"""Copyright 2008 Orbitz WorldWide

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."""
import pytz

from datetime import datetime, timedelta
from time import daylight

months = ['jan', 'feb', 'mar', 'apr', 'may', 'jun',
          'jul', 'aug', 'sep', 'oct', 'nov', 'dec']
weekdays = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat']


def parseATTime(s, tzinfo=None):
    if tzinfo is None:
        from ..app import app
        tzinfo = pytz.timezone(app.config['TIME_ZONE'])
    s = s.strip().lower().replace('_', '').replace(',', '').replace(' ', '')
    if s.isdigit():
        if (
            len(s) == 8 and
            int(s[:4]) > 1900 and
            int(s[4:6]) < 13 and
            int(s[6:]) < 32
        ):
            pass  # Fall back because its not a timestamp, its YYYYMMDD form
        else:
            return datetime.fromtimestamp(int(s), tzinfo)
    elif ':' in s and len(s) == 13:
        return tzinfo.localize(datetime.strptime(s, '%H:%M%Y%m%d'), daylight)
    if '+' in s:
        ref, offset = s.split('+', 1)
        offset = '+' + offset
    elif '-' in s:
        ref, offset = s.split('-', 1)
        offset = '-' + offset
    else:
        ref, offset = s, ''
    return (parseTimeReference(ref) +
            parseTimeOffset(offset)).astimezone(tzinfo)


def parseTimeReference(ref):
    if not ref or ref == 'now':
        return datetime.utcnow().replace(tzinfo=pytz.utc)

    # Time-of-day reference
    i = ref.find(':')
    hour, min = 0, 0
    if i != -1:
        hour = int(ref[:i])
        min = int(ref[i+1:i+3])
        ref = ref[i+3:]
        if ref[:2] == 'am':
            ref = ref[2:]
        elif ref[:2] == 'pm':
            hour = (hour + 12) % 24
            ref = ref[2:]
    if ref.startswith('noon'):
        hour, min = 12, 0
        ref = ref[4:]
    elif ref.startswith('midnight'):
        hour, min = 0, 0
        ref = ref[8:]
    elif ref.startswith('teatime'):
        hour, min = 16, 0
        ref = ref[7:]

    refDate = datetime.utcnow().replace(hour=hour, minute=min, second=0,
                                        tzinfo=pytz.utc)

    # Day reference
    if ref in ('yesterday', 'today', 'tomorrow'):  # yesterday, today, tomorrow
        if ref == 'yesterday':
            refDate = refDate - timedelta(days=1)
        if ref == 'tomorrow':
            refDate = refDate + timedelta(days=1)
    elif ref.count('/') == 2:  # MM/DD/YY[YY]
        m, d, y = map(int, ref.split('/'))
        if y < 1900:
            y += 1900
        if y < 1970:
            y += 100
        refDate = refDate.replace(year=y)
        refDate = replace_date(refDate, m, d)

    elif len(ref) == 8 and ref.isdigit():  # YYYYMMDD
        refDate = refDate.replace(year=int(ref[:4]))
        refDate = replace_date(refDate, int(ref[4:6]), int(ref[6:8]))

    elif ref[:3] in months:  # MonthName DayOfMonth
        month = months.index(ref[:3]) + 1
        if ref[-2:].isdigit():
            day = int(ref[-2])
        elif ref[-1:].isdigit():
            day = int(ref[-1:])
        else:
            raise Exception("Day of month required after month name")
        refDate = replace_date(refDate, month, day)
    elif ref[:3] in weekdays:  # DayOfWeek (Monday, etc)
        todayDayName = refDate.strftime("%a").lower()[:3]
        today = weekdays.index(todayDayName)
        twoWeeks = weekdays * 2
        dayOffset = today - twoWeeks.index(ref[:3])
        if dayOffset < 0:
            dayOffset += 7
        refDate -= timedelta(days=dayOffset)
    elif ref:
        raise Exception("Unknown day reference")
    return refDate


def replace_date(date, month, day):
    try:
        date = date.replace(month=month)
        date = date.replace(day=day)
    except ValueError:  # day out of range for month, or vice versa
        date = date.replace(day=day)
        date = date.replace(month=month)
    return date


def parseTimeOffset(offset):
    if not offset:
        return timedelta()

    t = timedelta()

    if offset[0].isdigit():
        sign = 1
    else:
        sign = {'+': 1, '-': -1}[offset[0]]
        offset = offset[1:]

    while offset:
        i = 1
        while offset[:i].isdigit() and i <= len(offset):
            i += 1
        num = int(offset[:i-1])
        offset = offset[i-1:]
        i = 1
        while offset[:i].isalpha() and i <= len(offset):
            i += 1
        unit = offset[:i-1]
        offset = offset[i-1:]
        unitString = getUnitString(unit)
        if unitString == 'months':
            unitString = 'days'
            num = num * 30
        if unitString == 'years':
            unitString = 'days'
            num = num * 365
        t += timedelta(**{unitString: sign * num})

    return t


def getUnitString(s):
    if s.startswith('s'):
        return 'seconds'
    if s.startswith('min'):
        return 'minutes'
    if s.startswith('h'):
        return 'hours'
    if s.startswith('d'):
        return 'days'
    if s.startswith('w'):
        return 'weeks'
    if s.startswith('mon'):
        return 'months'
    if s.startswith('y'):
        return 'years'
    raise Exception("Invalid offset unit '%s'" % s)
