package org.simantics.scl.compiler.types.util;

import java.util.ArrayList;

import org.simantics.scl.compiler.types.Skeletons;
import org.simantics.scl.compiler.types.TApply;
import org.simantics.scl.compiler.types.TForAll;
import org.simantics.scl.compiler.types.TFun;
import org.simantics.scl.compiler.types.TMetaVar;
import org.simantics.scl.compiler.types.TMetaVar.TMetaVarListener;
import org.simantics.scl.compiler.types.TPred;
import org.simantics.scl.compiler.types.Type;

public abstract class TypeListener {
    private ArrayList<TMetaVarListener> metaVarListeners = new ArrayList<TMetaVarListener>(2);
    public abstract void notifyAboutChange();
    
    private static class SubListener extends TMetaVarListener {
        private final TypeListener parent;
        public SubListener(TypeListener parent) {
            this.parent = parent;
        }        @Override
        public void notifyAboutChange() {
            for(TMetaVarListener otherListeners : parent.metaVarListeners)
                otherListeners.remove();
            parent.notifyAboutChange();
        }
    };
    
    public void listenSkeleton(Type type) {
        type = Skeletons.canonicalSkeleton(type);
        if(type instanceof TMetaVar) {
            TMetaVar metaVar = (TMetaVar)type;
            TMetaVarListener latestListener = metaVar.getLatestListener();
            if(latestListener instanceof SubListener &&
                    ((SubListener)latestListener).parent == this)
                return;
            
            SubListener subListener = new SubListener(this);
            metaVarListeners.add(subListener);
            metaVar.addListener(subListener);
        }
        else if(type instanceof TApply) {
            TApply apply = (TApply)type;
            listenSkeleton(apply.function);
            listenSkeleton(apply.parameter);
        }
        else if(type instanceof TFun) {
            TFun fun = (TFun)type;
            listenSkeleton(fun.domain);
            listenSkeleton(fun.range);
        }
        else if(type instanceof TForAll) {
            TForAll forAll = (TForAll)type;
            listenSkeleton(forAll.type);
        }
        else if(type instanceof TPred) {
            TPred pred = (TPred)type;
            for(Type parameter : pred.parameters)
                listenSkeleton(parameter);
        }
    }
}