#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (C) 2009-2011 Umeå University
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#            http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" 
Implements some usefull functions when dealing with validity of 
different types of information.
"""

import calendar
import re
import time
import sys

from datetime import timedelta
from datetime import datetime

TIME_FORMAT = "%Y-%m-%dT%H:%M:%SZ"
TIME_FORMAT_WITH_FRAGMENT = re.compile(
    "^(\d{4,4}-\d{2,2}-\d{2,2}T\d{2,2}:\d{2,2}:\d{2,2})\.\d*Z$")

# ---------------------------------------------------------------------------
# I'm sure this is implemented somewhere else can't find it now though, so I
# made an attempt.
#Implemented according to 
#http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/
#adding-durations-to-dateTimes


def f_quotient(arg0, arg1, arg2=0):
    if arg2:
        return int((arg0 - arg1) / (arg2 - arg1))
    elif not arg0:
        return 0
    else:
        return int(arg0 / arg1)


def modulo(arg0, arg1, arg2=0):
    if arg2:
        return ((arg0 - arg1) % (arg2 - arg1)) + arg1
    else:
        return arg0 % arg1


def maximum_day_in_month_for(year, month):
    return calendar.monthrange(year, month)[1]


D_FORMAT = [
    ("Y", "tm_year"),
    ("M", "tm_mon"),
    ("D", "tm_mday"),
    ("T", None),
    ("H", "tm_hour"),
    ("M", "tm_min"),
    ("S", "tm_sec")
]


def parse_duration(duration):
    # (-)PnYnMnDTnHnMnS
    index = 0
    if duration[0] == '-':
        sign = '-'
        index += 1
    else:
        sign = '+'
    assert duration[index] == "P"
    index += 1
    
    dic = dict([(typ, 0) for (code, typ) in D_FORMAT])
    
    for code, typ in D_FORMAT:
        #print duration[index:], code
        if duration[index] == '-':
            raise Exception("Negation not allowed on individual items")
        if code == "T":
            if duration[index] == "T":
                index += 1
                if index == len(duration):
                    raise Exception("Not allowed to end with 'T'")
            else:
                raise Exception("Missing T")
        else:
            try:
                mod = duration[index:].index(code)
                try:
                    dic[typ] = int(duration[index:index + mod])
                except ValueError:
                    if code == "S":
                        try:
                            dic[typ] = float(duration[index:index + mod])
                        except ValueError:
                            raise Exception("Not a float")
                    else:
                        raise Exception(
                            "Fractions not allow on anything byt seconds")
                index = mod + index + 1
            except ValueError:
                dic[typ] = 0

        if index == len(duration):
            break
        
    return sign, dic
    

def add_duration(tid, duration):
    
    (sign, dur) = parse_duration(duration)
    
    if sign == '+':
        #Months
        temp = tid.tm_mon + dur["tm_mon"]
        month = modulo(temp, 1, 13)
        carry = f_quotient(temp, 1, 13)
        #Years
        year = tid.tm_year + dur["tm_year"] + carry
        # seconds
        temp = tid.tm_sec + dur["tm_sec"]
        secs = modulo(temp, 60)
        carry = f_quotient(temp, 60)
        # minutes
        temp = tid.tm_min + dur["tm_min"] + carry
        minutes = modulo(temp, 60)
        carry = f_quotient(temp, 60)
        # hours
        temp = tid.tm_hour + dur["tm_hour"] + carry
        hour = modulo(temp, 60)
        carry = f_quotient(temp, 60)
        # days
        if dur["tm_mday"] > maximum_day_in_month_for(year, month):
            temp_days = maximum_day_in_month_for(year, month)
        elif dur["tm_mday"] < 1:
            temp_days = 1
        else:
            temp_days = dur["tm_mday"]
        days = temp_days + tid.tm_mday + carry
        while True:
            if days < 1:
                pass
            elif days > maximum_day_in_month_for(year, month):
                days -= maximum_day_in_month_for(year, month)
                carry = 1
            else:
                break
            temp = month + carry
            month = modulo(temp, 1, 13)
            year += f_quotient(temp, 1, 13)
    
        return time.localtime(time.mktime((year, month, days, hour, minutes,
                                           secs, 0, 0, -1)))
    else:
        pass

# ---------------------------------------------------------------------------


def time_in_a_while(days=0, seconds=0, microseconds=0, milliseconds=0,
                    minutes=0, hours=0, weeks=0):
    """
    format of timedelta:
        timedelta([days[, seconds[, microseconds[, milliseconds[,
                    minutes[, hours[, weeks]]]]]]])
    :return: UTC time
    """
    delta = timedelta(days, seconds, microseconds, milliseconds,
                      minutes, hours, weeks)
    return datetime.utcnow() + delta


def time_a_while_ago(days=0, seconds=0, microseconds=0, milliseconds=0,
                     minutes=0, hours=0, weeks=0):
    """
    format of timedelta:
        timedelta([days[, seconds[, microseconds[, milliseconds[,
                    minutes[, hours[, weeks]]]]]]])
    """
    delta = timedelta(days, seconds, microseconds, milliseconds,
                      minutes, hours, weeks)
    return datetime.utcnow() - delta


def in_a_while(days=0, seconds=0, microseconds=0, milliseconds=0,
               minutes=0, hours=0, weeks=0, format=TIME_FORMAT):
    """
    format of timedelta:
        timedelta([days[, seconds[, microseconds[, milliseconds[,
                    minutes[, hours[, weeks]]]]]]])
    """
    if format is None:
        format = TIME_FORMAT
        
    return time_in_a_while(days, seconds, microseconds, milliseconds,
                           minutes, hours, weeks).strftime(format)


def a_while_ago(days=0, seconds=0, microseconds=0, milliseconds=0,
                minutes=0, hours=0, weeks=0, format=TIME_FORMAT):
    return time_a_while_ago(days, seconds, microseconds, milliseconds,
                            minutes, hours, weeks).strftime(format)

# ---------------------------------------------------------------------------


def shift_time(dtime, shift):
    """ Adds/deletes an integer amount of seconds from a datetime specification

    :param dtime: The datatime specification
    :param shift: The wanted time shift (+/-)
    :return: A shifted datatime specification
    """
    return dtime + timedelta(seconds=shift)

# ---------------------------------------------------------------------------


def str_to_time(timestr, format=TIME_FORMAT):
    """

    :param timestr:
    :param format:
    :return: UTC time
    """
    if not timestr:
        return 0
    try:
        then = time.strptime(timestr, format)
    except ValueError:  # assume it's a format problem
        try:
            elem = TIME_FORMAT_WITH_FRAGMENT.match(timestr)
        except Exception, exc:
            print >> sys.stderr, "Exception: %s on %s" % (exc, timestr)
            raise
        then = time.strptime(elem.groups()[0] + "Z", TIME_FORMAT)

    return time.gmtime(calendar.timegm(then))


def instant(format=TIME_FORMAT):
    return time.strftime(format, time.gmtime())

# ---------------------------------------------------------------------------


def utc_now():
    return calendar.timegm(time.gmtime())

# ---------------------------------------------------------------------------


def before(point):
    """ True if point datetime specification is before now.

    NOTE: If point is specified it is supposed to be in local time.
    Not UTC/GMT !! This is because that is what gmtime() expects.
    """
    if not point:
        return True

    if isinstance(point, basestring):
        point = str_to_time(point)
    elif isinstance(point, int):
        point = time.gmtime(point)

    return time.gmtime() < point


def after(point):
    """ True if point datetime specification is equal or after now """
    if not point:
        return True
    else:
        return not before(point)


not_before = after

# 'not_on_or_after' is just an obscure name for 'before'
not_on_or_after = before

# a point is valid if it is now or sometime in the future, in other words,
# if it is not before now
valid = before


def later_than(after, before):
    """ True if then is later or equal to that """
    if isinstance(after, basestring):
        after = str_to_time(after)
    elif isinstance(after, int):
        after = time.gmtime(after)

    if isinstance(before, basestring):
        before = str_to_time(before)
    elif isinstance(before, int):
        before = time.gmtime(before)

    return after >= before