/**
 * Generates cartesian product out of input object.
 */
export function* cartesianProductGenerator<T>(
  input: Record<string, T[]> = {},
): Generator<Record<string, T>> {
  const entries = Object.entries(input);
  if (entries.length === 0) return;

  // Use iterative stack-based approach to yield results one at a time
  // This avoids recursion overhead while maintaining lazy evaluation
  const stack: { index: number; partial: Record<string, T> }[] = [
    { index: entries.length - 1, partial: {} },
  ];

  while (stack.length > 0) {
    const item = stack.pop();
    if (!item) break;
    const { index, partial } = item;

    if (index < 0) {
      yield partial;
      continue;
    }

    const [key, values] = entries[index];
    // Push in reverse order so we process in correct order
    for (let i = values.length - 1; i >= 0; i--) {
      stack.push({
        index: index - 1,
        partial: { ...partial, [key]: values[i] },
      });
    }
  }
}