# Licensed to the Software Freedom Conservancy (SFC) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The SFC licenses this file
# to you 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.
from subprocess import DEVNULL

import errno
import os
import subprocess
from platform import system
from subprocess import PIPE
from time import sleep
from selenium.common.exceptions import WebDriverException
from selenium.webdriver.common import utils


_HAS_NATIVE_DEVNULL = True


class Service(object):

    def __init__(self, executable, port=0, log_file=DEVNULL, env=None, start_error_message=""):
        self.path = executable

        self.port = port
        if self.port == 0:
            self.port = utils.free_port()

        if not _HAS_NATIVE_DEVNULL and log_file == DEVNULL:
            log_file = open(os.devnull, 'wb')

        self.start_error_message = start_error_message
        self.log_file = log_file
        # Default value for every python subprocess: subprocess.Popen(..., creationflags=0)
        self.creationflags = 0
        self.env = env or os.environ

    @property
    def service_url(self):
        """
        Gets the url of the Service
        """
        return "http://%s" % utils.join_host_port('localhost', self.port)

    def command_line_args(self):
        raise NotImplementedError("This method needs to be implemented in a sub class")

    def start(self):
        """
        Starts the Service.

        :Exceptions:
         - WebDriverException : Raised either when it can't start the service
           or when it can't connect to the service
        """
        try:
            cmd = [self.path]
            cmd.extend(self.command_line_args())
            self.process = subprocess.Popen(cmd, env=self.env,
                                            close_fds=system() != 'Windows',
                                            stdout=self.log_file,
                                            stderr=self.log_file,
                                            stdin=PIPE,
                                            creationflags=self.creationflags)
        except TypeError:
            raise
        except OSError as err:
            if err.errno == errno.ENOENT:
                raise WebDriverException(
                    "'%s' executable needs to be in PATH. %s" % (
                        os.path.basename(self.path), self.start_error_message)
                )
            elif err.errno == errno.EACCES:
                raise WebDriverException(
                    "'%s' executable may have wrong permissions. %s" % (
                        os.path.basename(self.path), self.start_error_message)
                )
            else:
                raise
        except Exception as e:
            raise WebDriverException(
                "The executable %s needs to be available in the path. %s\n%s" %
                (os.path.basename(self.path), self.start_error_message, str(e)))
        count = 0
        while True:
            self.assert_process_still_running()
            if self.is_connectable():
                break

            count += 1
            sleep(0.5)
            if count == 60:
                raise WebDriverException("Can not connect to the Service %s" % self.path)

    def assert_process_still_running(self):
        return_code = self.process.poll()
        if return_code:
            raise WebDriverException(
                'Service %s unexpectedly exited. Status code was: %s'
                % (self.path, return_code)
            )

    def is_connectable(self):
        return utils.is_connectable(self.port)

    def send_remote_shutdown_command(self):
        from urllib import request as url_request
        URLError = url_request.URLError

        try:
            url_request.urlopen("%s/shutdown" % self.service_url)
        except URLError:
            return

        for x in range(30):
            if not self.is_connectable():
                break
            else:
                sleep(1)

    def stop(self):
        """
        Stops the service.
        """
        if self.log_file != PIPE and not (self.log_file == DEVNULL and _HAS_NATIVE_DEVNULL):
            try:
                self.log_file.close()
            except Exception:
                pass

        if not self.process:
            return

        try:
            self.send_remote_shutdown_command()
        except TypeError:
            pass

        try:
            if self.process:
                for stream in [self.process.stdin,
                               self.process.stdout,
                               self.process.stderr]:
                    try:
                        stream.close()
                    except AttributeError:
                        pass
                self.process.terminate()
                self.process.wait()
                self.process.kill()
                self.process = None
        except OSError:
            pass

    def __del__(self):
        # `subprocess.Popen` doesn't send signal on `__del__`;
        # so we attempt to close the launched process when `__del__`
        # is triggered.
        try:
            self.stop()
        except Exception:
            pass