += '\n\nOptions:\n\t' + optional.map(a => {
			const flgs = `${a.alias ? `-${a.alias} ` : ''}--${a.key}${a.type && a.type != 'bool' ? `=${a.type}` : ''}`;
			const padding = 3 - ~~(flgs.length / 8);
			return `${flgs}${Array(padding).fill('\t').join('')} ${a.desc}`;
		}).join('\n\t');
		return `${message}\n\n`;
	}
}