import fs from 'node:fs'
import path from 'node:path'
import { spawnSync } from 'node:child_process'

function canRunPython(executable) {
  const result = spawnSync(executable, ['--version'], {
    encoding: 'utf8',
    stdio: 'ignore',
  })
  return !result.error && result.status === 0
}

/**
 * 解析设计构建管线唯一可用的 Python 入口。
 *
 * 顺序必须保持稳定：显式配置 > 项目虚拟环境 > Windows Python Manager >
 * 系统命令。这样既尊重调用方选择，也不会把 WindowsApps 的零字节执行别名
 * 误判为真实解释器。每个候选都必须实际执行 `--version`，文件存在本身不算可用。
 */
export function resolvePythonExecutable({
  pipelineDirectory,
  environment = process.env,
  platform = process.platform,
  pathExists = fs.existsSync,
  canRun = canRunPython,
} = {}) {
  if (!pipelineDirectory) throw new Error('解析 Python 入口时缺少 design-pipeline 目录')

  const configured = environment.PYTHON?.trim()
  if (configured) {
    if (canRun(configured)) return configured
    throw new Error(`PYTHON 指定的解释器不可用：${configured}`)
  }

  const pathApi = platform === 'win32' ? path.win32 : path.posix
  const candidates = []
  const virtualEnvironment = platform === 'win32'
    ? pathApi.join(pipelineDirectory, '.venv', 'Scripts', 'python.exe')
    : pathApi.join(pipelineDirectory, '.venv', 'bin', 'python')
  if (pathExists(virtualEnvironment)) candidates.push(virtualEnvironment)

  if (platform === 'win32' && environment.LOCALAPPDATA) {
    const managerPython = pathApi.join(environment.LOCALAPPDATA, 'Python', 'bin', 'python.exe')
    if (pathExists(managerPython)) candidates.push(managerPython)
  }

  candidates.push(platform === 'win32' ? 'python' : 'python3', 'python')
  for (const candidate of new Set(candidates)) {
    if (canRun(candidate)) return candidate
  }

  throw new Error(
    '未找到可用的 Python。请设置 PYTHON 为真实解释器路径，或在 design-pipeline/.venv 中安装项目虚拟环境。',
  )
}

/**
 * 通过统一入口执行 Python，保证任何构建和测试都不会向源码目录写入 `.pyc`。
 * 调用方只提供业务参数；`-B`、进程错误和退出码转换由这里集中负责。
 */
export function runPythonCommand({ executable, args, cwd, spawn = spawnSync } = {}) {
  if (typeof executable !== 'string' || executable.trim() === '') throw new Error('执行 Python 时缺少解释器')
  if (!Array.isArray(args)) throw new Error('执行 Python 时 args 必须为数组')
  if (typeof cwd !== 'string' || cwd.trim() === '') throw new Error('执行 Python 时缺少工作目录')

  const result = spawn(executable, ['-B', ...args], {
    cwd,
    encoding: 'utf8',
    stdio: 'inherit',
  })
  if (result.error) throw new Error(`无法启动 Python（${executable}）：${result.error.message}`)
  if (result.status !== 0) throw new Error(`Python 命令执行失败，退出码：${result.status ?? 'unknown'}`)
  return result
}