Tree.java

package scotch.compiler.parser;

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

import java.util.List;
import com.google.common.collect.ImmutableList;
import lombok.EqualsAndHashCode;

public abstract class Tree {

    public static Tree leaf(String value) {
        return new Leaf(value);
    }

    public static Tree node(String name, List<Tree> children) {
        return new Node(name, children);
    }

    public static String tree(String name, List<Tree> children) {
        return new Node(name, children).toString();
    }

    private Tree() {
        // intentionally empty
    }

    @Override
    public abstract boolean equals(Object o);

    @Override
    public abstract int hashCode();

    @Override
    public abstract String toString();

    @EqualsAndHashCode(callSuper = false)
    public static class Leaf extends Tree {

        private final String value;

        private Leaf(String value) {
            this.value = value;
        }

        @Override
        public String toString() {
            return value;
        }
    }

    @EqualsAndHashCode(callSuper = false)
    public static class Node extends Tree {

        private final String     name;
        private final List<Tree> children;

        private Node(String name, List<Tree> children) {
            this.name = name;
            this.children = ImmutableList.copyOf(children);
        }

        @Override
        public String toString() {
            return "(" + name + " " + children.stream().map(Object::toString).collect(joining(" ")) + ")";
        }
    }
}