/**
 * @module
 * AWS Signature Version 4 signing using Web Crypto (HMAC-SHA256).
 * Works on Node.js, Bun, Deno, and Cloudflare Workers.
 * No external dependencies.
 *
 * @example
 * ```ts
 * import { signRequest } from "sently/core/sigv4";
 * const signed = await signRequest({
 *   method: "POST",
 *   url: "https://email.us-east-1.amazonaws.com/v2/email/outbound-emails",
 *   headers: { "content-type": "application/json" },
 *   body: '{"..."}',
 *   credentials: { accessKeyId, secretAccessKey, region: "us-east-1", service: "ses" },
 * });
 * ```
 */
/** AWS credentials and signing scope for SigV4. */
export interface SigV4Credentials {
    /** AWS access key ID. */
    accessKeyId: string;
    /** AWS secret access key. */
    secretAccessKey: string;
    /** AWS region (e.g. `us-east-1`). */
    region: string;
    /** AWS service name (e.g. `ses`, `s3`). */
    service: string;
    /** Optional STS session token for temporary credentials. */
    sessionToken?: string;
}
/** HTTP request to sign with AWS Signature Version 4. */
export interface SigV4Request {
    /** HTTP method (e.g. `POST`). */
    method: string;
    /** Full request URL including path and query. */
    url: string;
    /** Request headers to include in the signature. */
    headers: Record<string, string>;
    /** Request body as a string (empty for GET). */
    body: string;
    /** AWS credentials and signing scope. */
    credentials: SigV4Credentials;
    /** Override datetime for testing. Full 'YYYYMMDDTHHMMSSZ' when provided. */
    _date?: string;
}
/** Signed request headers including Authorization. */
export interface SigV4Result {
    /** All headers including Authorization, x-amz-date, and x-amz-security-token */
    headers: Record<string, string>;
}
/**
 * Compute SHA-256 hash of a string using Web Crypto.
 * Returns lowercase hex string.
 * @internal
 */
export declare function sha256Hex(data: string): Promise<string>;
/**
 * Compute HMAC-SHA256 using Web Crypto.
 * @internal
 */
export declare function hmacSHA256(key: Uint8Array | string, data: string): Promise<Uint8Array>;
/**
 * Sign an HTTP request with AWS Signature Version 4.
 * Returns the complete set of headers to include in the request.
 */
export declare function signRequest(request: SigV4Request): Promise<SigV4Result>;