@applicvision/js-toolbox/src/parse-args.js

A collection of tools for modern JavaScript development

const optionRegex = /^--(?<option>[a-zA-Z-]+)(?:=(?<value>.+))?$/
const shortOptionRegex = /^-(?<option>[a-zA-Z])(?<value>.+)?/

class ArgumentParser {

	#availableOptions = {}
	#disableHelp = false
	#helpText = ''

	options = {}
	args = []

	constructor(args = typeof process !== 'undefined' ? process.argv.slice(2) : []) {
		this.argsArray = args
	}

	/**
	 * @param {string} name
	 * @param {{short?: string|false, args?: number, description?: string}=} options
	 */
	option(name, { short = name.replace('--', '')[0], args = 1, description } = {}) {
		const option = {
			name: name.replace('--', ''),
			shortName: short && short.replace('-', ''),
			args,
			description
		}
		this.#availableOptions[option.name] = option
		return this
	}

	/**
	 * @param {string} name
	 * @param {{short?: string|false, description?: string}=} options
	 */
	flag(name, { short, description } = {}) {
		return this.option(name, { short, args: 0, description })
	}

	help(textOrFalse) {
		if (textOrFalse === false) {
			this.#disableHelp = true
		} else {
			this.#helpText = textOrFalse
		}
		return this
	}

	get #helpTextToShow() {
		return `${this.#helpText}\n\nOptions:\n${optionsToString(this.#availableOptions)}`
	}

	#addOption(target, { name }, value) {
		if (!value) throw new Error(`option '${name}' requires a value`)
		if (target[name]) {
			target[name] = [].concat(target[name], value)
		} else {
			target[name] = value
		}
	}

	parse({ convertCasing = true } = {}) {

		const options = {}
		const args = []

		// Make a copy since we will modify it
		const argsToParse = this.argsArray.slice(0)

		for (let argToCheck = argsToParse.shift(); argToCheck; argToCheck = argsToParse.shift()) {
			// Double dash escapes option parsing, and consumes the rest as arguments
			if (argToCheck == '--') {
				args.push(...argsToParse.splice(0, argsToParse.length))
				break
			}
			const optionMatch = argToCheck.match(optionRegex)
			const shortOptionMatch = argToCheck.match(shortOptionRegex)

			if (optionMatch) {
				const { groups } = optionMatch

				if (groups.option == 'help' && !this.#disableHelp) return {
					args: [],
					options: {},
					help: this.#helpTextToShow
				}

				const option = this.#availableOptions[groups.option]
				if (!option) {
					throw new Error(`Error Unknown option '${groups.option}'\n\nAvailable options:\n${optionsToString(this.#availableOptions)}`)
				}
				if (option.args == 0) {
					options[option.name] = true
				} else {
					this.#addOption(options, option, groups.value ?? argsToParse.shift())
				}
			} else if (shortOptionMatch) {
				const { groups } = shortOptionMatch

				if (groups.option === 'h' && !this.#disableHelp) return {
					args: [],
					options: {},
					help: this.#helpTextToShow
				}

				const option = Object.values(this.#availableOptions).find(
					({ shortName }) => shortName == groups.option
				)
				if (!option) {
					throw new Error(`Error: Unknown switch '${groups.option}'\n\nAvailable options:\n${optionsToString(this.#availableOptions)}`)
				}
				if (option.args == 0) {
					options[option.name] = true
					if (groups.value) {
						argsToParse.unshift(`-${groups.value}`) // Put back without first character
					}
				} else {
					this.#addOption(options, option, groups.value ?? argsToParse.shift())
				}
			} else {
				args.push(argToCheck)
			}
		}

		return {
			options: convertCasing ? convertToCamelCase(options) : options,
			args
		}
	}
}


function optionsToString(options, omitHelp = false) {
	const optionsToShow = Object.values(options).concat(omitHelp ? [] : {
		name: 'help', shortName: 'h', description: 'Show this message and exit.'
	})
	const textsWithoutDescription = optionsToShow.map(option =>
		`  ${option.shortName ? `-${option.shortName}, ` : ''}--${option.name}`
	)
	const maxLength = Math.max(...(textsWithoutDescription.map(text => text.length)))

	return textsWithoutDescription.map(
		(text, index) => `${text.padEnd(maxLength + 5)}${optionsToShow[index].description}`
	).join('\n')
}

function convertToCamelCase(options) {
	return Object.fromEntries(Object.entries(options).map(
		([key, value]) => [
			key.replace(/-[a-z]/, match => match.at(1).toUpperCase()),
			value
		])
	)
}

export function parseArguments(options) {
	return new ArgumentParser(options)
}