Create LaunchDarkly adapter

packages/adapter-launchdarkly/package.json

@@ -43,7 +43,10 @@
     "test:watch": "vitest",
     "type-check": "tsc --noEmit"
   },
-  "dependencies": {},
+  "dependencies": {
+    "@launchdarkly/vercel-server-sdk": "1.3.21",
+    "@vercel/edge-config": "1.2.0"
+  },
   "devDependencies": {
     "@types/node": "20.11.17",
     "@vercel/flags": "workspace:*",
@@ -56,7 +59,6 @@
     "vite": "5.1.1",
     "vitest": "1.4.0"
   },
-  "peerDependencies": {},
   "publishConfig": {
     "access": "public"
   }

packages/adapter-launchdarkly/src/index.ts

@@ -0,0 +1,60 @@
+import type { Adapter } from '@vercel/flags';
+import { createClient } from '@vercel/edge-config';
+import { init, type LDContext } from '@launchdarkly/vercel-server-sdk';
+
+let defaultLaunchDarklyClient:
+  | ReturnType<typeof createLaunchDarklyAdapter>
+  | undefined;
+
+function assertEnv(name: string): string {
+  const value = process.env[name];
+  if (!value) {
+    throw new Error(
+      `LaunchDarkly Adapter: Missing ${name} environment variable`,
+    );
+  }
+  return value;
+}
+
+export function createLaunchDarklyAdapter({
+  ldProject,
+  ldClientSideKey,
+  edgeConfigConnectionString,
+}: {
+  ldProject: string;
+  ldClientSideKey: string;
+  edgeConfigConnectionString: string;
+}) {
+  const edgeConfigClient = createClient(edgeConfigConnectionString);
+  const ldClient = init(ldClientSideKey, edgeConfigClient);
+
+  return function launchDarklyAdapter<ValueType>(): Adapter<
+    ValueType,
+    LDContext
+  > {
+    return {
+      origin(key) {
+        return `https://app.launchdarkly.com/projects/${ldProject}/flags/${key}/`;
+      },
+      async decide({ key, entities }): Promise<ValueType> {
+        await ldClient.waitForInitialization();
+        return ldClient.variation(key, entities!, undefined) as ValueType;
+      },
+    };
+  };
+}
+
+export function launchDarkly<ValueType>(): Adapter<ValueType, LDContext> {
+  if (!defaultLaunchDarklyClient) {
+    const edgeConfigConnectionString = assertEnv('EDGE_CONFIG');
+    const ldClientSideKey = assertEnv('LD_CLIENT_SIDE_KEY');
+    const ldProject = assertEnv('LD_PROJECT');
+    defaultLaunchDarklyClient = createLaunchDarklyAdapter({
+      ldProject,
+      ldClientSideKey,
+      edgeConfigConnectionString,
+    });
+  }
+
+  return defaultLaunchDarklyClient();
+}