# Copyright (C) 2010 Google Inc. All rights reserved.
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# modification, are permitted provided that the following conditions are
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#     * Redistributions of source code must retain the above copyright
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import logging
import os
import re
import time

from webkitpy.layout_tests.port.server_process import ServerProcess
from webkitpy.layout_tests.port.driver import Driver
from webkitpy.common.system.file_lock import FileLock

_log = logging.getLogger(__name__)


class XvfbDriver(Driver):
    def __init__(self, *args, **kwargs):
        Driver.__init__(self, *args, **kwargs)
        self._guard_lock = None
        self._startup_delay_secs = 1.0

    def _next_free_display(self):
        running_pids = self._port.host.executive.run_command(['ps', '-eo', 'comm,command'])
        reserved_screens = set()
        for pid in running_pids.split('\n'):
            match = re.match('(X|Xvfb|Xorg)\s+.*\s:(?P<screen_number>\d+)', pid)
            if match:
                reserved_screens.add(int(match.group('screen_number')))
        for i in range(99):
            if i not in reserved_screens:
                _guard_lock_file = self._port.host.filesystem.join('/tmp', 'WebKitXvfb.lock.%i' % i)
                self._guard_lock = FileLock(_guard_lock_file)
                if self._guard_lock.acquire_lock():
                    return i

    def _start(self, pixel_tests, per_test_args):
        # Use even displays for pixel tests and odd ones otherwise. When pixel tests are disabled,
        # DriverProxy creates two drivers, one for normal and the other for ref tests. Both have
        # the same worker number, so this prevents them from using the same Xvfb instance.
        display_id = self._next_free_display()
        self._lock_file = "/tmp/.X%d-lock" % display_id

        run_xvfb = ["Xvfb", ":%d" % display_id, "-screen",  "0", "800x600x24", "-nolisten", "tcp"]
        with open(os.devnull, 'w') as devnull:
            self._xvfb_process = self._port.host.executive.popen(run_xvfb, stderr=devnull)

        # Crashes intend to occur occasionally in the first few tests that are run through each
        # worker because the Xvfb display isn't ready yet. Halting execution a bit should avoid that.
        time.sleep(self._startup_delay_secs)

        server_name = self._port.driver_name()
        environment = self._port.setup_environ_for_server(server_name)
        # We must do this here because the DISPLAY number depends on _worker_number
        environment['DISPLAY'] = ":%d" % display_id
        self._driver_tempdir = self._port._filesystem.mkdtemp(prefix='%s-' % self._port.driver_name())
        environment['DUMPRENDERTREE_TEMP'] = str(self._driver_tempdir)
        environment['LOCAL_RESOURCE_ROOT'] = self._port.layout_tests_dir()

        # Currently on WebKit2, there is no API for setting the application
        # cache directory. Each worker should have it's own and it should be
        # cleaned afterwards, so we set it to inside the temporary folder by
        # prepending XDG_CACHE_HOME with DUMPRENDERTREE_TEMP.
        environment['XDG_CACHE_HOME'] = self._port.host.filesystem.join(str(self._driver_tempdir), 'appcache')

        self._crashed_process_name = None
        self._crashed_pid = None
        self._server_process = self._port._server_process_constructor(self._port, server_name, self.cmd_line(pixel_tests, per_test_args), environment)
        self._server_process.start()

    def stop(self):
        super(XvfbDriver, self).stop()
        if self._guard_lock:
            self._guard_lock.release_lock()
            self._guard_lock = None
        if getattr(self, '_xvfb_process', None):
            self._port.host.executive.kill_process(self._xvfb_process.pid)
            self._xvfb_process = None
            if self._port.host.filesystem.exists(self._lock_file):
                self._port.host.filesystem.remove(self._lock_file)