feat: implement FlagStore for centralized flag management

Introduced a new FlagStore module to encapsulate flag management logic.

Author: pranjal-jately-ld

src/FlagStore.js

@@ -0,0 +1,98 @@
+const utils = require('./utils');
+
+function FlagStore() {
+  let flags = {};
+  let flagOverrides;
+
+  function get(key) {
+    // Check overrides first, then real flags
+    if (flagOverrides && utils.objectHasOwnProperty(flagOverrides, key) && flagOverrides[key]) {
+      return flagOverrides[key];
+    }
+
+    if (flags && utils.objectHasOwnProperty(flags, key) && flags[key] && !flags[key].deleted) {
+      return flags[key];
+    }
+
+    return null;
+  }
+
+  function getFlagsWithOverrides() {
+    const result = {};
+
+    // Add all flags first
+    for (const key in flags) {
+      const flag = get(key);
+      if (flag) {
+        result[key] = flag;
+      }
+    }
+
+    // Override with any flagOverrides (they take precedence)
+    if (flagOverrides) {
+      for (const key in flagOverrides) {
+        const override = get(key);
+        if (override) {
+          result[key] = override;
+        }
+      }
+    }
+
+    return result;
+  }
+
+  function setFlags(newFlags) {
+    flags = { ...newFlags };
+  }
+
+  function setOverride(key, value) {
+    if (!flagOverrides) {
+      flagOverrides = {};
+    }
+    flagOverrides[key] = { value };
+  }
+
+  function removeOverride(key) {
+    if (!flagOverrides || !flagOverrides[key]) {
+      return; // No override to remove
+    }
+
+    delete flagOverrides[key];
+
+    // If no more overrides, reset to undefined for performance
+    if (Object.keys(flagOverrides).length === 0) {
+      flagOverrides = undefined;
+    }
+  }
+
+  function clearAllOverrides() {
+    if (!flagOverrides) {
+      return {}; // No overrides to clear, return empty object for consistency
+    }
+
+    const clearedOverrides = { ...flagOverrides };
+    flagOverrides = undefined; // Reset to undefined
+    return clearedOverrides;
+  }
+
+  function getFlags() {
+    return flags;
+  }
+
+  function getFlagOverrides() {
+    return flagOverrides || {};
+  }
+
+  return {
+    clearAllOverrides,
+    get,
+    getFlagOverrides,
+    getFlags,
+    getFlagsWithOverrides,
+    removeOverride,
+    setFlags,
+    setOverride,
+  };
+}
+
+module.exports = FlagStore;