package org.simantics.scl.compiler.elaboration.query.compilation;

import org.simantics.scl.compiler.elaboration.expressions.EVariable;
import org.simantics.scl.compiler.elaboration.expressions.Variable;
import org.simantics.scl.compiler.elaboration.query.QAtom;

public class RelationConstraint extends QueryConstraint {

    // static
    QAtom atom;
    
    int[] optionalVariableByParameter;
    Variable[] parameters;

    long requiredVariablesMask;
    
    public RelationConstraint(int[] variables, Variable[] parameters, QAtom atom, int[] optionalVariableByParameter,
            long requiredVariablesMask) {
        super(variables);
        this.atom = atom;
        this.parameters = parameters;
        this.optionalVariableByParameter = optionalVariableByParameter;
        this.requiredVariablesMask = requiredVariablesMask;
    }

    @Override
    public boolean canBeSolvedFrom(long boundVariables) {
        return getSolutionBranching(boundVariables) != Double.POSITIVE_INFINITY;
    }
    
    @Override
    public double getSolutionBranching(long boundVariables) {
        if( (boundVariables&requiredVariablesMask) != requiredVariablesMask )
            return Double.POSITIVE_INFINITY;        
        return atom.relation.getSelectivity(getLocalBoundVariables(boundVariables));
    }
    
    @Override
    public double getSolutionCost(long boundVariables) {
        return 1.0;
    }
    
    @Override
    public void generate(QueryCompilationContext context) {
        atom.relation.generate(atom.location, 
                context, atom.typeParameters,
                parameters, getLocalBoundVariables(finalBoundVariables));
        for(int i=atom.parameters.length-1;i>=0;--i)
            if(optionalVariableByParameter[i] < 0 && !(atom.parameters[i] instanceof EVariable))
                context.let(parameters[i], atom.parameters[i]);
    }
    
    private int getLocalBoundVariables(long boundVariables) {
        int localBoundVariables = 0;
        for(int i=0;i<optionalVariableByParameter.length;++i) {
            int v = optionalVariableByParameter[i]; 
            if(v < 0 || ((boundVariables >> v)&1) != 0)
                localBoundVariables |= 1 << i;
        }
        return localBoundVariables;
    }
    
    @Override
    public String toString() {
        return atom.toString();
    }
}