feat: changed backend-pg to backend

backend/src/lib/fn/array.ts

@@ -0,0 +1,40 @@
+/**
+ * Sorts an array of items into groups. The return value is a map where the keys are
+ * the group ids the given getGroupId function produced and the value is an array of
+ * each item in that group.
+ */
+export const groupBy = <T, Key extends string | number | symbol>(
+  array: readonly T[],
+  getGroupId: (item: T) => Key
+): Record<Key, T[]> =>
+  array.reduce(
+    (acc, item) => {
+      const groupId = getGroupId(item);
+      if (!acc[groupId]) acc[groupId] = [];
+      acc[groupId].push(item);
+      return acc;
+    },
+    {} as Record<Key, T[]>
+  );
+
+/**
+ * Given a list of items returns a new list with only
+ * unique items. Accepts an optional identity function
+ * to convert each item in the list to a comparable identity
+ * value
+ */
+export const unique = <T, K extends string | number | symbol>(
+  array: readonly T[],
+  toKey?: (item: T) => K
+): T[] => {
+  const valueMap = array.reduce(
+    (acc, item) => {
+      const key = toKey ? toKey(item) : (item as any as string | number | symbol);
+      if (acc[key]) return acc;
+      acc[key] = item;
+      return acc;
+    },
+    {} as Record<string | number | symbol, T>
+  );
+  return Object.values(valueMap);
+};