/**
 * Persist the currently-running petdex CLI binary to a stable
 * location (~/.petdex/bin/petdex.js) so agent hooks can invoke it
 * with an absolute path.
 *
 * Why: hooks fire from the agent's shell, which doesn't necessarily
 * have `petdex` in PATH. Users who run `npx petdex init` have a
 * temporary binary that won't exist when the agent actually fires
 * the hook. We solve this by copying the running binary to a known
 * location at install time.
 *
 * The persisted copy is a SNAPSHOT: it doesn't auto-update. Users who
 * upgrade petdex (npx petdex@latest) just re-run `petdex init` (or
 * `petdex hooks install`) to refresh the snapshot. Worse outcomes —
 * silently using a stale snapshot on `petdex update` — would surprise
 * us when behavior diverges between the running CLI and the hooks.
 */

import { copyFile, mkdir } from "node:fs/promises";
import { homedir } from "node:os";
import { join } from "node:path";

export const PERSIST_DIR = join(homedir(), ".petdex", "bin");
export const PERSIST_PATH = join(PERSIST_DIR, "petdex.js");

/**
 * Best-effort copy. Returns the persisted path on success, null if
 * we couldn't snapshot (e.g. process.argv[1] points at something that
 * isn't a copyable file). Failures are logged via the caller.
 */
export async function persistRunningBinary(): Promise<{
  ok: boolean;
  path: string;
  reason?: string;
}> {
  // process.argv[1] is the entry script. For petdex CLI this is the
  // bundled JS at .../dist/petdex.js (compiled by `bun build`). We
  // copy it as-is — the shebang is already present.
  const source = process.argv[1];
  if (!source) {
    return { ok: false, path: PERSIST_PATH, reason: "no argv[1]" };
  }
  try {
    await mkdir(PERSIST_DIR, { recursive: true });
    await copyFile(source, PERSIST_PATH);
    // chmod is best-effort; copyFile preserves perms on most
    // platforms but we want exec bits unconditionally.
    const { chmod } = await import("node:fs/promises");
    try {
      await chmod(PERSIST_PATH, 0o755);
    } catch {}
    return { ok: true, path: PERSIST_PATH };
  } catch (err) {
    return {
      ok: false,
      path: PERSIST_PATH,
      reason: (err as Error).message,
    };
  }
}