deal_window.py

import collections
import csv
from datetime import datetime

defaultDate = datetime.today()


def get_time_with_ms(time):  # formatting shortcut
    return (datetime.fromtimestamp(time).strftime('%H:%M:%S.%f')[:-3])


def parserow(row):  # row parser
    time = datetime.strptime(row['Time'], '%H:%M:%S.%f').time()  ##convert terrible string to a nice timestamp
    time = datetime.combine(defaultDate, time)  # append a fictious date to avoid negative timestamps
    timestamp = time.timestamp() * 1000  # store miliseconds
    return (timestamp, row['EXCHANGE'])  # return timestamp and exchange name


def step(window, timestamp, interval=1000):  # main algorithm
    window.append(timestamp)  # append timestamp to theend of list
    if window:  # if not empty
        while timestamp - window[0]  > interval:  # While the list contains the timestamps outside the interval
            if window:  # if not empty
                left = window.popleft()  # pop another timestamp until we done

class DealWindow:
    def __init__(self):
        self.dealLog = {}
        self.maxDeals = {}
        self.topTimestamp = {}

    def add_exchange(self, name):
        self.dealLog[name] = collections.deque()
        self.maxDeals[name] = 0
        self.topTimestamp[name] = 0

    def update_deal_counter(self, exchange, timestamp):
        if len(self.dealLog[exchange]) > self.maxDeals[
            exchange]:  # check if we have more deals in the interval than before
            self.maxDeals[exchange] = len(self.dealLog[exchange])  # upd counter
            self.topTimestamp[exchange] = timestamp  # upd timestamp

    def analyze(self, reader):
        for row in reader:
            (timestamp, exchange) = parserow(row)  # parse row
            if not (exchange in self.dealLog):  # If met new exchange name
                self.add_exchange(exchange)
            step(self.dealLog[exchange], timestamp)  # put timestamp in the corresponding list and do the maths
            DealWindow.update_deal_counter(self, exchange, timestamp)

    def format_answer(self):
        out_strings = {}
        for exchange in self.dealLog:
            endOfWindow = get_time_with_ms(self.topTimestamp[exchange] / 1000)  # get back to readable format
            beginningOfWindow = get_time_with_ms(
                (self.topTimestamp[exchange] - 1000) / 1000 + 0.001)  # get the beginning of the current second
            out_strings[
                exchange] = "Maximum deals during one-second window was registered at exchange {} between {} and {}. {} deals were performed at that second".format(
                exchange, beginningOfWindow, endOfWindow, self.maxDeals[exchange])
            # TODO: ask, how do they prefer to define the interval? By the median, left or right border.
        return out_strings