TypeDescriptor.java

package scotch.symbol.type;

import static java.util.stream.Collectors.joining;

import java.util.Set;
import java.util.function.Function;
import scotch.symbol.Symbol;
import scotch.util.Pair;

public abstract class TypeDescriptor {

    public abstract <T> T accept(Visitor<T> visitor);

    @Override
    public abstract boolean equals(Object o);

    public abstract Set<Symbol> getContext();

    public abstract TypeDescriptor mapVariables(Function<TypeDescriptor, TypeDescriptor> function);

    @Override
    public abstract int hashCode();

    @Override
    public String toString() {
        return gatherContext() + toString_();
    }

    protected String gatherContext() {
        Set<Pair<VariableTypeDescriptor, Symbol>> context = gatherContext_();
        if (context.isEmpty()) {
            return "";
        } else {
            return "(" + context.stream()
                .map(pair -> pair.into((type, symbol) -> symbol.getSimpleName() + " " + type.getName()))
                .collect(joining(", ")) + ") => ";
        }
    }

    protected abstract Set<Pair<VariableTypeDescriptor, Symbol>> gatherContext_();

    protected abstract String toParenthesizedString();

    protected abstract String toString_();

    public interface Visitor<T> {

        T visit(ConstructorTypeDescriptor type);

        T visit(FunctionTypeDescriptor type);

        T visit(InstanceTypeDescriptor type);

        T visit(SumTypeDescriptor type);

        T visit(VariableTypeDescriptor type);
    }
}