/**
 * desktop/src/server-config.ts — build the env overrides fed to the backend's
 * loadConfig() for the embedded server.
 *
 * Starts from a COPY of the ambient env (never mutates it) and pins the four
 * values the desktop shell controls: PORT (the free port we already resolved),
 * BIND_HOST (private 127.0.0.1 by default; 0.0.0.0 only when LAN sharing is on),
 * SHELL_PATH (platform-aware default so Windows gets PowerShell), and USE_TMUX
 * (forced off on Windows — tmux is a *nix keepalive; elsewhere respect the
 * ambient env, defaulting to auto-detect). Every other ambient var passes through
 * untouched.
 */

import type { DesktopPrefs } from './types.js'
import { defaultShellForPlatform } from './shell.js'

/** Loopback bind host — private mode; the window connects here and always passes Origin checks. */
const PRIVATE_BIND_HOST = '127.0.0.1'
/** Wildcard bind host — LAN sharing (phones/tablets reconnect); opt-in, no auth. */
const LAN_BIND_HOST = '0.0.0.0'
/** tmux is a *nix keepalive, so Windows forces it off outright. */
const TMUX_OFF = '0'
/**
 * Everywhere else the desktop shell auto-detects (loadConfig's 'auto' → is the tmux
 * binary present?), which is what the standalone server already did.
 *
 * It used to default OFF, and that quietly broke the app's whole premise. Without
 * tmux the shell is a direct child of the embedded server, so quitting the app —
 * including the tray "Quit", including a logout — kills every session with it. The
 * point of this app is to hand Claude Code a task, walk away, and reconnect from
 * another device; a session that cannot survive the window closing does not do that.
 * With tmux the node-pty process is only a tmux CLIENT, so shutdown detaches and the
 * shell keeps running (see SessionManager.shutdown).
 *
 * An explicit ambient USE_TMUX still wins, so USE_TMUX=0 remains the way to opt out.
 */
const TMUX_AUTO = 'auto'

export interface ServerEnvInput {
  readonly prefs: DesktopPrefs
  readonly port: number
  readonly platform: NodeJS.Platform
  readonly env: NodeJS.ProcessEnv
}

/**
 * Produce the env-override object for loadConfig(). Immutable: input.env is
 * spread into a NEW object and is never mutated.
 */
export function buildServerEnv(input: ServerEnvInput): Record<string, string | undefined> {
  const { prefs, port, platform, env } = input
  return {
    ...env,
    PORT: String(port),
    BIND_HOST: prefs.lanSharing ? LAN_BIND_HOST : PRIVATE_BIND_HOST,
    SHELL_PATH: prefs.shellPath ?? defaultShellForPlatform(platform, env),
    USE_TMUX: platform === 'win32' ? TMUX_OFF : (env.USE_TMUX ?? TMUX_AUTO),
  }
}