package java_cup;

import java.util.HashMap;

/** This class represents a non-terminal symbol in the grammar.  Each
 *  non terminal has a textual name, an index, and a string which indicates
 *  the type of object it will be implemented with at runtime (i.e. the class
 *  of object that will be pushed on the parse stack to represent it). 
 *
 * @version last updated: 11/25/95
 * @author  Scott Hudson
 */

public class non_terminal extends symbol {

    /*-----------------------------------------------------------*/
    /*--- Constructor(s) ----------------------------------------*/
    /*-----------------------------------------------------------*/

    /** Full constructor.
     * @param nm  the name of the non terminal.
     * @param tp  the type string for the non terminal.
     */
    public non_terminal(String nm, String tp) {
        /* super class does most of the work */
        super(nm, tp);

        /* add to set of all non terminals and check for duplicates */
        Object conflict = _all.put(nm, this);
        if (conflict != null)
        // can't throw an exception here because these are used in static
        // initializers, so we crash instead
        // was: 
        // throw new internal_error("Duplicate non-terminal ("+nm+") created");
            new internal_error("Duplicate non-terminal (" + nm + ") created").crash();

        /* assign a unique index */
        _index = next_index++;

        /* add to by_index set */
        _all_by_index.put(new Integer(_index), this);
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Constructor with default type. 
     * @param nm  the name of the non terminal.
     */
    public non_terminal(String nm) {
        this(nm, null);
    }

    /*-----------------------------------------------------------*/
    /*--- (Access to) Static (Class) Variables ------------------*/
    /*-----------------------------------------------------------*/

    /** Table of all non-terminals -- elements are stored using name strings 
     *  as the key 
     */
    protected static HashMap<String, non_terminal> _all = new HashMap<>();

    //Hm Added clear  to clear all static fields
    public static void clear() {
        _all.clear();
        _all_by_index.clear();
        next_index = 0;
        next_nt = 0;
    }

    /** Access to all non-terminals. */
    public static Iterable<non_terminal> all() {
        return _all.values();
    }

    /** lookup a non terminal by name string */
    public static non_terminal find(String with_name) {
        if (with_name == null)
            return null;
        else return _all.get(with_name);
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Table of all non terminals indexed by their index number. */
    protected static HashMap<Integer, non_terminal> _all_by_index =
            new HashMap<>();

    /** Lookup a non terminal by index. */
    public static non_terminal find(int indx) {
        Integer the_indx = new Integer(indx);

        return _all_by_index.get(the_indx);
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Total number of non-terminals. */
    public static int number() {
        return _all.size();
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Static counter to assign unique indexes. */
    protected static int next_index = 0;

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Static counter for creating unique non-terminal names */
    static protected int next_nt = 0;

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** special non-terminal for start symbol */
    public static final non_terminal START_nt = new non_terminal("$START");

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** flag non-terminals created to embed action productions */
    public boolean is_embedded_action = false; /* added 24-Mar-1998, CSA */

    /*-----------------------------------------------------------*/
    /*--- Static Methods ----------------------------------------*/
    /*-----------------------------------------------------------*/

    /** Method for creating a new uniquely named hidden non-terminal using 
     *  the given string as a base for the name (or "NT$" if null is passed).
     * @param prefix base name to construct unique name from. 
     */
    static non_terminal create_new(String prefix) {
        return create_new(prefix, null); // TUM 20060608 embedded actions patch
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** static routine for creating a new uniquely named hidden non-terminal */
    static non_terminal create_new() {
        return create_new(null);
    }

    /**
     * TUM 20060608 bugfix for embedded action codes
     */
    static non_terminal create_new(String prefix, String type) {
        if (prefix == null) prefix = "NT$";
        return new non_terminal(prefix + next_nt++, type);
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Compute nullability of all non-terminals. */
    public static void compute_nullability() throws internal_error {
        boolean change = true;

        /* repeat this process until there is no change */
        while (change) {
            /* look for a new change */
            change = false;

            /* consider each non-terminal */
            for (non_terminal nt : all()) {

                /* only look at things that aren't already marked nullable */
                if (!nt.nullable()) {
                    if (nt.looks_nullable()) {
                        nt._nullable = true;
                        change = true;
                    }
                }
            }
        }

        /* do one last pass over the productions to finalize all of them */
        for (production prod : production.all()) {
            prod.set_nullable(prod.check_nullable());
        }
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Compute first sets for all non-terminals.  This assumes nullability has
     *  already computed.
     */
    public static void compute_first_sets() throws internal_error {
        boolean change = true;
        terminal_set prod_first;

        /* repeat this process until we have no change */
        while (change) {
            /* look for a new change */
            change = false;

            /* consider each non-terminal */
            for (non_terminal nt : all()) {

                /* consider every production of that non terminal */
                for (production prod : nt.productions()) {

                    /* get the updated first of that production */
                    prod_first = prod.check_first_set();

                    /* if this going to add anything, add it */
                    if (!prod_first.is_subset_of(nt._first_set)) {
                        change = true;
                        nt._first_set.add(prod_first);
                    }
                }
            }
        }
    }

    /*-----------------------------------------------------------*/
    /*--- (Access to) Instance Variables ------------------------*/
    /*-----------------------------------------------------------*/

    /** Table of all productions with this non terminal on the LHS. */
    protected HashMap<production, production> _productions = new HashMap<>();

    /** Access to productions with this non terminal on the LHS. */
    public Iterable<production> productions() {
        return _productions.values();
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Total number of productions with this non terminal on the LHS. */
    public int num_productions() {
        return _productions.size();
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Add a production to our set of productions. */
    public void add_production(production prod) throws internal_error {
        /* catch improper productions */
        if (prod == null || prod.lhs() == null
                || prod.lhs().the_symbol() != this)
            throw new internal_error("Attempt to add invalid production to non terminal production table");

        /* add it to the table, keyed with itself */
        _productions.put(prod, prod);
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Nullability of this non terminal. */
    protected boolean _nullable;

    /** Nullability of this non terminal. */
    public boolean nullable() {
        return _nullable;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** First set for this non-terminal. */
    protected terminal_set _first_set = new terminal_set();

    /** First set for this non-terminal. */
    public terminal_set first_set() {
        return _first_set;
    }

    /*-----------------------------------------------------------*/
    /*--- General Methods ---------------------------------------*/
    /*-----------------------------------------------------------*/

    /** Indicate that this symbol is a non-terminal. */
    @Override
    public boolean is_non_term() {
        return true;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Test to see if this non terminal currently looks nullable. */
    protected boolean looks_nullable() throws internal_error {
        /* look and see if any of the productions now look nullable */
        for (production pr : productions())
            /* if the production can go to empty, we are nullable */
            if (pr.check_nullable()) return true;

        /* none of the productions can go to empty, so we are not nullable */
        return false;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** convert to string */
    @Override
    public String toString() {
        return super.toString() + "[" + index() + "]" + (nullable() ? "*" : "");
    }

    /*-----------------------------------------------------------*/
}
