Implement CORS

index.ts

@@ -1,7 +1,9 @@
 import { config } from "./src/config.js";
 import { logger } from "./src/logger.js";
 import GET from "./src/fetch/GET.js";
+import OPTIONS from "./src/fetch/OPTIONS.js";
 import * as prometheus from "./src/prometheus.js";
+import { BadRequest } from "./src/fetch/cors.js";
 
 if (config.verbose) logger.enable();
 
@@ -10,8 +12,9 @@ const app = Bun.serve({
     port: config.port,
     fetch(req: Request) {
         if (req.method === "GET") return GET(req);
+        if (req.method === "OPTIONS") return OPTIONS(req);
         prometheus.request_error.inc({pathname: new URL(req.url).pathname, status: 400});
-        return new Response("Invalid request", { status: 400 });
+        return BadRequest
     }
 });
 

src/fetch/GET.ts

@@ -7,18 +7,19 @@ import * as prometheus from "../prometheus.js";
 import { logger } from "../logger.js";
 import swaggerHtml from "../../swagger/index.html"
 import swaggerFavicon from "../../swagger/favicon.png"
+import { NotFound, toFile, toJSON, toText } from "./cors.js";
 
 export default async function (req: Request) {
     const { pathname} = new URL(req.url);
     prometheus.request.inc({pathname});
-    if ( pathname === "/" ) return new Response(Bun.file(swaggerHtml));
-    if ( pathname === "/favicon.png" ) return new Response(Bun.file(swaggerFavicon));
+    if ( pathname === "/" ) return toFile(Bun.file(swaggerHtml));
+    if ( pathname === "/favicon.png" ) return toFile(Bun.file(swaggerFavicon));
     if ( pathname === "/health" ) return health(req);
-    if ( pathname === "/metrics" ) return new Response(await registry.metrics(), {headers: {"Content-Type": registry.contentType}});
-    if ( pathname === "/openapi" ) return new Response(openapi, {headers: {"Content-Type": "application/json"}});
+    if ( pathname === "/metrics" ) return toText(await registry.metrics());
+    if ( pathname === "/openapi" ) return toJSON(openapi);
     if ( pathname === "/chains" ) return chains(req);
     if ( pathname === "/block" ) return block(req);
     logger.warn(`Not found: ${pathname}`);
     prometheus.request_error.inc({pathname, status: 404});
-    return new Response("Not found", { status: 404 });
+    return NotFound;
 }

src/fetch/OPTIONS.ts

@@ -0,0 +1,5 @@
+import { CORS_HEADERS } from "./cors.js";
+
+export default async function (req: Request) {
+    return new Response('Departed', {headers: CORS_HEADERS});
+}

src/fetch/block.ts

@@ -2,17 +2,18 @@ import { makeQuery } from "../clickhouse/makeQuery.js";
 import { logger } from "../logger.js";
 import { Block, getBlock } from "../queries.js";
 import * as prometheus from "../prometheus.js";
+import { BadRequest, toJSON } from "./cors.js";
 
 export default async function (req: Request) {
   try {
     const { searchParams } = new URL(req.url);
     logger.info({searchParams: Object.fromEntries(Array.from(searchParams))});
     const query = await getBlock(searchParams);
     const response = await makeQuery<Block>(query)
-    return new Response(JSON.stringify(response.data), { headers: { "Content-Type": "application/json" } });
+    return toJSON(response.data);
   } catch (e: any) {
     logger.error(e);
     prometheus.request_error.inc({pathname: "/block", status: 400});
-    return new Response(e.message, { status: 400 });
+    return BadRequest
   }
 }

src/fetch/chains.ts

@@ -2,6 +2,7 @@ import { makeQuery } from "../clickhouse/makeQuery.js";
 import { logger } from "../logger.js";
 import * as prometheus from "../prometheus.js";
 import { getChain } from "../queries.js";
+import { BadRequest, toJSON } from "./cors.js";
 
 export async function supportedChainsQuery() {
   const response = await makeQuery<{chain: string}>(getChain());
@@ -11,10 +12,10 @@ export async function supportedChainsQuery() {
 export default async function (req: Request) {
   try {
     const chains = await supportedChainsQuery();
-    return new Response(JSON.stringify(chains), { headers: { "Content-Type": "application/json" } });
+    return toJSON(chains);
   } catch (e: any) {
     logger.error(e);
     prometheus.request_error.inc({pathname: "/chains", status: 400});
-    return new Response(e.message, { status: 400 });
+    return BadRequest;
   }
 }

src/fetch/cors.ts

@@ -0,0 +1,37 @@
+import { BunFile } from "bun";
+
+export const BadRequest = toText('Bad Request', 400);
+export const NotFound = toText('Not Found', 404);
+export const InternalServerError = toText("Internal Server Error", 500);
+
+export const CORS_HEADERS = new Headers({
+    "Access-Control-Allow-Origin": "*",
+    "Access-Control-Allow-Methods": "GET, POST, OPTIONS",
+    "Access-Control-Allow-Headers": "Content-Type, WWW-Authenticate",
+});
+export const JSON_HEADERS = new Headers({"Content-Type": "application/json"});
+export const TEXT_HEADERS = new Headers({"Content-Type": "text/plain; version=0.0.4; charset=utf-8"});
+
+export function appendHeaders(...args: Headers[]) {
+    const headers = new Headers(CORS_HEADERS); // CORS as default headers
+    for (const arg of args) {
+        for (const [key, value] of arg.entries()) {
+            headers.set(key, value);
+        }
+    }
+    return headers;
+};
+
+export function toJSON(body: any, status = 200, headers = new Headers()) {
+    const data = typeof body == "string" ? body : JSON.stringify(body, null, 2);
+    return new Response(data, { status, headers: appendHeaders(JSON_HEADERS, headers) });
+}
+
+export function toText(body: string, status = 200, headers = new Headers()) {
+    return new Response(body, { status, headers: appendHeaders(TEXT_HEADERS, headers) });
+}
+
+export function toFile(body: BunFile, status = 200, headers = new Headers()) {
+    const fileHeaders = new Headers({"Content-Type": body.type});
+    return new Response(body, { status, headers: appendHeaders(fileHeaders, headers) });
+}

src/fetch/health.ts

@@ -1,16 +1,17 @@
 import client from "../clickhouse/createClient.js";
 import { logger } from "../logger.js";
 import * as prometheus from "../prometheus.js";
+import { InternalServerError, toText } from "./cors.js";
 
 export default async function (req: Request) {
   try {
     const response = await client.ping();
     if (response.success === false) throw new Error(response.error.message);
-    if (response.success === true ) return new Response("OK");
-    return new Response("Unknown response from ClickHouse");
+    if (response.success === true ) return toText("OK");
+    return InternalServerError;
   } catch (e: any) {
     logger.error(e);
     prometheus.request_error.inc({ pathname: "/health", status: 500});
-    return new Response(e.message, { status: 500 });
+    return InternalServerError;
   }
 }