# $Id: N3Statement.py,v 1.6 2002/05/01 15:43:49 graham Exp $
#
# RDF statement class for use with N3 parser and model
#
#--------+---------+---------+---------+---------+---------+---------+---------+
#
# Copyright (c) 2002, G. KLYNE
# 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.
# 3. The name of the author may not be used to endorse or promote products
#    derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 THE AUTHOR 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.
#
#--------+---------+---------+---------+---------+---------+---------+---------+
# $Source: /file/cvsdev/PythonN3/N3Statement.py,v $
# $Author: graham $
# $Revision: 1.6 $ $Date: 2002/05/01 15:43:49 $
#--------+---------+---------+---------+---------+---------+---------+---------+
#        1         2         3         4         5         6         7         8

#import os
#import re
import sys
import string
import StringIO

from N3Node import N3Node

#--------+---------+---------+---------+---------+---------+---------+---------+
# N3Statement - represents any statement in the graph.
#
class N3Statement:
    def __init__( self, Subj, Prop, Obj ):
        """
        Construct statement from subject, property, object nodes.
        """
        self.Prop = Prop
        if Prop.isReversed():
            self.Subj = Obj
            self.Obj  = Subj
        else:
            self.Subj = Subj
            self.Obj  = Obj
        return

    def __eq__( self, Stmt ):
        """
        Compare for equality with another statement.

        Statements are equal if they have equal subject, property
        and object values.
        """
        return ( ( self.Subj == Stmt.Subj ) and
                 ( self.Prop == Stmt.Prop ) and
                 ( self.Obj  == Stmt.Obj ) )

    def __ne__( self, Stmt ):
        """
        Compare for inequality with another statement.

        (Complement of __eq__ above.)
        """
        return not self.__eq__( Stmt )

    def __str__( self ):
        return ( str(self.Subj) + " " +
                 str(self.Prop) + " " +
                 str(self.Obj)  + " ." )

    def __repr__( self ):
        return ( "'" +
                 str(self.Subj) + " " +
                 str(self.Prop) + " " +
                 str(self.Obj)  + " . '\n" )

    def getSubject( self ):
        """
        Return subject node of statement
        """
        return self.Subj

    def getProperty( self ):
        """
        Return property node for statement
        """
        return self.Prop

    def getObject( self ):
        """
        Return object node of statement
        """
        return self.Obj

    def match( self, Subj, Prop, Obj ):
        """
        Test for match with supplied subject, property and object.
        Values supplied as None match anything.
        """
        if Subj:
            if Subj != self.Subj: return 0
        if Prop:
            if Prop != self.Prop: return 0
        if Obj:
            if Obj  != self.Obj:  return 0
        return 1

    def getStmtDisplay( self, PrefixTable ):
        """
        Return convenient description for the statement, using the supplied
        prefix table.
        """
        return ( self.Subj.getNodeName( PrefixTable ) + " " +
                 self.Prop.getNodeName( PrefixTable ) + " " +
                 self.Obj.getNodeName( PrefixTable )  + " ." )

    # End of N3Statement

#--------+---------+---------+---------+---------+---------+---------+---------+
#
# Stand-alone test code follows:
#

if __name__ == '__main__':
    # Some basic tests
    sys.stdout.write( "Node tests\n" )
    Node1 = N3Node()
    sys.stdout.write( "Node 1: "+str(Node1)+"\n" )
    Node2 = N3Node( uri='http://example.org/base/local' )
    sys.stdout.write( "Node 2: "+str(Node2)+"\n" )
    Node3 = N3Node( ns='http://example.org/base/', name='local' )
    sys.stdout.write( "Node 3: "+str(Node3)+"\n" )
    Node4 = N3Node( lit='a string' )
    sys.stdout.write( "Node 4: "+str(Node4)+"\n" )
    if Node1 == Node1:
        sys.stdout.write( "Node1 == Node1 (OK)\n" )
    else:
        sys.stdout.write( "Node1 != Node1 (Error)\n" )
    if Node2 == Node3:
        sys.stdout.write( "Node2 == Node3 (OK)\n" )
    else:
        sys.stdout.write( "Node2 != Node3 (Error)\n" )

    sys.stdout.write( "Statement tests\n" )
    Stmt1 = N3Statement( Node1, Node2, Node4 )
    sys.stdout.write( "Stmt 1: "+str(Stmt1)+"\n" )
    Stmt2 = N3Statement( Node1, Node3, Node4 )
    sys.stdout.write( "Stmt 2: "+str(Stmt2)+"\n" )
    if Stmt1 == Stmt2:
        sys.stdout.write( "Stmt1 == Stmt2 (OK)\n" )
    else:
        sys.stdout.write( "Stmt1 != Stmt2 (Error)\n" )

    sys.stdout.write( "Exiting\n" )

#--------+---------+---------+---------+---------+---------+---------+---------+
#
# $Log: N3Statement.py,v $
# Revision 1.6  2002/05/01 15:43:49  graham
# Cleanup small details
#
# Revision 1.5  2002/04/25 19:00:13  graham
# Update CVS keyword fields
#
# Revision 1.4  2002/04/25 18:53:25  graham
# Add copyright and disclaimer notices
#
# Revision 1.3  2002/04/24 14:36:33  graham
# Save edits
#
# Revision 1.2  2002/04/23 17:09:57  graham
# Basic query and report generation works
#
# Revision 1.1  2002/04/19 22:07:39  graham
# Separated into smaller modules; basic N3Model functions working
#
# Revision 1.3  2002/04/18 07:39:42  graham
# Added TODO
#
# Revision 1.2  2002/04/17 23:41:31  graham
# Basic N3 parser is working
#