/*

  * #%L

  * StringElement.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * 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.

  * #L%

  */

 package com.allanbank.mongodb.bson.element;

 import static com.allanbank.mongodb.util.Assertions.assertNotNull;

 import com.allanbank.mongodb.bson.Element;

 import com.allanbank.mongodb.bson.ElementType;

 import com.allanbank.mongodb.bson.Visitor;

 import com.allanbank.mongodb.bson.io.StringEncoder;

 /**

  * A wrapper for a BSON string.

  * 

  * @api.yes This class is part of the driver's API. Public and protected members

  *          will be deprecated for at least 1 non-bugfix release (version

  *          numbers are <major>.<minor>.<bugfix>) before being

  *          removed or modified.

  * @copyright 2011-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class StringElement extends AbstractElement {

     /** The BSON type for a string. */

     public static final ElementType TYPE = ElementType.STRING;

     /** Serialization version for the class. */

     private static final long serialVersionUID = 2279503881395893379L;

     /**

      * Performs a comparison of the strings based strictly on the UTF-8 encoding

      * of the two strings. Normal Java comparisons use a collator.

      * 

      * @param lhs

      *            The left-hand-side of the comparison.

      * @param rhs

      *            The right-hand-side of the comparison.

      * @return A value less than zero if the {@code lhs} is less than the

      *         {@code rhs}. A value greater than zero if the {@code lhs} is

      *         greater than the {@code rhs}. Zero if the {@code lhs} is equal to

      *         the {@code rhs}.

      */

     /* package */static int utf8Compare(final String lhs, final String rhs) {

         final int lhsLength = lhs.length();

         final int rhsLength = rhs.length();

         int lhsIndex = 0;

         int rhsIndex = 0;

         while ((lhsIndex < lhsLength) && (rhsIndex < rhsLength)) {

             final int lhsCodePoint = Character.codePointAt(lhs, lhsIndex);

             final int rhsCodePoint = Character.codePointAt(rhs, rhsIndex);

             final int compare = compare(lhsCodePoint, rhsCodePoint);

             if (compare != 0) {

                 return compare;

             }

             // Move to the next character.

             lhsIndex += Character.charCount(lhsCodePoint);

             rhsIndex += Character.charCount(rhsCodePoint);

         }

         // The shorter string is "less than".

         return compare(lhsLength, rhsLength);

     }

     /**

      * Computes and returns the number of bytes that are used to encode the

      * element.

      * 

      * @param name

      *            The name for the element.

      * @param value

      *            The BSON string value.

      * @return The size of the element when encoded in bytes.

      */

     private static long computeSize(final String name, final String value) {

         long result = 7; // type (1) + name null byte (1) +

         // value length (4) + value null byte (1)

         result += StringEncoder.utf8Size(name);

         result += StringEncoder.utf8Size(value);

         return result;

     }

     /** The BSON string value. */

     private final String myValue;

     /**

      * Constructs a new {@link StringElement}.

      * 

      * @param name

      *            The name for the BSON string.

      * @param value

      *            The BSON string value.

      * @throws IllegalArgumentException

      *             If the {@code name} or {@code value} is <code>null</code>.

      */

     public StringElement(final String name, final String value) {

         this(name, value, computeSize(name, value));

     }

     /**

      * Constructs a new {@link StringElement}.

      * 

      * @param name

      *            The name for the BSON string.

      * @param value

      *            The BSON string value.

      * @param size

      *            The size of the element when encoded in bytes. If not known

      *            then use the

      *            {@link StringElement#StringElement(String, String)}

      *            constructor instead.

      * @throws IllegalArgumentException

      *             If the {@code name} or {@code value} is <code>null</code>.

      */

     public StringElement(final String name, final String value, final long size) {

         super(name, size);

         assertNotNull(value, "String element's value cannot be null.");

         myValue = value;

     }

     /**

      * Accepts the visitor and calls the {@link Visitor#visitString} method.

      * 

      * @see Element#accept(Visitor)

      */

     @Override

     public void accept(final Visitor visitor) {

         visitor.visitString(getName(), getValue());

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to compare the string values if the base class comparison is

      * equals.

      * </p>

      * <p>

      * Note that for MongoDB {@link SymbolElement} and {@link StringElement}

      * will return equal based on the type. Care is taken here to make sure that

      * the values return the same value regardless of comparison order.

      * </p>

      * <p>

      * Note: Comparison of strings in MongoDB does not use a collator. This

      * class emulates the MongoDB behavior and orders the string elements based

      * on the UTF-8 encoding of the strings.

      * </p>

      */

     @Override

     public int compareTo(final Element otherElement) {

         int result = super.compareTo(otherElement);

         if (result == 0) {

             // Might be a StringElement or SymbolElement.

             final ElementType otherType = otherElement.getType();

             if (otherType == ElementType.SYMBOL) {

                 result = utf8Compare(myValue,

                         ((SymbolElement) otherElement).getSymbol());

             }

             else {

                 result = utf8Compare(myValue,

                         ((StringElement) otherElement).getValue());

             }

         }

         return result;

     }

     /**

      * Determines if the passed object is of this same type as this object and

      * if so that its fields are equal.

      * 

      * @param object

      *            The object to compare to.

      * 

      * @see java.lang.Object#equals(java.lang.Object)

      */

     @Override

     public boolean equals(final Object object) {

         boolean result = false;

         if (this == object) {

             result = true;

         }

         else if ((object != null) && (getClass() == object.getClass())) {

             final StringElement other = (StringElement) object;

             result = super.equals(object)

                     && nullSafeEquals(myValue, other.myValue);

         }

         return result;

     }

     /**

      * {@inheritDoc}

      */

     @Override

     public ElementType getType() {

         return TYPE;

     }

     /**

      * Returns the BSON string value.

      * 

      * @return The BSON string value.

      */

     public String getValue() {

         return myValue;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns the {@link String} value.

      * </p>

      */

     @Override

     public String getValueAsObject() {

         return getValue();

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns the {@link String} value.

      * </p>

      */

     @Override

     public String getValueAsString() {

         return getValue();

     }

     /**

      * Computes a reasonable hash code.

      * 

      * @return The hash code value.

      */

     @Override

     public int hashCode() {

         int result = 1;

         result = (31 * result) + super.hashCode();

         result = (31 * result) + ((myValue != null) ? myValue.hashCode() : 3);

         return result;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Returns a new {@link StringElement}.

      * </p>

      */

     @Override

     public StringElement withName(final String name) {

         if (getName().equals(name)) {

             return this;

         }

         return new StringElement(name, myValue);

     }

 }