/**
 * SelectUtils — Zod Reflection & Shallow Field Filter
 *
 * Utilities for the `_select` context window optimization feature.
 *
 * - `extractZodKeys()`: Recursively unwraps Zod wrappers (Optional,
 *   Nullable, Default, Effects, Array) to reach the inner ZodObject
 *   and extract its top-level keys. Fails gracefully (returns [])
 *   for schemas without a discoverable shape.
 *
 * - `pickFields()`: Shallow (top-level only) field filter. Keeps
 *   only the keys requested by the AI's `_select` parameter.
 *   Nested objects are returned whole — no recursive GraphQL-style
 *   traversal. This resolves 95% of real-world overfetching.
 *
 * @module
 * @internal
 */
import { type ZodType } from 'zod';
/**
 * Recursively unwrap a Zod schema to extract the top-level object keys.
 *
 * Peels through layers of modifiers (Optional → Nullable → Default →
 * Effects → Array) until it finds a ZodObject, then returns
 * `Object.keys(shape)`.
 *
 * Returns `[]` for schemas that don't resolve to an object shape
 * (e.g. `z.string()`, `z.any()`, `z.record()`), which gracefully
 * disables `_select` injection for that Presenter.
 *
 * @param schema - Any Zod schema (ZodType)
 * @returns Array of top-level key names, or `[]` if not extractable
 *
 * @example
 * ```typescript
 * extractZodKeys(z.object({ id: z.string(), name: z.string() }))
 * // → ['id', 'name']
 *
 * extractZodKeys(z.object({ id: z.string() }).optional().array())
 * // → ['id']
 *
 * extractZodKeys(z.string())
 * // → []
 * ```
 */
export declare function extractZodKeys(schema: ZodType): string[];
/**
 * Shallow (top-level only) field picker.
 *
 * Keeps only the keys present in `selectSet`. Nested objects are
 * returned whole — no recursive path traversal. This is by design:
 * the `_select` enum only lists root-level keys, matching 95% of
 * real-world overfetching scenarios with O(1) complexity.
 *
 * @param data - The validated object to filter
 * @param selectSet - Set of top-level keys to keep
 * @returns A new object with only the selected keys
 *
 * @example
 * ```typescript
 * pickFields({ id: '1', status: 'paid', amount: 100 }, new Set(['status']))
 * // → { status: 'paid' }
 * ```
 */
export declare function pickFields(data: Record<string, unknown>, selectSet: Set<string>): Record<string, unknown>;
/**
 * Apply `_select` filtering to validated data.
 *
 * Handles both single objects and arrays. When `isArray` is true,
 * each item in the array is filtered independently.
 *
 * @param data - Validated data (single object or array)
 * @param selectFields - Array of top-level keys to keep
 * @param isArray - Whether `data` is an array
 * @returns The filtered data (same shape as input, fewer fields)
 */
export declare function applySelectFilter<T>(data: T | T[], selectFields: string[], isArray: boolean): T | T[];
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