#
# dexif.py - simple EXIF processing for Degal
# Copyright (C) 2008, Santtu Pajukanta <santtu@pajukanta.fi>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the
# Free Software Foundation, Inc.,
# 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#

from subprocess import Popen, PIPE

# TODO This should be user configurable
EXIFTOOL="/usr/bin/exiftool"

outputTags = [
# TODO Create date is in a useless format, needs some strptime love
    ("CreateDate", "Create date"),
    ("Model", "Camera model"),
    ("Aperture", "Aperture"),
    ("ExposureMode", "Exposure mode"),
    ("ExposureCompensation", "Exposure compensation"),
    ("ExposureTime", "Exposure time"),
    ("Flash", "Flash mode"),
    ("ISO", "ISO"),
    ("ShootingMode", "Shooting mode"),
    ("LensType", "Lens type"),
    ("FocalLength", "Focal length")
]


class ExifError(Exception):
    pass

def parse_exif(filepath):
    """parse_exif(filepath :: String) -> [(String, String)]

    Parse EXIF tags from an image file and return them in a dict.
    """

    args = [EXIFTOOL, "-s", "-t", filepath]
    etproc = Popen(args, stdout = PIPE)

    output, errors = etproc.communicate()
    
    if etproc.returncode < 0:
        raise ExifError, "exiftool terminated by signal %d" % (-etproc.returnco)
    elif etproc.returncode > 0:
        raise ExifError, "exiftool failed with return code %d" % etproc.returncode
    
    tags = dict(line.split("\t", 1) for line in output.split("\n") if line)
    result = [(descr, tags[key]) for (key, descr) in outputTags if tags.has_key(key)]
    return result