wind.py

#!/usr/bin/env python

"""Download and process the latest wind data

Usage:
  get-latest.py [--date=<YYYYMMDD>]
  get-latest.py [--dest=<filepath>]
  get-latest.py (-h | --help)
  get-latest.py --version

Options:
  -h --help          Show this screen.
  --version          Show version.
  --date=<YYYYMMDD>  Process wind data from a specific date.
  --dest=<filepath>  Destination filepath for the resulting JSON file

"""
from docopt import docopt
import datetime
from subprocess import call
import os
import errno
import urllib.request as urllib2
from time import strftime


def download_data(date):
    """Download wind data from NOAA.

    Downloads the GRIB (GRIdded Binary or General Regularly-distributed
    Information in Binary form) wind data from NOAA.
    Saves it in the data directory, adding a date string to the filename.

    Args:
        date: A string indicating the date of the data we want.

    Returns:
        A string of the downloaded GRIB filename.

    """

    iso_date_frag = (datetime.datetime.strptime(date, '%Y%m%d')
                     .strftime('%Y-%m-%d'))

    url = 'http://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_1p00.pl' + '?' + \
          'file=gfs.t00z.pgrb2.1p00.f000&' + \
          'lev_10_m_above_ground=on&' + \
          'var_UGRD=on&var_VGRD=on&' + \
          'leftlon=0&rightlon=360&toplat=90&bottomlat=-90&' + \
          'dir=%2Fgfs.' + date + '00'
    print (url)

    file_name = iso_date_frag + '_gfs.t00z.pgrbf00.grib2'
    try:
        u = urllib2.urlopen("%s" % (url))
        f = open('data/' + file_name, 'wb')
        block_sz = 8192
        while True:
            buffer = u.read(block_sz)
            if not buffer:
                break
            f.write(buffer)
        f.close()
        return f.name
    except (urllib2.HTTPError, e):
        print('HTTPError = ' + str(e.code))
        print
        print ('Unknown internet connection problem.')
        print
    except (urllib2.URLError, e):
        print ('URLError = ' + str(e.reason))
        print
        print ('Your internet connection is probably down.')
        print


def grib_2_json(grib_file, datestring,
                dest=None,
                apppath='/Applications/grib2json-0.8.0-SNAPSHOT/bin'):
    """Convert GRIB file to JSON.

    Converts the GRIB wind data into a JSON file that the Earth visualization
    system can read. Saves the file in date directories where Earth can
    access them. This assumes that you've setup Earth in your
    ~/src/wind/ directory.

    Args:
        grib_file: A string representing the filename of the GRIB file
        to be converted.
        datestring: A string representing the YYYYMMDD that this
        GRIB file represents
        dest: A string. The destination path for the JSON file.
        apppath: A string. The path to the grib2json script.

    Returns:
        A string of the converted JSON filename.

    """
    # Base dir for the weather data
    if dest is None:
        dest = (os.path.expanduser("~") +
                os.sep + 'src/wind/public/data/weather')

    current = (dest + os.sep + 'current' + os.sep +
               'current-wind-surface-level-gfs-1.0.json')

    # Data is read from year, month, and day directories,
    # so we need to create them.
    d = datetime.datetime.strptime(datestring, '%Y%m%d')
    dest = (os.path.normpath(dest) + os.sep +
            d.strftime('%Y') + os.sep +
            d.strftime('%m') + os.sep +
            d.strftime('%d') + os.sep)
    create_path(dest)

    # Convert files with the grib2json utility
    cmd = os.path.normpath(apppath) + os.sep + 'grib2json'
    dest = dest + '0000-wind-surface-level-gfs-1.0.json'
    cmd = (cmd + ' -d -n -o ' + dest + ' ' + grib_file)
    call(cmd, shell=True)

    # Make a symlink to the new file from the "current" path
    os.remove(current)
    os.symlink(dest, current)

    return dest


def create_path(path):
    """Try to create all the directories for a given filepath

    Args:
        path: A string of the filepath to create
    """
    try:
        os.makedirs(path)
    except OSError as exception:
        if exception.errno != errno.EEXIST:
            raise


if __name__ == '__main__':
    arguments = docopt(__doc__, version='Get Latest Data 0.0.1')
    if arguments['--date'] is None:
        date = datetime.datetime.now().strftime('%Y%m%d')
    else:
        date = arguments['--date']
    grib_file = download_data(date)
    if grib_file:
        json_file = grib_2_json(grib_file, date, arguments['--dest'])
    else:
        print ('''
You won't be able to get the latest wind data until the internet is reconnected
''')