# Copyright 2012 Matt Chaput. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#    1. Redistributions of source code must retain the above copyright notice,
#       this list of conditions and the following disclaimer.
#
#    2. Redistributions in binary form must reproduce the above copyright
#       notice, this list of conditions and the following disclaimer in the
#       documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY MATT CHAPUT ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
# EVENT SHALL MATT CHAPUT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
# OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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# The views and conclusions contained in the software and documentation are
# those of the authors and should not be interpreted as representing official
# policies, either expressed or implied, of Matt Chaput.

from whoosh.matching import ConstantScoreMatcher, NullMatcher, ReadTooFar
from whoosh.query.qcore import Query


class ColumnQuery(Query):
    """A query that matches per-document values stored in a column rather than
    terms in the inverted index.

    This may be useful in special circumstances, but note that this is MUCH
    SLOWER than searching an indexed field.
    """

    def __init__(self, fieldname, condition):
        """
        :param fieldname: the name of the field to look in. If the field does
            not have a column, this query will not match anything.
        :param condition: if this is a callable, it is called on each value
            in the column, and for documents where callable(docvalue) returns
            True are returned as matching documents. If this is not a callable,
            the document values are compared to it (using ``==``).
        """

        self.fieldname = fieldname
        self.condition = condition

    def is_leaf(self):
        return True

    def matcher(self, searcher, context=None):
        fieldname = self.fieldname
        condition = self.condition
        if callable(condition):
            comp = condition
        else:

            def comp(v):
                # Made this a function instead of a lambda so I could put
                # debug prints here if necessary ;)
                return v == condition

        reader = searcher.reader()
        if not reader.has_column(fieldname):
            return NullMatcher()

        creader = reader.column_reader(fieldname)
        return ColumnMatcher(creader, comp)


class ColumnMatcher(ConstantScoreMatcher):
    def __init__(self, creader, condition):
        self.creader = creader
        self.condition = condition
        self._i = 0
        self._find_next()

    def _find_next(self):
        condition = self.condition
        creader = self.creader

        while self._i < len(creader) and not condition(creader[self._i]):
            self._i += 1

    def is_active(self):
        return self._i < len(self.creader)

    def next(self):
        if not self.is_active():
            raise ReadTooFar
        self._i += 1
        self._find_next()

    def reset(self):
        self._i = 0
        self._find_next()

    def id(self):
        return self._i

    def all_ids(self):
        condition = self.condition
        for docnum, v in enumerate(self.creader):
            if condition(v):
                yield docnum

    def supports(self, astype):
        return False

    def skip_to_quality(self, minquality):
        if self._score <= minquality:
            self._i = len(self.creader)
            return True
