buildDwellTimes.py

def build_dwell_times(pings, max_dwell, min_dwell):
    """
      Builds a collection of dwell times from a collection of discrete pings.

      @param pings: array of dicts with these attributes: {"mac":, "signal_strength:, "first_seen":, "last_seen":, "count":}
      @param max_dwell: max time between pings before a new dwell time is added
      @param min_dwell: min time between pings before they're considered sessions
      @return an array of dwell times
    """
    dwell_times = []

    for index, this_ping in enumerate(pings):
        # Append the first ping and move on the second
        if index == 0:
            dwell_times.append(this_ping)
            continue

        # Grab the last dwell_time
        last_ping = dwell_times[-1]

        # Compare locations.
        if this_ping['node_mac'] == last_ping['node_mac']:
            # if this ping's first seen - last ping's last_seen is less than
            # the amount of time we set for max_dwell,
            # then make the last ping's last_seen = this ping's last_seen
            if this_ping["first_seen"] - last_ping["last_seen"] < max_dwell:
                last_ping["last_seen"] = this_ping["last_seen"]
                last_ping["count"] += this_ping["count"]

            # Create a new dwell time if a user leaves and come back.
            else:
                dwell_times.append(this_ping)
        # last ping isn't from the same device as this ping
        # if last ping is stronger than this ping
        # or if this ping's first seen - last ping's last_seen is greater than the amount we set for min_dwell
        # then create a new dwell time
        else:
            current_signal_stronger = last_ping["signal_strength"] < this_ping["signal_strength"]
            minimum_dwell_elapsed = this_ping["first_seen"] - last_ping["last_seen"] >= min_dwell
            # Create a new dwell time if the user moves to a different location.
            if current_signal_stronger or minimum_dwell_elapsed:
                dwell_times.append(this_ping)

    return dwell_times