Move legacy functions into separate utils file

app/soapbox/utils/legacy.ts

@@ -0,0 +1,68 @@
+import { default as lodashGet } from 'lodash/get';
+
+interface LegacyMap {
+  get(key: any): unknown
+  getIn(keyPath: any[]): unknown
+  toJS(): any
+}
+
+interface LegacyStore<T> extends LegacyMap {
+  get(key: any): T & LegacyMap | undefined
+  getIn(keyPath: any[]): unknown
+  find(predicate: (value: T & LegacyMap, key: string) => boolean): T & LegacyMap | undefined
+  filter(predicate: (value: T & LegacyMap, key: string) => boolean): (T & LegacyMap)[]
+}
+
+function immutableizeEntity<T extends Record<any, any>>(entity: T): T & LegacyMap {
+  return {
+    ...entity,
+
+    get(key: any): unknown {
+      return entity[key];
+    },
+
+    getIn(keyPath: any[]): unknown {
+      return lodashGet(entity, keyPath);
+    },
+
+    toJS() {
+      return entity;
+    },
+  };
+}
+
+function immutableizeStore<T, S extends Record<string, T | undefined>>(state: S): S & LegacyStore<T> {
+  return {
+    ...state,
+
+    get(id: any): T & LegacyMap | undefined {
+      const entity = state[id];
+      return entity ? immutableizeEntity(entity) : undefined;
+    },
+
+    getIn(keyPath: any[]): unknown {
+      return lodashGet(state, keyPath);
+    },
+
+    find(predicate: (value: T & LegacyMap, key: string) => boolean): T & LegacyMap | undefined {
+      const result = Object.entries(state).find(([key, value]) => value && predicate(immutableizeEntity(value), key))?.[1];
+      return result ? immutableizeEntity(result) : undefined;
+    },
+
+    filter(predicate: (value: T & LegacyMap, key: string) => boolean): (T & LegacyMap)[] {
+      return Object.entries(state).filter(([key, value]) => value && predicate(immutableizeEntity(value), key)).map(([key, value]) => immutableizeEntity(value!));
+    },
+
+    toJS() {
+      return state;
+    },
+  };
+}
+
+
+export {
+  immutableizeStore,
+  immutableizeEntity,
+  type LegacyMap,
+  type LegacyStore,
+};