/**
 * Package URL (purl) derivation for PackageLayer identities.
 *
 * A purl is a stable, ecosystem-qualified coordinate for a package — e.g.
 * `pkg:npm/@scope/name` or `pkg:pypi/requests`. PackageLayer carries no purl of
 * its own, so it is derived from the layer's `type` (which ecosystem) plus the
 * package `name`. The same derivation keys a package's own identity and the
 * identity of each declared dependency (a dependency lives in the same
 * ecosystem as the manifest that declares it), so the two are guaranteed to
 * match when joined.
 *
 * Note: the purl `type` component (npm/pypi/cargo/golang) is a different
 * vocabulary from the tool-detection `Ecosystem` (node/python/go/rust) in
 * ../strategies — they are intentionally not shared.
 */
import type { PackageLayer } from '../types/layer-types';
/** purl `type` component. */
export type PurlEcosystem = 'npm' | 'pypi' | 'cargo' | 'golang';
/** The purl `type` for a PackageLayer type, e.g. `'node'` -> `'npm'`. */
export declare function purlEcosystemForPackageType(packageType: PackageLayer['type']): PurlEcosystem;
/**
 * Derive a purl from a package type + name. The name is used verbatim (npm
 * scope included), so a package's own purl and a purl built from a dependency
 * entry that names it resolve to the same string. Returns undefined for an
 * empty name so callers can skip un-keyable packages rather than emit a
 * malformed `pkg:npm/` coordinate.
 */
export declare function derivePurl(packageType: PackageLayer['type'], name: string | undefined): string | undefined;
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