/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.reasoner.rulesys;

import java.util.HashSet;
import java.util.Iterator;
import java.util.List;

import org.apache.jena.graph.Factory;
import org.apache.jena.graph.Graph;
import org.apache.jena.rdf.model.Property;
import org.apache.jena.rdf.model.Resource;
import org.apache.jena.rdf.model.Statement;
import org.apache.jena.reasoner.IllegalParameterException;
import org.apache.jena.reasoner.InfGraph;
import org.apache.jena.reasoner.Reasoner;
import org.apache.jena.reasoner.ReasonerException;
import org.apache.jena.reasoner.ReasonerFactory;
import org.apache.jena.reasoner.rulesys.impl.LPRuleStore;
import org.apache.jena.reasoner.rulesys.impl.OWLRuleTranslationHook;
import org.apache.jena.vocabulary.ReasonerVocabulary;

/**
 * A reasoner interface that is able to invoke any of the useful
 * rule engine combinations. The rule set can be set after the reasoner
 * instance is created. The mode can be set to forward, backward or hybrid.
 * The OWL-specific rule augmentation can be included. Each of these settings
 * can be controlled using the configuration graph, specific methods calls or
 * generic setParameter calls.
 */
public class GenericRuleReasoner extends FBRuleReasoner {

    /** Prepared set of rules used for Backward-only mode */
    protected LPRuleStore bRuleStore;
    
    /** the current rule mode */
    protected RuleMode mode = HYBRID;
    
    /** Flag, if true we cache the closure of the pure rule set with its axioms */
    @SuppressWarnings("hiding")
    protected static final boolean cachePreload = true;
    
    /** Flag, if true then subClass and subProperty lattices will be optimized using TGCs, only applicable to HYBRID reasoners */
    protected boolean enableTGCCaching = false;
    
    /** Flag, if true then rules will be augmented by OWL translations of the schema */
    protected boolean enableOWLTranslation = false;
    
    /** Optional set of preprocessing hooks  to be run in sequence during preparation time, only applicable to HYBRID modes */
    protected HashSet<RulePreprocessHook> preprocessorHooks;
    
    /** Flag, if true then find results will be filtered to remove functors and illegal RDF */
    public boolean filterFunctors = true;
    
    /** A prebuilt copy of the OWL translation hook */
    private static final OWLRuleTranslationHook owlTranslator = new OWLRuleTranslationHook();
    
    /** Constant - the mode description for pure forward chaining */
    public static final RuleMode FORWARD = new RuleMode("forward");
    
    /** Constant - the mode description for pure forward chaining, using RETE engine */
    public static final RuleMode FORWARD_RETE = new RuleMode("forwardRETE");
    
    /** Constant - the mode description for pure backward chaining */
    public static final RuleMode BACKWARD = new RuleMode("backward");
    
    /** Constant - the mode description for mixed forward/backward, this is the default mode */
    public static final RuleMode HYBRID = new RuleMode("hybrid");
    
//  =======================================================================
//  Constructors
     
    /**
     * Constructor. This is the raw version that does not reference a ReasonerFactory
     * and so has no capabilities description. 
     * @param rules a list of Rule instances which defines the ruleset to process
     */
    public GenericRuleReasoner(List<Rule> rules) {
        super(rules);
    }
    
    /**
     * Constructor
     * @param factory the parent reasoner factory which is consulted to answer capability questions
     * @param configuration RDF node to configure the rule set and mode, can be null
     */
    public GenericRuleReasoner(ReasonerFactory factory, Resource configuration) {
        super(factory);
        this.configuration = configuration;
        if (configuration != null) loadConfiguration( configuration );
    }
    
    /**
     * Constructor
     * @param rules a list of Rule instances which defines the ruleset to process
     * @param factory the parent reasoner factory which is consulted to answer capability questions
     */
    public GenericRuleReasoner(List<Rule> rules, ReasonerFactory factory) {
        super(rules, factory);
    }
    
    /**
     * Internal constructor, used to generated a partial binding of a schema
     * to a rule reasoner instance.
     */
    protected GenericRuleReasoner(List<Rule> rules, Graph schemaGraph, ReasonerFactory factory, RuleMode mode) {
        this(rules, factory);
        this.schemaGraph = schemaGraph;
        this.mode = mode;
    }
    
//  =======================================================================
//  Parameter control

    /**
     * Set the direction of rule inference desired.
     * If set to a pure mode (FORWARD, BACKWARD) then the rules will be
     * interpreted as operating in that direction which ever direction
     * they were written in. In HYBRID mode then the direction of the rule
     * itself which control whether it is used in forward or backward mode. 
     * In addition, HYBRID mode allows forward rules to generate addition
     * backward rules.
     */
    public void setMode(RuleMode mode) {
        if (schemaGraph != null) {
            throw new ReasonerException("Can't change mode of a reasoner bound to a schema");
        }
        this.mode = mode;
        preload = null;
        bRuleStore = null;
    }
    
    /**
     * Set (or change) the rule set that this reasoner should execute.
     * This will not affect inference models already created from this reasoner.
     * @param rules a list of Rule objects
     */
    @Override
    public void setRules(List<Rule> rules) {
        // Currently redunant but it will differ from the inherited
        // version in the future
        super.setRules(rules);
    }
    
    /**
     * Set to true to enable translation of selected parts of an OWL schema
     * to additional rules. At present only intersection statements are handled this way.
     * The translation is only applicable in HYBRID mode.
     */
    public void setOWLTranslation(boolean enableOWLTranslation) {
        if (enableOWLTranslation && (mode != HYBRID)) {
            throw new ReasonerException("Can only enable OWL rule translation in HYBRID mode");
        }
        this.enableOWLTranslation = enableOWLTranslation;    
        if (enableOWLTranslation) {
            addPreprocessingHook(owlTranslator);    
        } else {
            removePreprocessingHook(owlTranslator);
        }
    }
    
    /**
     * Set to true to enable caching of subclass/subproperty lattices in a
     * specialized cache rather than using the rule systems. This has substantially
     * higher performance but it is done as a separate initialization pass and so
     * can only work correct with some rule sets. This is only guaranteed to be implemented
     * for the HYBRID mode.
     */
    public void setTransitiveClosureCaching(boolean enableTGCCaching) {
        this.enableTGCCaching = enableTGCCaching;
    }
   
    /**
     * Set to true to cause functor-valued literals to be dropped from rule output.
     * Default is true.
     */
    public void setFunctorFiltering(boolean param) {
        filterFunctors = param;
    }
    
    /**
     * Add a new preprocessing hook defining an operation that
     * should be run when the inference graph is being prepared. This can be
     * used to generate additional data-dependent rules or translations.
     * This is only guaranteed to be implemented for the HYBRID mode.
     */
    public void addPreprocessingHook(RulePreprocessHook hook) {
        if (preprocessorHooks == null) {
            preprocessorHooks = new HashSet<>();
        }
        preprocessorHooks.add(hook);
    }
    
    /**
     * Remove a preprocessing hook. defining an operation that
     */
    public void removePreprocessingHook(RulePreprocessHook hook) {
        if (preprocessorHooks != null) {
            preprocessorHooks.remove(hook);
        }
    }
        
    @Override
    protected boolean doSetResourceParameter( Property parameter, Resource value )
        {
        if (isRuleSetURL( parameter )) 
            addRules( Rule.rulesFromURL( value.getURI() ) );
        else if (isRuleSet( parameter )) 
            {
            addRulesFromURLs( value );
            addRulesFromStrings( value ); 
            }
        else
            return false;
        return true;
        }

    private void addRulesFromStrings( Resource value )
        {
        Iterator<Statement> it = getHasRuleStatements( value );
        while (it.hasNext()) addRuleFromString( it.next().getString() );
        }

    private void addRuleFromString( String ruleString )
        { addRules( Rule.parseRules( ruleString ) ); }

    private void addRulesFromURLs( Resource value )
        {
        Iterator<Statement> that = getRuleSetURLStatements( value );
        while (that.hasNext()) addRules( Rule.rulesFromURL( that.next().getResource().getURI() ) );
        }

    private Iterator<Statement> getHasRuleStatements( Resource value )
        { 
        return value.listProperties( ReasonerVocabulary.hasRule ); 
        }

    private Iterator<Statement> getRuleSetURLStatements( Resource value )
        {
        return value.listProperties( ReasonerVocabulary.ruleSetURL ); 
        }

    private boolean isHasRule( Property parameter )
        { 
        return parameter.equals( ReasonerVocabulary.hasRule ); 
        }

    private boolean isRuleSet( Property parameter )
        { 
        return  parameter.equals( ReasonerVocabulary.ruleSet ); 
        }

    private boolean isRuleSetURL( Property parameter )
        { 
        return parameter.equals( ReasonerVocabulary.ruleSetURL ); 
        }
    
    /**
     * Internal version of setParameter that does not directly raise an
     * exception on parameters it does not recognize.
     * @return false if the parameter was not recognized
     */
    @Override
    protected boolean doSetParameter(Property parameter, Object value) {
        if (parameter.equals(ReasonerVocabulary.PROPenableFunctorFiltering)) {
            filterFunctors =  Util.convertBooleanPredicateArg(parameter, value);
        } else if (isHasRule( parameter )) {
            addRuleFromString( value.toString() );
        } else if (parameter.equals(ReasonerVocabulary.PROPenableOWLTranslation)) {
            enableOWLTranslation =  Util.convertBooleanPredicateArg(parameter, value);
            if (enableOWLTranslation) {
                addPreprocessingHook(owlTranslator);    
            } else {
                removePreprocessingHook(owlTranslator);
            }
            
        } else if (parameter.equals(ReasonerVocabulary.PROPenableTGCCaching)) {
            enableTGCCaching =  Util.convertBooleanPredicateArg(parameter, value);
            
        } else if (parameter.equals(ReasonerVocabulary.PROPruleMode)) {
            if (value.equals(FORWARD.name)) {
                mode = FORWARD;
            } else if (value.equals(FORWARD_RETE.name)) {
                mode = FORWARD_RETE;
            } else if (value.equals(BACKWARD.name)) {
                mode = BACKWARD;
            } else if (value.equals(HYBRID.name)) {
                mode = HYBRID;
            } else {
                throw new IllegalParameterException("PROPruleMode can only be 'forward'm 'forwardRETE', 'backward', 'hybrid', not " + value);
            }
            
        } else if (parameter.equals(ReasonerVocabulary.PROPruleSet)) {
            if (value instanceof String) {
                addRules( loadRules( (String)value ) );
            } else {
                throw new IllegalParameterException("PROPruleSet value should be a URI string. Was a " + value.getClass());
            }
        } else {
            return super.doSetParameter( parameter, value );
        }
        return true;
    }
    
//  =======================================================================
//  Implementation methods

    /**
     * Precompute the implications of a schema graph. The statements in the graph
     * will be combined with the data when the final InfGraph is created.
     */
    @Override
    public Reasoner bindSchema(Graph tbox) throws ReasonerException {
        if (schemaGraph != null) {
            throw new ReasonerException("Can only bind one schema at a time to a GenericRuleReasoner");
        }
        Graph graph = null;
        if (mode == FORWARD) {
            graph = new BasicForwardRuleInfGraph(this, rules, null, tbox);
            ((InfGraph)graph).prepare();
        } else if (mode == FORWARD_RETE) {
                graph = new RETERuleInfGraph(this, rules, null, tbox);
                ((InfGraph)graph).prepare();
        } else if (mode == BACKWARD) {
            graph = tbox;
        } else {
            List<Rule> ruleSet = rules;
            graph = new FBRuleInfGraph(this, ruleSet, getPreload(), tbox);
            if (enableTGCCaching) ((FBRuleInfGraph)graph).setUseTGCCache();
            ((FBRuleInfGraph)graph).prepare();
        }
        GenericRuleReasoner grr = new GenericRuleReasoner(rules, graph, factory, mode);
        grr.setDerivationLogging(recordDerivations);
        grr.setTraceOn(traceOn);
        grr.setTransitiveClosureCaching(enableTGCCaching);
        grr.setFunctorFiltering(filterFunctors);
        if (preprocessorHooks != null) {
            for ( RulePreprocessHook preprocessorHook : preprocessorHooks )
            {
                grr.addPreprocessingHook( preprocessorHook );
            }
        }
        return grr;
    }
    
    /**
     * Attach the reasoner to a set of RDF data to process.
     * The reasoner may already have been bound to specific rules or ontology
     * axioms (encoded in RDF) through earlier bindRuleset calls.
     * 
     * @param data the RDF data to be processed, some reasoners may restrict
     * the range of RDF which is legal here (e.g. syntactic restrictions in OWL).
     * @return an inference graph through which the data+reasoner can be queried.
     * @throws ReasonerException if the data is ill-formed according to the
     * constraints imposed by this reasoner.
     */
    @Override
    public InfGraph bind(Graph data) throws ReasonerException {
        Graph schemaArg = schemaGraph == null ? getPreload() : schemaGraph;
        InfGraph graph = null; 
        if (mode == FORWARD) {
            graph = new BasicForwardRuleInfGraph(this, rules, schemaArg);
            ((BasicForwardRuleInfGraph)graph).setTraceOn(traceOn);
        } else if (mode == FORWARD_RETE) {
                graph = new RETERuleInfGraph(this, rules, schemaArg);
                ((BasicForwardRuleInfGraph)graph).setTraceOn(traceOn);
                ((BasicForwardRuleInfGraph)graph).setFunctorFiltering(filterFunctors);
        } else if (mode == BACKWARD) {
            graph = new LPBackwardRuleInfGraph(this, getBruleStore(), data, schemaArg);
            ((LPBackwardRuleInfGraph)graph).setTraceOn(traceOn);
        } else {
            List<Rule> ruleSet = ((FBRuleInfGraph)schemaArg).getRules();
            FBRuleInfGraph fbgraph = new FBRuleInfGraph(this, ruleSet, schemaArg);
            graph = fbgraph; 
            if (enableTGCCaching) fbgraph.setUseTGCCache();
            fbgraph.setTraceOn(traceOn);
            fbgraph.setFunctorFiltering(filterFunctors);
            if (preprocessorHooks!= null) {
                for ( RulePreprocessHook preprocessorHook : preprocessorHooks )
                {
                    fbgraph.addPreprocessingHook( preprocessorHook );
                }
            }
        }
        graph.setDerivationLogging(recordDerivations);
        graph.rebind(data);
        return graph;
    }
    
    /**
     * Get the single static precomputed rule closure.
     */
    @Override
    protected synchronized InfGraph getPreload() {
        // We only support this in HYBRID mode
        if (cachePreload && preload == null && mode == HYBRID) {
            preload = new FBRuleInfGraph( this, rules, null, Factory.createDefaultGraph() );
            if (enableTGCCaching) ((FBRuleInfGraph)preload).setUseTGCCache();
            preload.prepare();
        }
        return preload;
    }
    
    /**
     * Return the prepared backward only rules.
     */
    protected LPRuleStore getBruleStore() {
        if (bRuleStore == null) {
            bRuleStore = new LPRuleStore(rules);
        }
        return bRuleStore;
    }
    
//  =======================================================================
//  Inner classes

    /** 
     * Class used as an enum for describing rule modes.
     */
    public static class RuleMode {
        /** Name for the mode */
        String name;
        
        /** Constructor */
        protected RuleMode(String name) {
            this.name = name;
        }
        
        @Override
        public String toString() {
            return name;
        }
    }
    
}
