/**
 * FHIRPath Sandbox (P-3)
 *
 * Static safety pre-flight for user-defined FHIRPath expressions
 * (Custom Rules). fhirpath.js is synchronous and cannot be hard-timed
 * out from the calling thread without a worker, so the only reliable
 * defence against a pathological customer-supplied expression is to
 * reject it before it runs.
 *
 * The sandbox enforces three bounds:
 *
 *   - **expressionLength**: total characters. Defaults to 4096.
 *   - **functionCallCount**: total `name(...)` invocations. Defaults
 *     to 64.
 *   - **nestingDepth**: maximum parenthesis depth. Defaults to 16.
 *
 * The bounds are deliberately generous for legitimate validation
 * expressions (the largest core constraints in HL7's FHIR shipped
 * package — `dom-2`/`dom-3`/`dom-4`/`dom-5`/`dom-6` plus the
 * `compliesWith` family — sit comfortably under all three limits) but
 * tight enough to reject the common DoS shapes: unbounded `repeat()`
 * recursion, deeply-nested `where(where(where(...)))`, and
 * megabyte-sized regex strings inside `matches()`.
 *
 * Runs in microseconds — single linear pass over the expression
 * string, no fhirpath parser involvement, no `eval`.
 */
export interface SandboxLimits {
    /** Maximum total characters in the expression. */
    expressionLength?: number;
    /** Maximum number of `name(...)` function calls. */
    functionCallCount?: number;
    /** Maximum parenthesis nesting depth. */
    nestingDepth?: number;
}
export interface SandboxResult {
    /** True when every limit was respected. */
    ok: boolean;
    /** Human-readable rejection reason when `ok` is false. */
    reason?: string;
    /** Measured metrics — exposed for ops dashboards / logging. */
    metrics: {
        expressionLength: number;
        functionCallCount: number;
        nestingDepth: number;
    };
}
/**
 * Statically analyse a FHIRPath expression string against the
 * configured limits.
 *
 * The function-call detector counts identifiers immediately followed
 * by `(`. This catches both built-ins (`where(`, `exists(`,
 * `iif(`, `repeat(`) and user-defined names — the customer's intent
 * doesn't matter; what matters is that an expression with hundreds of
 * `where(...)` calls is treated as suspicious regardless.
 *
 * Identifiers inside string literals are not counted. The walk skips
 * single- and double-quoted spans (with backslash escape handling)
 * because a regex argument like `matches('a(b|c)+d')` should not
 * inflate the function-call count.
 */
export declare function checkFhirpathSandbox(expression: string, limits?: SandboxLimits): SandboxResult;
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