Custom exceptions, redirect in case of non-html content

src/errors.ts

@@ -0,0 +1,3 @@
+export class EngineParseError extends Error {}
+export class InvalidParameterError extends Error {}
+export class NotHtmlMimetypeError extends Error {}

src/handlers/google.ts

@@ -9,7 +9,9 @@ export default async function google(
   );
 
   if (!googleAnchors) {
-    throw new Error("Failed to find anchors in search result [google]");
+    throw new EngineParseError(
+      "Failed to find anchors in search result [google]"
+    );
   }
   const results = [...googleAnchors];
 

src/handlers/main.ts

@@ -8,6 +8,8 @@ import readability from "./readability";
 import google from "./google";
 import { generateProxyUrl } from "../utils";
 
+import { InvalidParameterError, NotHtmlMimetypeError } from "../errors";
+
 export default async function handlePage(
   url: string,
   requestUrl: URL,
@@ -15,18 +17,24 @@ export default async function handlePage(
 ): Promise<IHandlerOutput> {
 
   if (engine && engineList.indexOf(engine) === -1) {
-    throw new Error("Invalid engine");
+    throw new InvalidParameterError("Invalid engine");
   }
 
   const response = await axios.get(url);
+  const mime: string | undefined = (
+    response.headers["content-type"]?.toString()
+  );
+
+  if (mime && mime.indexOf("text/html") === -1) {
+    throw new NotHtmlMimetypeError();
+  }
+
   const window = new JSDOM(response.data, { url: url }).window;
 
   [...window.document.getElementsByTagName("a")].forEach((link) => {
     link.href = generateProxyUrl(requestUrl, link.href, engine);
   });
 
-  // maybe implement image proxy?
-
   if (engine) {
     return engines[engine](window);
   }

src/handlers/readability.ts

@@ -9,7 +9,7 @@ export default async function readability(
   const parsed = reader.parse();
 
   if (!parsed) {
-    throw new Error("Failed to parse [readability]");
+    throw new EngineParseError("Failed to parse [readability]");
   }
 
   return {

src/routes/get.ts

@@ -4,34 +4,39 @@ import { GetRequest } from "../types/requests";
 import handlePage from "../handlers/main";
 import { generateRequestUrl } from "../utils";
 
+import { NotHtmlMimetypeError } from "../errors";
+
 export default async function getRoute(fastify: FastifyInstance) {
   fastify.get("/get", async (request: GetRequest, reply) => {
     const remoteUrl = request.query.url;
     const engine = request.query.engine;
 
-    let format: string;
+    let parsed;
+    try {
+      parsed = await handlePage(
+        remoteUrl,
+        generateRequestUrl(
+          request.protocol,
+          request.hostname,
+          request.originalUrl
+        ),
+        engine
+      );
+    }
+    catch (err) {
+      if (err instanceof NotHtmlMimetypeError) {
+        return reply.redirect(301, remoteUrl);
+      }
+      else {
+        throw err;
+      }
+    }
 
     if (request.query.format === "text") {
       reply.type("text/plain; charset=utf-8");
-      format = "text";
-    } else {
-      reply.type("text/html; charset=utf-8");
-      format = "html";
-    }
-
-    const parsed = await handlePage(
-      remoteUrl,
-      generateRequestUrl(
-        request.protocol,
-        request.hostname,
-        request.originalUrl
-      ),
-      engine
-    );
-
-    if (format === "text") {
       return parsed.textContent;
     } else {
+      reply.type("text/html; charset=utf-8");
       return reply.view("/templates/get.ejs", { parsed: parsed });
     }
   });