#!/usr/bin/env python3

"""Utilities related to dates and times and datetimes."""

import datetime
import logging
import re
from typing import NewType

import pytz

import constants

logger = logging.getLogger(__name__)


def now_pst() -> datetime.datetime:
    return datetime.datetime.now(tz=pytz.timezone("US/Pacific"))


def now() -> datetime.datetime:
    return datetime.datetime.now()


def datetime_to_string(
    dt: datetime.datetime,
    *,
    date_time_separator=" ",
    include_timezone=True,
    include_dayname=False,
    include_seconds=True,
    include_fractional=False,
    twelve_hour=True,
) -> str:
    """A nice way to convert a datetime into a string."""
    fstring = ""
    if include_dayname:
        fstring += "%a/"
    fstring = f"%Y/%b/%d{date_time_separator}"
    if twelve_hour:
        fstring += "%I:%M"
        if include_seconds:
            fstring += ":%S"
        fstring += "%p"
    else:
        fstring += "%H:%M"
        if include_seconds:
            fstring += ":%S"
    if include_fractional:
        fstring += ".%f"
    if include_timezone:
        fstring += "%z"
    return dt.strftime(fstring).strip()


def timestamp() -> str:
    """Return a timestamp for now in Pacific timezone."""
    ts = datetime.datetime.now(tz=pytz.timezone("US/Pacific"))
    return datetime_to_string(ts, include_timezone=True)


def time_to_string(
    dt: datetime.datetime,
    *,
    include_seconds=True,
    include_fractional=False,
    include_timezone=False,
    twelve_hour=True,
) -> str:
    """A nice way to convert a datetime into a time (only) string."""
    fstring = ""
    if twelve_hour:
        fstring += "%l:%M"
        if include_seconds:
            fstring += ":%S"
        fstring += "%p"
    else:
        fstring += "%H:%M"
        if include_seconds:
            fstring += ":%S"
    if include_fractional:
        fstring += ".%f"
    if include_timezone:
        fstring += "%z"
    return dt.strftime(fstring).strip()


def seconds_to_timedelta(seconds: int) -> datetime.timedelta:
    """Convert a delta in seconds into a timedelta."""
    return datetime.timedelta(seconds=seconds)


MinuteOfDay = NewType("MinuteOfDay", int)


def minute_number(hour: int, minute: int) -> MinuteOfDay:
    """Convert hour:minute into minute number from start of day."""
    return MinuteOfDay(hour * 60 + minute)


def datetime_to_minute_number(dt: datetime.datetime) -> MinuteOfDay:
    """Convert a datetime into a minute number (of the day)"""
    return minute_number(dt.hour, dt.minute)


def minute_number_to_time_string(minute_num: MinuteOfDay) -> str:
    """Convert minute number from start of day into hour:minute am/pm string."""
    hour = minute_num // 60
    minute = minute_num % 60
    ampm = "a"
    if hour > 12:
        hour -= 12
        ampm = "p"
    if hour == 12:
        ampm = "p"
    if hour == 0:
        hour = 12
    return f"{hour:2}:{minute:02}{ampm}"


def parse_duration(duration: str) -> int:
    """Parse a duration in string form."""
    seconds = 0
    m = re.search(r'(\d+) *d[ays]*', duration)
    if m is not None:
        seconds += int(m.group(1)) * 60 * 60 * 24
    m = re.search(r'(\d+) *h[ours]*', duration)
    if m is not None:
        seconds += int(m.group(1)) * 60 * 60
    m = re.search(r'(\d+) *m[inutes]*', duration)
    if m is not None:
        seconds += int(m.group(1)) * 60
    m = re.search(r'(\d+) *s[econds]*', duration)
    if m is not None:
        seconds += int(m.group(1))
    return seconds


def describe_duration(age: int) -> str:
    """Describe a duration."""
    days = divmod(age, constants.SECONDS_PER_DAY)
    hours = divmod(days[1], constants.SECONDS_PER_HOUR)
    minutes = divmod(hours[1], constants.SECONDS_PER_MINUTE)

    descr = ""
    if days[0] > 1:
        descr = f"{int(days[0])} days, "
    elif days[0] == 1:
        descr = "1 day, "
    if hours[0] > 1:
        descr = descr + f"{int(hours[0])} hours, "
    elif hours[0] == 1:
        descr = descr + "1 hour, "
    if len(descr) > 0:
        descr = descr + "and "
    if minutes[0] == 1:
        descr = descr + "1 minute"
    else:
        descr = descr + f"{int(minutes[0])} minutes"
    return descr


def describe_duration_briefly(age: int) -> str:
    """Describe a duration briefly."""
    days = divmod(age, constants.SECONDS_PER_DAY)
    hours = divmod(days[1], constants.SECONDS_PER_HOUR)
    minutes = divmod(hours[1], constants.SECONDS_PER_MINUTE)

    descr = ""
    if days[0] > 0:
        descr = f"{int(days[0])}d "
    if hours[0] > 0:
        descr = descr + f"{int(hours[0])}h "
    descr = descr + f"{int(minutes[0])}m"
    return descr