import { escapeTable, unescapeTable } from "./table"

/**
 * escape string to HTML special entities
 * @param str string
 * @returns 
 */
export function escape(str: string) {
	const buffer: Array<string> = []
	let prev = 0
	for (let i = 0; i < str.length; ++i) {
		const cc = str.charCodeAt(i)
		const name = escapeTable[cc]
		if (name) {
			buffer.push(str.substring(prev, i))
			buffer.push(`&${name};`)
			prev = i + 1
		}
	}
	buffer.push(str.substring(prev))
	return buffer.join('')
}

/**
 * unescape HTML special entities to normal string
 * @param str string
 * @returns 
 */
export function unescape(str: string) {
	return str.replace(/&((\w+)|(#\d+));/g, (match, name) => {
		const code = (name[0] == '#') ? parseInt(name.substr(1)) : unescapeTable[name]
		if (!code || isNaN(code)) return match
		return String.fromCharCode(code)
	})
}

export default { escape, unescape }