AToMPM/mt/ptcal/pytcore/tcore/matcher.py

'''This file is part of AToMPM - A Tool for Multi-Paradigm Modelling
Copyright 2011 by the AToMPM team and licensed under the LGPL
See COPYING.lesser and README.md in the root of this project for full details'''

from copy import deepcopy
from ..util.infinity import INFINITY
from ..core.match_algo import HimesisMatcher
from ..core.himesis import HConstants as HC
from rule_primitive import RulePrimitive
from messages import MatchSet, Match, TransformationException


class Matcher(RulePrimitive):
    '''
        Binds the source graph according to the pre-condition pattern.
    '''
    def __init__(self, condition, max=INFINITY):
        '''
            Binds the source graph according to the pre-condition pattern.
            @param condition: The pre-condition pattern.
            @param max: The maximum number of matches.
        '''
        super(Matcher, self).__init__()
        self.max = max
        self.condition = condition
    
    def __str__(self):
        s = super(Matcher, self).__str__()
        s = s.split(' ')
        s.insert(1, '[%s]' % self.condition.name)
        return reduce(lambda x, y: '%s %s' % (x,y), s)
    
    def packet_in(self, packet):
        self.exception = None
        self.is_success = False
        if self.condition[HC.GUID] in packet.match_sets:
            matchSet = packet.match_sets[self.condition[HC.GUID]]
        else:
            matchSet = MatchSet()
        
        # Find the matches
        try:
            i = 1
            if i <= self.max:
                for mapping in self._match(packet.graph, packet.global_pivots):
                    # Convert the mapping to a Match object
                    match = Match()
                    match.from_mapping(mapping, packet.graph, self.condition)
                    matchSet.matches.append(match)
                    i += 1
                    if i > self.max:
                        # We don't need any more matches
                        break
        except Exception, e:
            self.is_success = False
            self.exception = TransformationException(e)
            self.exception.packet = packet
            self.exception.transformation_unit = self
            return packet
        
        # Don't forget to add the match set to the packet, even if no matches were found
        if len(matchSet.matches) > 0:
            packet.match_sets[self.condition[HC.GUID]] = matchSet
        
        # Identify that this is the condition we are currently processing
        packet.current = self.condition[HC.GUID]
        
        # Success only if matches were found
        self.is_success = len(matchSet.matches) > 0
        return packet

    def _match(self, graph, pivots) :
        '''
            Matcher with pivots and (possibly) multiple NACs
            1. Verify that no unbound NAC has a match
            2. Let the "bridge" denote the biggest graph that is the intersection of the LHS and a NAC, among all NACs
            3. Match the common part between the LHS & the NAC, i.e., the "bridge"
            3.1 Continue the matching ensuring no occurrence of the NAC
            3.2. If a NAC is found, ignore the current bridge mapping
            3.3. Continue to find complete matches of the LHS,
                 given each partial match found in 3.1.
            3.4. For each valid match, verify that no occurrence of any remaining bound NAC is found,
                 given the mapping found in 3.3.
        '''
        pred1 = {}  # To optimize the matcher, since otherwise matcher will compute the predecessors of the source graph many times
        succ1 = {}  # To optimize the matcher, since otherwise matcher will compute the successors of the source graph many times
        
        # Cache the pivot nodes of the source graph
        pivots = deepcopy(pivots)
        pivots.to_source_node_indices(graph)
        
        #===================================================================
        # First process the NACs that are not bound to the LHS
        #===================================================================
        for NAC in self.condition.getUnboundNACs():
            # Look for a NAC match
            nacMatcher = HimesisMatcher(source_graph=graph, pattern_graph=NAC)
            # Convert the pivots
            nac_pivots = pivots.to_mapping(graph, NAC)
            try:
                for mapping in nacMatcher.match_iter(context=nac_pivots):
                    # Make the mapping into {...,NAClabel:graphIndex,...}
                    match = Match()
                    match.from_mapping(mapping, graph, self.condition)
                    if NAC[HC.MT_CONSTRAINT](match.to_label_mapping(graph), graph):
                        # An unbound NAC has been found: this pattern can never match
                        return
            except: raise
            finally: nacMatcher.reset_recursion_limit()
            # For further matching optimizations
            pred1 = nacMatcher.pred1
            succ1 = nacMatcher.succ1
        
        # Either there are no NACs, or there were only unbound NACs that do not match, so match the LHS now
        if not self.condition.hasBoundNACs():
            lhsMatcher = HimesisMatcher(source_graph=graph, pattern_graph=self.condition, pred1=pred1, succ1=succ1)
            # Convert the pivots
            lhs_pivots = pivots.to_mapping(graph, self.condition)
            try:
                for mapping in lhsMatcher.match_iter(context=lhs_pivots):
                    # Make the mapping into {...,LHSlabel:graphIndex,...}
                    match = Match()
                    match.from_mapping(mapping, graph, self.condition)
                    if self.condition[HC.MT_CONSTRAINT](match.to_label_mapping(graph), graph):
                        yield mapping
            except: raise
            finally: lhsMatcher.reset_recursion_limit()
            
            # The matching is complete
            return
        
        #===================================================================
        # Now process the NACs that have some nodes bound to the LHS
        #===================================================================
        
        # Continue the matching looking for the LHS now
        lhsMatcher = HimesisMatcher(source_graph=graph, pattern_graph=self.condition, pred1=pred1, succ1=succ1)
        # Augment the bridge mapping with the pivot mappings
        lhs_pivots = pivots.to_mapping(graph, self.condition)
        
        try:
            for mapping in lhsMatcher.match_iter(context=lhs_pivots):
                # Make the mapping into {...,LHSlabel:graphIndex,...}
                match = Match()
                match.from_mapping(mapping, graph, self.condition)
                if self.condition[HC.MT_CONSTRAINT](match.to_label_mapping(graph), graph):
                    # A match of the LHS is found: ensure that no remaining NAC do match
                    invalid = False
                    for NAC in self.condition.getBoundNACs():
                        # This mapping represents the mapping of the bridge of this NAC with the LHS
                        bridgeMapping = match.to_mapping(graph, NAC)
                        
                        # Now continue the matching looking for a match of the corresponding NAC
                        nacMatcher = HimesisMatcher(source_graph=graph, pattern_graph=NAC, pred1=pred1, succ1=succ1)
                        for nac_mapping in nacMatcher.match_iter(context=bridgeMapping):
                            # Make the mapping into {...,NAClabel:graphIndex,...}
                            match = Match()
                            match.from_mapping(nac_mapping, graph, NAC)
                            if NAC[HC.MT_CONSTRAINT](match.to_label_mapping(graph), graph):
                                # An occurrence of the NAC is found: current mapping is not valid
                                invalid = True
                                break
                        if invalid:
                            # An occurrence of the NAC was found: current mapping is not valid
                            break
                    else:
                        # Either there are no bound NACs or no occurrence of any bound NAC was found: current mapping is valid
                        yield mapping
        except: raise
        finally: lhsMatcher.reset_recursion_limit()