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/**
 * (c) Copyright 2020 IBM Corporation
 * 1 New Orchard Road, 
 * Armonk, New York, 10504-1722
 * United States
 * +1 914 499 1900
 * support: Nathaniel Mills [email protected]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package com.mdfromhtml.core;

import java.io.Serializable;
import java.util.Base64;
import java.util.UUID;

/**
 * Implementation of the MDfromHTMLID class which provides a unique identifier
 * for an MDfromHTML object.
 * 
 */
public class MDfromHTMLID
                implements Serializable, Comparable, Cloneable {

    static public int ID_LENGTH = 22; // matches database settings
    static public final String ID_UNDEFINED = MDfromHTMLConstants.UNDEFINED_ID;
    static private final long serialVersionUID = 2726688498762622537L;
    static public final MDfromHTMLID UNDEFINED_ID = new MDfromHTMLID();
    static public final String val_safe = new String(
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_=");

    static {
        UNDEFINED_ID._id = MDfromHTMLConstants.UNDEFINED_ID;
    }

    /**
     * General purpose factory constructor
     * 
     * @return a new MDfromHTMLID
     */
    public static MDfromHTMLID generateNewID() {
        return new MDfromHTMLID();
    }

    /**
     * Constructor
     * 
     * @param uuid
     *            - UUID of this MDfromHTMLID
     */
    public static MDfromHTMLID getExistingID(String uuid) {
        if (uuid != null && uuid.length() == ID_LENGTH) {
            if (uuid.compareTo(MDfromHTMLConstants.UNDEFINED_ID) == 0) {
                return MDfromHTMLID.UNDEFINED_ID;
            }
            // check for valid characters
            byte[] uuidBytes = uuid.getBytes();
            for (byte uuidByte : uuidBytes) {
                if (val_safe.indexOf((int) uuidByte) == -1) {
                    return MDfromHTMLID.UNDEFINED_ID;
                }
            }
            MDfromHTMLID id = new MDfromHTMLID(uuid);
            return id;
        }
        return MDfromHTMLID.UNDEFINED_ID;
    }

    static public boolean isUndefined(MDfromHTMLID test) {
        if (test == null) {
            return true;
        }
        return test.isUndefined();
    }

    static public void main(String[] args) {
        if (MDfromHTMLID
            .isUndefined(MDfromHTMLID.getExistingID("too_small")) == false) {
            System.out.println("Error for \"too_small\"");
        } else if (MDfromHTMLID.isUndefined(MDfromHTMLID
            .getExistingID("much_much_much_much_too_long")) == false) {
            System.out.println("Error for \"much_much_much_much_too_long\"");
        } else if (MDfromHTMLID.isUndefined(
            MDfromHTMLID.getExistingID("bad char______________")) == false) {
            System.out.println("Error for \"bad char______________\"");
        } else if (MDfromHTMLID.isUndefined(
            MDfromHTMLID.getExistingID("??????????????????????")) == false) {
            System.out.println("Error for \"??????????????????????\"");
        } else if (MDfromHTMLID.isUndefined(
            MDfromHTMLID.getExistingID("ABCDEFGHIJKLMNOPQRSTUV"))) {
            System.out.println("Error for \"ABCDEFGHIJKLMNOPQRSTUV\"");
        } else {
            System.out.println("Everything is okay.");
        }
        while (true) {
            String quit = MDfromHTMLUtils.prompt("Enter quit to exit:");
            if ("quit".compareToIgnoreCase(quit) == 0) {
                break;
            }
            System.out.println(
                "MDfromHTMLID: \"" + MDfromHTMLID.generateNewID() + "\"");
        }
        System.out.println("Goodbye");
    }

    private String _id = ID_UNDEFINED;

    /**
     * Construct a compressed MDfromHTMLID based on
     * {@link MDfromHTMLBASE64Codec#encode(byte[],boolean)} of the bytes gleaned
     * from {@link UUID#randomUUID()}
     */
    public MDfromHTMLID() {
        _id = getUUID();
    }

    /**
     * Constructor
     * 
     * @param uuid
     *            - UUID of this MDfromHTMLID
     */
    private MDfromHTMLID(String uuid) {
        _id = uuid;
    }

    public MDfromHTMLID clone() {
        return getExistingID(_id);
    }

    @Override
    public int compareTo(Object o) {
        if (o == null) {
            o = MDfromHTMLID.UNDEFINED_ID;
        }
        if (o instanceof MDfromHTMLID) {
            return _id.compareTo(((MDfromHTMLID) o).toString());
        }
        return this.toString().compareTo(o.toString());
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (MDfromHTMLID.class.isInstance(obj)) {
            if (isUndefined() == false
                && this._id.equals(((MDfromHTMLID) obj)._id)) {
                return true;
            } else if (isUndefined()
                && MDfromHTMLID.isUndefined((MDfromHTMLID) obj)) {
                return true;
            }
        }
        return false;
    }

    private String getUUID() {
        UUID uuid = UUID.randomUUID();
        long msb = uuid.getMostSignificantBits();
        long lsb = uuid.getLeastSignificantBits();
        byte[] bUUID = new byte[16];
        for (int i = 0; i < 8; i++) {
            bUUID[i] = (byte) (msb >>> 8 * (7 - i));
        }
        for (int i = 8; i < 16; i++) {
            bUUID[i] = (byte) (lsb >>> 8 * (7 - i));
        }
        /**
         * strip the trailing "==" from the Base64 encoding and use URL Safe
         * content
         */
        return Base64.getUrlEncoder().encodeToString(bUUID).substring(0, 22);
    }

    @Override
    public int hashCode() {
        if (_id != null && _id.trim().length() != 0
            && _id.compareTo("?") != 0) {
            return _id.hashCode();
        } else {
            return 0;
        }
    }

    /**
     * @return true if the MDfromHTMLID is uninitialized
     */
    public boolean isUndefined() {
        return ID_UNDEFINED.equals(_id);
    }

    /**
     * @return the string representation of the MDfromHTMLID
     */
    @Override
    public String toString() {
        return this._id;
    }

}
    

    

    

            

    

            



    
    






    
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