#!/usr/bin/env python

"""

Managing and presenting periods of time.

Copyright (C) 2014, 2015 Paul Boddie <paul@boddie.org.uk>

This program 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 3 of the License, or (at your option) any later

version.

This program 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

this program.  If not, see <http://www.gnu.org/licenses/>.

"""

from bisect import bisect_left, insort_left

from imiptools.dates import get_datetime, get_start_of_day, to_timezone

# Time management.

def have_conflict(freebusy, periods, get_conflicts=False):

    """

    Return whether any period in 'freebusy' overlaps with the given 'periods',

    returning a collection of such overlapping periods if 'get_conflicts' is

    set to a true value.

    """

    conflicts = []

    for start, end in periods:

        overlapping = period_overlaps(freebusy, (start, end), get_conflicts)

        if overlapping:

            if get_conflicts:

                conflicts += overlapping

            else:

                return True

    if get_conflicts:

        return conflicts

    else:

        return False

def insert_period(freebusy, period):

    insort_left(freebusy, period)

def remove_period(freebusy, uid):

    i = 0

    while i < len(freebusy):

        t = freebusy[i]

        if len(t) >= 3 and t[2] == uid:

            del freebusy[i]

        else:

            i += 1

def period_overlaps(freebusy, period, get_periods=False):

    """

    Return whether any period in 'freebusy' overlaps with the given 'period',

    returning a collection of overlapping periods if 'get_periods' is set to a

    true value.

    """

    dtstart, dtend = period[:2]

    found = bisect_left(freebusy, (dtstart, dtend, None, None))

    overlapping = []

    # Find earlier overlapping periods.

    i = found

    while i > 0 and freebusy[i - 1][1] > dtstart:

        if get_periods:

            overlapping.insert(0, freebusy[i - 1])

        else:

            return True

        i -= 1

    # Find later overlapping periods.

    i = found

    while i < len(freebusy) and (dtend is None or freebusy[i][0] < dtend):

        if get_periods:

            overlapping.append(freebusy[i])

        else:

            return True

        i += 1

    if get_periods:

        return overlapping

    else:

        return False

# Period layout.

def convert_periods(periods, tzid):

    "Convert 'periods' to use datetime objects employing the given 'tzid'."

    l = []

    for t in periods:

        start, end = t[:2]

        start = to_timezone(get_datetime(start), tzid)

        end = to_timezone(get_datetime(end), tzid)

        l.append((start, end) + tuple(t[2:]))

    return l

def get_scale(periods):

    """

    Return an ordered time scale from the given list 'periods', with the first

    two elements of each tuple being start and end times.

    The given 'tzid' is used to make sure that the times are defined according

    to the chosen time zone.

    The returned scale is a mapping from time to (starting, ending) tuples,

    where starting and ending are collections of tuples from 'periods'.

    """

    scale = {}

    for t in periods:

        start, end = t[:2]

        # Add a point and this event to the starting list.

        if not scale.has_key(start):

            scale[start] = [], []

        scale[start][0].append(t)

        # Add a point and this event to the ending list.

        if not scale.has_key(end):

            scale[end] = [], []

        scale[end][1].append(t)

    return scale

def get_slots(scale):

    """

    Return an ordered list of time slots from the given 'scale'.

    Each slot is a tuple of the form (point, (endpoint, active)), where 'point'

    indicates the start of the slot, 'endpoint' the end of the slot (or None),

    and 'active' provides a list of parallel event tuples, with each tuple

    containing the original details of an event.

    """

    slots = []

    active = []

    points = scale.items()

    points.sort()

    # Maintain a current slot so that the end can be added.

    current = None

    for point, (starting, ending) in points:

        # Discard all active events ending at or before this start time.

        # Free up the position in the active list.

        for t in ending:

            i = active.index(t)

            active[i] = None

        # For each event starting at the current point, fill any newly-vacated

        # position or add to the end of the active list.

        for t in starting:

            try:

                i = active.index(None)

                active[i] = t

            except ValueError:

                active.append(t)

        # Discard vacant positions from the end of the active list.

        while active and active[-1] is None:

            active.pop()

        if current:

            _point, _active = current

            slots.append((_point, (point, _active)))

        current = point, active[:]

    if current:

        _point, _active = current

        slots.append((_point, (None, _active)))

    return slots

def add_day_start_points(slots):

    """

    Introduce into the 'slots' any day start points required by multi-day

    periods.

    """

    new_slots = []

    current_date = None

    previously_active = []

    for point, (endpoint, active) in slots:

        start_of_day = get_start_of_day(point)

        this_date = point.date()

        # For each new day, add a slot for the start of the day where no such

        # slot already exists.

        if this_date != current_date:

            current_date = this_date

            # Add any continuing periods.

            if point != start_of_day:

                new_slots.append((start_of_day, (point, previously_active)))

        # Add the currently active periods at this point in time.

        previously_active = active

    for t in new_slots:

        insort_left(slots, t)

def add_slots(slots, points):

    """

    Introduce into the 'slots' entries for those in 'points' that are not

    already present, propagating active periods from time points preceding

    those added.

    """

    for point in points:

        i = bisect_left(slots, (point, ()))

        # Ignore points of time for which slots already exist.

        if i < len(slots) and slots[i][0] == point:

            continue

        # Update the endpoint of any preceding slot to refer to this new point.

        if i > 0:

            _point, (_endpoint, previously_active) = slots[i-1]

            slots[i-1] = _point, (point, previously_active)

        else:

            previously_active = []

        # Either insert a new slot before any following ones.

        if i < len(slots):

            _point, (_endpoint, _active) = slots[i]

            slots.insert(i, (point, (_point, previously_active)))

        # Or add a new slot at the end of the list.

        else:

            slots.append((point, (None, previously_active)))

def partition_by_day(slots):

    """

    Return a mapping from dates to entries provided by 'slots'.

    """

    d = {}

    for point, (endpoint, value) in slots:

        day = point.date()

        if not d.has_key(day):

            d[day] = []

        d[day].append((point, (endpoint, value)))

    return d

def get_spans(slots):

    "Inspect the given 'slots', returning a mapping of event uids to spans."

    points = [point for point, (endpoint, active) in slots]

    spans = {}

    for point, (endpoint, active) in slots:

        for t in active:

            if t and len(t) >= 2:

                start, end, uid, key = get_freebusy_details(t)

                try:

                    start_slot = points.index(start)

                except ValueError:

                    start_slot = 0

                try:

                    end_slot = points.index(end)

                except ValueError:

                    end_slot = len(slots)

                spans[key] = end_slot - start_slot

    return spans

def get_freebusy_details(t):

    "Return a tuple of the form (start, end, uid, key) from 't'."

    # Handle both complete free/busy details...

    if len(t) > 2:

        start, end, uid = t[:3]

        key = uid

    # ...and published details without specific event details.

    else:

        start, end = t[:2]

        uid = None

        key = (start, end)

    return start, end, uid, key

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