export type UpdateChannel = "stable" | "canary";
export type Fetch = (input: string | URL | Request, init?: RequestInit) => Promise<Response>;
/** Build service origin used when `PI_BUILD_URL` is unset. */
export declare const DEFAULT_BUILD_URL = "https://build.stencil.so";
/** Build service origin: `PI_BUILD_URL` without trailing slashes, else {@link DEFAULT_BUILD_URL}. */
export declare function buildServiceUrl(): string;
/** Where this host's builds live on the build service. */
export interface BuildHost {
    /** Build service target, e.g. `macos-arm64` or `linux-musl-x86_64`. */
    target: string;
    /** Name of the target's file, the release asset name (e.g. `omp-darwin-arm64`). */
    fileName: string;
}
/** The build service target and file name for a platform, architecture, and libc. */
export declare function resolveBuildHost(platform: NodeJS.Platform, arch: string, musl: boolean): BuildHost;
/**
 * Detect a musl-libc Linux host (Alpine, Void-musl) so self-update replaces a
 * musl binary with the musl build instead of the glibc one, which would fail
 * to start on the next run. The loader file alone is not sufficient: glibc
 * hosts may have musl installed for cross-compilation.
 */
interface MuslDetectionOptions {
    platform: NodeJS.Platform;
    alpineRelease: boolean;
    lddOutput: string;
}
/** Test seam for libc detection. */
export declare function isMuslLinuxForTest(options: MuslDetectionOptions): boolean;
/** This host's {@link BuildHost}, detected once per process. */
export declare function currentBuildHost(): Promise<BuildHost>;
/** The answered build's file for this host. */
export interface BuildFile {
    name: string;
    size: number;
    /** Lowercase hex SHA-256. */
    sha256: string;
}
/** HDiffPatch single-stream patch (`HDIFFSF20`) from an installed file to {@link BuildFile}. */
export interface BuildPatch {
    /** Lowercase hex SHA-256 of the file the patch applies to. */
    fromSha256: string;
    /** Version the check named as installed (`from_version`), for progress output. */
    fromVersion?: string;
    size: number;
    /** Lowercase hex SHA-256 of the patch itself. */
    sha256: string;
    /** Presigned HTTPS URL of the patch. */
    url: string;
}
/** A checked build service answer. */
export interface BuildAnswer {
    version: string;
    file: BuildFile;
    /** Presigned HTTPS URL of the whole file, valid for minutes. */
    download: string;
    patch?: BuildPatch;
}
/**
 * Check a build service answer for the file named `fileName`.
 *
 * Throws when the answer cannot be installed safely: a version that is not
 * semver, a file other than `fileName`, a size or SHA-256 that is not exact,
 * or a download that is not HTTPS. A `patch` is kept only when it is a
 * complete `format: "file"` patch; any other patch is dropped, not an error.
 * `fromVersion` is the `from_version` the check sent.
 */
export declare function parseBuildAnswer(body: unknown, fileName: string, fromVersion?: string): BuildAnswer;
/** Which build to ask for: the newest on a channel, or one exact version. */
export type BuildSelector = {
    channel: UpdateChannel;
} | {
    version: string;
};
export interface FetchBuildOptions {
    /** Installed version to ask a patch from (`from_version`). */
    fromVersion?: string;
    timeoutMs?: number;
    fetchImpl?: Fetch;
    /** Defaults to {@link currentBuildHost}. */
    host?: BuildHost;
}
/** Ask the build service for a build of this host's target ({@link BuildSelector}). */
export declare function fetchBuild(selector: BuildSelector, options?: FetchBuildOptions): Promise<BuildAnswer>;
export {};