# standard imports
import os
import sys

# local imports
from chainlib.jsonrpc import JSONRPCRequest
from chainlib.chain import ChainSpec
from chainlib.connection import (
        JSONRPCHTTPConnection,
        RPCConnection,
        ConnType,
        )


# set up node connection and execute rpc call
rpc_provider = os.environ.get('RPC_PROVIDER', 'http://localhost:8545')
RPCConnection.register_constructor(ConnType.HTTP, JSONRPCHTTPConnection)

tag = 'baz'
chain_spec = ChainSpec('foo', 'bar', 42, tag=tag)
RPCConnection.register_location(rpc_provider, chain_spec, tag='default')
conn = RPCConnection.connect(chain_spec, 'default')

# check the connection
if not conn.check():
    sys.stderr.write('node {} not usable\n'.format(rpc_provider))
    sys.exit(1)

# build and send rpc call
g = JSONRPCRequest()
o = g.template()
o['method'] = 'eth_blockNumber'
r = conn.do(o)

# interpret result for humans
try:
    block_number = int(r, 10)
except ValueError:
    block_number = int(r, 16)

print('block number {}'.format(block_number))