#!/usr/bin/env python3

"""
=head1 NAME

etherscan_balance_ - Munin plugin to monitor your ethereum (ETH) balance

=head1 APPLICABLE SYSTEMS

All systems with "python" and "munin"

=head1 CONFIGURATION

etherscan_balance_<YOUR_PUBLIC_ETHEREUM_ADDRESS>

=head1 SYNOPSIS

  ln -s /usr/share/munin/plugins/etherscan_balance_ \
  /etc/munin/plugins/etherscan_balance_0x3257bde8cf067ae6f1ddc0e4b140fe02e3c5e44f

=head1 INTERPRETATION

This plugin shows the ether balance (ETH) of a given ethereum address.
Account balance is queried via etherscan.io API L<https://etherscan.io/apis>.

=head1 VERSION

0.0.1

=head1 AUTHOR

L<Nils Knieling|https://github.com/Cyclenerd>

=head1 LICENSE

GPLv2

=head1 MAGIC MARKERS

 #%# family=manual

=cut
"""

from __future__ import print_function

import sys
import json
import codecs

try:
    # python3
    from urllib.request import urlopen
    from urllib.request import Request
except ImportError:
    # python2
    from urllib2 import urlopen
    from urllib2 import Request

command = ''
if len(sys.argv) > 1:
    command = sys.argv[1]


api_action, eth_address = sys.argv[0].split("_")[1:]

if not eth_address:
    print("The filename of this plugin (or its symlink) should follow this pattern: "
          "'etherscan_balance_<YOUR_PUBLIC_ETHEREUM_ADDRESS>'", file=sys.stderr)
    sys.exit(9)

"""
API result is in Wei. Convert Wei to Ether (ETH) via 'fieldname.cdef'
1     : Wei
10^12 : Szabo
10^15 : Finney
10^18 : Ether
233874700000000000000000 Wei = 233,874.7 Ether
"""
if command == 'config':
    print("graph_title Ether {}".format(eth_address))
    print("graph_info Ethereum Account Balance for Address {}".format(eth_address))
    print("graph_vlabel Ethereum Balance")
    print("graph_category htc")
    print("wei_balance_{0}.cdef wei_balance_{0},1000000000000000000,/".format(eth_address))
    print("wei_balance_{}.label ETH".format(eth_address))
    sys.exit(0)

ethercan_balance_api_url = ('https://api.etherscan.io/api'
                            '?module=account&action=balance&tag=latest&address=' + eth_address)

etherscan_req = Request(ethercan_balance_api_url)
# User-Agent to bypass Cloudflare
etherscan_req.add_header('User-Agent', 'Etherscan Munin Plugin/1.0')

try:
    etherscan_balance_raw = urlopen(etherscan_req, timeout=15)
except IOError as exc:
    print("Failed to request etherscan.io API: {}".format(exc), file=sys.stderr)
    sys.exit(9)

reader = codecs.getreader("utf-8")

try:
    etherscan_balance = json.load(reader(etherscan_balance_raw))
except ValueError:
    # Error in decoding operation or in JSON parsing throw a ValueError
    print("Failed to parse JSON response.", file=sys.stderr)
    sys.exit(9)

try:
    eth = int(etherscan_balance['result'])
except (KeyError, ValueError):
    print("JSON result error!", file=sys.stderr)
    sys.exit(9)

print("wei_balance_{}.value {}".format(eth_address, eth))