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/*
 * (C) Copyright Taligent, Inc. 1996-1998 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996-1998 - All Rights Reserved
 *
 * The original version of this source code and documentation is copyrighted
 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
 * materials are provided under terms of a License Agreement between Taligent
 * and Sun. This technology is protected by multiple US and International
 * patents. This notice and attribution to Taligent may not be removed.
 * Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.text;

import java.lang.ref.SoftReference;
import java.text.spi.CollatorProvider;
import java.util.Locale;
import java.util.ResourceBundle;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import sun.util.locale.provider.LocaleProviderAdapter;
import sun.util.locale.provider.LocaleServiceProviderPool;


/**
 * The <code>Collator</code> class performs locale-sensitive
 * <code>String</code> comparison. You use this class to build
 * searching and sorting routines for natural language text.
 *
 * <p>
 * <code>Collator</code> is an abstract base class. Subclasses
 * implement specific collation strategies. One subclass,
 * <code>RuleBasedCollator</code>, is currently provided with
 * the Java Platform and is applicable to a wide set of languages. Other
 * subclasses may be created to handle more specialized needs.
 *
 * <p>
 * Like other locale-sensitive classes, you can use the static
 * factory method, <code>getInstance</code>, to obtain the appropriate
 * <code>Collator</code> object for a given locale. You will only need
 * to look at the subclasses of <code>Collator</code> if you need
 * to understand the details of a particular collation strategy or
 * if you need to modify that strategy.
 *
 * <p>
 * The following example shows how to compare two strings using
 * the <code>Collator</code> for the default locale.
 * <blockquote>
 * <pre>{@code
 * // Compare two strings in the default locale
 * Collator myCollator = Collator.getInstance();
 * if( myCollator.compare("abc", "ABC") < 0 )
 * System.out.println("abc is less than ABC");
 * else
 * System.out.println("abc is greater than or equal to ABC");
 * }</pre>
 * </blockquote>
 *
 * <p>
 * You can set a <code>Collator</code>'s <em>strength</em> property
 * to determine the level of difference considered significant in
 * comparisons. Four strengths are provided: <code>PRIMARY</code>,
 * <code>SECONDARY</code>, <code>TERTIARY</code>, and <code>IDENTICAL</code>.
 * The exact assignment of strengths to language features is
 * locale dependent. For example, in Czech, "e" and "f" are considered
 * primary differences, while "e" and "&#283;" are secondary differences,
 * "e" and "E" are tertiary differences and "e" and "e" are identical.
 * The following shows how both case and accents could be ignored for
 * US English.
 * <blockquote>
 * <pre>
 * //Get the Collator for US English and set its strength to PRIMARY
 * Collator usCollator = Collator.getInstance(Locale.US);
 * usCollator.setStrength(Collator.PRIMARY);
 * if( usCollator.compare("abc", "ABC") == 0 ) {
 * System.out.println("Strings are equivalent");
 * }
 * </pre>
 * </blockquote>
 * <p>
 * For comparing <code>String</code>s exactly once, the <code>compare</code>
 * method provides the best performance. When sorting a list of
 * <code>String</code>s however, it is generally necessary to compare each
 * <code>String</code> multiple times. In this case, <code>CollationKey</code>s
 * provide better performance. The <code>CollationKey</code> class converts
 * a <code>String</code> to a series of bits that can be compared bitwise
 * against other <code>CollationKey</code>s. A <code>CollationKey</code> is
 * created by a <code>Collator</code> object for a given <code>String</code>.
 * <br>
 * <strong>Note:</strong> <code>CollationKey</code>s from different
 * <code>Collator</code>s can not be compared. See the class description
 * for {@link CollationKey}
 * for an example using <code>CollationKey</code>s.
 *
 * @see RuleBasedCollator
 * @see CollationKey
 * @see CollationElementIterator
 * @see Locale
 * @author Helena Shih, Laura Werner, Richard Gillam
 * @since 1.1
 */

public abstract class Collator
 implements java.util.Comparator<Object>, Cloneable
{
 /**
 * Collator strength value. When set, only PRIMARY differences are
 * considered significant during comparison. The assignment of strengths
 * to language features is locale dependent. A common example is for
 * different base letters ("a" vs "b") to be considered a PRIMARY difference.
 * @see java.text.Collator#setStrength
 * @see java.text.Collator#getStrength
 */
 public static final int PRIMARY = 0;
 /**
 * Collator strength value. When set, only SECONDARY and above differences are
 * considered significant during comparison. The assignment of strengths
 * to language features is locale dependent. A common example is for
 * different accented forms of the same base letter ("a" vs "\u00E4") to be
 * considered a SECONDARY difference.
 * @see java.text.Collator#setStrength
 * @see java.text.Collator#getStrength
 */
 public static final int SECONDARY = 1;
 /**
 * Collator strength value. When set, only TERTIARY and above differences are
 * considered significant during comparison. The assignment of strengths
 * to language features is locale dependent. A common example is for
 * case differences ("a" vs "A") to be considered a TERTIARY difference.
 * @see java.text.Collator#setStrength
 * @see java.text.Collator#getStrength
 */
 public static final int TERTIARY = 2;

 /**
 * Collator strength value. When set, all differences are
 * considered significant during comparison. The assignment of strengths
 * to language features is locale dependent. A common example is for control
 * characters ("&#092;u0001" vs "&#092;u0002") to be considered equal at the
 * PRIMARY, SECONDARY, and TERTIARY levels but different at the IDENTICAL
 * level. Additionally, differences between pre-composed accents such as
 * "&#092;u00C0" (A-grave) and combining accents such as "A&#092;u0300"
 * (A, combining-grave) will be considered significant at the IDENTICAL
 * level if decomposition is set to NO_DECOMPOSITION.
 */
 public static final int IDENTICAL = 3;

 /**
 * Decomposition mode value. With NO_DECOMPOSITION
 * set, accented characters will not be decomposed for collation. This
 * is the default setting and provides the fastest collation but
 * will only produce correct results for languages that do not use accents.
 * @see java.text.Collator#getDecomposition
 * @see java.text.Collator#setDecomposition
 */
 public static final int NO_DECOMPOSITION = 0;

 /**
 * Decomposition mode value. With CANONICAL_DECOMPOSITION
 * set, characters that are canonical variants according to Unicode
 * standard will be decomposed for collation. This should be used to get
 * correct collation of accented characters.
 * <p>
 * CANONICAL_DECOMPOSITION corresponds to Normalization Form D as
 * described in
 * <a href="http://www.unicode.org/unicode/reports/tr15/tr15-23.html">Unicode
 * Technical Report #15</a>.
 * @see java.text.Collator#getDecomposition
 * @see java.text.Collator#setDecomposition
 */
 public static final int CANONICAL_DECOMPOSITION = 1;

 /**
 * Decomposition mode value. With FULL_DECOMPOSITION
 * set, both Unicode canonical variants and Unicode compatibility variants
 * will be decomposed for collation. This causes not only accented
 * characters to be collated, but also characters that have special formats
 * to be collated with their norminal form. For example, the half-width and
 * full-width ASCII and Katakana characters are then collated together.
 * FULL_DECOMPOSITION is the most complete and therefore the slowest
 * decomposition mode.
 * <p>
 * FULL_DECOMPOSITION corresponds to Normalization Form KD as
 * described in
 * <a href="http://www.unicode.org/unicode/reports/tr15/tr15-23.html">Unicode
 * Technical Report #15</a>.
 * @see java.text.Collator#getDecomposition
 * @see java.text.Collator#setDecomposition
 */
 public static final int FULL_DECOMPOSITION = 2;

 /**
 * Gets the Collator for the current default locale.
 * The default locale is determined by java.util.Locale.getDefault.
 * @return the Collator for the default locale.(for example, en_US)
 * @see java.util.Locale#getDefault
 */
 public static synchronized Collator getInstance() {
 return getInstance(Locale.getDefault());
 }

 /**
 * Gets the Collator for the desired locale.
 * @param desiredLocale the desired locale.
 * @return the Collator for the desired locale.
 * @see java.util.Locale
 * @see java.util.ResourceBundle
 */
 public static Collator getInstance(Locale desiredLocale) {
 SoftReference<Collator> ref = cache.get(desiredLocale);
 Collator result = (ref != null) ? ref.get() : null;
 if (result == null) {
 LocaleProviderAdapter adapter;
 adapter = LocaleProviderAdapter.getAdapter(CollatorProvider.class,
 desiredLocale);
 CollatorProvider provider = adapter.getCollatorProvider();
 result = provider.getInstance(desiredLocale);
 if (result == null) {
 result = LocaleProviderAdapter.forJRE()
 .getCollatorProvider().getInstance(desiredLocale);
 }
 while (true) {
 if (ref != null) {
 // Remove the empty SoftReference if any
 cache.remove(desiredLocale, ref);
 }
 ref = cache.putIfAbsent(desiredLocale, new SoftReference<>(result));
 if (ref == null) {
 break;
 }
 Collator cachedColl = ref.get();
 if (cachedColl != null) {
 result = cachedColl;
 break;
 }
 }
 }
 return (Collator) result.clone(); // make the world safe
 }

 /**
 * Compares the source string to the target string according to the
 * collation rules for this Collator. Returns an integer less than,
 * equal to or greater than zero depending on whether the source String is
 * less than, equal to or greater than the target string. See the Collator
 * class description for an example of use.
 * <p>
 * For a one time comparison, this method has the best performance. If a
 * given String will be involved in multiple comparisons, CollationKey.compareTo
 * has the best performance. See the Collator class description for an example
 * using CollationKeys.
 * @param source the source string.
 * @param target the target string.
 * @return Returns an integer value. Value is less than zero if source is less than
 * target, value is zero if source and target are equal, value is greater than zero
 * if source is greater than target.
 * @see java.text.CollationKey
 * @see java.text.Collator#getCollationKey
 */
 public abstract int compare(String source, String target);

 /**
 * Compares its two arguments for order. Returns a negative integer,
 * zero, or a positive integer as the first argument is less than, equal
 * to, or greater than the second.
 * <p>
 * This implementation merely returns
 * <code> compare((String)o1, (String)o2) </code>.
 *
 * @return a negative integer, zero, or a positive integer as the
 * first argument is less than, equal to, or greater than the
 * second.
 * @exception ClassCastException the arguments cannot be cast to Strings.
 * @see java.util.Comparator
 * @since 1.2
 */
 @Override
 public int compare(Object o1, Object o2) {
 return compare((String)o1, (String)o2);
 }

 /**
 * Transforms the String into a series of bits that can be compared bitwise
 * to other CollationKeys. CollationKeys provide better performance than
 * Collator.compare when Strings are involved in multiple comparisons.
 * See the Collator class description for an example using CollationKeys.
 * @param source the string to be transformed into a collation key.
 * @return the CollationKey for the given String based on this Collator's collation
 * rules. If the source String is null, a null CollationKey is returned.
 * @see java.text.CollationKey
 * @see java.text.Collator#compare
 */
 public abstract CollationKey getCollationKey(String source);

 /**
 * Convenience method for comparing the equality of two strings based on
 * this Collator's collation rules.
 * @param source the source string to be compared with.
 * @param target the target string to be compared with.
 * @return true if the strings are equal according to the collation
 * rules. false, otherwise.
 * @see java.text.Collator#compare
 */
 public boolean equals(String source, String target)
 {
 return (compare(source, target) == Collator.EQUAL);
 }

 /**
 * Returns this Collator's strength property. The strength property determines
 * the minimum level of difference considered significant during comparison.
 * See the Collator class description for an example of use.
 * @return this Collator's current strength property.
 * @see java.text.Collator#setStrength
 * @see java.text.Collator#PRIMARY
 * @see java.text.Collator#SECONDARY
 * @see java.text.Collator#TERTIARY
 * @see java.text.Collator#IDENTICAL
 */
 public synchronized int getStrength()
 {
 return strength;
 }

 /**
 * Sets this Collator's strength property. The strength property determines
 * the minimum level of difference considered significant during comparison.
 * See the Collator class description for an example of use.
 * @param newStrength the new strength value.
 * @see java.text.Collator#getStrength
 * @see java.text.Collator#PRIMARY
 * @see java.text.Collator#SECONDARY
 * @see java.text.Collator#TERTIARY
 * @see java.text.Collator#IDENTICAL
 * @exception IllegalArgumentException If the new strength value is not one of
 * PRIMARY, SECONDARY, TERTIARY or IDENTICAL.
 */
 public synchronized void setStrength(int newStrength) {
 if ((newStrength != PRIMARY) &&
 (newStrength != SECONDARY) &&
 (newStrength != TERTIARY) &&
 (newStrength != IDENTICAL)) {
 throw new IllegalArgumentException("Incorrect comparison level.");
 }
 strength = newStrength;
 }

 /**
 * Get the decomposition mode of this Collator. Decomposition mode
 * determines how Unicode composed characters are handled. Adjusting
 * decomposition mode allows the user to select between faster and more
 * complete collation behavior.
 * <p>The three values for decomposition mode are:
 * <UL>
 * <LI>NO_DECOMPOSITION,
 * <LI>CANONICAL_DECOMPOSITION
 * <LI>FULL_DECOMPOSITION.
 * </UL>
 * See the documentation for these three constants for a description
 * of their meaning.
 * @return the decomposition mode
 * @see java.text.Collator#setDecomposition
 * @see java.text.Collator#NO_DECOMPOSITION
 * @see java.text.Collator#CANONICAL_DECOMPOSITION
 * @see java.text.Collator#FULL_DECOMPOSITION
 */
 public synchronized int getDecomposition()
 {
 return decmp;
 }
 /**
 * Set the decomposition mode of this Collator. See getDecomposition
 * for a description of decomposition mode.
 * @param decompositionMode the new decomposition mode.
 * @see java.text.Collator#getDecomposition
 * @see java.text.Collator#NO_DECOMPOSITION
 * @see java.text.Collator#CANONICAL_DECOMPOSITION
 * @see java.text.Collator#FULL_DECOMPOSITION
 * @exception IllegalArgumentException If the given value is not a valid decomposition
 * mode.
 */
 public synchronized void setDecomposition(int decompositionMode) {
 if ((decompositionMode != NO_DECOMPOSITION) &&
 (decompositionMode != CANONICAL_DECOMPOSITION) &&
 (decompositionMode != FULL_DECOMPOSITION)) {
 throw new IllegalArgumentException("Wrong decomposition mode.");
 }
 decmp = decompositionMode;
 }

 /**
 * Returns an array of all locales for which the
 * <code>getInstance</code> methods of this class can return
 * localized instances.
 * The returned array represents the union of locales supported
 * by the Java runtime and by installed
 * {@link java.text.spi.CollatorProvider CollatorProvider} implementations.
 * It must contain at least a Locale instance equal to
 * {@link java.util.Locale#US Locale.US}.
 *
 * @return An array of locales for which localized
 * <code>Collator</code> instances are available.
 */
 public static synchronized Locale[] getAvailableLocales() {
 LocaleServiceProviderPool pool =
 LocaleServiceProviderPool.getPool(CollatorProvider.class);
 return pool.getAvailableLocales();
 }

 /**
 * Overrides Cloneable
 */
 @Override
 public Object clone()
 {
 try {
 return (Collator)super.clone();
 } catch (CloneNotSupportedException e) {
 throw new InternalError(e);
 }
 }

 /**
 * Compares the equality of two Collators.
 * @param that the Collator to be compared with this.
 * @return true if this Collator is the same as that Collator;
 * false otherwise.
 */
 @Override
 public boolean equals(Object that)
 {
 if (this == that) {
 return true;
 }
 if (that == null) {
 return false;
 }
 if (getClass() != that.getClass()) {
 return false;
 }
 Collator other = (Collator) that;
 return ((strength == other.strength) &&
 (decmp == other.decmp));
 }

 /**
 * Generates the hash code for this Collator.
 */
 @Override
 public abstract int hashCode();

 /**
 * Default constructor. This constructor is
 * protected so subclasses can get access to it. Users typically create
 * a Collator sub-class by calling the factory method getInstance.
 * @see java.text.Collator#getInstance
 */
 protected Collator()
 {
 strength = TERTIARY;
 decmp = CANONICAL_DECOMPOSITION;
 }

 private int strength = 0;
 private int decmp = 0;
 private static final ConcurrentMap<Locale, SoftReference<Collator>> cache
 = new ConcurrentHashMap<>();

 //
 // FIXME: These three constants should be removed.
 //
 /**
 * LESS is returned if source string is compared to be less than target
 * string in the compare() method.
 * @see java.text.Collator#compare
 */
 static final int LESS = -1;
 /**
 * EQUAL is returned if source string is compared to be equal to target
 * string in the compare() method.
 * @see java.text.Collator#compare
 */
 static final int EQUAL = 0;
 /**
 * GREATER is returned if source string is compared to be greater than
 * target string in the compare() method.
 * @see java.text.Collator#compare
 */
 static final int GREATER = 1;
 }