import { createReadStream } from 'node:fs'
import { stat } from 'node:fs/promises'
import { createServer } from 'node:http'
import path from 'node:path'
import { pipeline } from 'node:stream/promises'
import { fileURLToPath } from 'node:url'
import {
  loadCatalog,
  loadDefaultNavigation,
  readOrCreateNavigation,
  validateNavigation,
  writeJsonAtomic,
} from './navigation.mjs'

const serverFile = fileURLToPath(import.meta.url)
const serverDir = path.dirname(serverFile)
const projectRoot = path.resolve(serverDir, '..')
export const MAX_JSON_BODY_SIZE = 64 * 1024
export const DEFAULT_PORT = 9000

const mimeTypes = new Map([
  ['.css', 'text/css; charset=utf-8'],
  ['.html', 'text/html; charset=utf-8'],
  ['.ico', 'image/x-icon'],
  ['.js', 'text/javascript; charset=utf-8'],
  ['.json', 'application/json; charset=utf-8'],
  ['.map', 'application/json; charset=utf-8'],
  ['.png', 'image/png'],
  ['.svg', 'image/svg+xml'],
  ['.txt', 'text/plain; charset=utf-8'],
  ['.webmanifest', 'application/manifest+json; charset=utf-8'],
  ['.woff2', 'font/woff2'],
])

function applySecurityHeaders(response) {
  response.setHeader('Content-Security-Policy', "default-src 'self'; img-src 'self' blob: data:; style-src 'self'; script-src 'self'; font-src 'self'; connect-src 'self'; object-src 'none'; base-uri 'none'; form-action 'self'; frame-ancestors 'none'")
  response.setHeader('Cross-Origin-Opener-Policy', 'same-origin')
  response.setHeader('Permissions-Policy', 'camera=(), microphone=(), geolocation=()')
  response.setHeader('Referrer-Policy', 'no-referrer')
  response.setHeader('X-Content-Type-Options', 'nosniff')
  response.setHeader('X-Frame-Options', 'DENY')
}

function sendJson(response, statusCode, payload, headers = {}) {
  const body = `${JSON.stringify(payload)}\n`
  response.statusCode = statusCode
  response.setHeader('Cache-Control', 'no-store')
  response.setHeader('Content-Type', 'application/json; charset=utf-8')
  response.setHeader('Content-Length', Buffer.byteLength(body))
  for (const [name, value] of Object.entries(headers)) response.setHeader(name, value)
  response.end(body)
}

function sendText(response, statusCode, body, headers = {}) {
  response.statusCode = statusCode
  response.setHeader('Cache-Control', 'no-store')
  response.setHeader('Content-Type', 'text/plain; charset=utf-8')
  response.setHeader('Content-Length', Buffer.byteLength(body))
  for (const [name, value] of Object.entries(headers)) response.setHeader(name, value)
  response.end(body)
}

async function readJsonBody(request) {
  const contentLength = Number(request.headers['content-length'])
  if (Number.isFinite(contentLength) && contentLength > MAX_JSON_BODY_SIZE) throw new Error('请求内容过大')

  const chunks = []
  let size = 0
  for await (const chunk of request) {
    size += chunk.length
    if (size > MAX_JSON_BODY_SIZE) throw new Error('请求内容过大')
    chunks.push(chunk)
  }
  return JSON.parse(Buffer.concat(chunks).toString('utf8'))
}

function isMissingFile(error) {
  return error?.code === 'ENOENT' || error?.code === 'ENOTDIR'
}

export async function assertProductionBuild(staticRoot = path.join(projectRoot, 'dist')) {
  const indexPath = path.join(path.resolve(staticRoot), 'index.html')
  let details
  try {
    details = await stat(indexPath)
  } catch (error) {
    if (!isMissingFile(error)) throw error
  }
  if (!details?.isFile()) {
    throw new Error(`Production build not found: ${indexPath}. Run "npm.cmd ci --include=dev" and "npm.cmd run build" before starting the server.`)
  }
}

function acceptsHtmlNavigation(request, pathname) {
  if (path.extname(pathname)) return false
  return String(request.headers.accept || '').split(',').some((value) => value.trim().toLowerCase().startsWith('text/html'))
}

async function serveStatic(request, response, staticRoot) {
  const url = new URL(request.url, 'http://localhost')
  let pathname
  try {
    pathname = decodeURIComponent(url.pathname)
  } catch {
    sendText(response, 400, 'Bad request\n')
    return
  }

  const requested = pathname === '/' ? '/index.html' : pathname
  const candidate = path.resolve(staticRoot, `.${requested}`)
  if (!candidate.startsWith(`${staticRoot}${path.sep}`)) {
    sendText(response, 403, 'Forbidden\n')
    return
  }

  let filePath = candidate
  let details
  try {
    details = await stat(filePath)
  } catch (error) {
    if (!isMissingFile(error)) throw error
  }
  if (!details?.isFile()) {
    if (!acceptsHtmlNavigation(request, pathname)) {
      sendText(response, 404, 'Not found\n')
      return
    }
    filePath = path.join(staticRoot, 'index.html')
    details = await stat(filePath)
    if (!details.isFile()) throw new Error('静态入口文件不存在')
  }

  response.statusCode = 200
  response.setHeader('Content-Type', mimeTypes.get(path.extname(filePath).toLowerCase()) || 'application/octet-stream')
  response.setHeader('Content-Length', details.size)
  if (path.basename(filePath) === 'index.html') response.setHeader('Cache-Control', 'no-cache')
  else response.setHeader('Cache-Control', 'public, max-age=31536000, immutable')
  if (request.method === 'HEAD') {
    response.end()
    return
  }
  await pipeline(createReadStream(filePath), response)
}

export async function createWebToolsServer(options = {}) {
  const staticRoot = path.resolve(options.staticRoot || path.join(projectRoot, 'dist'))
  const dataDir = path.resolve(options.dataDir || process.env.DATA_DIR || path.join(projectRoot, 'data'))
  const navigationPath = path.join(dataDir, 'navigation.json')
  const catalog = options.catalog || await loadCatalog()
  const defaults = options.defaults || await loadDefaultNavigation()
  const logger = options.logger || console

  return createServer(async (request, response) => {
    applySecurityHeaders(response)
    try {
      const url = new URL(request.url, 'http://localhost')
      if (request.method === 'GET' && url.pathname === '/healthz') {
        sendJson(response, 200, { status: 'ok' })
        return
      }
      if (url.pathname === '/api/navigation') {
        if (request.method === 'GET') {
          sendJson(response, 200, await readOrCreateNavigation(navigationPath, catalog, defaults))
          return
        }
        if (request.method === 'PUT') {
          if (request.headers['sec-fetch-site'] === 'cross-site') {
            sendJson(response, 403, { error: '不允许跨站写入配置' })
            return
          }
          let navigation
          try {
            navigation = validateNavigation(await readJsonBody(request), catalog)
          } catch (error) {
            sendJson(response, 400, { error: error instanceof Error ? error.message : '配置格式无效' })
            return
          }
          await writeJsonAtomic(navigationPath, navigation)
          sendJson(response, 200, navigation)
          return
        }
        sendJson(response, 405, { error: '请求方法不支持' }, { Allow: 'GET, PUT' })
        return
      }
      if (url.pathname.startsWith('/api/')) {
        sendJson(response, 404, { error: '接口不存在' })
        return
      }
      if (request.method !== 'GET' && request.method !== 'HEAD') {
        sendText(response, 405, '', { Allow: 'GET, HEAD' })
        return
      }
      await serveStatic(request, response, staticRoot)
    } catch (error) {
      logger.error(error)
      if (response.headersSent) response.destroy()
      else sendJson(response, 500, { error: '服务器错误' })
    }
  })
}

export async function startWebToolsServer() {
  const host = process.env.HOST || '0.0.0.0'
  const port = Number(process.env.PORT || DEFAULT_PORT)
  const staticRoot = path.join(projectRoot, 'dist')
  await assertProductionBuild(staticRoot)
  const server = await createWebToolsServer({ staticRoot })
  server.listen(port, host, () => {
    console.log(`Web Tools listening on http://${host}:${port}`)
    console.log(`Navigation config: ${path.resolve(process.env.DATA_DIR || path.join(projectRoot, 'data'), 'navigation.json')}`)
  })
  return server
}

if (process.argv[1] && path.resolve(process.argv[1]) === serverFile) {
  startWebToolsServer().catch((error) => {
    console.error(error)
    process.exitCode = 1
  })
}