import { getDatabase } from '@happyvertical/sql';
type DatabaseInterface = Awaited<ReturnType<typeof getDatabase>>;
export declare const USER_EMAIL_KEY_BACKFILL_NAME = "@happyvertical/smrt-users:user-email-keys:v1";
export interface DuplicateUserEmailKey {
    emailKey: string;
    userCount: number;
}
export interface BackfillUserEmailKeysResult {
    updated: number;
}
export type UserEmailKeyBackfillErrorCode = 'duplicate_email' | 'transaction_required';
/**
 * Raised before any rows are changed when legacy User emails are ambiguous.
 */
export declare class UserEmailKeyBackfillError extends Error {
    readonly code: UserEmailKeyBackfillErrorCode;
    readonly duplicates: DuplicateUserEmailKey[];
    constructor(code: UserEmailKeyBackfillErrorCode, message: string, duplicates?: DuplicateUserEmailKey[]);
}
/**
 * Populate the durable normalized-email key for Users created before the
 * `emailKey` field existed.
 *
 * Apply the schema migration first, stop or upgrade legacy writers, then call
 * this once from a single deploy process. The operation is idempotent. It
 * fails before changing any rows when two non-blank emails normalize to the
 * same key, so operators can reconcile those Users explicitly.
 */
export declare function backfillUserEmailKeys(db: DatabaseInterface): Promise<BackfillUserEmailKeysResult>;
export {};
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