const MetadataExtractor = class {
	/* 
	 * MetadataExtractor class
	 * This class is used to extract metadata from a BLOB object.
	*/
	constructor(BLOB) {
		this.blob = BLOB;

		this.extract([`fieldname`, `encoding`, `originalname`, `mimetype`, `size`]);
	}

	/* 
	 * Extract data from the blob. 
	*/
	extract(FIELDS) {
		// Verify the validity of the blob.
		if (!this.blob) {
			throw new Error("Invalid BLOB object");
		};

		// Extract the relevant fields. 
		let RESPONSE = {};
		FIELDS.forEach((FIELD) => {
			if (!(this.blob[FIELD] === undefined)) {
				this[FIELD] = this.blob[FIELD];
				RESPONSE[FIELD] = this.blob[FIELD];
			}
		});

		// Return the response.
		return (RESPONSE);
	}
}

module.exports = MetadataExtractor;