form-data.js

import {randomBytes} from 'crypto';

import {isBlob} from './is.js';

const carriage = '\r\n';
const dashes = '-'.repeat(2);
const carriageLength = Buffer.byteLength(carriage);

/**
 * @param {string} boundary
 */
const getFooter = boundary => `${dashes}${boundary}${dashes}${carriage.repeat(2)}`;

/**
 * @param {string} boundary
 * @param {string} name
 * @param {*} field
 *
 * @return {string}
 */
function getHeader(boundary, name, field) {
	let header = '';

	header += `${dashes}${boundary}${carriage}`;
	header += `Content-Disposition: form-data; name="${name}"`;

	if (isBlob(field)) {
		header += `; filename="${field.name}"${carriage}`;
		header += `Content-Type: ${field.type || 'application/octet-stream'}`;
	}

	return `${header}${carriage.repeat(2)}`;
}

/**
 * @return {string}
 */
export const getBoundary = () => randomBytes(8).toString('hex');

/**
 * @param {FormData} form
 * @param {string} boundary
 */
export async function * formDataIterator(form, boundary) {
	for (const [name, value] of form) {
		yield getHeader(boundary, name, value);

		if (isBlob(value)) {
			yield * value.stream();
		} else {
			yield value;
		}

		yield carriage;
	}

	yield getFooter(boundary);
}

/**
 * @param {FormData} form
 * @param {string} boundary
 */
export function getFormDataLength(form, boundary) {
	let length = 0;

	for (const [name, value] of form) {
		length += Buffer.byteLength(getHeader(boundary, name, value));

		if (isBlob(value)) {
			length += value.size;
		} else {
			length += Buffer.byteLength(String(value));
		}

		length += carriageLength;
	}

	length += Buffer.byteLength(getFooter(boundary));

	return length;
}