feat: adding support to .redirect on Response

https://developer.mozilla.org/en-US/docs/Web/API/Response/redirect
https://fetch.spec.whatwg.org/#dom-response-redirect

Author: matchs

src/headers.js

@@ -22,6 +22,12 @@ function validateValue(value) {
 	}
 }
 
+function checkGuard(obj) {
+	if (obj._guard === 'immutable') {
+		throw new TypeError("Cannot modify header. Immutable guard is set.")
+	}
+}
+
 /**
  * Find the key in the map object given a header name.
  *
@@ -46,9 +52,10 @@ export default class Headers {
 	 * Headers class
 	 *
 	 * @param   Object  headers  Response headers
+	 * @param 	Object 	options 	
 	 * @return  Void
 	 */
-	constructor(init = undefined) {
+	constructor(init = undefined, options = undefined) {
 		this[MAP] = Object.create(null);
 
 		if (init instanceof Headers) {
@@ -101,6 +108,19 @@ export default class Headers {
 		} else {
 			throw new TypeError('Provided initializer must be an object');
 		}
+
+		if (options == null) {
+			// no op
+		} else if (typeof options === 'object') {
+			if (options.guard) {
+				// @TODO validate values for guard
+				this._guard = options.guard;
+			} else {
+				this._guard = 'none';
+			}
+		} else {
+			throw new TypeError('Provided options must be an object');
+		}
 	}
 
 	/**
@@ -146,6 +166,8 @@ export default class Headers {
 	 * @return  Void
 	 */
 	set(name, value) {
+		checkGuard(this);
+
 		name = `${name}`;
 		value = `${value}`;
 		validateName(name);
@@ -162,6 +184,8 @@ export default class Headers {
 	 * @return  Void
 	 */
 	append(name, value) {
+		checkGuard(this);
+
 		name = `${name}`;
 		value = `${value}`;
 		validateName(name);
@@ -193,6 +217,8 @@ export default class Headers {
 	 * @return  Void
 	 */
 	delete(name) {
+		checkGuard(this);
+
 		name = `${name}`;
 		validateName(name);
 		const key = find(this[MAP], name);

src/response.js

@@ -6,6 +6,7 @@
  */
 
 import { STATUS_CODES } from 'http';
+import { parse as parse_url } from 'url';
 import Headers from './headers.js';
 import Body, { cloneBody , getInstanceName} from './body';
 
@@ -74,6 +75,34 @@ export default class Response {
 			name: `cloned(${getInstanceName(this)})`
 		});
 	}
+
+	static redirect(url, status) {
+		//1. Let parsedURL be the result of parsing url with current settings object’s API base URL.
+		//2. If parsedURL is failure, then throw a TypeError.
+		const parsedURL = parse_url(url);
+
+		//3. If status is not a redirect status, then throw a RangeError.
+		let intStatus = parseInt(status, 10);å
+		if(intStatus < 300 || intStatus > 399) {
+			throw new RangeError('Not a redirect status');
+		}
+
+		//4. Let r be a new Response object, whose response is a new response.
+		//5. Set r’s headers to a new Headers object whose guard is "immutable".
+		//6. Set r’s response’s status to status.
+		//7. Append `Location` to parsedURL, serialized and isomorphic encoded, in r’s response’s header list.
+		const r = new Response(new Body(""), {
+			url,
+			status: intStatus,
+			name: `redirected(${url})`,
+			headers: new Headers({
+				Location: url,
+			}, { guard: 'immutable' }),
+		});
+
+		//8. Return r.
+		return r;
+	}
 }
 
 Body.mixIn(Response.prototype);