"""
 Utility code in speaking the neo4j REST api
"""

import json
import urllib2

def post_neo4j(url, data):
    """
    @return dict object from the neo4j json POST response
    @raise exception: if the 'errors' key is not empty
    """
    ret = post(url, data)
    ret_data = json.load(ret)

    if ret_data['errors']:
        raise Exception('neo4j exception: ' + str(ret_data['errors']))

    return ret_data

def post(url, data):
    assert(isinstance(data, dict))  # make sure we're not handed json strings

    post_data_json = json.dumps(data)

    req = urllib2.Request(url)
    req.add_header('User-Agent', 'rhizi-server/0.1')
    req.add_header('Accept', 'application/json; charset=UTF-8')
    req.add_header('Content-Type', 'application/json')

    try:
        ret = urllib2.urlopen(req, post_data_json)
    except urllib2.HTTPError as e:
        raise Exception('post request failed: code: {0}, reason: {1}'.format(e.code, e.reason))

    return ret

def statement_to_REST_form(query, parameters={}):
    """
    turn cypher query to neo4j json API format
    """
    assert isinstance(query, basestring)
    assert isinstance(parameters, dict)

    return {'statement' : query, 'parameters': parameters}

def statement_set_to_REST_form(statement_set):
    assert isinstance(statement_set, list)

    return {'statements': statement_set}

def where_clause_from_filter_attr_map(filter_attr_map, node_param_name="n"):
    """
    convert a filter attribute map to a parameterized Cypher where clause, eg.
    in: { 'att_foo': [ 'a', 'b' ], 'att_goo': [1,2] }
    out: where n.att_foo in {att_foo} and n.att_goo in {att_goo} ...
    
    @param filter_attr_map: may be None or empty 
    """
    if not filter_attr_map:
        return ""
    
    filter_arr = []
    for k in filter_attr_map.keys():
        # create a cypher query parameter place holder for each attr set
        # eg. n.foo in {foo}, where foo is passed as a query parameter
        f_attr = "{0}.{1} in {{{1}}}".format(node_param_name, k)
        filter_arr.append(f_attr)
    filter_str = "where {0}".format(' and '.join(filter_arr))
    return filter_str