text: """
      livereload.server
      ~~~~~~~~~~~~~~~~~
  
      WSGI app server for livereload.
  
      :copyright: (c) 2013 - 2015 by Hsiaoming Yang
      :license: BSD, see LICENSE for more details.
  """
  
  import os
  import time
  import shlex
  import logging
  import threading
  import webbrowser
  from subprocess import Popen, PIPE
  
  from tornado.wsgi import WSGIContainer
  from tornado.ioloop import IOLoop
  from tornado.autoreload import add_reload_hook
  from tornado import web
  from tornado import escape
  from tornado import httputil
  from tornado.log import LogFormatter
  from .handlers import LiveReloadHandler, LiveReloadJSHandler
  from .handlers import ForceReloadHandler, StaticFileHandler
  from .watcher import get_watcher_class
  
  import sys
  
  if sys.version_info >= (3, 7):
      import errno
  else:
      from os import errno
  
  if sys.version_info >= (3, 8) and sys.platform == 'win32':
      import asyncio
      asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
  
  logger = logging.getLogger('livereload')
  
  HEAD_END = b'</head>'
  
  
  def set_header(fn, name, value):
      """Helper Function to Add HTTP headers to the server"""
      def set_default_headers(self, *args, **kwargs):
          fn(self, *args, **kwargs)
          self.set_header(name, value)
      return set_default_headers
  
  
  def shell(cmd, output=None, mode='w', cwd=None, shell=False):
      """Execute a shell command.
  
      You can add a shell command::
  
          server.watch(
              'style.less', shell('lessc style.less', output='style.css')
          )
  
      :param cmd: a shell command, string or list
      :param output: output stdout to the given file
      :param mode: only works with output, mode ``w`` means write,
                   mode ``a`` means append
      :param cwd: set working directory before command is executed.
      :param shell: if true, on Unix the executable argument specifies a
                    replacement shell for the default ``/bin/sh``.
      """
      if not output:
          output = os.devnull
      else:
          folder = os.path.dirname(output)
          if folder and not os.path.isdir(folder):
              os.makedirs(folder)
  
      if not isinstance(cmd, (list, tuple)) and not shell:
          cmd = shlex.split(cmd)
  
      def run_shell():
          try:
              p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE, cwd=cwd,
                        shell=shell)
          except OSError as e:
              logger.error(e)
              if e.errno == errno.ENOENT:  # file (command) not found
                  logger.error("maybe you haven't installed %s", cmd[0])
              return e
          stdout, stderr = p.communicate()
          if stderr:
              logger.error(stderr)
              return stderr
          #: stdout is bytes, decode for python3
          stdout = stdout.decode()
          with open(output, mode) as f:
              f.write(stdout)
  
      return run_shell
  
  
  class LiveScriptInjector(web.OutputTransform):
      def __init__(self, request):
          super().__init__(request)
  
      def transform_first_chunk(self, status_code, headers, chunk, finishing):
          if HEAD_END in chunk:
              chunk = chunk.replace(HEAD_END, self.script + HEAD_END)
              if 'Content-Length' in headers:
                  length = int(headers['Content-Length']) + len(self.script)
                  headers['Content-Length'] = str(length)
          return status_code, headers, chunk
  
  
  class LiveScriptContainer(WSGIContainer):
      def __init__(self, wsgi_app, script=''):
          self.wsgi_app = wsgi_app
          self.script = script
  
      def __call__(self, request):
          data = {}
          response = []
  
          def start_response(status, response_headers, exc_info=None):
              data["status"] = status
              data["headers"] = response_headers
              return response.append
  
          app_response = self.wsgi_app(
              WSGIContainer.environ(request), start_response)
          try:
              response.extend(app_response)
              body = b"".join(response)
          finally:
              if hasattr(app_response, "close"):
                  app_response.close()
          if not data:
              raise Exception("WSGI app did not call start_response")
  
          status_code, reason = data["status"].split(' ', 1)
          status_code = int(status_code)
          headers = data["headers"]
          header_set = {k.lower() for (k, v) in headers}
          body = escape.utf8(body)
  
          if HEAD_END in body:
              body = body.replace(HEAD_END, self.script + HEAD_END)
  
          if status_code != 304:
              if "content-type" not in header_set:
                  headers.append((
                      "Content-Type",
                      "application/octet-stream; charset=UTF-8"
                  ))
              if "content-length" not in header_set:
                  headers.append(("Content-Length", str(len(body))))
  
          if "server" not in header_set:
              headers.append(("Server", "LiveServer"))
  
          start_line = httputil.ResponseStartLine(
              "HTTP/1.1", status_code, reason
          )
          header_obj = httputil.HTTPHeaders()
          for key, value in headers:
              if key.lower() == 'content-length':
                  value = str(len(body))
              header_obj.add(key, value)
          request.connection.write_headers(start_line, header_obj, chunk=body)
          request.connection.finish()
          self._log(status_code, request)
  
  
  class Server:
      """Livereload server interface.
  
      Initialize a server and watch file changes::
  
          server = Server(wsgi_app)
          server.serve()
  
      :param app: a wsgi application instance
      :param watcher: A Watcher instance, you don't have to initialize
                      it by yourself. Under Linux, you will want to install
                      pyinotify and use INotifyWatcher() to avoid wasted
                      CPU usage.
      """
      def __init__(self, app=None, watcher=None):
          self.root = None
  
          self.app = app
          if not watcher:
              watcher_cls = get_watcher_class()
              watcher = watcher_cls()
          self.watcher = watcher
          self.SFH = StaticFileHandler
  
      def setHeader(self, name, value):
          """Add or override HTTP headers at the at the beginning of the 
             request.
  
          Once you have intialized a server, you can add one or more 
          headers before starting the server::
  
              server.setHeader('Access-Control-Allow-Origin', '*')
              server.setHeader('Access-Control-Allow-Methods', '*')
              server.serve()
  
          :param name: The name of the header field to be defined.
          :param value: The value of the header field to be defined.
          """
          StaticFileHandler.set_default_headers = set_header(
                  StaticFileHandler.set_default_headers, name, value)
          self.SFH = StaticFileHandler
  
      def watch(self, filepath, func=None, delay=None, ignore=None):
          """Add the given filepath for watcher list.
  
          Once you have intialized a server, watch file changes before
          serve the server::
  
              server.watch('static/*.stylus', 'make static')
              def alert():
                  print('foo')
              server.watch('foo.txt', alert)
              server.serve()
  
          :param filepath: files to be watched, it can be a filepath,
                           a directory, or a glob pattern
          :param func: the function to be called, it can be a string of
                       shell command, or any callable object without
                       parameters
          :param delay: Delay sending the reload message. Use 'forever' to
                        not send it. This is useful to compile sass files to
                        css, but reload on changed css files then only.
          :param ignore: A function return True to ignore a certain pattern of
                         filepath.
          """
          if isinstance(func, str):
              cmd = func
              func = shell(func)
              func.name = f"shell: {cmd}"
  
          self.watcher.watch(filepath, func, delay, ignore=ignore)
  
      def application(self, port, host, liveport=None, debug=None,
                      live_css=True):
          LiveReloadHandler.watcher = self.watcher
          LiveReloadHandler.live_css = live_css
          if debug is None and self.app:
              debug = True
  
          live_handlers = [
              (r'/livereload', LiveReloadHandler),
              (r'/forcereload', ForceReloadHandler),
              (r'/livereload.js', LiveReloadJSHandler)
          ]
  
          # The livereload.js snippet.
          # Uses JavaScript to dynamically inject the client's hostname.
          # This allows for serving on 0.0.0.0.
          live_script = (
              '<script type="text/javascript">(function(){'
              'var s=document.createElement("script");'
              'var port=%s;'
              's.src="//"+window.location.hostname+":"+port'
              '+ "/livereload.js?port=" + port;'
              'document.head.appendChild(s);'
              '})();</script>'
          )
          if liveport:
              live_script = escape.utf8(live_script % liveport)
          else:
              live_script = escape.utf8(live_script % "(window.location.port || (window.location.protocol == 'https:' ? 443: 80))")
  
          web_handlers = self.get_web_handlers(live_script)
  
          class ConfiguredTransform(LiveScriptInjector):
              script = live_script
  
          if not liveport:
              handlers = live_handlers + web_handlers
              app = web.Application(
                  handlers=handlers,
                  debug=debug,
                  transforms=[ConfiguredTransform]
              )
              app.listen(port, address=host)
          else:
              app = web.Application(
                  handlers=web_handlers,
                  debug=debug,
                  transforms=[ConfiguredTransform]
              )
              app.listen(port, address=host)
              live = web.Application(handlers=live_handlers, debug=False)
              live.listen(liveport, address=host)
  
      def get_web_handlers(self, script):
          if self.app:
              fallback = LiveScriptContainer(self.app, script)
              return [(r'.*', web.FallbackHandler, {'fallback': fallback})]
          return [
              (r'/(.*)', self.SFH, {
                  'path': self.root or '.',
                  'default_filename': self.default_filename,
              }),
          ]
  
      def serve(self, port=5500, liveport=None, host=None, root=None, debug=None,
                open_url=False, restart_delay=2, open_url_delay=None,
                live_css=True, default_filename='index.html'):
          """Start serve the server with the given port.
  
          :param port: serve on this port, default is 5500
          :param liveport: live reload on this port
          :param host: serve on this hostname, default is 127.0.0.1
          :param root: serve static on this root directory
          :param debug: set debug mode, which autoreloads the app on code changes
                        via Tornado (and causes polling). Defaults to True when
                        ``self.app`` is set, otherwise False.
          :param open_url_delay: open webbrowser after the delay seconds
          :param live_css: whether to use live css or force reload on css.
                           Defaults to True
          :param default_filename: launch this file from the selected root on startup
          """
          host = host or '127.0.0.1'
          if root is not None:
              self.root = root
  
          self._setup_logging()
          logger.info(f'Serving on http://{host}:{port}')
  
          self.default_filename = default_filename
  
          self.application(
              port, host, liveport=liveport, debug=debug, live_css=live_css)
  
          # Async open web browser after 5 sec timeout
          if open_url:
              logger.error('Use `open_url_delay` instead of `open_url`')
          if open_url_delay is not None:
  
              def opener():
                  time.sleep(open_url_delay)
                  webbrowser.open(f'http://{host}:{port}')
              threading.Thread(target=opener).start()
  
          try:
              self.watcher._changes.append(('__livereload__', restart_delay))
              LiveReloadHandler.start_tasks()
              add_reload_hook(lambda: IOLoop.instance().close(all_fds=True))
              IOLoop.instance().start()
          except KeyboardInterrupt:
              logger.info('Shutting down...')
  
      def _setup_logging(self):
          logger.setLevel(logging.INFO)
  
          channel = logging.StreamHandler()
          channel.setFormatter(LogFormatter())
          logger.addHandler(channel)
  
          # need a tornado logging handler to prevent IOLoop._setup_logging
          logging.getLogger('tornado').addHandler(channel)
  