package org.simantics.scl.compiler.internal.deriving;

import java.util.ArrayList;

import org.simantics.scl.compiler.common.datatypes.Constructor;
import org.simantics.scl.compiler.elaboration.errors.NotPatternException;
import org.simantics.scl.compiler.elaboration.expressions.EApply;
import org.simantics.scl.compiler.elaboration.expressions.EVar;
import org.simantics.scl.compiler.elaboration.expressions.EVariable;
import org.simantics.scl.compiler.elaboration.expressions.Expression;
import org.simantics.scl.compiler.elaboration.expressions.Variable;
import org.simantics.scl.compiler.elaboration.modules.TypeConstructor;
import org.simantics.scl.compiler.environment.AmbiguousNameException;
import org.simantics.scl.compiler.environment.Environment;
import org.simantics.scl.compiler.environment.Environments;
import org.simantics.scl.compiler.errors.ErrorLog;
import org.simantics.scl.compiler.internal.parsing.declarations.DDerivingInstanceAst;
import org.simantics.scl.compiler.internal.parsing.declarations.DInstanceAst;
import org.simantics.scl.compiler.internal.parsing.declarations.DValueAst;
import org.simantics.scl.compiler.internal.parsing.expressions.Expressions;
import org.simantics.scl.compiler.internal.parsing.translation.ProcessedDInstanceAst;
import org.simantics.scl.compiler.internal.parsing.translation.ValueRepository;
import org.simantics.scl.compiler.internal.parsing.types.TVarAst;
import org.simantics.scl.compiler.types.TCon;

class EqDeriver implements InstanceDeriver {

    @Override
    public void derive(
            ErrorLog errorLog,
            Environment environment,
            ArrayList<ProcessedDInstanceAst> instancesAst,
            DDerivingInstanceAst der) {
     // Analyze
        if(der.types.length != 1) {
            errorLog.log(der.location, "Invalid number of parameters to " + der.name);
            return;
        }
        TVarAst headType = DerivingUtils.getHeadType(der.types[0]);
        if(headType == null) {
            errorLog.log(der.types[0].location, "Cannot derive Eq instance for the type " + headType + ".");
            return;
        }
        TCon con;
        try {
            con = Environments.getTypeConstructorName(environment, headType.name);
        } catch (AmbiguousNameException e1) {
            errorLog.log(headType.location, e1.getMessage());
            return;
        }
        if(con == null) {
            errorLog.log(headType.location, "Couldn't resolve " + headType.name);
            return;
        }
        TypeConstructor tcon = environment.getTypeConstructor(con);
        if(tcon == null) {
            errorLog.log(headType.location, "Didn't find type constructor for " + headType.name);
            return;
        }
        if(tcon.isOpen) {
            errorLog.log(headType.location, "Cannot derive instance for open data types.");
            return;
        }
        
        // Generate
        DInstanceAst instanceAst = new DInstanceAst(der.location, der.context, der.name, der.types);
        ValueRepository valueDefs = new ValueRepository();
        for(Constructor constructor : tcon.constructors) {
            int l = constructor.parameterTypes.length;
            String[] par1 = new String[l];
            String[] par2 = new String[l];
            for(int i=0;i<l;++i) {
                par1[i] = "a" + i;
                par2[i] = "b" + i;
            }
            Expression lhs = new EApply(
                    new EVar("=="),
                    new EApply(new EVar(constructor.name.name), Expressions.vars(par1)),
                    new EApply(new EVar(constructor.name.name), Expressions.vars(par2))
                    );
            Expression value = new EVar("True");
            for(int i=l-1;i>=0;--i)
                value = new EApply(
                        new EVar("&&"),
                        new EApply(
                                new EVar("=="), 
                                new EVar(par1[i]), 
                                new EVar(par2[i])),
                        value);
            try {
                DValueAst valueAst = new DValueAst(lhs, value);
                valueAst.setLocationDeep(der.location);
                valueDefs.add(valueAst);
            } catch (NotPatternException e) {
                errorLog.log(e.getExpression().location, "Not a pattern.");
            }
        }
        {
            Expression lhs = new EApply(
                    new EVar("=="),
                    new EVariable(new Variable("_")),
                    new EVariable(new Variable("_")));
            Expression value = new EVar("False");
            try {
                DValueAst valueAst = new DValueAst(lhs, value);
                valueAst.setLocationDeep(der.location);
                valueDefs.add(valueAst);
                /*valueDefs.addAnnotation("==", new DAnnotationAst(new EVar("@private"), 
                        Collections.<Expression>emptyList()));*/
            } catch (NotPatternException e) {
                errorLog.log(e.getExpression().location, "Not a pattern.");
            }
        }
        instancesAst.add(new ProcessedDInstanceAst(instanceAst, valueDefs));
    }

}