"""
Transformations for common technical indicators.
TODO: add MACD transform
TODO: add trailing stop
"""

import datetime

from zipline.messaging import BaseTransform
import zipline.util as qutil

class MovingAverage(BaseTransform):
    """
    Calculate a unweighted moving average for props['sid'] security
    TODO: add sid -> mvavg dict.
    """

    def __init__(self, name, days):
        BaseTransform.__init__(self, name)
        self.window = datetime.timedelta(days = days)

        self.init()

    def init(self):
        self.events         = []
        self.current_total  = 0

    def transform(self, event):
        """
        Update the moving average with the latest data point.
        """

        self.events.append(event)
        self.current_total += event.price
        event_date = event.dt

        index = 0

        for cur_event in self.events:
            cur_date = cur_event.dt
            if(cur_date - event_date) >= self.window:
                self.events.pop(index)
                self.current_total -= cur_event.price
                index += 1
            else:
                break

        if len(self.events) == 0:
            return 0.0

        self.average = self.current_total/len(self.events)
        self.state['value'] = self.average

        return self.state