/**
 * One line for `doctor`: what is installed, what is published, and what to run.
 *
 * WHY THIS EXISTS AS A SEPARATE STEP FROM THE LOOKUP. A version behind is only
 * actionable alongside the install method -- `npm install -g` fixes a stale
 * global and silently does nothing for a stale copy in a project's
 * `node_modules`. Composing the two here keeps `doctor` from having to know the
 * rules, and keeps the rules testable without a network.
 *
 * AND WHY IT NEVER SAYS "UP TO DATE" WHEN IT DOES NOT KNOW. A check that cannot
 * reach the registry reports that it could not, because a reassuring line
 * printed from a failed lookup is worse than no line: it is the reader's
 * evidence that they looked.
 */
import { InstallMethod } from './install-method.js';
/** Where a copy stands against what is published. */
export declare enum UpdateState {
    /** Installed version equals the published one. */
    Current = "Current",
    /** Something newer is published. */
    Behind = "Behind",
    /** Installed version is newer -- a prerelease, or a local build. */
    Ahead = "Ahead",
    /** The lookup did not answer, or a version could not be parsed. */
    Unknown = "Unknown"
}
export interface UpdateReport {
    readonly state: UpdateState;
    readonly installed: string;
    readonly latest: string | null;
    readonly method: InstallMethod;
    /** What to run, or null when there is nothing this package should suggest. */
    readonly command: string | null;
    /** Why the state is Unknown, or null. */
    readonly refused: string | null;
}
/**
 * Ask, compare, and say what to do about it.
 *
 * `moduleUrl` defaults to this module's own location, which is the one that
 * answers the question for a real install; a test passes a path instead.
 */
export declare function checkForUpdate(options?: {
    readonly env?: NodeJS.ProcessEnv;
    readonly fetcher?: typeof fetch;
    readonly moduleUrl?: string;
    readonly installed?: string;
}): Promise<UpdateReport>;
/** The report as the lines `doctor` prints, without any leading indent. */
export declare function describeUpdate(report: UpdateReport): string[];
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