#############################################################################################
# 2022-09-20
# Python example script using pycurl with EarthScope Command Line Interface (CLI) to 
#  authenticate for data access at data-idm.unavco.org (soon to be needed for data.unavco.org)
# + Calls the CLI in a subprocess to get an access token (CLI refreshes tokens automatically, as needed)
# + See instructions for registering for data access and setting up and using the CLI at: 
#    https://www.unavco.org/data/gps-gnss/file-server/command-line-interface.html
# + Takes command line argument for URL
#    e.g., https://data-idm.unavco.org/archive/gnss/rinex/obs/2022/060/p1230600.22d.Z
# Usage: python3 python-pycurl-cli-example.py https://data-idm.unavco.org/archive/gnss/rinex/obs/2022/060/p1230600.22d.Z
#
# Please take this basic script and use/extend it for your needs.
############################################################################################

import subprocess
import sys
from pycurl import Curl

# Reads the URL from the command line argument.
url = sys.argv[1]

# Assigns the local downloaded file's name from the last part of the URL.
filename = url.split('/')[-1]

# Run the CLI to get token.
es_return = subprocess.run(['es', 'sso', 'access', '--token'], capture_output=True)
es_stdout = es_return.stdout.decode().rstrip()  # Read subprocess standard output, convert binary to string and remove trailing white space

############################################
## Make cURL request of URL, and write file.
############################################
curl = Curl()

# Set protocol to HTTP1.1 vs default HTTP2. For installs of libcurl/pycurl built against older versions of openssl that don't support the ALPN used for HTTP2.
# Note: HTTP2 is a more performant protocal. To use it comment out the following line.
curl.setopt(curl.HTTP_VERSION, curl.CURL_HTTP_VERSION_1_1)

# Turn on verbose output for debugging purposes.
curl.setopt(curl.VERBOSE, 1)

curl.setopt(curl.URL, url)
curl.setopt(curl.FOLLOWLOCATION, True)

# Pass in the token as a http header.
curl.setopt(curl.HTTPHEADER, [f'Authorization: Bearer {es_stdout}'])

# Save file with original filename from url.
with open(filename, 'wb') as bf:
    curl.setopt(curl.WRITEDATA, bf)
    curl.perform()
    curl.close()