import {regExpEscape} from './regexp.js';

/**
 * Created a RegExp that matches an existing empty template parameter with the
 * given name.
 */
const existingEmptyParameterRegExp = paramName =>
	new RegExp(`^( *\\| *${regExpEscape(paramName)}( *)=) *$`, 'm');

/**
 * Sets the value of an existing empty parameter.
 * @param {string} pageContent
 * @param {string} paramName
 * @param {string} value
 * @returns {string | null}
 */
export function setEmptyParameter (pageContent, paramName, value) {
	const regexp = existingEmptyParameterRegExp(paramName)
	if (pageContent.match(regexp)) {
		return pageContent.replace(regexp, `$1$2${value}`);
	}
	return null;
}

/**
 * Creates a RegExp that matches an existing template parameter with the given
 * name.
 */
const existingParameterRegExp = paramName =>
	new RegExp(`^( *)\\|( *)${regExpEscape(paramName)}( *)=( *).*$`, 'm');

/**
 * Inserts a new parameter before or after an existing parameter.
 * @param {string} pageContent
 * @param {string} existingParamName
 * @param {'before' | 'after'} location
 * @param {string} newParamName
 * @param {string} value
 * @returns {string | null}
 */
export function addParameterBesideExistingParameter (pageContent, newParamName, value, location, existingParamName) {
	let regexp = existingParameterRegExp(existingParamName);
	if (pageContent.match(regexp)) {
		let newParameterPattern = `$1|$2${newParamName}$3=$4${value}`;
		return pageContent.replace(
			regexp,
			location === 'before' ? `${newParameterPattern}\n$&` : `$&\n${newParameterPattern}`
		);
	}
	return null;
}