"""\
@file iterators.py
@brief Useful general-purpose iterators.

$LicenseInfo:firstyear=2008&license=mit$

Copyright (c) 2008-2010, Linden Research, Inc.

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"""

from __future__ import nested_scopes

def iter_chunks(rows, aggregate_size=100):
    """
    Given an iterable set of items (@p rows), produces lists of up to @p
    aggregate_size items at a time, for example:
    
    iter_chunks([1,2,3,4,5,6,7,8,9,10], 3)

    Values for @p aggregate_size < 1 will raise ValueError.

    Will return a generator that produces, in the following order:
    - [1, 2, 3]
    - [4, 5, 6]
    - [7, 8, 9]
    - [10]
    """
    if aggregate_size < 1:
        raise ValueError()

    def iter_chunks_inner():
        row_iter = iter(rows)
        done = False
        agg = []
        while not done:
            try:
                row = row_iter.next()
                agg.append(row)
            except StopIteration:
                done = True
            if agg and (len(agg) >= aggregate_size or done):
                yield agg
                agg = []
    
    return iter_chunks_inner()