"""
Small classes to assist with db access, timezone calculations, and so on.
"""

import datetime
import pytz

class DocWrap():
    """
        Provides attribute access style on top of dictionary results from pymongo. 
        Allows you to access result['field'] as result.field.
        Aliases result['_id'] to result.id.
        
    """
    def __init__(self, store=None):
        if(store == None):
            self.store = {}
        else:
            self.store = store.copy()
        if(self.store.has_key('_id')):
            self.store['id'] = self.store['_id']
            del(self.store['_id'])
        
    def __setitem__(self,key,value):
        if(key == '_id'):
            self.store['id'] = value
        else:
            self.store[key] = value
        
    def __getitem__(self, key):
        if self.store.has_key(key):
            return self.store[key]
            
    def __getattr__(self,attrname):
        if self.store.has_key(attrname):
            return self.store[attrname]
        else:
            raise AttributeError("No attribute named {name}".format(name=attrname))
            
def parse_date(dt_str):
    """parse strings according to the same format as generated by format_date"""
    if(dt_str == None):
        return None
    parts = dt_str.split(".")
    dt = datetime.datetime.strptime(parts[0], '%Y/%m/%d-%H:%M:%S').replace(microsecond=int(parts[1]+"000")).replace(tzinfo = pytz.utc)
    return dt
    
def format_date(dt):
    """Format the date into a date with millesecond resolution and string/alphabetical sorting that is equivalent to datetime sorting"""
    if(dt == None):
        return None
    dt_str = dt.strftime('%Y/%m/%d-%H:%M:%S') + "." + str(dt.microsecond / 1000)
    return dt_str