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

import java.util.Comparator;

import org.simantics.scl.compiler.types.TApply;
import org.simantics.scl.compiler.types.TCon;
import org.simantics.scl.compiler.types.TFun;
import org.simantics.scl.compiler.types.TPred;
import org.simantics.scl.compiler.types.TUnion;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.Types;

public enum TypeComparator implements Comparator<Type> {
    INSTANCE;
    
    @Override
    public int compare(Type t1, Type t2) {
        t1 = Types.canonical(t1);
        t2 = Types.canonical(t2);
        int id1 = t1.getClassId();
        int id2 = t2.getClassId();
        if(id1 < id2)
            return -1;
        if(id1 > id2)
            return 1;
        int cur;
        switch(id1) {
        case Type.APPLY_ID: {
            TApply p1 = (TApply)t1;
            TApply p2 = (TApply)t2;
            cur = compare(p1.function, p2.function);
            if(cur != 0)
                return cur;
            return compare(p1.parameter, p2.parameter);
        }
        case Type.CON_ID:
            return TConComparator.INSTANCE.compare((TCon)t1, (TCon)t2);
        case Type.FORALL_ID:
            return 0; // TODO hard to compare
        case Type.PRED_ID: {
            TPred p1 = (TPred)t1;
            TPred p2 = (TPred)t2;
            cur = TConComparator.INSTANCE.compare(p1.typeClass, p2.typeClass);
            if(cur != 0)
                return cur;
            cur = p1.parameters.length - p2.parameters.length;
            if(cur != 0)
                return cur;
            for(int i=0;i<p1.parameters.length;++i) {
                cur = compare(p1.parameters[i], p2.parameters[i]);
                if(cur != 0)
                    return cur;
            }
            return 0;
        }
        case Type.FUN_ID: {
            TFun p1 = (TFun)t1;
            TFun p2 = (TFun)t2;
            cur = compare(p1.domain, p2.domain);
            if(cur != 0)
                return cur;
            cur = compare(p1.range, p2.range);
            if(cur != 0)
                return cur;
            return compare(p1.effect, p2.effect);
        }
        case Type.UNION_ID: {
            TUnion p1 = (TUnion)t1;
            TUnion p2 = (TUnion)t2;
            cur = p1.effects.length - p2.effects.length;
            if(cur != 0)
                return cur;
            return 0; // TODO
        }
        case Type.METAVAR_ID: 
            return 0; // cannot compare
        case Type.VAR_ID:
            return 0; // cannot compare
        default:
            throw new IllegalArgumentException();
        }
    }

}