# Copyright 2013 Daniel Narvaez
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging
import os
import plog
import time


def start():
    xvfb_display = _find_free_display()

    xvfb_proc = plog.LoggedProcess(args=["Xvfb", xvfb_display])
    xvfb_proc.execute()

    orig_display = os.environ.get("DISPLAY", None)
    os.environ["DISPLAY"] = xvfb_display

    tries = 30
    while not _try_display(xvfb_display):
        time.sleep(1)
        if tries > 0:
            tries = tries - 1
            logging.error("Cannot access Xvfb display, retrying...")
        else:
            logging.error("Giving up.")
            break

    return (xvfb_proc, orig_display)


def stop(xvfb_proc, orig_display):
    if orig_display is not None:
        os.environ["DISPLAY"] = orig_display

    xvfb_proc.terminate()


def _try_display(display):
    process = plog.LoggedProcess(["xdpyinfo", "-display", display])
    process.execute()

    return process.wait(print_error=False) == 0


def _find_free_display():
    for i in range(100, 1000):
        display = ":%s" % i
        if not _try_display(display):
            return display

# Copyright 2013 Daniel Narvaez
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging
import os
import plog
import time


def start():
    xvfb_display = _find_free_display()

    xvfb_proc = plog.LoggedProcess(args=["Xvfb", xvfb_display])
    xvfb_proc.execute()

    orig_display = os.environ.get("DISPLAY", None)
    os.environ["DISPLAY"] = xvfb_display

    tries = 30
    while not _try_display(xvfb_display):
        time.sleep(1)
        if tries > 0:
            tries = tries - 1
            logging.error("Cannot access Xvfb display, retrying...")
        else:
            logging.error("Giving up.")
            break

    return (xvfb_proc, orig_display)


def stop(xvfb_proc, orig_display):
    if orig_display is not None:
        os.environ["DISPLAY"] = orig_display

    xvfb_proc.terminate()


def _try_display(display):
    process = plog.LoggedProcess(["xdpyinfo", "-display", display])
    process.execute()

    return process.wait(print_error=False) == 0


def _find_free_display():
    for i in range(100, 1000):
        display = ":%s" % i

        if not os.path.exists("/tmp", ".X%s-lock" % i):
            if not _try_display(display):
                return display

Check the X lock