/**
 * CLI self-update — the first step of `celilo system update` per
 * CELILO_UPDATE D2.
 *
 * Compares the running CLI version against the latest published
 * `@celilo/cli` on npm and runs `bun update -g @celilo/cli` if newer.
 * On success the caller re-execs with the new binary so subsequent
 * module work uses the new code.
 *
 * Both the version-check and the bun-update invocation are
 * dependency-injected so the orchestrator can be tested against
 * canned responses without touching npm or the running shell.
 */

import { compareSemver } from '../audit/cli-version';
import type { SelfUpdateResult } from './types';

export type CliVersionFetcher = () => Promise<string | null>;
export type CliUpdater = () => Promise<{ ok: boolean; stderr: string }>;

export interface SelfUpdateDeps {
  /** Currently running CLI version (read from package.json). */
  installedVersion: string;
  /** Resolves the latest @celilo/cli on npm; returns null on transport failure. */
  fetcher: CliVersionFetcher;
  /** Runs `bun update -g @celilo/cli` (or equivalent). */
  updater: CliUpdater;
  /**
   * If true, skip self-update entirely. Set when `system update`
   * detects the CLI is running from local source (cele2e dev loop)
   * — there's nothing to update against and any npm install would
   * step on the mounted source tree.
   */
  devMode?: boolean;
}

export async function performSelfUpdate(deps: SelfUpdateDeps): Promise<SelfUpdateResult> {
  if (deps.devMode) {
    return { performed: false, reason: 'dev-mode' };
  }

  const latest = await deps.fetcher();
  if (latest === null) {
    return { performed: false, reason: 'no-network' };
  }

  if (compareSemver(deps.installedVersion, latest) >= 0) {
    return { performed: false, reason: 'already-current' };
  }

  const result = await deps.updater();
  if (!result.ok) {
    throw new Error(`bun update failed: ${result.stderr || 'unknown error'}`);
  }

  return { performed: true, from: deps.installedVersion, to: latest };
}