/**
 * JSON serialization helpers for IEmailMetadata.
 *
 * Maps in IEmailMetadata (customHeaders, deliveryReceipts, readReceipts,
 * encryptedKeys) do not survive JSON.stringify/parse. These helpers convert
 * Map fields to/from plain objects so the data round-trips through REST APIs.
 *
 * Server-side: call serializeEmailMetadataForJson before sending responses.
 * Client-side: call deserializeEmailMetadataFromJson after receiving responses.
 */
import type { IDeliveryReceipt } from '../../interfaces/messaging/emailDelivery';
import type { IEmailMetadata } from '../../interfaces/messaging/emailMetadata';
/**
 * JSON-safe representation of IEmailMetadata where Map fields are plain objects.
 * TID defaults to string for frontend DTO usage.
 */
export type IEmailMetadataJson<TID extends string = string> = Omit<IEmailMetadata<TID>, 'customHeaders' | 'deliveryReceipts' | 'readReceipts' | 'encryptedKeys' | 'date'> & {
    customHeaders: Record<string, string[]>;
    deliveryReceipts: Record<string, IDeliveryReceipt<TID>>;
    readReceipts: Record<string, string>;
    encryptedKeys?: Record<string, string>;
    date: string;
};
/**
 * Converts an IEmailMetadata into a JSON-safe plain object.
 * Call this server-side before sending API responses.
 */
export declare function serializeEmailMetadataForJson<TID extends string = string>(email: IEmailMetadata<TID>): IEmailMetadataJson<TID>;
/**
 * Converts a batch of IEmailMetadata objects for JSON serialization.
 */
export declare function serializeEmailMetadataArrayForJson<TID extends string = string>(emails: IEmailMetadata<TID>[]): IEmailMetadataJson<TID>[];
/**
 * Reconstructs an IEmailMetadata from a JSON-parsed plain object.
 * Call this client-side after receiving API responses.
 */
export declare function deserializeEmailMetadataFromJson<TID extends string = string>(json: IEmailMetadataJson<TID>): IEmailMetadata<TID>;
/**
 * Reconstructs a batch of IEmailMetadata objects from JSON.
 */
export declare function deserializeEmailMetadataArrayFromJson<TID extends string = string>(jsons: IEmailMetadataJson<TID>[]): IEmailMetadata<TID>[];
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