root/StormSiren/History.py

#!/usr/bin/env python

"""
StormSiren
Copyright (C) 2008  Chris Freeze <cfreeze/cfreeze_com\>

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 THE AUTHOR ``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 THE AUTHOR 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 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""

"""
This is StormSiren a program inspired by the StormSiren application
written by Roy McManus <slorf/users_sourceforge_net>.  Much like the
original StormSiren written by Roy McManus <slorf/users_sourceforge_net>,
this program is a simple script capable of scanning and providing
notifications of weather bulletins issued by the National
Weather Service.  StormSiren supports a wide range of paging devices
and filtering of alert types per alert device.  While inspired by
StormSiren, StormSiren is a complete rewrite that is capable of using
the new CAP/XML feeds provided at http://www.weather.gov/alerts/.

For more information there is see the README.TXT file located in the root
of this directory.
"""

import sys
import os
import logging

DEFAULT_MAX_HISTORICAL_EVENTS = 200

class History:
        def __init__(self, file, max_events = DEFAULT_MAX_HISTORICAL_EVENTS):
                self.file = file
                self.loaded = False
                self.history = {}
                self.new_history = []
                self.max_events = max_events
                self.log = logging.getLogger('History')
                self.modified = False

                self.log.setLevel(logging.INFO)

                # See if we can open the history file.  
                self.log.info("Loading history file %s" % self.file)
                try:
                        hist = open(self.file, 'r')
                        for line in hist:
                                cline = line.strip("\n")
                                self.history[cline] = cline
                        hist.close()
                        self.loaded = True

                # Don't worry if we can't open it.  We'll open it later during the writing stage
                except IOError:
                        self.log.debug("Unable to load history file [%s] assuming empty file" % self.file)
                        pass

        def exists(self,id):
                if(id in self.history):
                        return True
                else:
                        return False

        def add(self,id):
                self.modified = True
                self.history[id] = id
                self.new_history.append(id)

        def save(self):
                if(self.modified):
                        if((len(self.history) + len(self.new_history)) > self.max_events):
                                self.log.info("Saving history file, but trimming first")
                                self.saveWithTrim()
                        else:
                                self.log.info("Saving history file")
                                self.saveWithoutTrim()
                else:
                        self.log.debug("No modifications detected")

        def __write_list(self,list):
                try:
                        hist = open(self.file + ".tmp", 'w')
                        for a in list:
                                hist.write(a + '\n')
                        hist.close()
                except IOError:
                        self.log.error("Unable to write to temporary file: %s" % (self.file + ".tmp"))
                        sys.exit(2)

                try:
                        os.rename(self.file + ".tmp", self.file)
                except OSError,e:
                        self.log.error("Unable to overwrite history file: %s" % self.file)
                        sys.exit(2)

        def saveWithoutTrim(self):
                newlist = []
                for a in self.history.keys():
                        newlist.append(a)
                self.__write_list(newlist)

        def saveWithTrim(self):
                newlist = []

                #Read the original list back into an array first so that we can chop off the top
                try:
                        hist = open(self.file, 'r')
                        for line in hist:
                                cline = line.strip("\n")
                                newlist.append(cline)
                        hist.close()
                except IOError:
                        self.log.error("Unable to read history file: %s" % (self.file))
                        sys.exit(2)

                newlist.extend(self.new_history)
                newlist = newlist[-self.max_events:] #Slice off the end

                self.__write_list(newlist)

        def __str__(self):
                str = "History\n"
                str += "Items: %i\n" % len(self.history)
                str += "Added Items: %i\n" % len(self.new_history)
                str += "Max Events: %i\n" % self.max_events
                if((len(self.history) + len(self.new_history)) > self.max_events):
                        str += "Trim Required: yes\n"
                else:
                        str += "Trim Required: no\n"
                str += "Items\n\t"
                str += "\n\t".join(self.history)
                return str

        def display(self):
                print self.__str__()