"""Add geotagged images to a kml for viewing in Google Earth.

This script takes a folder of images, and creates a placemark with a thumbnail
of each image, based on the GPS coordinates in the EXIF tags.

Usage:
  photo_to_kml [-h] IMAGE_FOLDER

Positional arguments:
  IMAGE_FOLDER  name of input folder

Optional arguments:
  -h, --help    show this help message and exit

Examples:

Create a kml for a folder of photos, named 'image_folder'.
> photo_to_kml image_folder

"""

import os
import sys
import argparse
from PIL import Image
from PIL.ExifTags import TAGS, GPSTAGS
import simplekml


def get_exif_data(image):
    """
    Return a dictionary from the exif data of an PIL Image object, and convert
    the GPS uags.
    https://gist.github.com/valgur/2fbed04680864fab1bfc
    """

    info = image._getexif()
    if not info:
        return {}
    exif_data = {TAGS.get(tag, tag): value for tag, value in info.items()}

    def is_fraction(val):
        return isinstance(val, tuple) and len(val) == 2 and isinstance(
            val[0], int) and isinstance(val[1], int)

    def frac_to_dec(frac):
        return float(frac[0]) / float(frac[1])

    if 'GPSInfo' in exif_data:
        gpsinfo = {
            GPSTAGS.get(t, t): v
            for t, v in exif_data['GPSInfo'].items()
        }
        for tag, value in gpsinfo.items():
            if is_fraction(value):
                gpsinfo[tag] = frac_to_dec(value)
            elif all(is_fraction(x) for x in value):
                gpsinfo[tag] = tuple(map(frac_to_dec, value))
        exif_data['GPSInfo'] = gpsinfo

    return exif_data


def get_lat_lon(exif_data):
    """
    Return the latitude and longitude (if available) from exif_data.
    https://gist.github.com/valgur/2fbed04680864fab1bfc
    """
    lat = None
    lon = None
    gps_info = exif_data.get('GPSInfo')

    def convert_to_degrees(value):
        d, m, s = value
        return d + (m / 60.0) + (s / 3600.0)

    if gps_info:
        gps_latitude = gps_info.get('GPSLatitude')
        gps_latitude_ref = gps_info.get('GPSLatitudeRef')
        gps_longitude = gps_info.get('GPSLongitude')
        gps_longitude_ref = gps_info.get('GPSLongitudeRef')

        if (gps_latitude and gps_latitude_ref and gps_longitude and
                gps_longitude_ref):
            lat = convert_to_degrees(gps_latitude)
            if gps_latitude_ref == 'S':
                lat = -lat

            lon = convert_to_degrees(gps_longitude)
            if gps_longitude_ref == 'W':
                lon = -lon

    return lat, lon


def export_kml_file(dirname, fnames, dirname_thumbs, kml_name):
    """
    Create the kml document
    """
    kml = simplekml.Kml()

    for fname in fnames:
        print('Reading {}...'.format(fname))
        with Image.open(os.path.join(dirname, fname)) as image:
            # Get EXIF tags
            exif_data = get_exif_data(image)

            # Save thumbnail
            image.thumbnail((128, 128))
            image.save(os.path.join(dirname_thumbs, fname), 'jpeg')

        lat, lon = get_lat_lon(exif_data)
        pnt = kml.newpoint(name=fname)
        pnt.coords = [(lon, lat)]

        # Add popup window with full-size image
        pnt.description = (
            '<![CDATA[ <img src="{}"" height="500px" />]]>'.format(
                os.path.join(dirname, fname)))

        # Show groups of photos as camera icon
        pnt.stylemap.normalstyle.iconstyle.scale = 1
        pnt.stylemap.normalstyle.iconstyle.icon.href = (
            'http://maps.google.com/'
            'mapfiles/kml/shapes/camera.png')

        # Show placemark as image thumbnail
        pnt.stylemap.highlightstyle.iconstyle.scale = 3
        pnt.stylemap.highlightstyle.iconstyle.icon.href = os.path.join(
            dirname_thumbs, fname)

    kml.save(kml_name)


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument(
        'folder',
        metavar='IMAGE_FOLDER',
        help='name of input folder',
        default=None)

    # Print usage if no arguments are provided
    if len(sys.argv) == 1:
        parser.print_help(sys.stderr)
        sys.exit(1)

    args = parser.parse_args()

    # Get files in image directory
    ext = ['.jpg', '.jpeg', '.tif', '.tiff']
    dirname = args.folder
    fnames = [
        f for f in os.listdir(dirname)
        if os.path.splitext(f)[-1].lower() in ext
    ]

    # Create thumbnails folder beside originals
    dirname_thumbs = os.path.join(os.path.dirname(dirname), 'thumbs')
    try:
        os.mkdir(dirname_thumbs)
    except FileExistsError:
        pass

    # Create kml file
    kml_name = dirname + '.kml'
    export_kml_file(dirname, fnames, dirname_thumbs, kml_name)


if __name__ == '__main__':
    main()