[Tools] adding introspect tools to extract remote schema from existing GraphQL endpoints

package.json

@@ -20,6 +20,7 @@
   "name": "hydra",
   "dependencies": {
     "@graphql-tools/schema": "^10.0.0",
+    "graphql": "^16.8.1",
     "graphql-yoga": "^5.0.0",
     "itty-durable": "^2.1.0",
     "jest": "^29.7.0",

packages/core/src/utils/introspect.ts

@@ -0,0 +1,86 @@
+import fetch from "node-fetch";
+import { getIntrospectionQuery, buildClientSchema, printSchema } from "graphql";
+const fs = require("fs");
+
+interface IntrospectionResponse {
+  data?: {
+    __schema: any; // This should be a more specific type representing the introspected schema
+  };
+}
+
+async function introspectRemoteSchema(endpointUrl: string) {
+  try {
+    // Send an introspection query to the GraphQL endpoint
+    const response = await fetch(endpointUrl, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify({ query: getIntrospectionQuery() }),
+    });
+
+    if (!response.ok) {
+      throw new Error(
+        `Failed to fetch introspection query: ${response.status}`,
+      );
+    }
+
+    // Parse response as JSON
+    const introspectionResult: IntrospectionResponse = await response.json();
+
+    // Check for network-related errors
+    if (!introspectionResult || !introspectionResult.data) {
+      throw new Error("Invalid introspection result");
+    }
+
+    // Build a client schema from the introspection result
+    const clientSchema = buildClientSchema(introspectionResult.data);
+    const schemaString = printSchema(clientSchema);
+
+    // Create a multi-line string enclosed within backticks
+    return `${schemaString}`;
+  } catch (error) {
+    console.error(`Error: ${error.message}`);
+    return null; // Return null or handle the error appropriately
+  }
+}
+
+/**
+ *
+ * @param schemas - remote GraphQL schemas to introspect, typically from hydra.config.ts
+ * @param outputPath - path to write the introspected schemas to
+ */
+export const buildSchemaIntrospection = async (
+  schemas: { id: string; uri: string }[],
+  outputPath: string,
+) => {
+  let schemaWithIntrospection = [];
+
+  for (const schema of schemas) {
+    const introspected = await introspectRemoteSchema(schema.uri);
+    const output = {
+      name: schema.id,
+      url: schema.uri,
+      introspected,
+    };
+    schemaWithIntrospection.push(output);
+  }
+
+  const exportStatements = schemaWithIntrospection.map(
+    (s) =>
+      `export const ${s.name} = {
+        name: "${s.name}",
+        url: "${s.url}",
+        introspected: ${JSON.stringify(s.introspected, null, 2)}
+      };`,
+  );
+
+  const fileContent = `${exportStatements.join("\n")}\n`;
+
+  try {
+    fs.writeFileSync(outputPath, fileContent);
+    console.log(`${outputPath} written`);
+  } catch (err) {
+    console.error(err);
+  }
+};