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package org.aksw.jena_sparql_api.views;


import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

import org.apache.jena.sparql.core.Var;


/**
 * View instances relate variables (usually those of of a
 * SPARQL query subject to rewriting) to the variables and
 * constants of a view.
 *
 * A view instance is comprised of
 * - A view definition
 * - A binding, which relates query variables to variables of the view and constants
 *
 * TODO View instances should implement a common interface with mappings
 *
 * @author Claus Stadler 
 *
 */
public class ViewInstance {


    private T viewDefinition;
    private VarBinding binding;


    public ViewInstance(T viewDefinition, VarBinding binding) {
        this.viewDefinition = viewDefinition;
        this.binding = binding;
    }


    public T getViewDefinition() {
        return viewDefinition;
    }


    public VarBinding getBinding() {
        return binding;
    }


    /*
    public Set getViewVariablesForQueryVariable(Var var) {

    }*/


    /**
     * How the query variables map to the parent view
     * Given a query with var a, and a virtual graph with ?s:
     *
     * e.g. {?view1_s=[?a]}
     *
     *
     * @return
     */
//	public SetMultimap getParentToQueryBinding()
//	{
//		TwoWayBinding twb = null;
//		throw new RuntimeException("To implement");
//		/*
//		SetMultimap result = HashMultimap.create();
//		//binding.g
//
//		for(Entry entry : binding.getEquiMap().getEquivalences().entries()) {
//			Var back = (Var)renamer.inverse().get(entry.getValue());
//			if(back == null) {
//				continue;
//			}
//
//			result.put(back, entry.getKey());
//		}
//
//		return result;
//		*/
//	}



    /**
     * Convenience getter.
     *
     * Returns the set of definitions associated with a view variable.
     *
     * @param viewVar
     * @return
     */
    public Set getDefinitionsForViewVariable(Var viewVar) {
        Collection defs = viewDefinition.getVarDefinition().getDefinitions(viewVar);

        Set result = new HashSet(defs);
        return result;
    }


    /**
     * Convenience getter.
     *
     * Returns the variable definitions underlying this instance.
     * @return
     *
     * @return
     */
    public VarDefinition getVarDefinition() {
        return viewDefinition.getVarDefinition();
    }

    /*
    public T getViewDefinition() {
        return viewDefinition;
    }
    */


    /**
     * Returns for a query variable the set of definitions that is indirectly associated with it via the binding
     *
     * @param queryVar
     */
    /*
    public Set getDefinitionsForQueryVariable(Var queryVar) {
        Set viewVars = binding.getViewVariablesForQueryVariable(queryVar);

        Set result = new HashSet();

        for(Var viewVar : viewVars) {
            Collection varDefs = viewDefinition.getMapping().getVariableDefinitions().get(viewVar);
            result.addAll(varDefs);
        }

        return result;
    }
    */

    /*
    public getSqlNode()
    {
        return viewDefinition.getMapping().getSqlNode();
    }*/

    //public



    @Override
    public String toString() {
        String result = "ViewInstance for " + viewDefinition.getName() + ", binding: " + binding;
        return result;

        //return "ViewInstance [viewDefinition=" + viewDefinition + ", binding="
        //		+ binding + "]";
    }


    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((binding == null) ? 0 : binding.hashCode());
        result = prime * result
                + ((viewDefinition == null) ? 0 : viewDefinition.hashCode());
        return result;
    }


    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        ViewInstance other = (ViewInstance) obj;
        if (binding == null) {
            if (other.binding != null)
                return false;
        } else if (!binding.equals(other.binding))
            return false;
        if (viewDefinition == null) {
            if (other.viewDefinition != null)
                return false;
        } else if (!viewDefinition.equals(other.viewDefinition))
            return false;
        return true;
    }
}