Added support for LAADS downloads

Still not very functional (e.g. no spatial subsetting), basically
you select a product, a year(s) and DoY(s) and it will download
everything in the (usually) 5-minute granules. Not super-tested,
and it seems LAADS doesn't require usernames and/or passwords, so
it's all pretty good.

Addresses #14

get_laads.py

@@ -0,0 +1,166 @@
+#!/usr/bin/env python
+
+import json
+import logging
+import optparse
+import sys
+from concurrent import futures
+from pathlib import Path
+
+import requests
+from tqdm.auto import tqdm
+
+__author__ = "J Gomez-Dans"
+__copyright__ = "Copyright 2020 J Gomez-Dans"
+__version__ = "1.0.0"
+__license__ = "GPLv3"
+__email__ = "j.gomez-dans@ucl.ac.uk"
+
+HELP_TEXT = """
+SYNOPSIS
+./get_laads.py [-h,--help] 
+[--verbose, -v] 
+[--product=PRODUCT, -p PRODUCT]      [--year=YEAR, -y YEAR]
+[--output=DIR_OUT, -o DIR_OUT]     [--doys=DOY,DOY, -b DOY,DOY]
+DESCRIPTION
+A program to download MODIS data from the LAADS website using the HTTP
+transport. 
+EXIT STATUS
+    No exit status yet, can't be bothered.
+AUTHOR
+    J Gomez-Dans <j.gomez-dans@ucl.ac.uk>
+    See also http://github.com/jgomezdans/get_modis/
+"""
+
+
+LOG = logging.getLogger(__name__)
+OUT_HDLR = logging.StreamHandler(sys.stdout)
+OUT_HDLR.setFormatter(logging.Formatter("%(asctime)s %(message)s"))
+OUT_HDLR.setLevel(logging.INFO)
+LOG.addHandler(OUT_HDLR)
+LOG.setLevel(logging.DEBUG)
+
+HEADERS = {"User-Agent": "get_modis Python %s" % __version__}
+
+CHUNKS = 65536
+
+
+URL = "https://ladsweb.modaps.eosdis.nasa.gov/archive/allData/61"
+
+
+def download_products(url, loc):
+    fname = loc / url.split("/")[-1]
+    r = requests.get(url)
+    with fname.open(mode="wb") as fp:
+        fp.write(r.content)
+    LOG.debug("Saved " + str(fname))
+
+
+def download_filelist(url):
+    r = requests.get(url)
+    return json.loads(r.content)
+
+
+def make_query(location, product, years, doys, n_threads=8):
+    location = Path(location)
+    grabber = lambda x: download_products(x, location)
+    if not location.exists():
+        raise IOError(f"Destination folder {location} does not exist!")
+    if type(doys) != list:
+        doys = [
+            doys,
+        ]
+    if type(years) != list:
+        years = [
+            years,
+        ]
+    for year in years:
+        LOG.info(f"Doing year {year}")
+        urls = [f"{URL}/{product}/{year}/{doy:03d}.json" for doy in doys]
+        dload_files = []
+        with futures.ThreadPoolExecutor(max_workers=n_threads) as executor:
+            dload_files = list(
+                tqdm(executor.map(download_filelist, urls), total=len(urls))
+            )
+        datas = list(zip(doys, dload_files))
+        req_products = [
+            f"{URL}/{years}/{doy:03}/{x['name']}"
+            for doy, z in datas
+            for x in z
+        ]
+        LOG.info(
+            f"\tWill now download {len(req_products)} products in total..."
+        )
+        with futures.ThreadPoolExecutor(max_workers=n_threads) as executor:
+            dload_files = list(
+                tqdm(
+                    executor.map(grabber, req_products),
+                    total=len(req_products),
+                )
+            )
+        LOG.info("\tDone with this year!")
+
+
+def main():
+    parser = optparse.OptionParser(
+        formatter=optparse.TitledHelpFormatter(), usage=HELP_TEXT
+    )
+    parser.add_option(
+        "-v",
+        "--verbose",
+        action="store_true",
+        default=False,
+        help="verbose output",
+    )
+    parser.add_option(
+        "-p",
+        "--product",
+        action="store",
+        dest="product",
+        type=str,
+        help="MODIS product name "
+        + "(e.g. MOD05_L2)",
+    )
+    parser.add_option(
+        "-o",
+        "--output",
+        action="store",
+        dest="dir_out",
+        default=".",
+        type=str,
+        help="Output directory",
+    )
+    parser.add_option(
+        "-y",
+        "--year",
+        action="store",
+        dest="year",
+        type=str,
+        help="Years to consider (comma-separated)",
+    )
+    parser.add_option(
+        "-d",
+        "--doys",
+        action="store",
+        dest="doys",
+        type=str,
+        default=None,
+        help="Doys to consider (comma-separated)",
+    )
+
+    (options, args) = parser.parse_args()
+    if options.verbose:
+        LOG.setLevel(logging.DEBUG)
+    else:
+        LOG.setLevel(logging.INFO)
+    product = options.product.upper()
+    years = list(map(int, options.year.split(",")))
+    doys = list(map(int, options.doys.split(",")))
+    LOG.info("MODIS downloader by J Gomez-Dans...")
+    LOG.info("Starting downloading")
+
+    make_query(options.dir_out, product, years, doys)
+
+
+if __name__ == "__main__":
+    main()