/**
 * Where an apt repository built by reprepro files a package.
 *
 * `apt.celilo.computer` is a reprepro repository, and reprepro does not keep
 * packages flat in `pool/`. It files each one under
 *
 *     pool/<component>/<prefix>/<source>/<package>_<version>_<arch>.deb
 *
 * where `<prefix>` is the first letter of the source name, or its first four
 * when the name starts with `lib`. Every caller in this repo once assumed
 * `pool/<file>`; that URL returns 404 on the real repository, and the e2e apt
 * simulator served it anyway, so the suite agreed with the simulator and with
 * nothing real (celilo#1505).
 *
 * The rule lives here, once, for the code that stages packages into the
 * simulator and for the gate that holds the signal module to it.
 */

import { cpSync, mkdirSync } from 'node:fs';
import { basename, dirname, join } from 'node:path';

/** The control fields that decide where a package is filed. */
export interface DebControl {
  package: string;
  version: string;
  architecture: string;
  /** The `Source:` field, when it differs from `Package:`. */
  source?: string;
}

/**
 * Control fields read from a `.deb` file name, `<package>_<version>_<arch>.deb`.
 *
 * A file name cannot carry a `Source:` that differs from the package name. The
 * packages this repo stages (celilo, celilo-bootstrap, libsignal-jni) declare
 * none, so the name is enough for them.
 */
export function controlFromDebName(fileName: string): DebControl {
  const match = basename(fileName).match(/^([^_]+)_([^_]+)_([^_]+)\.deb$/);
  if (!match) {
    throw new Error(`${fileName} is not named <package>_<version>_<arch>.deb`);
  }
  return { package: match[1], version: match[2], architecture: match[3] };
}

/** The path reprepro serves a package at, relative to the repository root. */
export function repreproPoolPath(control: DebControl, component = 'main'): string {
  const source = control.source ?? control.package;
  const prefix = source.startsWith('lib') ? source.slice(0, 4) : source.slice(0, 1);
  // An epoch (`1:2.0`) orders versions and is not written into file names.
  const version = control.version.replace(/^\d+:/, '');
  const file = `${control.package}_${version}_${control.architecture}.deb`;
  return `pool/${component}/${prefix}/${source}/${file}`;
}

/**
 * Copy a `.deb` into the simulator's staging directory where reprepro would
 * file it. `repoCacheDir` is the directory that holds `pool/`.
 *
 * Returns the staged path.
 */
export function stageDebInPool(repoCacheDir: string, debPath: string): string {
  const staged = join(repoCacheDir, repreproPoolPath(controlFromDebName(debPath)));
  mkdirSync(dirname(staged), { recursive: true });
  // `force` explicit: a rebuilt .deb at the same version must replace the one
  // already staged, or build-infra serves stale bytes.
  cpSync(debPath, staged, { force: true });
  return staged;
}