@ai-sdk/provider-utils/src/to-json-schema/zod3-to-json-schema/parsers/native-enum.ts

import type { ZodNativeEnumDef } from 'zod/v3';

export type JsonSchema7NativeEnumType = {
  type: 'string' | 'number' | ['string', 'number'];
  enum: (string | number)[];
};

export function parseNativeEnumDef(
  def: ZodNativeEnumDef,
): JsonSchema7NativeEnumType {
  const object = def.values;
  const actualKeys = Object.keys(def.values).filter((key: string) => {
    return typeof object[object[key]] !== 'number';
  });

  const actualValues = actualKeys.map((key: string) => object[key]);

  const parsedTypes = Array.from(
    new Set(actualValues.map((values: string | number) => typeof values)),
  );

  return {
    type:
      parsedTypes.length === 1
        ? parsedTypes[0] === 'string'
          ? 'string'
          : 'number'
        : ['string', 'number'],
    enum: actualValues,
  };
}