/**
 * Data URI parser.
 *
 * Based on:
 * https://github.com/TooTallNate/node-data-uri-to-buffer/blob/main/src/index.ts (MIT)
 */
export default class DataURIParser {
	/**
	 * Returns a Buffer instance from the given data URI `uri`.
	 *
	 * @param uri Data URI.
	 * @returns Buffer.
	 */
	public static parse(uri: string): {
		type: string;
		charset: string;
		buffer: Buffer;
	} {
		if (!/^data:/i.test(uri)) {
			throw new TypeError('`uri` does not appear to be a Data URI (must begin with "data:")');
		}

		// Strip newlines
		uri = uri.replace(/\r?\n/g, '');

		// Split the URI up into the "metadata" and the "data" portions
		const firstComma = uri.indexOf(',');
		if (firstComma === -1 || firstComma <= 4) {
			throw new TypeError('malformed data: URI');
		}

		// Remove the "data:" scheme and parse the metadata
		const meta = uri.substring(5, firstComma).split(';');
		let charset = '';
		let base64 = false;
		let type = meta[0] || 'text/plain';

		for (let i = 1; i < meta.length; i++) {
			if (meta[i] === 'base64') {
				base64 = true;
			} else if (meta[i]) {
				type += `;${meta[i]}`;
				if (meta[i].indexOf('charset=') === 0) {
					charset = meta[i].substring(8);
				}
			}
		}

		// Defaults to US-ASCII only if type is not provided
		if (!meta[0] && !charset.length) {
			type += ';charset=US-ASCII';
			charset = 'US-ASCII';
		}

		// Get the encoded data portion and decode URI-encoded chars
		const encoding = base64 ? 'base64' : 'ascii';
		const data = unescape(uri.substring(firstComma + 1));
		const buffer = Buffer.from(data, encoding);

		return {
			type,
			charset,
			buffer
		};
	}
}