/**
 * Pure, DOM-free SMS encoding + segmentation helpers.
 *
 * SMS messages are plain text, but how many "segments" (billable parts) a
 * message costs depends on its characters:
 *
 * - **GSM-7**: the default 7-bit alphabet. 160 chars in a single segment, 153
 *   per segment once the message is split (the extra 7 bits per segment go to
 *   the multipart UDH header). A handful of characters (`^ { } \ [ ] ~ | €` and
 *   form-feed) live in an "extension table" and cost **two** characters each.
 * - **UCS-2**: used when any character is outside GSM-7 (e.g. emoji, many
 *   non-Latin scripts). 70 chars single, 67 per segment when split. Counted in
 *   UTF-16 code units, so emoji built from surrogate pairs cost two.
 *
 * Reference: 3GPP TS 23.038.
 */
/** Which physical encoding the carrier will use for the message. */
export type SmsEncoding = 'GSM-7' | 'UCS-2';
/** A full segmentation report for a piece of text. */
export interface SmsSegmentInfo {
    /** Encoding the message forces. */
    encoding: SmsEncoding;
    /** Weighted character count (GSM-7 extension chars count as 2). */
    length: number;
    /** Number of billable segments. */
    segments: number;
    /** Capacity of a single segment for the active encoding (160 or 70). */
    maxSingle: number;
    /** Capacity per segment once the message is multipart (153 or 67). */
    maxMulti: number;
    /** Characters left before the next segment boundary. */
    remaining: number;
}
/**
 * Determine whether `text` can be sent as GSM-7 or must fall back to UCS-2.
 */
export declare function detectEncoding(text: string): SmsEncoding;
/**
 * Weighted length of `text` for the given encoding. In GSM-7, extension-table
 * characters count as two. In UCS-2, the count is in UTF-16 code units (so a
 * surrogate-pair emoji counts as two).
 */
export declare function countChars(text: string, encoding: SmsEncoding): number;
/**
 * Produce a full segmentation report for `text`: encoding, weighted length,
 * segment count, per-segment capacity and remaining characters.
 */
export declare function segment(text: string): SmsSegmentInfo;