#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Purpose
-------

This module contains functions related to time measurement
and date formatting.

Code documentation
------------------
"""


import sys
import functools
import datetime as dt


def get_datetime():
    """Return datetime object for current date and hour."""
    current_datetime = dt.datetime.now()

    return current_datetime


def datetime_str(datetime_obj, date_format='%Y-%m-%dT%H:%M:%S'):
    """Convert datetime module object to formatted string.

    Parameters
    ----------
    datetime_obj : datetime.datetime
        Datetime module object.
    date_format : str
        Format for string representation of the date
        object.

    Returns
    -------
    dt_str : str
        String representation of the date according
        to specified format.
    """
    dt_str = dt.datetime.strftime(datetime_obj, date_format)

    return dt_str


def datetime_obj(datetime_str, date_format='%Y-%m-%dT%H:%M:%S'):
    """Convert formatted string to datetime module object.

    Parameters
    ----------
    datetime_str : str
        String to convert to datetime object.
    date_format : str
        Format of the string representation of the date
        object.

    Returns
    -------
    dt_obj : datetime.datetime
        Datetime module object.
    """
    dt_obj = dt.datetime.strptime(datetime_str, date_format)

    return dt_obj


def datetime_diff(sdate, edate):
    """Return the difference in minutes and seconds between two dates.

    Parameters
    ----------
    sdate : datetime.datetime
        Datetime module object corresponding to
        the oldest date.
    edate : datetime.datetime
        Datetime module object corresponding to
        the most recent date.

    Returns
    -------
    A list with the following elements:
        minutes : float
            Time difference between the two dates
            in minutes.
        seconds : float
            The remaining time difference in seconds.
    """
    delta = edate - sdate
    minutes, seconds = divmod(delta.total_seconds(), 60)

    return [minutes, seconds]


def validate_date(date, date_format='%Y-%m-%dT%H:%M:%S.%f'):
    """Check if date is in specified format.

    Parameters
    ----------
    date : str
        String representing a date.
    date_format : str
        Date format.

    Returns
    -------
    valid : str
        The string representing the date if it
        is in the specified format.
    """
    valid = False
    try:
        date = dt.datetime.strptime(date, date_format)
        valid = date
    except ValueError:
        date = dt.datetime.strptime(date+'.0', date_format)
        valid = date

    return valid


def process_header(process):
    """Print a header with the name of the process."""
    header = 'chewBBACA - {0}'.format(process)
    hf = '='*(len(header)+4)
    print('{0}\n  {1}\n{0}'.format(hf, header))


# decorator to time main processes
def process_timer(func):
    # use functools to preserve info about wrapped function
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        # get process name and print header
        process_header(sys.argv[1])

        # do not measure time if it is only needed to print the help message
        if any([option in ['-h', '--help'] for option in sys.argv]) is False:
            start = get_datetime()
            start_str = datetime_str(start)
            print('Started at: {0}\n'.format(start_str))

        # run function
        func(*args, **kwargs)

        # does not print elapsed time if the help message is printed
        end = get_datetime()
        end_str = datetime_str(end)
        print('\nFinished at: {0}'.format(end_str))

        minutes, seconds = datetime_diff(start, end)
        print('Took {0: .0f}m{1: .0f}s.'.format(minutes, seconds))

    return wrapper
