##############################################################################
#
# Copyright (c) 2002 Zope Foundation and Contributors.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################

######################################################################
# Sequence batching support

import util

__allow_access_to_unprotected_subobjects__={'batch': 1}
__roles__=None


class batch(util.Base):
    """Create a sequence batch"""

    def __init__(self, sequence, size, start=0, end=0,
                 orphan=3, overlap=0):

        start=start+1

        start,end,sz=opt(start,end,size,orphan,sequence)

        self._last=end-1
        self._first=start-1

        self._sequence=sequence
        self._size=size
        self._start=start
        self._end=end
        self._orphan=orphan
        self._overlap=overlap

    def previous_sequence(self): return self._first

    def previous_sequence_end_number(self):
        start,end,spam=opt(0, self._start-1+self._overlap,
                           self._size, self._orphan, self._sequence)
        return end

    def previous_sequence_start_number(self):
        start,end,spam=opt(0, self._start-1+self._overlap,
                           self._size, self._orphan, self._sequence)
        return start

    def previous_sequence_end_item(self):
        start,end,spam=opt(0, self._start-1+self._overlap,
                           self._size, self._orphan, self._sequence)
        return self._sequence[end-1]

    def previous_sequence_start_item(self):
        start,end,spam=opt(0, self._start-1+self._overlap,
                           self._size, self._orphan, self._sequence)
        return self._sequence[start-1]

    def next_sequence_end_number(self):
        start,end,spam=opt(self._end+1-self._overlap, 0,
                           self._size, self._orphan, self._sequence)
        return end

    def next_sequence_start_number(self):
        start,end,spam=opt(self._end+1-self._overlap, 0,
                           self._size, self._orphan, self._sequence)
        return start

    def next_sequence_end_item(self):
        start,end,spam=opt(self._end+1-self._overlap, 0,
                           self._size, self._orphan, self._sequence)
        return self._sequence[end-1]

    def next_sequence_start_item(self):
        start,end,spam=opt(self._end+1-self._overlap, 0,
                           self._size, self._orphan, self._sequence)
        return self._sequence[start-1]


    def next_sequence(self):
        try: self._sequence[self._end]
        except IndexError: return 0
        else: return 1

    def __getitem__(self, index):
        if index > self._last: raise IndexError, index
        return self._sequence[index+self._first]

def opt(start,end,size,orphan,sequence):
    if size < 1:
        if start > 0 and end > 0 and end >= start:
            size=end+1-start
        else: size=7

    if start > 0:

        try: sequence[start-1]
        except: start=len(sequence)

        if end > 0:
            if end < start: end=start
        else:
            end=start+size-1
            try: sequence[end+orphan-1]
            except: end=len(sequence)
    elif end > 0:
        try: sequence[end-1]
        except: end=len(sequence)
        start=end+1-size
        if start - 1 < orphan: start=1
    else:
        start=1
        end=start+size-1
        try: sequence[end+orphan-1]
        except: end=len(sequence)
    return start,end,size
