Covered Time by Intervals

covered_time.py

def covered_time(begin: datetime, end: datetime, ranges: List[List[datetime,datetime]]) -> timedelta:
    """Calculate the covered timespan of a range by other ranges
    Takes a base range defined by begin, end,
    and several other ranges, and calculates the amount of time covered
    within the base range by the other ranges (overlap time)
    Args:
        begin: base range begin datetime
        end: base range end datetime
        range: [begin, end] lists of covering timestamps
    Returns:
        overlap: timedelta
    """
    if (len(ranges) == 0):
        return timedelta(0)
    # Cut down each time to the base range
    for span in ranges:
        begin_delta = begin - span[0]
        span[0] = span[0] + begin_delta if begin_delta > timedelta(0) else span[0]
        end_delta = span[1] - end
        span[1] = span[1] - end_delta   if end_delta   > timedelta(0) else span[1]
    
    times = []
    for begin, end in ranges:
        times.append({'type': 'begin', 'time': begin})
        times.append({'type': 'end', 'time': end})
    # Count covered time using a state machine
    covered = timedelta(0) # Covered time in base range
    previous_begin = times[0]
    depth = 0
    for time in times:
        if time['type'] == 'begin':
            depth += 1
        elif time['type'] == 'end':
            depth -= 1
        if depth == 1: # Entered first nested covered interval
            previous_begin = time['time']
        elif depth == 0: # Exited last nested covered interval
            covered += time['time'] - previous_begin
    return covered