Preloads JSON & images for our University Museums offline JavaScript applicaiton

preloader.py

import json
import urllib2
import os
import codecs

from urlparse import urlparse
from string import Template

build_dir = os.environ['TARGET_FOLDER']

MUSEUMS_ENDPOINT = "SNIP!"
PRELOAD_IMAGE_PATH = "%s/images/preloaded" % build_dir
INDEX_PATH = "%s/index.html" % build_dir
HAL_EMBED = '_embedded'


def get_json():
    return json.load(urllib2.urlopen(MUSEUMS_ENDPOINT))


def preload_url(url):
    parsed = urlparse(url)
    download_path = os.path.join(PRELOAD_IMAGE_PATH, parsed.path[1:])
    try:
        os.makedirs(download_path.rpartition('/')[0])
    except OSError:
        pass  # Just means the path already exists
    with open(download_path, 'w') as fp:
        fp.write(urllib2.urlopen(url).read())
    path = download_path.partition('/')[2]
    print "Image preloaded: %s -> %s" % (url, path)
    return path


def preload(response):
    """Reads our JSON response and mirrors the images of Floorplans and Museum
    items into the phonegap build folder. Returns a dictionary of all the files
    original locations and their mirrored location within the phonegap build.
    """
    try:
        os.makedirs(PRELOAD_IMAGE_PATH)
    except OSError:
        pass
    preloaded = {}
    for museum in response[HAL_EMBED]:
        preloaded[museum[HAL_EMBED]['floorplan']['image']] = preload_url(museum[HAL_EMBED]['floorplan']['image'])
        preloaded[museum['front_page_image_url']] = preload_url(museum['front_page_image_url'])
        for item in museum[HAL_EMBED]['items']:
            preloaded[item['cropped_image_resize']] = preload_url(item['cropped_image_resize'])
    return preloaded


def write_json(bootstrap, preloaded):
    """Uses a simple Python string template to write a "bootstrappped" JSON
    response into the index.html for our phonegap build. This way we always
    ship with the most up-to-date JSON.

    Also writes the JSON for which images have been preloaded. Handled in JS
    by app/preloaded.js
    """
    with codecs.open(INDEX_PATH, 'r+', 'utf-8') as indexfp:
        index = Template(indexfp.read())
        indexfp.seek(0)
        jsons = json.dumps(bootstrap)
        preloaded = json.dumps(preloaded)
        indexfp.write(index.substitute(museums=jsons, preload=preloaded))
        print "Embedded JSON"


if __name__ == '__main__':
    bootstrap = get_json()
    preloaded_files = preload(bootstrap)
    write_json(bootstrap, preloaded_files)
    print "Done."