/**
 * Provides methods to manipulate the Trie. <br />
 * The Trie only saves the root Node of which every Trie-Operation starts.
 */
public class Trie {

    /**
     * The root Node of the Trie.
     */
    private Node root;
    /**
     * creates new Trie.
     */
    public Trie() {
        this.root = new Node();
    }

    /**
     * adds new Student <code>key</code> with
     * points <code>points</code> to the Trie.
     * @param key Student to add
     * @param points points of Student
     * @return <code>true</code> if add was successful or <br />
     *          <code>false</code> if Student already exists
     */
    public boolean add(String key, Integer points) {
        Node iterator = this.root;
        for (int i = 0; i < key.length(); i++) {
            if (iterator.getChild(key.charAt(i)) == null) {
                new Node(key.charAt(i), iterator);
            }
                iterator = iterator.getChild(key.charAt(i));
        }
        if (iterator.getPoints() == null) {
            iterator.setPoints(points);
            return true;
        } else {
            return false;
        }
    }

    /**
     * deletes Student <code>key</code> in the Trie.
     * @param key Student to delete
     * @return <code>true</code> if delete was successful or <br />
     *          <code>false></code> if Student does not exist
     */
    public boolean delete(String key) {
        Node hlp = this.root.find(key);
        if (hlp == null) {
            return false;
        }
        if (hlp.getPoints() != null) {
            hlp.deleteMe();
            return true;
        } else {
        return false;
        }
    }

    /**
     * changes points <code>points</code> of Student <code>key</code>
     * in the Trie.
     * @param key Student to change
     * @param points points of Student to change
     * @return <code>true</code> if change was successful or<br />
     *          <code>false</code> if Student does not exist
     */
    public boolean change(String key, Integer points) {
        Node hlp = this.root.find(key);
        if (hlp == null) {
            return false;
        }
        if (hlp.getPoints() != null) {
            hlp.setPoints(points);
            return true;
        } else {
        return false;
        }
    }

    /**
     * Getter for points of Student <code>key</code> in the Trie.
     * @param key Student to search for
     * @return <code>points</code> of Student or<br />
     *          <code>null</code> if Student does not exist
     */
    public Integer points(String key) {
        Node hlp = this.root.find(key);
        if (hlp != null) {
            return hlp.getPoints();
        }
        return null;
    }

    /**
     * Method to print the hole Trie.
     * @return <code>string</code> of the Trie in the requested format
     */
    public String toString() {
        return this.root.toString();
    }
}