// Backend subcommand routing for the desktop-managed Hermes process.
//
// The desktop app launches its own headless backend via `hermes serve` — it
// must NEVER depend on or launch the browser `dashboard`. But `serve` is a
// newer subcommand: a runtime that predates it (an older managed install the
// app hasn't updated yet, or an older `hermes` resolved from PATH) only knows
// `dashboard --no-open`. To avoid bricking those users mid-upgrade we detect
// whether the resolved runtime understands `serve` and, only when it does not,
// fall back to the legacy `dashboard --no-open` invocation. Both produce the
// exact same headless gateway; `serve` is just the decoupled name.
//
// These helpers are pure so they can be unit-tested without Electron.

import { backendProfileArg } from './profile-id-guard'

/**
 * Build the canonical headless backend argv (always `serve`).
 * @param {string} [profile] optional Hermes profile to pin via `--profile`.
 */
export function serveBackendArgs(profile?: string) {
  // A non-slug value (numeric roster id, display label) must never cross into
  // spawn argv: the CLI used to str()-coerce it into a phantom profiles/0 dir (#88842).
  const pinned = backendProfileArg(profile)
  const head = pinned ? ['--profile', pinned] : []

  return [...head, 'serve', '--host', '127.0.0.1', '--port', '0']
}

// Flags that consume the next token; the subcommand is the first bare token
// that is not one of their values. `--profile=serve` never collides (it is a
// different string), but the two-token `--profile serve` / `-p serve` do.
const VALUE_FLAGS = new Set(['-m', '--profile', '-p'])

/**
 * Rewrite a resolved backend argv from `serve` to the legacy
 * `dashboard --no-open` form, preserving every other argument (incl. a leading
 * `-m hermes_cli.main` and any `--profile <name>`). Returns a copy; if there is
 * no `serve` subcommand token the argv is returned unchanged.
 */
export function dashboardFallbackArgs(args) {
  let i = 0

  while (i < args.length && args[i] !== 'serve') {
    i += VALUE_FLAGS.has(args[i]) ? 2 : 1
  }

  if (i >= args.length) {
    return args.slice()
  }

  return [...args.slice(0, i), 'dashboard', '--no-open', ...args.slice(i + 1)]
}

/**
 * True when a runtime's `hermes_cli/subcommands/dashboard.py` source registers
 * the `serve` subcommand. Matches `add_parser("serve"` / `add_parser('serve'`
 * specifically so the substring "server" (e.g. "start_server", "web server")
 * never produces a false positive.
 */
export function sourceDeclaresServe(dashboardPySource) {
  return /add_parser\(\s*["']serve["']/.test(String(dashboardPySource || ''))
}