import { type Address, type Hex } from "viem";
import type { Metadata } from "../types/index.js";
/**
 * Adds metadata to a transaction object by concatenating additional
 * hex-encoded data to the transaction's `data` field. The additional
 * data may include a timestamp and an origin identifier derived
 * from the metadata.
 *
 * The function ensures that the transaction data is correctly formatted
 * and includes optional metadata elements if provided.
 *
 * `metadata.origin` accepts either a raw hex string (`"cafe"`) or a
 * 0x-prefixed hex string (`"0xcafe"` / `"0Xcafe"`); both produce the same
 * appended 4-byte origin tag. The 0x/0X prefix is stripped case-insensitively
 * before length-validation, so an origin of `"0xdeadbeef"` (10 chars
 * including prefix, 8 raw hex chars) is accepted while `"0xdeadbeef00"`
 * (10 raw hex chars) is rejected and a warning is logged. Odd-length raw
 * fragments (e.g. `"abc"`, `"0xabc"`) are also rejected — concatenating
 * a non-byte-aligned fragment would corrupt the trailing analytics byte
 * once viem's `concatHex` pads it to a whole byte at broadcast time.
 *
 * @param {Object} tx - The original transaction object.
 * @param {Hex} tx.data - The existing hex-encoded data for the transaction.
 * @param {bigint} tx.value - The value to be sent with the transaction.
 * @param {Address} tx.to - The recipient address of the transaction.
 * @param {Metadata} metadata - An object containing optional metadata fields
 * such as `timestamp` and `origin`.
 *
 * @returns The same `tx` object when `data` is missing, an empty string, or
 * canonical empty calldata (`"0x"`); otherwise, a new transaction object
 * with `data` containing any appended metadata. The input is never mutated.
 */
export declare function addTransactionMetadata(tx: {
    data: Hex;
    value: bigint;
    to: Address;
}, metadata: Metadata): {
    data: Hex;
    value: bigint;
    to: Address;
};