#!/usr/bin/env python
# Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
# Copyright (C) 2010 Andras Becsi (abecsi@inf.u-szeged.hu), University of Szeged
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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"""This class helps to block NRWT threads when more NRWTs run
http and websocket tests in a same time."""

import glob
import logging
import os
import sys
import tempfile
import time

from webkitpy.common.system.executive import Executive


_log = logging.getLogger("webkitpy.layout_tests.port.http_lock")


class HttpLock(object):

    def __init__(self, lock_path, lock_file_prefix="WebKitHttpd.lock.",
                 guard_lock="WebKit.lock"):
        self._lock_path = lock_path
        if not self._lock_path:
            self._lock_path = tempfile.gettempdir()
        self._lock_file_prefix = lock_file_prefix
        self._lock_file_path_prefix = os.path.join(self._lock_path,
                                                   self._lock_file_prefix)
        self._guard_lock_file = os.path.join(self._lock_path, guard_lock)
        self._process_lock_file_name = ""
        self._executive = Executive()
        # maximum wait time for the lock creation
        self._guard_lock_max_wait = 1 * 60

    def cleanup_http_lock(self):
        """Delete the lock file if exists."""
        if os.path.exists(self._process_lock_file_name):
            _log.debug("Removing lock file: %s" % self._process_lock_file_name)
            os.unlink(self._process_lock_file_name)

    def _extract_lock_number(self, lock_file_name):
        """Return the lock number from lock file."""
        prefix_length = len(self._lock_file_path_prefix)
        return int(lock_file_name[prefix_length:])

    def _lock_file_list(self):
        """Return the list of lock files sequentially."""
        lock_list = glob.glob(self._lock_file_path_prefix + '*')
        lock_list.sort(key=self._extract_lock_number)
        return lock_list

    def _next_lock_number(self):
        """Return the next available lock number."""
        lock_list = self._lock_file_list()
        if not lock_list:
            return 0
        return self._extract_lock_number(lock_list[-1]) + 1

    def _curent_lock_pid(self):
        """Return with the current lock pid. If the lock is not valid
        it deletes the lock file."""
        lock_list = self._lock_file_list()
        if not lock_list:
            return
        try:
            current_lock_file = open(lock_list[0], 'r')
            current_pid = current_lock_file.readline()
            current_lock_file.close()
            if not (current_pid and self._executive.check_running_pid(int(current_pid))):
                _log.debug("Removing stuck lock file: %s" % lock_list[0])
                os.unlink(lock_list[0])
                return
        except IOError, OSError:
            return
        return int(current_pid)

    def _create_lock_file(self):
        """The lock files are used to schedule the running test sessions in first
        come first served order. The sequential guard lock ensures that the lock
        numbers are sequential."""
        if not os.path.exists(self._lock_path):
            _log.debug("Lock directory does not exist: %s" % self._lock_path)
            return False

        start_time = time.time()
        while(True):
            try:
                sequential_guard_lock = os.open(self._guard_lock_file, os.O_CREAT | os.O_EXCL)
                self._process_lock_file_name = (self._lock_file_path_prefix +
                                                str(self._next_lock_number()))
                lock_file = open(self._process_lock_file_name, 'w')
                _log.debug("Creating lock file: %s" % self._process_lock_file_name)
                lock_file.write(str(os.getpid()))
                lock_file.close()
                os.close(sequential_guard_lock)
                os.unlink(self._guard_lock_file)
                return True
            except OSError:
                if time.time() - start_time > self._guard_lock_max_wait:
                    _log.debug("Lock does not created: %s" % str(sys.exc_info()))
                    return False

    def wait_for_httpd_lock(self):
        """Create a lock file and wait until it's turn comes. If something goes wrong
        it wont do any locking."""
        if not self._create_lock_file():
            _log.debug("Warning, http locking failed!")
            return

        while self._curent_lock_pid() != os.getpid():
            time.sleep(1)