#!python
import re
from sys import exit, argv
from os import listdir, rename

test = False

try:
    if argv[1] == "-t":
        test = True
        argv.remove("-t")
except:
    pass

if len(argv) < 2:
    print "Please: OLDPREFIX NEWPREFIX"
    exit(1)

old_prefix = argv[1]
new_prefix = argv[2]

try:
    dir = argv[3]
    while dir[-1] == "/": dir = dir[0:-1]
except IndexError:
    dir = "."

files = listdir(dir)
if len(files) == 0:
    print "No files here"
    exit(1)

for file in files:
    newfile = re.sub(old_prefix, new_prefix, file)
    if newfile[-3:] == 'JPG': newfile = newfile[0:-3] + "jpg"
    if newfile[-3:] == 'MPG': newfile = newfile[0:-3] + "mpg"
    if file != newfile:
        print file + " => " + newfile
        if not test:
            rename(dir + "/" + file, dir + "/" + newfile )