#!/usr/bin/env python
import os
import sys
import time

instances = os.popen("pgrep -fl generate_thumbnails").read().split("\n")
if len(instances) > 3: sys.exit(0)

def main():
    fnames = [l.strip().split('\t') for l in open('all_pdf_files')] 
    
    while 1:
        index, fname = get_file(fnames)
        if fname == None: break
        print fname
        os.system('convert -limit memory 32 -limit map 32 -thumbnail x300 "%s[0]" "%s.gif"' % (fname, fname))

        fnames[index] = ('2', fname)
        o = open('all_pdf_files','wb')
        for i, (c, f) in enumerate(fnames):
            o.write('%s\t%s\n' % (c, f))
        o.close()

def get_file(fnames):
    for index, (code, fname) in enumerate(fnames):
        if code == '0':
            fnames[index] = ('1', fname)
            o = open('all_pdf_files','wb')
            for i, (c, f) in enumerate(fnames):
                o.write('%s\t%s\n' % (c, f))
            o.close()
            return index, fname
    return None, None 

main()