Function updateInDeeply

src/functional/updateIn.ts:129–180

(
  inImmutable: boolean,
  existing: C,
  keyPath: Array<K>,
  i: number,
  notSetValue: NSV | undefined,
  updater: UpdaterFunctionWithNSV<K, C, NSV> | UpdaterFunction<K, C>
)

}

function updateInDeeply<
  K,
  TProps extends object,
  C extends PossibleCollection<unknown, unknown, TProps>,
  NSV,
>(
  inImmutable: boolean,
  existing: C,
  keyPath: Array<K>,
  i: number,
  notSetValue: NSV | undefined,
  updater: UpdaterFunctionWithNSV<K, C, NSV> | UpdaterFunction<K, C>
): C {
  const wasNotSet = existing === NOT_SET;
  if (i === keyPath.length) {
    const existingValue = wasNotSet ? notSetValue : existing;
    // @ts-expect-error mixed type with optional value
    const newValue = updater(existingValue);
    // @ts-expect-error mixed type
    return newValue === existingValue ? existing : newValue;
  }
  if (!wasNotSet && !isDataStructure(existing)) {
    throw new TypeError(
      'Cannot update within non-data-structure value in path [' +
        Array.from(keyPath).slice(0, i).map(quoteString) +
        ']: ' +
        existing
    );
  }
  const key = keyPath[i];

  const nextExisting = wasNotSet ? NOT_SET : get(existing, key, NOT_SET);
  const nextUpdated = updateInDeeply(
    nextExisting === NOT_SET ? inImmutable : isImmutable(nextExisting),
    // @ts-expect-error mixed type
    nextExisting,
    keyPath,
    i + 1,
    notSetValue,
    updater
  );

  return nextUpdated === nextExisting
    ? existing
    : nextUpdated === NOT_SET
      ? remove(existing, key)
      : set(
          wasNotSet ? (inImmutable ? emptyMap() : {}) : existing,
          key,
          nextUpdated
        );
}