Merge pull request #26 from kakasoo/kakasoo/deep-strict-flat

feat: add deepStrictPick runtime function

Author: kakasoo

src/functions/DeepStrictAssert.ts

@@ -10,6 +10,8 @@ import { DeepStrictPick } from '../types/DeepStrictPick';
  *
  * This is the runtime counterpart of the {@link DeepStrictPick} type.
  *
+ * @deprecated Use {@link deepStrictPick} instead. This curried form will be removed in a future version.
+ *
  * @template T - The object type of the input
  * @param input - The source object to extract properties from
  * @returns A function that accepts a key path `K` and returns the deeply-picked result

src/functions/DeepStrictPick.ts

@@ -0,0 +1,60 @@
+import { DeepStrictObjectKeys } from '../types/DeepStrictObjectKeys';
+import { DeepStrictPick } from '../types/DeepStrictPick';
+
+/**
+ * @title Runtime Function for Type-Safe Deep Property Picking.
+ *
+ * Takes an object and a dot-notation key path, and returns a new object
+ * containing only the specified nested property, preserving the original structure.
+ *
+ * This is the runtime counterpart of the {@link DeepStrictPick} type.
+ *
+ * @template T - The object type of the input
+ * @template K - The key path to pick
+ * @param input - The source object to extract properties from
+ * @param key - A dot-notation key path specifying which property to pick
+ * @returns A new object containing only the picked property with its original structure
+ *
+ * @example
+ * ```ts
+ * const result = deepStrictPick({ a: { b: 1, c: 2 } }, 'a.b');
+ * // result: { a: { b: 1 } }
+ * ```
+ */
+export const deepStrictPick = <T extends object, K extends DeepStrictObjectKeys<T>>(
+  input: T,
+  key: K,
+): DeepStrictPick<T, K> => {
+  const keys = key.split(/(?:\[\*\])?\./g).filter(Boolean);
+
+  const traverse = (input: Record<string, any> | Record<string, any>[], keys: string[]): any => {
+    const [first, ...rest] = keys;
+
+    if (input instanceof Array) {
+      const elements = input.map((element) => {
+        if (first in element) {
+          if (typeof element[first] === 'object' && element[first] !== null && rest.length > 0) {
+            return { [first]: traverse(element[first], rest) };
+          }
+
+          return { [first]: element[first] };
+        }
+
+        return element;
+      });
+
+      return elements;
+    } else {
+      if (first in input) {
+        if (typeof input[first] === 'object' && input[first] !== null && rest.length > 0) {
+          return { [first]: traverse(input[first], rest) };
+        }
+        return { [first]: input[first] };
+      }
+
+      throw new Error(`input doesn\'t has key: ${first}`);
+    }
+  };
+
+  return traverse(input, keys) as DeepStrictPick<T, K>;
+};

src/functions/index.ts

@@ -1,2 +1,3 @@
 export * from './DeepStrictAssert';
 export * from './DeepStrictObjectKeys';
+export * from './DeepStrictPick';