##############################################################################
#
# Copyright (c) 2002 Zope Corporation and Contributors.
# All Rights Reserved.
#
# 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.
#
##############################################################################
"""Text index.

$Id: textindex.py 28610 2004-12-09 20:56:05Z jim $
"""

from persistent import Persistent
from zope.interface import implements

from zope.index.text.okapiindex import OkapiIndex
from zope.index.text.lexicon import Lexicon
from zope.index.text.lexicon import Splitter, CaseNormalizer, StopWordRemover
from zope.index.text.queryparser import QueryParser

from zope.index.interfaces import IInjection, IIndexSearch, IStatistics

class TextIndex(Persistent):

    implements(IInjection, IIndexSearch, IStatistics)

    def __init__(self, lexicon=None, index=None):
        """Provisional constructor.

        This creates the lexicon and index if not passed in."""
        if lexicon is None:
            lexicon = Lexicon(Splitter(), CaseNormalizer(), StopWordRemover())
        if index is None:
            index = OkapiIndex(lexicon)
        self.lexicon = lexicon
        self.index = index

    def index_doc(self, docid, text):
        self.index.index_doc(docid, text)

    def unindex_doc(self, docid):
        self.index.unindex_doc(docid)

    def clear(self):
        self.index.clear()

    def documentCount(self):
        """Return the number of documents in the index."""
        return self.index.documentCount()

    def wordCount(self):
        """Return the number of words in the index."""
        return self.index.wordCount()

    def apply(self, querytext, start=0, count=None):
        parser = QueryParser(self.lexicon)
        tree = parser.parseQuery(querytext)
        results = tree.executeQuery(self.index)
        if results:
            qw = self.index.query_weight(tree.terms())
            
            # Hack to avoid ZeroDivisionError
            if qw == 0:
                qw = 1.0

            qw *= 1.0

            for docid, score in results.iteritems():
                try:
                    results[docid] = score/qw
                except TypeError:
                    # We overflowed the score, perhaps wildly unlikely.
                    # Who knows.
                    results[docid] = sys.maxint/10

        return results