"""
Provides a 'pyramid' command as a replacement to the 'start' command.

The reloading strategy is heavily inspired by (and partially copied from)
the pyramid script 'pserve'.
"""
import atexit
import errno
import os
import signal
import sys
import time
import threading
import subprocess

from cubicweb import BadCommandUsage, ExecutionError
from cubicweb.cwconfig import CubicWebConfiguration as cwcfg
from cubicweb.cwctl import CWCTL, InstanceCommand, init_cmdline_log_threshold

from pyramid_cubicweb import make_cubicweb_application
import waitress

MAXFD = 1024


class PyramidStartHandler(InstanceCommand):
    """Start an interactive pyramid server.

    This command requires http://hg.logilab.org/review/pyramid_cubicweb/

    <instance>
      identifier of the instance to configure.
    """
    name = 'pyramid'

    options = (
        ("debug",
         {'short': 'D', 'action': 'store_true',
          'help': 'start server in the foreground.'}),
        ('reload',
         {'action': 'store_true',
          'help': 'Restart the server if any source file is changed'}),
        ('reload-interval',
         {'type': 'int', 'default': 1,
          'help': 'Interval, in seconds, between file modifications checks'}),
        ('loglevel',
         {'short': 'l', 'type': 'choice', 'metavar': '<log level>',
          'default': None, 'choices': ('debug', 'info', 'warning', 'error'),
          'help': 'debug if -D is set, error otherwise',
          }),
    )

    _reloader_environ_key = 'CW_RELOADER_SHOULD_RUN'

    def debug(self, msg):
        print('DEBUG - %s' % msg)

    def info(self, msg):
        print('INFO - %s' % msg)

    def ordered_instances(self):
        instances = super(PyramidStartHandler, self).ordered_instances()
        if (self['debug'] or self['reload']) and len(instances) > 1:
            raise BadCommandUsage(
                '--debug and --reload can be used on a single instance only')
        return instances

    def quote_first_command_arg(self, arg):
        """
        There's a bug in Windows when running an executable that's
        located inside a path with a space in it.  This method handles
        that case, or on non-Windows systems or an executable with no
        spaces, it just leaves well enough alone.
        """
        if (sys.platform != 'win32' or ' ' not in arg):
            # Problem does not apply:
            return arg
        try:
            import win32api
        except ImportError:
            raise ValueError(
                "The executable %r contains a space, and in order to "
                "handle this issue you must have the win32api module "
                "installed" % arg)
        arg = win32api.GetShortPathName(arg)
        return arg

    def _remove_pid_file(self, written_pid, filename):
        current_pid = os.getpid()
        if written_pid != current_pid:
            # A forked process must be exiting, not the process that
            # wrote the PID file
            return
        if not os.path.exists(filename):
            return
        with open(filename) as f:
            content = f.read().strip()
        try:
            pid_in_file = int(content)
        except ValueError:
            pass
        else:
            if pid_in_file != current_pid:
                msg = "PID file %s contains %s, not expected PID %s"
                self.out(msg % (filename, pid_in_file, current_pid))
                return
        self.info("Removing PID file %s" % filename)
        try:
            os.unlink(filename)
            return
        except OSError as e:
            # Record, but don't give traceback
            self.out("Cannot remove PID file: (%s)" % e)
        # well, at least lets not leave the invalid PID around...
        try:
            with open(filename, 'w') as f:
                f.write('')
        except OSError as e:
            self.out('Stale PID left in file: %s (%s)' % (filename, e))
        else:
            self.out('Stale PID removed')

    def record_pid(self, pid_file):
        pid = os.getpid()
        self.debug('Writing PID %s to %s' % (pid, pid_file))
        with open(pid_file, 'w') as f:
            f.write(str(pid))
        atexit.register(
            self._remove_pid_file, pid, pid_file)

    def daemonize(self, pid_file):
        pid = live_pidfile(pid_file)
        if pid:
            raise ExecutionError(
                "Daemon is already running (PID: %s from PID file %s)"
                % (pid, pid_file))

        self.debug('Entering daemon mode')
        pid = os.fork()
        if pid:
            # The forked process also has a handle on resources, so we
            # *don't* want proper termination of the process, we just
            # want to exit quick (which os._exit() does)
            os._exit(0)
        # Make this the session leader
        os.setsid()
        # Fork again for good measure!
        pid = os.fork()
        if pid:
            os._exit(0)

        # @@: Should we set the umask and cwd now?

        import resource  # Resource usage information.
        maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
        if (maxfd == resource.RLIM_INFINITY):
            maxfd = MAXFD
        # Iterate through and close all file descriptors.
        for fd in range(0, maxfd):
            try:
                os.close(fd)
            except OSError:  # ERROR, fd wasn't open to begin with (ignored)
                pass

        if (hasattr(os, "devnull")):
            REDIRECT_TO = os.devnull
        else:
            REDIRECT_TO = "/dev/null"
        os.open(REDIRECT_TO, os.O_RDWR)  # standard input (0)
        # Duplicate standard input to standard output and standard error.
        os.dup2(0, 1)  # standard output (1)
        os.dup2(0, 2)  # standard error (2)

    def restart_with_reloader(self):
        self.debug('Starting subprocess with file monitor')

        while True:
            args = [self.quote_first_command_arg(sys.executable)] + sys.argv
            new_environ = os.environ.copy()
            new_environ[self._reloader_environ_key] = 'true'
            proc = None
            try:
                try:
                    proc = subprocess.Popen(args, env=new_environ)
                    exit_code = proc.wait()
                    proc = None
                    print "Process exited with ", exit_code
                except KeyboardInterrupt:
                    self.info('^C caught in monitor process')
                    return 1
            finally:
                if proc is not None:
                    proc.terminate()
                    self.info(
                        'Waiting for the server to stop. Hit CTRL-C to exit')
                    exit_code = proc.wait()

            if exit_code != 3:
                return exit_code

            self.info('%s %s %s' % ('-' * 20, 'Restarting', '-' * 20))

    def set_needreload(self):
        self._needreload = True

    def install_reloader(self, poll_interval, extra_files):
        mon = Monitor(
            poll_interval=poll_interval, extra_files=extra_files,
            atexit=self.set_needreload)
        mon_thread = threading.Thread(target=mon.periodic_reload)
        mon_thread.daemon = True
        mon_thread.start()

    def pyramid_instance(self, appid):
        self._needreload = False

        if self['reload'] and not os.environ.get(self._reloader_environ_key):
            return self.restart_with_reloader()

        cwconfig = cwcfg.config_for(appid, debugmode=self['debug'])

        if self['reload']:
            _turn_sigterm_into_systemexit()
            self.debug('Running reloading file monitor')
            extra_files = [sys.argv[0], cwconfig.main_config_file()]
            self.install_reloader(self['reload-interval'], extra_files)

        if not self['reload'] and not self['debug']:
            self.daemonize(cwconfig['pid-file'])
            self.record_pid(cwconfig['pid-file'])

        init_cmdline_log_threshold(cwconfig, self['loglevel'])

        host = cwconfig['interface']
        port = cwconfig['port'] or 8080

        pyramid_config = make_cubicweb_application(cwconfig)

        repo = cwconfig.repository()
        try:
            repo.start_looping_tasks()
            waitress.serve(
                pyramid_config.make_wsgi_app(), host=host, port=port)
        finally:
            repo.shutdown()
        if self._needreload:
            return 3
        return 0

CWCTL.register(PyramidStartHandler)


def live_pidfile(pidfile):  # pragma: no cover
    """(pidfile:str) -> int | None
    Returns an int found in the named file, if there is one,
    and if there is a running process with that process id.
    Return None if no such process exists.
    """
    pid = read_pidfile(pidfile)
    if pid:
        try:
            os.kill(int(pid), 0)
            return pid
        except OSError as e:
            if e.errno == errno.EPERM:
                return pid
    return None


def read_pidfile(filename):
    if os.path.exists(filename):
        try:
            with open(filename) as f:
                content = f.read()
            return int(content.strip())
        except (ValueError, IOError):
            return None
    else:
        return None


def _turn_sigterm_into_systemexit():
    """
    Attempts to turn a SIGTERM exception into a SystemExit exception.
    """
    try:
        import signal
    except ImportError:
        return

    def handle_term(signo, frame):
        raise SystemExit
    signal.signal(signal.SIGTERM, handle_term)


class Monitor(object):
    """
    A file monitor and server stopper.

    It is a simplified version of pyramid pserve.Monitor, with little changes:

    -   The constructor takes extra_files and atexit
    -   The process is stopped by auto-kill with signal SIGTERM
    """
    def __init__(self, poll_interval, extra_files=[], atexit=None):
        self.module_mtimes = {}
        self.keep_running = True
        self.poll_interval = poll_interval
        self.extra_files = extra_files
        self.atexit = atexit

    def _exit(self):
        if self.atexit:
            self.atexit()
        os.kill(os.getpid(), signal.SIGTERM)

    def periodic_reload(self):
        while True:
            if not self.check_reload():
                self._exit()
                break
            time.sleep(self.poll_interval)

    def check_reload(self):
        filenames = list(self.extra_files)

        for module in list(sys.modules.values()):
            try:
                filename = module.__file__
            except (AttributeError, ImportError):
                continue
            if filename is not None:
                filenames.append(filename)

        for filename in filenames:
            try:
                stat = os.stat(filename)
                if stat:
                    mtime = stat.st_mtime
                else:
                    mtime = 0
            except (OSError, IOError):
                continue
            if filename.endswith('.pyc') and os.path.exists(filename[:-1]):
                mtime = max(os.stat(filename[:-1]).st_mtime, mtime)
            if not filename in self.module_mtimes:
                self.module_mtimes[filename] = mtime
            elif self.module_mtimes[filename] < mtime:
                print('%s changed; reloading...' % filename)
                return False

        return True