From b9d570ba45f5c4b68251fd10f211060d8c5a7ecd Mon Sep 17 00:00:00 2001
From: Dan Ditomaso <dan.ditomaso@gmail.com>
Date: Fri, 22 Aug 2025 12:12:38 -0400
Subject: [PATCH] added feature flag system

---
 packages/web/src/App.tsx                      |  3 +-
 packages/web/src/components/UI/Footer.tsx     | 17 +++-
 .../web/src/core/hooks/useFeatureFlags.ts     | 22 +++++
 .../web/src/core/services/dev-overrides.ts    | 13 +++
 .../web/src/core/services/featureFlags.ts     | 83 +++++++++++++++++++
 5 files changed, 135 insertions(+), 3 deletions(-)
 create mode 100644 packages/web/src/core/hooks/useFeatureFlags.ts
 create mode 100644 packages/web/src/core/services/dev-overrides.ts
 create mode 100644 packages/web/src/core/services/featureFlags.ts

diff --git a/packages/web/src/App.tsx b/packages/web/src/App.tsx
index e56d391e..12cfca58 100644
--- a/packages/web/src/App.tsx
+++ b/packages/web/src/App.tsx
@@ -12,6 +12,8 @@ import { Outlet } from "@tanstack/react-router";
 import { TanStackRouterDevtools } from "@tanstack/react-router-devtools";
 import { ErrorBoundary } from "react-error-boundary";
 import { MapProvider } from "react-map-gl/maplibre";
+// Import feature flags and dev overrides
+import "@core/services/dev-overrides.ts";
 
 export function App() {
   const { getDevice } = useDeviceStore();
@@ -31,7 +33,6 @@ export function App() {
           setConnectDialogOpen(open);
         }}
       />
-      {/* <Toaster /> */}
       <TanStackRouterDevtools position="bottom-right" />
       <DeviceWrapper device={device}>
         <div
diff --git a/packages/web/src/components/UI/Footer.tsx b/packages/web/src/components/UI/Footer.tsx
index 552e6c49..4bd3c829 100644
--- a/packages/web/src/components/UI/Footer.tsx
+++ b/packages/web/src/components/UI/Footer.tsx
@@ -1,4 +1,5 @@
 import { cn } from "@core/utils/cn.ts";
+import React from "react";
 import { Trans } from "react-i18next";
 
 type FooterProps = {
@@ -6,6 +7,18 @@ type FooterProps = {
 };
 
 const Footer = ({ className, ...props }: FooterProps) => {
+  const version = React.useMemo(
+    () => String(import.meta.env.VITE_VERSION)?.toUpperCase() || "",
+    [],
+  );
+  const commitHash = React.useMemo(
+    () =>
+      String(import.meta.env.VITE_COMMIT_HASH)
+        ?.toUpperCase()
+        .slice(0, 7) || "unk",
+    [],
+  );
+
   return (
     <footer
       className={cn(
@@ -16,13 +29,13 @@ const Footer = ({ className, ...props }: FooterProps) => {
     >
       <div className="px-2">
         <span className="font-semibold text-gray-500/40 dark:text-gray-400/40">
-          {String(import.meta.env.VITE_VERSION)?.toUpperCase()}
+          {version}
         </span>
         <span className="font-semibold text-gray-500/40 dark:text-gray-400/40 mx-2">
           -
         </span>
         <span className="font-semibold text-gray-500/40 dark:text-gray-400/40">
-          {`#${String(import.meta.env.VITE_COMMIT_HASH)?.toUpperCase()}`}
+          {`#${commitHash}`}
         </span>
       </div>
       <p className="ml-auto mr-auto text-gray-500 dark:text-gray-400">
diff --git a/packages/web/src/core/hooks/useFeatureFlags.ts b/packages/web/src/core/hooks/useFeatureFlags.ts
new file mode 100644
index 00000000..b67b3c9a
--- /dev/null
+++ b/packages/web/src/core/hooks/useFeatureFlags.ts
@@ -0,0 +1,22 @@
+import {
+  type FlagKey,
+  type Flags,
+  featureFlags,
+} from "@core/services/featureFlags.ts";
+import * as React from "react";
+
+export function useFeatureFlags(): Flags {
+  return React.useSyncExternalStore(
+    (cb) => featureFlags.subscribe(cb),
+    () => featureFlags.all(),
+    () => featureFlags.all(),
+  );
+}
+
+export function useFeatureFlag(key: FlagKey): boolean {
+  return React.useSyncExternalStore(
+    (cb) => featureFlags.subscribe(cb),
+    () => featureFlags.get(key),
+    () => featureFlags.get(key),
+  );
+}
diff --git a/packages/web/src/core/services/dev-overrides.ts b/packages/web/src/core/services/dev-overrides.ts
new file mode 100644
index 00000000..d553b3aa
--- /dev/null
+++ b/packages/web/src/core/services/dev-overrides.ts
@@ -0,0 +1,13 @@
+import { featureFlags } from "@core/services/featureFlags";
+
+const isDev =
+  (typeof import.meta !== "undefined" && import.meta.env?.DEV) ||
+  (typeof process !== "undefined" &&
+    (process.env.mode === "development" ||
+      process.env.NODE_ENV === "development"));
+
+if (isDev) {
+  featureFlags.setOverrides({
+    persistNodeDB: true,
+  });
+}
diff --git a/packages/web/src/core/services/featureFlags.ts b/packages/web/src/core/services/featureFlags.ts
new file mode 100644
index 00000000..5a66db8d
--- /dev/null
+++ b/packages/web/src/core/services/featureFlags.ts
@@ -0,0 +1,83 @@
+import { z } from "zod";
+
+/** Map feature keys -> env var names (Vite exposes only VITE_*). */
+export const FLAG_ENV = {
+  persistNodeDB: "VITE_PERSIST_NODE_DB",
+  persistMessages: "VITE_PERSIST_MESSAGES",
+} as const;
+
+export type FlagKey = keyof typeof FLAG_ENV;
+export type Flags = Record<FlagKey, boolean>;
+
+type Listener = () => void;
+
+const present = z
+  .string()
+  .optional()
+  .transform((v) => v !== undefined);
+
+const mutableShape: Record<string, z.ZodTypeAny> = {};
+for (const envName of Object.values(FLAG_ENV)) {
+  mutableShape[envName] = present;
+}
+const EnvSchema = z.object(mutableShape);
+
+class FeatureFlags {
+  private base: Flags;
+  private overrides: Partial<Flags> = {};
+  private listeners = new Set<Listener>();
+
+  constructor(base: Flags) {
+    this.base = base;
+  }
+
+  get(key: FlagKey): boolean {
+    return this.overrides[key] ?? this.base[key];
+  }
+
+  /** Get all flags */
+  all(): Flags {
+    return { ...this.base, ...this.overrides };
+  }
+
+  /** Optional dev/test override. Pass null to clear. */
+  setOverride(key: FlagKey, val: boolean | null) {
+    if (val === null) {
+      delete this.overrides[key];
+    } else {
+      this.overrides[key] = val;
+    }
+    this.emit();
+  }
+
+  /** Set many at once */
+  setOverrides(partial: Partial<Flags>) {
+    for (const [k, v] of Object.entries(partial)) {
+      this.setOverride(k as FlagKey, v as boolean);
+    }
+  }
+
+  subscribe(fn: Listener) {
+    this.listeners.add(fn);
+    return () => this.listeners.delete(fn);
+  }
+
+  private emit() {
+    for (const listener of this.listeners) {
+      listener();
+    }
+  }
+}
+
+export function createFeatureFlags(env: Record<string, unknown>): FeatureFlags {
+  const parsed = EnvSchema.parse(env);
+  const base = Object.fromEntries(
+    (Object.keys(FLAG_ENV) as FlagKey[]).map((k) => [
+      k,
+      parsed[FLAG_ENV[k]] as boolean,
+    ]),
+  ) as Flags;
+  return new FeatureFlags(base);
+}
+
+export const featureFlags = createFeatureFlags(import.meta.env);