#!/usr/bin/python

__version__ = '$Id: exif_redater.py 469 2008-03-05 06:09:01Z mn $'

USAGE = "exif_redater.py\n\tredate .jpg/.jpeg files according to EXIF data"

"""
Iterates through a directory, reading the EXIF data from each jpg/jpeg file.
Parses the date/time from EXIF data and if it differs from file
modification date/time then changes file date/time

author: Michal Niklas
"""

import os
import os.path
import sys
import time

import EXIF

ALL_CNT = 0
CHANGED_CNT = 0

EXTENSIONS = ('.jpg', '.jpeg')

def show_fdt(fdt):
    """human readable format of file modification datetime"""
    return time.strftime("%Y-%m-%d %H:%M:%S", time.gmtime(fdt))


# 2005:10:20 23:22:28
def exif_info2time(ts):
    """changes EXIF date ('2005:10:20 23:22:28') to number of seconds since 1970-01-01"""
    tpl = time.strptime(ts, '%Y:%m:%d %H:%M:%S')
    return time.mktime(tpl)


def redate_by_exif(fn):
    """reads EXIF from jpg/jpeg and if file datetime differs from EXIF changes file date"""
    global ALL_CNT, CHANGED_CNT
    ALL_CNT += 1
    exif_time = None
    s = os.stat(fn)
    f = open(fn, 'rb')
    try:
        tags = EXIF.process_file(f)
        dt_value = "%s" % tags["Image DateTime"]
        file_time = s[8]
        exif_time = exif_info2time(dt_value)
    finally:
        f.close()
    if exif_time:
        secs_diff = file_time - exif_time
        MAX_DIFF = 130.0
        if secs_diff > MAX_DIFF or secs_diff < -MAX_DIFF:
            print "%s    %s -> %s" % (fn, show_fdt(file_time), show_fdt(exif_time))
            os.utime(fn, (exif_time, exif_time))
            CHANGED_CNT += 1


def process_dir(_, dir_name, files):
    """looks for .jpg/.jpeg file in dir"""
    for fname in files:
        can_change = False
        fnl = fname.lower()
        for ext in EXTENSIONS:
            if fnl.endswith(ext):
                can_change = True
                break
        if can_change:
            fname = dir_name + '/' + fname
            if os.path.isfile(fname):
                try:
                    redate_by_exif(fname)
                except:
                    pass


def main():
    os.path.walk('.', process_dir, None)
    print '\nChecked: %d\nChanged %d\n' % (ALL_CNT, CHANGED_CNT)


if '--version' in sys.argv:
    print __version__
else:
    if __name__ == '__main__':
        if '--help' in sys.argv:
            print USAGE
        else:
            main()