fix: edge function should not operate if not targeting definition fil…

…es (#2543)

README.md

@@ -162,7 +162,32 @@ All AsyncAPI JSON Schema definition files are being served within the `/definiti
 This is possible thanks to the following:
 
 1. A [Netlify Rewrite rule](https://docs.netlify.com/routing/redirects/rewrites-proxies/) located in the [netlify.toml](netlify.toml) file, which acts as proxy for all requests to the `/definitions/<file>` path, serving the content from GH without having an HTTP redirect.
-2. A [Netlify Edge Function](https://docs.netlify.com/netlify-labs/experimental-features/edge-functions/) that modifies the `Content-Type` header of the rewrite response to become `application/schema+json`. This lets tooling, such as [Hyperjump](https://json-schema.hyperjump.io), to fetch the schemas directly from their URL.
+2. A [Netlify Edge Function](https://docs.netlify.com/netlify-labs/experimental-features/edge-functions/) that modifies the `Content-Type` header of the rewrite response to become `application/schema+json`. This lets tooling, such as [Hyperjump](https://json-schema.hyperjump.io), to fetch the schemas directly from their URL.  
+  Please find a flowchart explaining the flow this edge function should accomplish:
+  ```mermaid
+  flowchart TD
+    Request(Request) -->schema-related{Is it requesting Schemas?}
+    schema-related -->|No| req_no_schemas[Let the original request go through]
+    req_no_schemas --> Response(Response)
+    schema-related -->|Yes| req_schemas[Fetch from GitHub]
+    req_schemas-->req_json{Was requesting a .json file?}
+    
+    req_json -->|No| Response(Response)
+    req_json -->|Yes| response_status{Response Status?}
+    
+    response_status -->|2xx| response_ok[OK]
+    response_status -->|304| response_cached[Not Modified]
+    response_status -->|Any other| response_ko
+
+    response_ok --> set_headers[Set Response Content-Type header to application/schema+json]
+    set_headers --> send_metric_success[Send success metric]
+    response_cached -- cached:true --> send_metric_success
+    response_ko --> send_metric_error[Send error metric]
+
+    send_metric_success -- file served from raw GH --> Response(Response)
+    send_metric_error --the errored response --> Response(Response)
+  ```
+   
 
 ## Project structure
 

netlify/edge-functions/serve-definitions.ts

@@ -7,28 +7,27 @@ const NR_METRICS_ENDPOINT = Deno.env.get("NR_METRICS_ENDPOINT") || "https://metr
 const URL_DEST_SCHEMAS = "https://raw.githubusercontent.com/asyncapi/spec-json-schemas/master/schemas";
 const URL_DEST_DEFINITIONS = "https://raw.githubusercontent.com/asyncapi/spec-json-schemas/master/definitions";
 
-// Legitimate request:
+// Schemas-related request:
 //   Patterns: /<source> OR /<source>/<file> OR /<source>/<version>/<file>
 //   Examples: /definitions OR /schema-store/2.5.0-without-$id.json OR /definitions/2.4.0/info.json
-// Non-legitimate request:
+// Schemas-unrelated request:
 //   Patterns: /<source>/<randompath>/*
 //   Examples: /definitions/asyncapi.yaml OR /schema-store/2.4.0.JSON (uppercase)
 //
-// Non-legitimate requests should not use our GitHub Token and affect the rate limit. Those shouldn't send metrics to NR either as they just add noise.
-const legitimateRequestRegex = /^\/[\w\-]*\/?(?:([\w\-\.]*\/)?([\w\-$%\.]*\.json))?$/
+// Schemas-unrelated requests should not use our GitHub Token and affect the rate limit. Those shouldn't send metrics to NR either as they just add noise.
+const SchemasRelatedRequestRegex = /^\/[\w\-]*\/?(?:([\w\-\.]*\/)?([\w\-$%\.]*\.json))?$/
 
 export default async (request: Request, context: Context) => {
   let rewriteRequest = buildRewrite(request);
   let response: Response;
   if (rewriteRequest === null) {
-    rewriteRequest = request;
-
-    response = await context.next();
-  } else {
-    // Fetching the definition file
-    response = await fetch(rewriteRequest);
+    // This is a Schema-unrelated request. Let it go through and do not intercept it.
+    return await context.next();
   }
 
+  // Fetching the definition file
+  response = await fetch(rewriteRequest);
+
   const isRequestingAFile = request.url.endsWith('.json');
   if (isRequestingAFile) {
     var metricName: string
@@ -56,6 +55,7 @@ export default async (request: Request, context: Context) => {
         default:
           // Notifying NR of the error.
           metricName = "asyncapi.jsonschema.download.error";
+          console.log("Error downloading JSON Schema file: " + response.status + " " + response.statusText);
           break;
       }
     }
@@ -68,7 +68,7 @@ export default async (request: Request, context: Context) => {
 };
 
 function buildRewrite(originalRequest: Request): (Request | null) {
-  const extractResult = legitimateRequestRegex.exec(new URL(originalRequest.url).pathname);
+  const extractResult = SchemasRelatedRequestRegex.exec(new URL(originalRequest.url).pathname);
   if (extractResult === null) {
     return null;
   }