/**
 * Schedule expression parsing and next-run-time computation.
 *
 * Supports two formats:
 * - **Interval shorthand**: `"<number><unit>"` where unit is s/m/h/d (min 10s)
 * - **Cron expressions**: Standard 5-field cron syntax via `cron-parser`
 */
/**
 * Parse an interval shorthand expression to milliseconds.
 *
 * @param expr - e.g. "30s", "5m", "1h", "1d"
 * @returns Duration in milliseconds
 * @throws If the expression is invalid or below the minimum (10s)
 */
export declare function parseDuration(expr: string): number;
/**
 * Detect whether an expression is interval shorthand (vs. cron).
 *
 * @param expr - Schedule expression string
 * @returns true if the expression matches interval shorthand format
 */
export declare function isIntervalExpression(expr: string): boolean;
/**
 * Compute the next run time for a schedule expression.
 *
 * For intervals: if `lastRunAt + interval` is in the future, use that (prevents
 * drift). Otherwise use `now + interval` (prevents burst-firing after downtime).
 *
 * For cron: next occurrence after now.
 *
 * @param expr - Schedule expression (interval or cron)
 * @param lastRunAt - ISO timestamp of the last fire (undefined for first fire)
 * @returns ISO timestamp of the next fire
 */
export declare function computeNextRunAt(expr: string, lastRunAt?: string): string;
/**
 * Validate a schedule expression. Throws if invalid.
 *
 * @param expr - Schedule expression to validate
 * @throws If the expression is neither valid interval shorthand nor valid cron
 */
export declare function validateExpression(expr: string): void;
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