exchangerates.py

# -*- coding: utf-8 -*-

from __future__ import absolute_import, division, print_function, unicode_literals

# stdlib
from datetime import datetime
from traceback import format_exc

# anyjson
from anyjson import loads

# lxml
from lxml import etree

# Zato
from zato.server.service import Service

class GetExchangeRateList(Service):
    class SimpleIO:
        response_elem = 'rates'
        input_required = ('from', 'to')
        output_required = ('provider', 'rate', 'ts')
        output_repeated = True
        
    def get_yahoo(self, from_, to):
        
        # Response template
        out = {'provider':'Yahoo! Finance', 'rate':None, 'ts':None}
        
        # Grab a connection by its name
        conn = self.outgoing.plain_http.get('Yahoo! Finance').conn
   
        # Y! Finance needs a query string in that format
        # ?s=HRKEUR=X&f=snl1d1t1ab
        url_params = {'s':'{}{}=X'.format(from_, to), 'f':'snl1d1t1ab'}
        
        # Invoking the .get method issues a GET request
        response = conn.get(self.cid, url_params)
        
        # Y! gives us a CSV response
        response = response.text.split(',')
        
        # The string we receive is something like
        # u'"EURHRK=X","EUR to HRK",7.4608,"6/14/2013","5:55pm",7.4629,7.4588\r\n'
        # and we need the 3rd item.
        out['rate'] = response[2]
        out['ts'] = datetime.utcnow().isoformat()
        
        return out
    
    def get_google(self, from_, to):
        out = {'provider':'Google', 'rate':None, 'ts':None}
        
        # Grab a connection by its name
        conn = self.outgoing.plain_http.get('Google Calculator').conn
   
        # Google needs a query string in that format
        # ?q=1EUR=HRK
        url_params = {'q': '1{}={}'.format(from_, to)}
        
        # Invoking the .get method issues a GET request
        response = conn.get(self.cid, url_params)
        
        # Convert the pseudo-JSON from 
        # {lhs: "1 Euro",rhs: "7.46464923 Croatian kune",error: "",icc: true} ->
        # {"lhs": "1 Euro","rhs": "7.46464923 Croatian kune","error": "","icc": true}
        # so it can be parsed as JSON.
        json = response.text
        replace = ('lhs', 'rhs', 'error', 'icc')
        for name in replace:
            json = json.replace(name, '"{}"'.format(name))
            
        rate = loads(json)['rhs'].split()[0]
        
        out['rate'] = rate
        out['ts'] = datetime.utcnow().isoformat()
        
        return out
    
    def get_ecb(self, from_, to):
        out = {'provider':'European Central Bank', 'rate':None, 'ts':None}
        
        # Grab a connection by its name
        conn = self.outgoing.plain_http.get('European Central Bank').conn
        
        response = conn.get(self.cid)
        xml = etree.fromstring(response.text.encode('utf-8'))
        
        ns = {'xref': 'http://www.ecb.int/vocabulary/2002-08-01/eurofxref'}
        rate = xml.xpath(
            "//xref:Cube[@currency='{}']/@rate".format(to), namespaces=ns)[0]
        
        out['rate'] = rate
        out['ts'] = datetime.utcnow().isoformat()
        
        return out
        
    def handle(self):
        from_ = self.request.input.get('from')
        to = self.request.input.to
        
        for func in(self.get_yahoo, self.get_google, self.get_ecb):
            try:
                rate = func(from_, to)
            except Exception, e:
                self.logger.warn('Caught an exception {}'.format(format_exc(e)))
            else:
                self.response.payload.append(rate)