release: WRNexusJS 0.3.0

packages/core/src/features.ts

@@ -0,0 +1,21 @@
+import type { Context } from "./context.ts";
+
+export type FeatureValue = boolean | string | number;
+export type FeatureRule = FeatureValue | ((ctx: Context) => FeatureValue | Promise<FeatureValue>);
+
+export interface FeatureFlags {
+  get(name: string, ctx: Context): Promise<FeatureValue | undefined>;
+  enabled(name: string, ctx: Context): Promise<boolean>;
+}
+
+export function defineFeatureFlags(rules: Record<string, FeatureRule>): FeatureFlags {
+  return {
+    async get(name, ctx) {
+      const rule = rules[name];
+      return typeof rule === "function" ? rule(ctx) : rule;
+    },
+    async enabled(name, ctx) {
+      return (await this.get(name, ctx)) === true;
+    },
+  };
+}