import time;
import urllib;
import re;
import os;
from shutil import move;

class PollItem:
    def __init__(self, url, period):
        self.url=url;
        self.period=period;
        self.remaining=0;

    def elapse(self, time):
        self.remaining -= time;

    def reset(self):
        self.remaining=self.period;

    def __cmp__(self, item):
        if self.remaining < item.remaining:
            return -1;
        if self.remaining > item.remaining:
            return 1;
        return 0;


class FeedWatcher:

    def __init__(self, feeds, dest, dirapi):
        self.feeds=feeds
        self.dest=dest
        self.dirapi="%s/feeds/download"%dirapi
        self.pollitems=[]

        file = open(feeds, 'r')

        for line in file:
            if line.startswith("FEED"):
                (type, url, period)=line.split(' ')
                period=float(period)
                self.pollitems.append(PollItem(url, period))

        while(1):
            while(self.pollitems[0].remaining <= 0):
                print "Checking",self.pollitems[0].url
                self.check(self.pollitems[0].url)
                self.pollitems[0].reset()
                self.pollitems.sort()
            next=float(self.pollitems[0].remaining)
            print "Next check in",next
            time.sleep(next)
            for item in self.pollitems:
                item.elapse(next);

    def check(self, url):
        site=urllib.urlopen(url);
        outurl=re.sub("/",".",url)
        outurl=outurl[7:]
        destfilename="%s/%s"%(self.dest,outurl)
        difffilename="%s/%s-diff"%(self.dirapi,outurl)
        tempfilename="%s/current"%(self.dest)


        #If the file exists, create an empty file
        #System works by always sending a diff, so
        #The initial condition is a diff against empty file
        if not os.path.isfile(destfilename):
            outfile=open(destfilename,'w');
            outfile.close();

        #The file current is a temp file that holds the
        #latest fetched feed for comparison.
        outfile=open(tempfilename,'w')
        for line in site:
            outfile.write(line)
        outfile.close()

        #Now, do the diff, write to difffilename
        diffcmd="diff -u %s %s"%(destfilename,tempfilename)
        print diffcmd
        diff=os.popen(diffcmd).readlines()
        if len(diff)>0:
            outfile=open(difffilename,'w')
            outfile.write("FEED %s\n"%outurl)
            for line in diff:
                outfile.write(line);
            outfile.close()

        #Finally, copy the whole thing in case we need to send it all
        #over, later.
        move(tempfilename, destfilename)





if __name__=="__main__":
        watcher = FeedWatcher("src/feeds.conf","feeds")