/**
 * Gmail helpers — MIME building, header extraction, encoding utilities.
 */
import type { gmail_v1 } from '@googleapis/gmail';
import type { GmailMessage, AttachmentInfo, SendOptions, BufferAttachment } from './types.js';
/**
 * Extract a header value from a Gmail message payload.
 */
export declare function getHeader(headers: gmail_v1.Schema$MessagePartHeader[] | undefined, name: string): string;
/**
 * Parse address lists like "a@b.com, c@d.com" into arrays.
 */
export declare function parseAddressList(value: string): string[];
/**
 * Extract attachments metadata from a message payload.
 */
export declare function extractAttachments(payload: gmail_v1.Schema$MessagePart | undefined): AttachmentInfo[];
/**
 * Extract body text and HTML from a message payload.
 */
export declare function extractBody(payload: gmail_v1.Schema$MessagePart | undefined): {
    text?: string;
    html?: string;
};
/**
 * Decode base64url-encoded string (as used by Gmail API).
 */
export declare function base64Decode(data: string): string;
/**
 * Encode string to base64url (for Gmail API raw messages).
 */
export declare function base64UrlEncode(data: string | Buffer): string;
/**
 * RFC 2047 encode a header value if it contains non-ASCII characters.
 * Uses Base64 encoding: =?UTF-8?B?<base64>?=
 *
 * Returns the value unchanged if it's pure ASCII.
 */
export declare function rfc2047Encode(value: string): string;
/**
 * RFC 2047 encode the display name portion of a single email address.
 * "Júlia Fargas <julia@example.com>" → "=?UTF-8?B?...?= <julia@example.com>"
 * Plain addresses like "julia@example.com" are returned unchanged.
 */
export declare function rfc2047EncodeAddress(address: string): string;
/**
 * RFC 2047 encode a comma-separated list of email addresses.
 * Each display name is encoded individually if it contains non-ASCII chars.
 */
export declare function rfc2047EncodeAddressList(addresses: string): string;
/**
 * Parse a raw Gmail API message into our GmailMessage shape.
 */
export declare function parseMessage(raw: gmail_v1.Schema$Message): GmailMessage;
/**
 * Build a MIME message string from SendOptions.
 * Supports plain text, HTML multipart, and file attachments.
 */
export declare function buildMimeMessage(from: string, opts: SendOptions, extraHeaders?: Record<string, string>): Promise<string>;
/**
 * Build a MIME message for forwarding, with in-memory Buffer attachments.
 *
 * Similar to buildMimeMessage but accepts BufferAttachment[] instead of file paths.
 * Builds the forwarded body with quoted original content.
 */
export declare function buildForwardMime(from: string, to: string, subject: string, userBody: string | undefined, originalBody: {
    text?: string;
    html?: string;
}, bufferAttachments: BufferAttachment[], extraHeaders?: Record<string, string>, userHtml?: string): Promise<string>;
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