migrate basic http client and response cache into library repo

.gitea/workflows/build-and-publish.yaml

@@ -2,7 +2,7 @@
 name: Build and publish
 
 on:
-  workflow_dispatch: { }
+- workflow_dispatch
   # push:
   #   branches:
   #   - master
@@ -23,8 +23,14 @@ jobs:
 
       - name: Login to package registry
         run: |
-          npm config set @<scope name>:registry https://gitea.jbrumond.me/api/packages/<scope name>/npm/
+          npm config set @js:registry https://gitea.jbrumond.me/api/packages/js/npm/
-          npm config set -- '//gitea.jbrumond.me/api/packages/<scope name>/npm/:_authToken' "$NPM_PUBLISH_TOKEN"
+          npm config set -- '//gitea.jbrumond.me/api/packages/js/npm/:_authToken' "$NPM_PUBLISH_TOKEN"
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Compile TypeScript
+        run: npm run tsc
 
       - name: Publish package
         run: npm publish

.gitea/workflows/build-and-test.yaml

@@ -0,0 +1,40 @@
+
+name: Build and test
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18.x, 20.x]
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v3
+
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v3
+        with:
+          node-version: ${{ matrix.node-version }}
+
+      # - name: Login to package registry
+      #   run: |
+      #     npm config set @js:registry https://gitea.jbrumond.me/api/packages/js/npm/
+      #     npm config set -- '//gitea.jbrumond.me/api/packages/js/npm/:_authToken' "$NPM_PUBLISH_TOKEN"
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Compile TypeScript
+        run: npm run tsc
+
+      # todo: tests
+      - name: Run tests
+        run: exit 0

package-lock.json

@@ -1,17 +1,27 @@
 {
-  "name": "@templates/typescript-library",
+  "name": "@js/http-client",
   "version": "1.0.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
-      "name": "@templates/typescript-library",
+      "name": "@js/http-client",
       "version": "1.0.0",
       "license": "ISC",
       "devDependencies": {
+        "@types/node": "^20.5.1",
         "typescript": "^5.1.3"
+      },
+      "engines": {
+        "node": ">=18"
       }
     },
+    "node_modules/@types/node": {
+      "version": "20.5.1",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-20.5.1.tgz",
+      "integrity": "sha512-4tT2UrL5LBqDwoed9wZ6N3umC4Yhz3W3FloMmiiG4JwmUJWpie0c7lcnUNd4gtMKuDEO4wRVS8B6Xa0uMRsMKg==",
+      "dev": true
+    },
     "node_modules/typescript": {
       "version": "5.1.6",
       "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.1.6.tgz",

package.json

@@ -1,7 +1,7 @@
 {
-  "name": "@templates/typescript-library",
+  "name": "@js/http-client",
   "version": "1.0.0",
-  "description": "Template project for creating new TypeScript library packages",
+  "description": "HTTP client utilities",
   "main": "build/index.js",
   "types": "build/index.d.ts",
   "scripts": {
@@ -9,15 +9,20 @@
     "clean": "rm -rf ./build"
   },
   "publishConfig": {
-    "registry": "https://gitea.jbrumond.me/api/packages/templates/npm/"
+    "registry": "https://gitea.jbrumond.me/api/packages/js/npm/"
   },
   "repository": {
     "type": "git",
-    "url": "https://gitea.jbrumond.me/templates/typescript-library.git"
+    "url": "https://gitea.jbrumond.me/js/http-client.git"
+  },
+  "engines": {
+    "node": ">=18"
   },
   "author": "James Brumond <https://jbrumond.me>",
   "license": "ISC",
   "devDependencies": {
+    "@js/types": "^0.1.0",
+    "@types/node": "^20.5.1",
     "typescript": "^5.1.3"
   }
 }

readme.md

@@ -1,30 +1,70 @@
 
-Template project for creating new TypeScript library packages
+Bare-minimum HTTP client library
+
+Features:
+
+- **Zero** dependencies
+- Built-in response cache
 
 ---
 
-## Get Started
+## Install
-
-### Pull down the code
 
 ```bash
-git init
+# Update project npm config to refer to correct registry for the @js scope
-git pull https://gitea.jbrumond.me/templates/typescript-library.git master
+echo '@js:registry=https://gitea.jbrumond.me/api/packages/js/npm/' >> ./.npmrc
+
+npm install --save @js/http-client
+
+# optional - additional supporting typescript definitions
+npm install --save-dev @js/types
 ```
 
-### Update configuration
 
-- In `package.json`, update any fields like `name`, `description`, `repository`, etc.
+
-- In `.gitea/workflows/publish.yaml`, update `<scope name>` placeholders
+## Usage
+
+```ts
+import { create_http_client } from '@js/http-client';
+
+const http = create_http_client({
+	// Default configuration:
+	logger: null,  // (optional) expects a pino logger or compatible
+	https_only: false,
+	cache: {
+		// These settings are based on the recommendations in [RFC 9111], with the
+		// exception of not caching POST responses (because its not very commonly
+		// useful and is complicated) and with the addition of invalidating caches
+		// on successful PATCH requests (because they are fairly common use and
+		// are expected to modify the referenced resource)
+		// 
+		// [RFC 9111]: https://www.rfc-editor.org/rfc/rfc9111.html
+		cacheable_methods: [ 'GET', 'HEAD' ],
+		cache_invalidating_methods: [ 'POST', 'PUT', 'PATCH', 'DELETE' ],
+		cacheable_status_codes: [
+			200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, 501
+		],
+	},
+});
+
+const { status, headers, content } = await http.get('https://example.com', {
+	'accept': 'application/json'
+});
+
+if (status === 200) {
+	const json = JSON.parse(content);
+	console.log('received data', json);
+}
+```
 
 
 
-## Building
+## Building Locally (for development)
 
 ```bash
+npm ci
 npm run tsc
 ```
 
 
 
-

src/index.ts

@@ -1,4 +1,217 @@
 
-export function hello() : string {
+import { URL } from 'url';
-	return 'hello';
+import { request as https_request } from 'https';
+import { request as http_request, OutgoingHttpHeaders, IncomingHttpHeaders } from 'http';
+import { ResponseCacheConfig, create_response_cache, validate_response_cache_conf } from './response-cache';
+import { noop_logger } from './noop-logger';
+import type { HttpURL, Logger } from '@js/types';
+
+export { ResponseCacheConfig, validate_response_cache_conf } from './response-cache';
+
+let next_id = 1;
+const timeout = 5000;
+
+export interface HttpResult {
+	url: URL;
+	status: number;
+	headers: IncomingHttpHeaders;
+	content: string;
+}
+
+export interface HttpClientConfig {
+	logger?: Logger;
+	https_only?: boolean;
+	cache?: ResponseCacheConfig;
+}
+
+export function validate_http_conf(conf: unknown) : asserts conf is HttpClientConfig {
+	if (typeof conf !== 'object' || ! conf) {
+		throw new Error('Configuration must be an object');
+	}
+
+	if ('logger' in conf) {
+		// todo: validate
+	}
+
+	if ('https_only' in conf) {
+		if (typeof conf.https_only !== 'boolean') {
+			throw new Error('"https_only" must be a boolean if provided');
+		}
+	}
+
+	if ('cache' in conf) {
+		validate_response_cache_conf(conf.cache);
+	}
+}
+
+export type HttpClient = ReturnType<typeof create_http_client>;
+
+export function create_http_client(conf: HttpClientConfig) {
+	const { logger = noop_logger } = conf;
+	const response_cache = create_response_cache(conf.cache ?? { }, logger);
+
+	return {	
+		req: http_req,	
+		get(url_str: HttpURL, headers?: OutgoingHttpHeaders, skip_cache = false) {
+			return http_req('GET', url_str, headers, null, skip_cache);
+		},
+		head(url_str: HttpURL, headers?: OutgoingHttpHeaders, skip_cache = false) {
+			return http_req('HEAD', url_str, headers, null, skip_cache);
+		},
+		post(url_str: HttpURL, headers?: OutgoingHttpHeaders, body?: string, skip_cache = false) {
+			return http_req('POST', url_str, headers, body, skip_cache);
+		},
+		put(url_str: HttpURL, headers?: OutgoingHttpHeaders, body?: string, skip_cache = false) {
+			return http_req('PUT', url_str, headers, body, skip_cache);
+		},
+		patch(url_str: HttpURL, headers?: OutgoingHttpHeaders, body?: string, skip_cache = false) {
+			return http_req('PATCH', url_str, headers, body, skip_cache);
+		},
+		delete(url_str: HttpURL, headers?: OutgoingHttpHeaders, body?: string, skip_cache = false) {
+			return http_req('DELETE', url_str, headers, body, skip_cache);
+		},
+	};
+
+	async function http_req(method: string, url_str: HttpURL, headers?: OutgoingHttpHeaders, body?: string, skip_cache = false) {
+		const url = new URL(url_str);
+		const make_request
+			= url.protocol === 'https:' ? https_request
+			: url.protocol === 'http:' ? http_request
+			: null;
+	
+		if (! make_request) {
+			throw new Error('illegal protocol');
+		}
+	
+		if (url.protocol !== 'https:' && conf.https_only) {
+			throw new Error('non-secure http requests not allowed (by configuration)');
+		}
+	
+		if (url.username || url.password) {
+			throw new Error('urls containing user credentials not allowed');
+		}
+
+		const req_headers = headers ? structuredClone(headers) : { };
+	
+		const result: HttpResult = {
+			url,
+			status: null,
+			content: null,
+			headers: null,
+		};
+	
+		const path = url.pathname + (url.search || '');
+		const port = url.port ? parseInt(url.port, 10) : (url.protocol === 'https:' ? 443 : 80);
+		const log = logger.child({
+			req_id: next_id++,
+			method: method,
+			protocol: url.protocol,
+			hostname: url.hostname,
+			port: port,
+			path: path,
+		});
+
+		const cached = skip_cache
+			? null
+			: response_cache.check_for_cached_response(method, url_str, req_headers);
+
+		if (cached) {
+			const revalidation = response_cache.determine_revalidation_needed(cached);
+
+			if (! revalidation.should_revalidate) {
+				log.info('serving request from cache (no revalidation required)');
+				result.status = cached.status;
+				result.content = cached.body;
+				result.headers = structuredClone(cached.res_headers);
+				return Promise.resolve(result);
+			}
+
+			// if (! revalidation.must_revalidate) {
+			// 	// todo: lazy revalidation option
+			// }
+
+			log.info('cached response found, but requires revalidation');
+			Object.assign(req_headers, revalidation.headers);
+		}
+	
+		log.info('starting outbound http request');
+	
+		return new Promise<HttpResult>((resolve, reject) => {
+			const start = Date.now();
+			const req = make_request({
+				method: method,
+				protocol: url.protocol,
+				hostname: url.hostname,
+				port: port,
+				path: path,
+				headers: req_headers
+			}, (res) => {
+				// result.res = res;
+				result.status = res.statusCode;
+
+				log.info({
+					status: res.statusCode,
+					duration: Date.now() - start,
+				}, `headers received`);
+
+				switch (result.status) {
+					case 304:
+						log.info({ status: cached.status }, 're-using cached response (not modified)');
+						result.status = cached.status;
+						result.content = cached.body;
+						result.headers = structuredClone(cached.res_headers);
+						response_cache.freshen_cache(cached, res.headers);
+						resolve(result);
+						break;
+
+					case 500:
+					case 502:
+					case 503:
+					case 504:
+						if (cached?.cache_info?.cache_control?.stale_if_error) {
+							log.info({ status: cached.status }, 're-using cached response (response returned an error status, and `stale-if-error` directive was provided)');
+							result.status = cached.status;
+							result.content = cached.body;
+							result.headers = structuredClone(cached.res_headers);
+							resolve(result);
+							break;
+						}
+						// nobreak
+
+					default: {
+						const start = Date.now();
+						let data = '';
+			
+						res.on('data', (chunk) => {
+							data += chunk;
+						});
+			
+						res.on('end', () => {
+							log.info({ duration: Date.now() - start }, `response finished`);
+							result.content = data;
+							result.headers = res.headers;
+							response_cache.add_response_to_cache(method, url_str, req_headers, result);
+							resolve(result);
+						});
+					};
+				}
+			});
+	
+			req.setTimeout(timeout, () => {
+				log.error('request timeout');
+				req.destroy();
+			});
+		
+			req.on('error', (error) => {
+				log.error('request error ' + error.stack);
+				reject(error);
+			});
+	
+			if (body) {
+				req.write(body);
+			}
+	
+			req.end();
+		});
+	}
 }

src/noop-logger.ts

@@ -0,0 +1,13 @@
+
+import type { Logger } from '@js/types';
+
+export const noop_logger: Logger = {
+	child() { return noop_logger; },
+	fatal() { },
+	error() { },
+	warn() { },
+	info() { },
+	debug() { },
+	trace() { },
+	silent() { },
+};

src/parse-cache-headers.ts

@@ -0,0 +1,110 @@
+
+import type { IncomingHttpHeaders } from 'http';
+
+export interface ParsedCacheHeaders {
+	age?: number;
+	etag?: string;
+	vary?: string[];
+	date?: Date;
+	cache_control?: CacheControl;
+	expires?: Date;
+	last_modified?: Date;
+}
+
+export interface CacheControl {
+	public?: boolean;
+	private?: boolean;
+	no_store?: boolean;
+	no_cache?: boolean;
+	max_age?: number;
+	s_max_age?: number;
+	must_revalidate?: boolean;
+	proxy_revalidate?: boolean;
+	immutable?: boolean;
+	stale_while_revalidate?: boolean;
+	stale_if_error?: boolean;
+	must_understand?: boolean;
+}
+
+export function parse_cache_headers(headers: IncomingHttpHeaders) {
+	const result: ParsedCacheHeaders = { };
+
+	if (headers['age']) {
+		result.age = parseInt(headers['age'], 10);
+	}
+
+	if (headers['etag']) {
+		result.etag = headers['etag'];
+	}
+
+	if (headers['vary']) {
+		result.vary = headers['vary'].split(',').map((str) => str.trim().toLowerCase());
+	}
+
+	if (headers['date']) {
+		result.date = new Date(Date.parse(headers['date']));
+	}
+
+	if (headers['cache-control']) {
+		result.cache_control = { };
+
+		for (let directive of headers['cache-control'].split(',')) {
+			directive = directive.trim();
+
+			switch (directive) {
+				case 'public':
+					result.cache_control.public = true;
+					break;
+				case 'private':
+					result.cache_control.private = true;
+					break;
+				case 'no-store':
+					result.cache_control.no_store = true;
+					break;
+				case 'no-cache':
+					result.cache_control.no_cache = true;
+					break;
+				case 'must-revalidate':
+					result.cache_control.must_revalidate = true;
+					break;
+				case 'proxy-revalidate':
+					result.cache_control.proxy_revalidate = true;
+					break;
+				case 'immutable':
+					result.cache_control.immutable = true;
+					break;
+				case 'stale-while-revalidate':
+					result.cache_control.stale_while_revalidate = true;
+					break;
+				case 'stale-if-error':
+					result.cache_control.stale_if_error = true;
+					break;
+				case 'must-understand':
+					result.cache_control.must_understand = true;
+					break;
+				default:
+					if (directive.startsWith('max-age=')) {
+						result.cache_control.max_age = parseInt(directive.slice(8), 10);
+						break;
+					}
+
+					if (directive.startsWith('s-maxage=')) {
+						result.cache_control.s_max_age = parseInt(directive.slice(10), 10);
+						break;
+					}
+
+					// todo: log something here about unknown directive
+			}
+		}
+	}
+
+	if (headers['expires']) {
+		result.expires = new Date(Date.parse(headers['expires']));
+	}
+
+	if (headers['last-modified']) {
+		result.last_modified = new Date(Date.parse(headers['last-modified']));
+	}
+
+	return result;
+}

src/response-cache.ts

@@ -0,0 +1,257 @@
+
+import { parse_cache_headers, ParsedCacheHeaders } from './parse-cache-headers';
+import type { HttpResult } from './index';
+import type { HttpURL, Logger } from '@js/types';
+import type { OutgoingHttpHeaders, IncomingHttpHeaders } from 'http';
+
+export interface ResponseCacheConfig {
+	cacheable_methods?: string[];
+	cacheable_status_codes?: number[];
+	cache_invalidating_methods?: string[];
+	// todo: support for configurable limits:
+	max_records?: number;  // max number of cached responses
+	max_length?: number;  // max content-length for one response
+	evict_after?: number;  // period of time unused after which a response should be evicted
+}
+
+export interface CachedResponse {
+	cache_key: string;
+	cached_time: Date;
+	is_stale: boolean;
+	url: HttpURL;
+	method: string;
+	status: number;
+	body: string;
+	res_headers: IncomingHttpHeaders;
+	cache_info: ParsedCacheHeaders;
+	expire_timer: NodeJS.Timeout;
+}
+
+export function validate_response_cache_conf(conf: unknown) : asserts conf is ResponseCacheConfig {
+	// todo: validate config
+}
+
+export type ResponseCache = ReturnType<typeof create_response_cache>;
+
+export function create_response_cache(conf: ResponseCacheConfig, logger: Logger) {
+	type URLCache = Record<string, CachedResponse>;
+	const cached_responses: Record<HttpURL, URLCache> = Object.create(null);
+
+	const cacheable_methods = new Set(conf.cacheable_methods ?? [ 'GET', 'HEAD' ]);
+	const cache_invalidating_methods = new Set(conf.cache_invalidating_methods ?? [ 'POST', 'PUT', 'PATCH', 'DELETE' ]);
+	const cacheable_status_codes = new Set(conf.cacheable_status_codes ?? [
+		200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, 501
+	]);
+
+	return {
+		/**
+		 * Should be called before making a new request to check if a cached response already exists
+		 */
+		check_for_cached_response(method: string, url_str: HttpURL, headers?: OutgoingHttpHeaders) : Readonly<CachedResponse> {
+			if (! cached_responses[url_str]) {
+				return;
+			}
+
+			for (const [cache_key, cached] of Object.entries(cached_responses[url_str])) {
+				if (cache_key === header_cache_key(method, cached.cache_info.vary, headers)) {
+					return cached;
+				}
+			}
+		},
+
+		/**
+		 * Should be called when a cached response is found, to determine what if any revalidation is
+		 * required before re-using the response
+		 */
+		determine_revalidation_needed(cached: CachedResponse) {
+			const { cache_control, etag, date, last_modified } = cached.cache_info;
+
+			const must_revalidate = Boolean(cache_control?.must_revalidate || cache_control?.no_cache);
+			const should_revalidate = must_revalidate || cached.is_stale;
+			const headers: OutgoingHttpHeaders = { };
+
+			if (etag) {
+				headers['if-none-match'] = etag;
+			}
+
+			if (last_modified || date) {
+				headers['if-modified-since'] = last_modified?.toUTCString() ?? date?.toUTCString();
+			}
+
+			else {
+				headers['if-modified-since'] = cached.cached_time.toUTCString();
+			}
+
+			return {
+				must_revalidate,
+				should_revalidate,
+				headers,
+			};
+		},
+
+		/**
+		 * Should be called when receiving a non-`304 Not Modified` response from a request, either
+		 * as a novel request, or during a revalidation request
+		 */
+		add_response_to_cache(method: string, url_str: HttpURL, headers: OutgoingHttpHeaders, result: HttpResult) {
+			if (! cacheable_methods.has(method) || ! cacheable_status_codes.has(result.status)) {
+				logger.info({ method, status: result.status }, 'method/status not cacheable');
+				return;
+			}
+
+			const cache_info = parse_cache_headers(result.headers);
+
+			if (headers.authorization) {
+				// todo: caching authenticated requests
+				// see <https://www.rfc-editor.org/rfc/rfc9111#section-3.5>
+				return;
+			}
+
+			// todo: if `vary` has changed, invalidate all stored responses
+			// todo: source link for ^
+
+			if (cache_info.vary.includes('*')) {
+				logger.info(cache_info, 'response contains "Vary: *" header that prevents caching');
+				return;
+			}
+
+			if (cache_info.cache_control?.no_store || cache_info.cache_control?.private) {
+				logger.info(cache_info, 'response contains "Cache-Control" directives that prevent caching');
+				return;
+			}
+			
+			const cache_key = header_cache_key(method, cache_info.vary, headers);
+			unset_expire_timer(url_str, cache_key);
+
+			const cached: CachedResponse = {
+				cache_key,
+				cached_time: new Date(Date.now()),
+				is_stale: false,
+				url: url_str,
+				method,
+				// req_headers: structuredClone(headers),
+				status: result.status,
+				body: result.content,
+				res_headers: structuredClone(result.headers),
+				cache_info,
+				expire_timer: null,
+			};
+
+			logger.info(cache_info, 'caching response');
+			store_to_cache(cached, cache_info);
+		},
+
+		/**
+		 * Should be called when receiving a `304 Not Modified` response during a revalidation request
+		 * to update the cache with more recent freshness info
+		 */
+		freshen_cache(cached: CachedResponse, headers: IncomingHttpHeaders) {
+			const cache_info = parse_cache_headers(headers);
+			unset_expire_timer(cached.url, cached.cache_key);
+			store_to_cache(cached, cache_info);
+		},
+
+		/**
+		 * 
+		 */
+		invalidate_cache_for_update(method: string, url_str: HttpURL, status: number, headers: IncomingHttpHeaders) {
+			if (! cache_invalidating_methods.has(method)) {
+				return;
+			}
+
+			if (status < 200 || status >= 400) {
+				return;
+			}
+		},
+	};
+
+	function store_to_cache(cached: CachedResponse, cache_info: ParsedCacheHeaders) {
+		if (! cached_responses[cached.url]) {
+			cached_responses[cached.url] = Object.create(null);
+		}
+
+		cached_responses[cached.url][cached.cache_key] = cached;
+		cached.is_stale = false;
+
+		if (cache_info.cache_control?.max_age) {
+			let ttl_ms = cache_info.cache_control.max_age * 1000;
+
+			if (cache_info.age) {
+				ttl_ms -= cache_info.age * 1000;
+			}
+
+			if (ttl_ms <= 0) {
+				cached.is_stale = true;
+				return;
+			}
+
+			cached.expire_timer = set_expire_timer(cached.url, cached.cache_key, ttl_ms);
+		}
+
+		else if (cache_info.expires) {
+			const ttl_ms = cache_info.expires.getTime() - Date.now();
+
+			if (ttl_ms <= 0) {
+				cached.is_stale = true;
+				return;
+			}
+
+			cached.expire_timer = set_expire_timer(cached.url, cached.cache_key, ttl_ms);
+		}
+
+		// If no cache-control or expires header is given, default to the
+		// recommended 10% of time since last-modified
+		else if (cache_info.last_modified) {
+			const last_modified_ago_ms = Date.now() - cache_info.last_modified.getTime();
+
+			if (last_modified_ago_ms <= 0) {
+				cached.is_stale = true;
+				return;
+			}
+
+			const ttl_ms = (last_modified_ago_ms / 10) | 0;
+			cached.expire_timer = set_expire_timer(cached.url, cached.cache_key, ttl_ms);
+		}
+	}
+
+	function unset_expire_timer(url_str: HttpURL, cache_key: string) {
+		const cached = cached_responses[url_str]?.[cache_key];
+
+		if (cached?.expire_timer) {
+			clearTimeout(cached.expire_timer);
+		}
+	}
+
+	function set_expire_timer(url_str: HttpURL, cache_key: string, ttl_ms: number) {
+		const timer = setTimeout(expire, ttl_ms);
+		timer.unref();
+		return timer;
+
+		function expire() {
+			if (cached_responses[url_str]?.[cache_key]) {
+				cached_responses[url_str][cache_key].is_stale = true;
+			}
+		};
+	}
+}
+
+function header_cache_key(method: string, vary: string[], headers: OutgoingHttpHeaders) {
+	const parts: string[] = [ method ];
+
+	if (vary?.length) {
+		for (const header of vary) {
+			if (Array.isArray(headers[header])) {
+				const values = (headers[header] as string[]).sort();
+				for (const value of values) {
+					parts.push(`${header}: ${value}`);
+				}
+			}
+
+			else if (headers[header]) {
+				parts.push(`${header}: ${headers[header]}`);
+			}
+		}
+	}
+
+	return parts.join('\0');
+}