feat: add LaunchDarkly integration

Author: WitoDelnat

package-lock.json

@@ -33,13 +33,15 @@
   },
   "devDependencies": {
     "@types/react": "18.0.9",
+    "launchdarkly-js-client-sdk": "3.1.0",
     "react": "18.1.0",
     "react-dom": "18.1.0",
     "rimraf": "3.0.2",
     "typescript": "4.9.4",
     "vitest": "0.12.6"
   },
   "peerDependencies": {
+    "launchdarkly-js-client-sdk": "^3.0",
     "react": "^18.0 || ^17.0 || ^16.0",
     "react-dom": "^18.0 || ^17.0 || ^16.0"
   },
@@ -49,6 +51,9 @@
     },
     "react-dom": {
       "optional": true
+    },
+    "launchdarkly-js-client-sdk": {
+      "optional": true
     }
   }
 }

package.json

@@ -74,7 +74,13 @@ export function keatCore<TFeatures extends AnyFeatures>({
     if (!rules) return variates[variates.length - 1];
 
     let result: unknown;
-    let ctx: EvalCtx = { feature, variates, rules, user, configId };
+    let ctx: EvalCtx = {
+      feature,
+      variates,
+      rules,
+      user,
+      configId,
+    };
 
     const preApi: OnEvalApi = {
       setUser: (newUser) => {
@@ -84,11 +90,10 @@ export function keatCore<TFeatures extends AnyFeatures>({
 
     plugins.forEach((p) => p.onPreEvaluate?.(ctx, preApi));
 
-
     for (let i = 0; i < variates.length; i++) {
       const variate = variates[i];
       const rule = rules[i];
-      const ok = evaluateVariate(ctx, plugins, rule);
+      const ok = evaluateVariate({ ...ctx, variate }, plugins, rule);
 
       if (ok) {
         result = variate;
@@ -108,7 +113,10 @@ export function keatCore<TFeatures extends AnyFeatures>({
 
   return {
     ready: (display: Display = defaultDisplay) => loader.ready(display),
-    setUser: (user?: User) => (defaultUser = user),
+    identify: (user?: User) => {
+      defaultUser = user;
+      plugins.forEach(p => p.onIdentify)
+    },
     setDisplay: (display: Display) => (defaultDisplay = display),
     variation: <TFeature extends keyof TFeatures>(
       feature: TFeature,

src/core/keat.ts

@@ -28,10 +28,19 @@ export type OnPluginInitApi = {
   onChange: () => void;
 };
 
+export type OnPluginIdentifyHook = (
+  ctx: OnPluginIdentifyCtx
+) => void | Promise<void>;
+
+export type OnPluginIdentifyCtx = {
+  user?: User;
+};
+
 export type onPreEvaluateHook = (ctx: EvalCtx, api: OnEvalApi) => void;
 
 export type EvalCtx = {
   feature: string;
+  variate?: any;
   variates: any[];
   rules: Rule[];
   user: User | undefined;
@@ -57,6 +66,11 @@ export type Plugin<M extends Matcher = Matcher> = {
    */
   onPluginInit?: OnPluginInitHook;
 
+  /**
+   * Invoked when a user is identifier.
+   */
+  onIdentify?: OnPluginIdentifyHook;
+
   /**
    * Whether a literal matches this plugin.
    */
@@ -93,6 +107,10 @@ export function createNopPlugin(): Plugin {
   };
 }
 
+export const isAny: Matcher<any> = (literal) => {
+  return literal;
+};
+
 export const isBoolean: Matcher<boolean> = (literal) => {
   return typeof literal === "boolean" ? literal : null;
 };

src/core/plugin.ts

@@ -29,9 +29,7 @@ export type IdentityFn = (user: User) => string;
 export type Display = "block" | "swap" | "fallback" | "optional";
 
 export type Literal = boolean | string | number;
-export type Rule =
-  | { OR: readonly Rule[] }
-  | Literal;
+export type Rule = { OR: readonly Rule[] } | Literal;
 
 export type Feature =
   | Rule
@@ -54,7 +52,7 @@ export type KeatInit<TFeatures extends AnyFeatures> = {
 
 export type KeatApi<TFeatures extends AnyFeatures> = {
   ready(display?: Display): Promise<void>;
-  setUser(user?: User): void;
+  identify(user?: User): void;
   setDisplay(display: Display): void;
   variation<TFeature extends keyof TFeatures>(
     feature: TFeature,

src/core/types.ts

@@ -0,0 +1,63 @@
+import {
+  initialize,
+  LDClient,
+  LDContext,
+  LDFlagChangeset,
+  LDFlagSet,
+} from "launchdarkly-js-client-sdk";
+import { isAny, Plugin } from "../core/plugin";
+
+type LaunchDarklyPluginOptions = {
+  clientId: string;
+};
+
+export const remoteConfig = (options: LaunchDarklyPluginOptions): Plugin => {
+  let client: LDClient;
+  let flags: LDFlagSet = {};
+
+  return {
+    onPluginInit: async (_ctx, { onChange }) => {
+      client = initialize(options.clientId, {
+        anonymous: true,
+        kind: "user",
+      });
+
+      return new Promise<void>((r) => {
+        function cleanup() {
+          client.off("ready", handleReady);
+          client.off("failed", handleFailure);
+        }
+        function handleFailure() {
+          cleanup();
+          r();
+        }
+        function handleReady() {
+          cleanup();
+          flags = client.allFlags();
+          r();
+        }
+        client.on("failed", handleFailure);
+        client.on("ready", handleReady);
+
+        client.on("change", (changes: LDFlagChangeset) => {
+          for (const [flag, { current }] of Object.entries(changes)) {
+            flags[flag] = current;
+          }
+          onChange();
+        });
+      });
+    },
+    onIdentify({ user }) {
+      const context: LDContext = {
+        kind: "user",
+        key: user?.id ?? user?.sub ?? user?.email,
+        ...user,
+      };
+      client.identify(context);
+    },
+    matcher: isAny,
+    evaluate({ feature, variate }) {
+      return flags[feature] === variate;
+    },
+  };
+};