// 跨平台默认 shell 选择
import { platform } from 'node:process'
import { execSync } from 'node:child_process'

export interface ShellSpec {
  file: string
  args: string[]
  label: string
}

function which(bin: string): string | null {
  try {
    const cmd = platform === 'win32' ? `where ${bin}` : `command -v ${bin}`
    const out = execSync(cmd, { stdio: ['ignore', 'pipe', 'ignore'] }).toString().trim().split(/\r?\n/)[0]
    return out || null
  } catch {
    return null
  }
}

export function defaultShell(): ShellSpec {
  switch (platform) {
    case 'win32': {
      // 优先 PowerShell 7 (pwsh), 否则 Windows PowerShell 5 (powershell)
      const pwsh = which('pwsh.exe') || which('pwsh')
      if (pwsh) return { file: pwsh, args: ['-NoLogo'], label: 'PowerShell 7' }
      const ps5 = which('powershell.exe') || which('powershell')
      if (ps5) return { file: ps5, args: ['-NoLogo'], label: 'Windows PowerShell' }
      return { file: 'powershell.exe', args: ['-NoLogo'], label: 'PowerShell' }
    }
    case 'darwin':
    case 'linux': {
      const envShell = process.env.SHELL
      if (envShell) {
        const name = envShell.split('/').pop() || envShell
        return { file: envShell, args: [], label: name }
      }
      if (platform === 'darwin') {
        const zsh = which('zsh')
        if (zsh) return { file: zsh, args: [], label: 'zsh' }
        const bash = which('bash')
        if (bash) return { file: bash, args: ['-l'], label: 'bash' }
      } else {
        const bash = which('bash')
        if (bash) return { file: bash, args: ['-l'], label: 'bash' }
        const sh = which('sh')
        if (sh) return { file: sh, args: [], label: 'sh' }
      }
      return { file: '/bin/sh', args: [], label: 'sh' }
    }
    default:
      return { file: '/bin/sh', args: [], label: 'sh' }
  }
}

// 终端的初始工作目录
// Windows 上通常没有 HOME, 但装了 Git Bash / MSYS 之后 HOME 可能被设成 POSIX 路径
// (比如 /c/Users/xxx), 那个路径在 Win32 下不存在 -> pty 起不来, 所以 win32 优先 USERPROFILE。
export function defaultCwd(): string {
  const home = platform === 'win32'
    ? (process.env.USERPROFILE || process.env.HOME)
    : (process.env.HOME || process.env.USERPROFILE)
  return home || process.cwd()
}