# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4; coding:utf-8 -*-
#
# Copyright 2002 Ben Escoto
# Copyright 2007 Kenneth Loafman
#
# This file is part of duplicity.
#
# Duplicity is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#
# Duplicity is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with duplicity; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

"""
Provide time related exceptions and functions
"""

import calendar
import re
import time

from duplicity import config
from duplicity import util


class TimeException(Exception):
    """
    Base exception for time-related errors.
    """

    pass


_interval_conv_dict = {
    "s": 1,
    "m": 60,
    "h": 3600,
    "D": 86400,
    "W": 7 * 86400,
    "M": 30 * 86400,
    "Y": 365 * 86400,
}
_integer_regexp = re.compile("^[0-9]+$")
_interval_regexp = re.compile("^([0-9]+)([smhDWMY])")
_genstr_date_regexp1 = re.compile("^(?P<year>[0-9]{4})[-/]" "(?P<month>[0-9]{1,2})[-/]" "(?P<day>[0-9]{1,2})$")
_genstr_date_regexp2 = re.compile("^(?P<month>[0-9]{1,2})[-/]" "(?P<day>[0-9]{1,2})[-/]" "(?P<year>[0-9]{4})$")
_genstr_date_regexp3 = re.compile("^(?P<year>[0-9]{4})" "(?P<month>[0-9]{2})" "(?P<day>[0-9]{2})Z$")
curtime = curtimestr = None
prevtime = prevtimestr = None

bad_interval_string = _("""\
Bad interval string "%s"

Intervals are specified like 2Y (2 years) or 2h30m (2.5 hours).  The
allowed special characters are s, m, h, D, W, M, and Y.  See the man
page for more information.""")

bad_time_string = _("""\
Bad time string "%s"

The acceptible time strings are intervals (like "3D64s"), w3-datetime
strings, like "2002-04-26T04:22:01-07:00" (strings like
"2002-04-26T04:22:01" are also acceptable - duplicity will use the
current time zone), or ordinary dates like 2/4/1997 or 2001-04-23
(various combinations are acceptable, but the month always precedes
the day).""")


def setcurtime(time_in_secs=None):
    """
    Set the current time in ``curtime`` and ``curtimestr``.

    :param int time_in_secs: The time in seconds since the epoch.
    """
    global curtime, curtimestr
    t = time_in_secs or int(time.time())
    assert isinstance(t, int), "curtime must be an integer"
    curtime, curtimestr = t, timetostring(t)


def setprevtime(time_in_secs):
    """
    Set the previous time in ``prevtime`` and ``prevtimestr``.

    :param int time_in_secs: The time in seconds since the epoch.
    """
    global prevtime, prevtimestr
    assert isinstance(time_in_secs, int), "prevtime must be an integer"
    prevtime, prevtimestr = time_in_secs, timetostring(time_in_secs)


def timetostring(timeinseconds):
    """
    Return a W3C or Duplicity compliant datetime string for the given time.

    :param int timeinseconds: The time in seconds since the epoch.
    :returns: The formatted datetime string.
    :rtype: str
    """

    # DST never applies to UTC
    lcltime = time.gmtime(timeinseconds)
    return time.strftime("%Y%m%dT%H%M%SZ", lcltime)


def stringtotime(timestring):
    """
    Return the time in seconds from a W3C or Duplicity datetime string.

    :param str timestring: The datetime string to parse.
    :returns: The time in seconds since the epoch, or None if parsing fails.
    :rtype: int or None
    """
    try:
        date, daytime = timestring[:19].split("T")
        if len(timestring) == 16:
            # new format for filename time
            year, month, day = list(map(int, [date[0:4], date[4:6], date[6:8]]))
            hour, minute, second = list(map(int, [daytime[0:2], daytime[2:4], daytime[4:6]]))
        else:
            # old format for filename time
            year, month, day = list(map(int, date.split("-")))
            hour, minute, second = list(map(int, daytime.split(config.time_separator)))
        assert 1900 < year < 2100, f"year {year} out of supported range (1901..2099)"
        assert 1 <= month <= 12, f"month {month} out of range (1..12)"
        assert 1 <= day <= 31, f"day {day} out of range (1..31)"
        assert 0 <= hour <= 23, f"hour {hour} out of range (0..23)"
        assert 0 <= minute <= 59, f"minute {minute} out of range (0..59)"
        assert 0 <= second <= 61, f"second {second} out of range (0..61, allowing leap seconds)"  # leap seconds
        # We want to return the time in units of seconds since the
        # epoch. Unfortunately the only functin that does this
        # works in terms of the current timezone and we have a
        # timezone offset in the string.
        timetuple = (year, month, day, hour, minute, second, -1, -1, 0)

        if len(timestring) == 16:
            # as said in documentation, time.gmtime() and timegm() are each others' inverse.
            # As far as UTC format is used in new file format,
            # do not rely on system's python DST and tzdata settings
            # and use functions that working with UTC
            utc_in_secs = calendar.timegm(timetuple)
        else:
            # mktime assumed that the tuple was a local time. Compensate
            # by subtracting the value for the current timezone.
            # We don't need to worry about DST here because we turned it
            # off in the tuple
            local_in_secs = time.mktime(timetuple)
            utc_in_secs = local_in_secs - time.timezone
        # Now apply the offset that we were given in the time string
        # This gives the correct number of seconds from the epoch
        # even when we're not in the same timezone that wrote the
        # string
        if len(timestring) == 16:
            return int(utc_in_secs)
        else:
            return int(utc_in_secs + tzdtoseconds(timestring[19:]))
    except (TypeError, ValueError, AssertionError):
        return None


def timetopretty(timeinseconds):
    """
    Return a human-readable version of the given time.

    :param int timeinseconds: The time in seconds since the epoch.
    :returns: The pretty time string.
    :rtype: str
    """
    return time.asctime(time.localtime(timeinseconds))


def stringtopretty(timestring):
    """
    Return pretty version of time given w3 time string
    """
    return timetopretty(stringtotime(timestring))


def inttopretty(seconds):
    """
    Convert num of seconds to readable string like "2 hours".
    """
    partlist = []
    hours, seconds = divmod(seconds, 3600)
    if hours > 1:
        partlist.append(f"{int(hours)} hours")
    elif hours == 1:
        partlist.append("1 hour")

    minutes, seconds = divmod(seconds, 60)
    if minutes > 1:
        partlist.append(f"{int(minutes)} minutes")
    elif minutes == 1:
        partlist.append("1 minute")

    if seconds == 1:
        partlist.append("1 second")
    elif not partlist or seconds > 1:
        if isinstance(seconds, int):
            partlist.append(f"{seconds} seconds")
        else:
            partlist.append(f"{seconds:.2f} seconds")
    return " ".join(partlist)


def intstringtoseconds(interval_string):
    """
    Convert a string expressing an interval (e.g. "4D2s") to seconds.

    :param str interval_string: The interval string.
    :returns: The total number of seconds.
    :rtype: int
    :raises TimeException: If the interval string is invalid.
    """

    def error():
        raise TimeException(bad_interval_string % util.escape(interval_string))

    if len(interval_string) < 2:
        error()

    total = 0
    while interval_string:
        match = _interval_regexp.match(interval_string)
        if not match:
            error()
        num, ext = int(match.group(1)), match.group(2)
        if ext not in _interval_conv_dict or num < 0:
            error()
        total += num * _interval_conv_dict[ext]
        interval_string = interval_string[match.end(0) :]
    return total


def gettzd(dstflag):
    """Return w3's timezone identification string.

    Expresed as [+/-]hh:mm.  For instance, PST is -08:00.  Zone is
    coincides with what localtime(), etc., use.

    """
    # time.daylight doesn't help us. It's a flag that indicates that we
    # have a dst option for the current timezone. Compensate by allowing
    # the caller to pass a flag to indicate that DST applies. This flag
    # is in the same format as the last member of the tuple returned by
    # time.localtime()

    if dstflag > 0:
        offset = -1 * time.altzone // 60
    else:
        offset = -1 * time.timezone // 60
    if offset > 0:
        prefix = "+"
    elif offset < 0:
        prefix = "-"
    else:
        return "Z"  # time is already in UTC

    hours, minutes = list(map(abs, divmod(offset, 60)))
    assert 0 <= hours <= 23, f"hours component {hours} out of range (0..23)"
    assert 0 <= minutes <= 59, f"minutes component {minutes} out of range (0..59)"
    return f"{prefix}{int(hours):02}{config.time_separator}{int(minutes):02}"


def tzdtoseconds(tzd):
    """
    Given w3 compliant TZD, return how far ahead UTC is
    """
    if tzd == "Z":
        return 0
    assert (
        len(tzd) == 6
    ), "TZD must be 6 characters in the form ±HH:MM (e.g., +08:00)"  # only accept forms like +08:00 for now
    assert (tzd[0] == "-" or tzd[0] == "+") and (
        tzd[3] == config.time_separator
    ), "TZD must start with +/- and include the correct time separator at position 3 (±HH:MM)"
    return -60 * (60 * int(tzd[:3]) + int(tzd[4:]))


def cmp(time1, time2):
    """
    Compare time1 and time2 and return -1, 0, or 1
    """
    if isinstance(time1, str):
        time1 = stringtotime(time1)
        assert time1 is not None, "time1 string could not be parsed into a valid timestamp"
    if isinstance(time2, str):
        time2 = stringtotime(time2)
        assert time2 is not None, "time2 string could not be parsed into a valid timestamp"

    if time1 < time2:
        return -1
    elif time1 == time2:
        return 0
    else:
        return 1


def genstrtotime(timestr, override_curtime=None):
    """
    Convert a generic time string to a time in seconds
    """
    if override_curtime is None:
        override_curtime = curtime
    if timestr == "now":
        return override_curtime

    def error():
        raise TimeException(bad_time_string % util.escape(timestr))

    # Test for straight integer
    if _integer_regexp.search(timestr):
        return int(timestr)

    # Test for w3-datetime format, possibly missing tzd
    # This is an ugly hack. We need to know if DST applies when doing
    # gettzd. However, we don't have the flag to pass. Assume that DST
    # doesn't apply and pass 0. Getting a reasonable default from
    # localtime() is a bad idea, since we transition to/from DST between
    # calls to this method on the same run

    t = stringtotime(timestr) or stringtotime(timestr + gettzd(0))
    if t:
        return t

    try:  # test for an interval, like "2 days ago"
        return override_curtime - intstringtoseconds(timestr)
    except TimeException:
        pass

    # Now check for dates like 2001/3/23
    match = (
        _genstr_date_regexp1.search(timestr)
        or _genstr_date_regexp2.search(timestr)
        or _genstr_date_regexp3.search(timestr)
    )
    if not match:
        error()
    timestr = (
        f"{match.group('year')}-{int(int(match.group('month'))):02}-{int(int(match.group('day'))):02}"
        f"T00:00:00{gettzd(0)}"
    )
    t = stringtotime(timestr)
    if t:
        return t
    else:
        error()


def genstrtoseconds(timestr, override_curtime=None):
    """
    Convert a generic time string to a time in seconds since curtime
    """
    if override_curtime is None:
        if curtime is None:
            setcurtime()
        override_curtime = curtime
    return override_curtime - genstrtotime(timestr, override_curtime)
