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

import org.cojen.classfile.TypeDesc;
import org.objectweb.asm.Label;
import org.simantics.scl.compiler.common.exceptions.InternalCompilerError;
import org.simantics.scl.compiler.constants.FunctionValue;
import org.simantics.scl.compiler.constants.LocalVariableConstant;
import org.simantics.scl.compiler.internal.codegen.continuations.Cont;
import org.simantics.scl.compiler.internal.codegen.references.IVal;
import org.simantics.scl.compiler.internal.codegen.references.Val;
import org.simantics.scl.compiler.internal.codegen.types.JavaTypeTranslator;
import org.simantics.scl.compiler.internal.codegen.utils.Constants;
import org.simantics.scl.compiler.internal.codegen.utils.LocalVariable;
import org.simantics.scl.compiler.internal.codegen.utils.MethodBuilder;
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.exceptions.MatchException;
import org.simantics.scl.compiler.types.kinds.Kinds;

public class ListConstructor extends FunctionValue {

    private static final TVar A = Types.var(Kinds.STAR);
    
    public final int arity;
    
    public ListConstructor(int arity) {
        super(new TVar[] {A}, Types.NO_EFFECTS, Types.list(A), parameterList(arity));
        this.arity = arity;
    }

    private static Type[] parameterList(int arity) {
        Type[] parameters = new Type[arity];
        for(int i=0;i<arity;++i)
            parameters[i] = A;  
        return parameters;
    }


    @Override
    public Type applyExact(MethodBuilder mb, Val[] parameters) {
        mb.loadConstant(arity);
        mb.newObject(Constants.OBJECT_ARRAY, 1);
        for(int i=0;i<arity;++i) {
            mb.dup();
            mb.loadConstant(i);
            mb.pushBoxed(parameters[i]);
            mb.storeToArray(TypeDesc.OBJECT);
        }
        mb.invokeStatic("java/util/Arrays", "asList", Constants.LIST, 
                new TypeDesc[] {Constants.OBJECT_ARRAY});
        return getReturnType();
    }
    
    @Override
    public void deconstruct(MethodBuilder mb, IVal parameter, Cont success,
            Label failure) {
        if(failure == null)
            throw new InternalCompilerError("List deconstruction may always fail");
        if(success.getArity() != arity)
            throw new InternalCompilerError("Arity of the list constructor (" + arity +
                    ") is different from the arity of the success continuation (" + success.getArity() + ").");
        parameter.push(mb);
        mb.invokeInterface(Constants.LIST, "size", TypeDesc.INT, Constants.EMPTY_TYPEDESC_ARRAY);
        mb.loadConstant(arity);
        mb.ifComparisonBranch(failure, "!=", TypeDesc.INT);
        
        JavaTypeTranslator translator = mb.getJavaTypeTranslator();
        IVal[] parameters = new IVal[arity];
        for(int i=0;i<arity;++i) {
            parameter.push(mb);
            mb.loadConstant(i);
            mb.invokeInterface(Constants.LIST, "get", TypeDesc.OBJECT, new TypeDesc[] {TypeDesc.INT});
            try {
                mb.unbox(Types.matchApply(Types.LIST,parameter.getType()));
            } catch (MatchException e) {
                throw new InternalCompilerError("Expected list type.");
            }
            
            Type pType = success.getParameterType(i);
            TypeDesc pTypeDesc = translator.toTypeDesc(pType);
            LocalVariable lv = mb.createLocalVariable("temp", pTypeDesc);
            mb.storeLocal(lv);
            
            parameters[i] = new LocalVariableConstant(pType, lv);
        }
        
        mb.jump(success, parameters);
    }
    
    @Override
    public int constructorTag() {
        return arity;
    }
    
    @Override
    public String toString() {
        return "[.." + arity + "..]";
    }

}