/*
 This file is part of the software framework JStatCom, 
 a library for building applications for data based analysis.

 Copyright (C) 2000-2005  Markus Kraetzig

 This library is free software; you can redistribute it and/or modify
 it under the terms of the GNU Lesser General Public License as
 published by the Free Software Foundation; either version 2.1 of the
 License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 USA
 */

package com.jstatcom.model;

/**
 * This class contains miscellaneous constants for the data model. The class
 * might be extended to create subclasses that add further constants by using
 * the following declaration:
 * 

 * public static final JSCConstants NEW_CONSTANT = new JSCConstants("NEW_CONSTANT"); 
 * 
 * @author Markus Kraetzig
 */

public class JSCConstants {

    private final String name;

    /**
     * Debug flag that can be set with the DEBUG property.
     */
    public static boolean DEBUG = false;

    /**
     * Missing value.
     */
    public static final Double NaN = new Double(Double.NaN);

    /**
     * Missing value as long.
     */
    public static final long NaNLongBits = Double.doubleToLongBits(Double.NaN);

    /**
     * Positive infinity.
     */
    public static final Double POS_INF = new Double(Double.POSITIVE_INFINITY);

    /**
     * Negative infinity.
     */
    public static final Double NEG_INF = new Double(Double.NEGATIVE_INFINITY);

    protected JSCConstants(String name) {
        this.name = name;
    }

    /**
     * Checks whether name is a valid variable name and throws an
     * exception of not.
     * 

     * Important:

     * null is allowed as an argument because this is often
     * convenient. In this case null is returned.
     * 
     * @param name
     *            the string to check
     * @return trimmed name if ok or null if
     *         name was null
     * @throws IllegalArgumentException
     *             with error string
     *             if (JSCConstants.isValidName(name) != null)
     */
    public static String checkNameThrowEx(String name) {

        if (name == null)
            return null;
        name = name.trim();
        String error = null;
        if ((error = JSCConstants.isValidName(name)) != null)
            throw new IllegalArgumentException(error);
        return name;
    }

    /**
     * Override prevention method to enforce a.equals(b) if and
     * only if a==b.
     * 
     * @param o
     *            object to compare with
     * @return true if equal, false otherwise
     */
    public final boolean equals(Object o) {
        return super.equals(o);
    }

    /**
     * Override prevention method invokes super method.
     * 
     * @return hash code
     */
    public final int hashCode() {
        return super.hashCode();
    }

    /**
     * Checks whether name conforms to the rules for valid
     * variable names. Valid names must not be null or empty and
     * must begin with either a letter or '_' . They may contain letters, digits
     * and '_', but no other characters or whitespace.
     * 
     * @param name
     *            the name to be checked
     * @return null if ok, error message otherwise
     */
    public static String isValidName(String name) {
        if (name == null)
            return "Name cannot be null.";

        if (name.trim().length() == 0)
            return "Name cannot be empty.";

        char c = name.charAt(0);
        if (!(Character.isLetter(c) || c == '_'))
            return "\"" + name + "\" does not start with a letter or '_'.";
        for (int i = 1; i < name.length(); i++) {
            c = name.charAt(i);
            if (!(Character.isLetter(c) || c == '_' || Character.isDigit(c)))
                return "\"" + name + "\" contains invalid characters.";
        }

        return null;
    }

    /**
     * Gets string representation of this object.
     * 
     * @return a string
     */
    public String toString() {
        return name;
    }

    /**
     * Reads out the system property java.io.tempdir.
     * 
     * @return the directory name of the temporary directory
     * @throws RuntimeException
     *             if property is empty
     */
    public static String getSystemTemp() {
        String temp = System.getProperty("java.io.tmpdir");
        if (temp != null)
            return temp;

        throw new RuntimeException("Property java.io.tmpdir is empty.");

    }

    /**
     * Reads out the system property user.dir.
     * 
     * @return the directory name of the user directory
     * @throws RuntimeException
     *             if property is empty
     */
    public static String getUserDir() {
        String userDir = System.getProperty("user.dir");
        if (userDir != null)
            return userDir;

        throw new RuntimeException("Property user.dir is empty.");

    }

    /**
     * Reads out the system property home.
     * 
     * @return the directory name of the user's home directory
     * @throws RuntimeException
     *             if property is empty
     */
    public static String getUserHome() {
        String userDir = System.getProperty("user.home");
        if (userDir != null)
            return userDir;

        throw new RuntimeException("Property user.home is empty.");

    }
}