package org.simantics.scl.compiler.elaboration.relations;

import static org.simantics.scl.compiler.elaboration.expressions.Expressions.apply;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.newVar;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.tuple;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.var;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.vars;

import org.simantics.scl.compiler.common.exceptions.InternalCompilerError;
import org.simantics.scl.compiler.common.names.Names;
import org.simantics.scl.compiler.elaboration.expressions.EVariable;
import org.simantics.scl.compiler.elaboration.expressions.Expressions;
import org.simantics.scl.compiler.elaboration.expressions.Variable;
import org.simantics.scl.compiler.elaboration.query.compilation.QueryCompilationContext;
import org.simantics.scl.compiler.types.TVar;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.Types;
import org.simantics.scl.compiler.types.kinds.Kinds;

public class LocalRelation extends AbstractRelation {
    String name;
    Type[] parameterTypes;
    public Variable table;
    
    public LocalRelation(String name, int arity) {
        this.name = name;
        this.parameterTypes = new Type[arity];
        for(int i=0;i<arity;++i)
            parameterTypes[i] = Types.metaVar(Kinds.STAR);
        createTable();
    }
    
    public LocalRelation(String name, Type[] parameterTypes) {
        this.name = name;
        this.parameterTypes = parameterTypes;
        createTable();
    }
    
    private void createTable() {
        this.table = newVar("table" + name, 
                Types.apply(Names.MSet_T, Types.tuple(parameterTypes)));
    }
    
    public int getArity() {
        return parameterTypes.length;
    }

    public String getName() {
        return name;
    }
    
    @Override
    public TVar[] getTypeVariables() {
        return TVar.EMPTY_ARRAY;
    }

    @Override
    public Type[] getParameterTypes() {
        return parameterTypes;
    }
    
    @Override
    public double getSelectivity(int boundVariabes) {
        double s = 0.95;
        for(int i=0;i<parameterTypes.length;++i,boundVariabes>>=1)
            if( (boundVariabes&1) == 0 )
                s *= 10.0;
        return s;
    }
    
    @Override
    public int getRequiredVariablesMask() {
        return 0;
    }
    
    @Override
    public void generate(long location,
            QueryCompilationContext context,
            Type[] typeParameters, Variable[] parameters, int boundVariables) {
        if(table == null)
            throw new InternalCompilerError(location, "Variable table is undefined.");
        if(boundVariables + 1 == 1 << parameters.length)
            context.condition(apply(context.getCompilationContext(), Types.PROC,
                    Names.MSet_contains, Types.tuple(parameterTypes),
                    var(table),
                    tuple(vars(parameters))
                    ));
        else {
            Variable[] aux = new Variable[parameters.length];
            for(int i=0;i<parameters.length;++i)
                if(((boundVariables>>i)&1) == 1)
                    aux[i] = new Variable("aux_" + parameters[i].getName(), parameters[i].getType());
                else
                    aux[i] = parameters[i];
            Variable row = new Variable("row", Types.tuple(parameterTypes));
            for(int i=0;i<parameters.length;++i)
                if(((boundVariables>>i)&1) == 1)
                    context.condition(apply(context.getCompilationContext(), Types.NO_EFFECTS,
                            Names.Builtin_equals, parameterTypes[i],
                            var(aux[i]),
                            var(parameters[i])
                            ));
            context.match(Expressions.tuple(Expressions.vars(aux)), new EVariable(row), false);
            context.iterateMSet(row, new EVariable(table));
        }
    }
    
    @Override
    public String toString() {
        return name;
    }
}