/*
 *******************************************************************************
 * Copyright (C) 1996-2008, International Business Machines Corporation and    *
 * others. All Rights Reserved.                                                *
 *******************************************************************************
 */

package com.ibm.icu.text;

import java.util.Comparator;
import java.util.Locale;

import com.ibm.icu.util.ULocale;

/**
* <p>Collator performs locale-sensitive string comparison.</p>
*
* <p>Following the <a href=http://www.unicode.org>Unicode
* Consortium</a>'s specifications for the
* <a href="http://www.unicode.org/unicode/reports/tr10/"> Unicode Collation
* Algorithm (UCA)</a>, there are 5 different levels of strength used
* in comparisons:
*
* <ul>
* <li>PRIMARY strength: Typically, this is used to denote differences between
*     base characters (for example, "a" &lt; "b").
*     It is the strongest difference. For example, dictionaries are divided
*     into different sections by base character.
* <li>SECONDARY strength: Accents in the characters are considered secondary
*     differences (for example, "as" &lt; "&agrave;s" &lt; "at"). Other
*     differences
*     between letters can also be considered secondary differences, depending
*     on the language. A secondary difference is ignored when there is a
*     primary difference anywhere in the strings.
* <li>TERTIARY strength: Upper and lower case differences in characters are
*     distinguished at tertiary strength (for example, "ao" &lt; "Ao" &lt;
*     "a&ograve;"). In addition, a variant of a letter differs from the base
*     form on the tertiary strength (such as "A" and "&#9398;"). Another
*     example is the
*     difference between large and small Kana. A tertiary difference is ignored
*     when there is a primary or secondary difference anywhere in the strings.
* <li>QUATERNARY strength: When punctuation is ignored
*     <a href="http://www.icu-project.org/userguide/Collate_Concepts.html#Ignoring_Punctuation">
*     (see Ignoring Punctuations in the user guide)</a> at PRIMARY to TERTIARY
*     strength, an additional strength level can
*     be used to distinguish words with and without punctuation (for example,
*     "ab" &lt; "a-b" &lt; "aB").
*     This difference is ignored when there is a PRIMARY, SECONDARY or TERTIARY
*     difference. The QUATERNARY strength should only be used if ignoring
*     punctuation is required.
* <li>IDENTICAL strength:
*     When all other strengths are equal, the IDENTICAL strength is used as a
*     tiebreaker. The Unicode code point values of the NFD form of each string
*     are compared, just in case there is no difference.
*     For example, Hebrew cantellation marks are only distinguished at this
*     strength. This strength should be used sparingly, as only code point
*     value differences between two strings is an extremely rare occurrence.
*     Using this strength substantially decreases the performance for both
*     comparison and collation key generation APIs. This strength also
*     increases the size of the collation key.
* </ul>
*
* Unlike the JDK, ICU4J's Collator deals only with 2 decomposition modes,
* the canonical decomposition mode and one that does not use any decomposition.
* The compatibility decomposition mode, java.text.Collator.FULL_DECOMPOSITION
* is not supported here. If the canonical
* decomposition mode is set, the Collator handles un-normalized text properly,
* producing the same results as if the text were normalized in NFD. If
* canonical decomposition is turned off, it is the user's responsibility to
* ensure that all text is already in the appropriate form before performing
* a comparison or before getting a CollationKey.</p>
*
* <p>For more information about the collation service see the
* <a href="http://www.icu-project.org/userguide/Collate_Intro.html">users
* guide</a>.</p>
*
* <p>Examples of use
* <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");
* }
*
* The following example shows how to compare two strings using the
* Collator for the default locale.
*
* // Compare two strings in the default locale
* Collator myCollator = Collator.getInstance();
* myCollator.setDecomposition(NO_DECOMPOSITION);
* if (myCollator.compare("&agrave;&#92;u0325", "a&#92;u0325&#768;") != 0) {
*     System.out.println("&agrave;&#92;u0325 is not equals to a&#92;u0325&#768; without decomposition");
*     myCollator.setDecomposition(CANONICAL_DECOMPOSITION);
*     if (myCollator.compare("&agrave;&#92;u0325", "a&#92;u0325&#768;") != 0) {
*         System.out.println("Error: &agrave;&#92;u0325 should be equals to a&#92;u0325&#768; with decomposition");
*     }
*     else {
*         System.out.println("&agrave;&#92;u0325 is equals to a&#92;u0325&#768; with decomposition");
*     }
* }
* else {
*     System.out.println("Error: &agrave;&#92;u0325 should be not equals to a&#92;u0325&#768; without decomposition");
* }
* </pre>
* </p>
* @see CollationKey
* @author Syn Wee Quek
* @stable ICU 2.8
*/
public class Collator implements Comparator, Cloneable
{
    /**
     * @internal
     */
    private final java.text.Collator collator;

    /**
     * @internal
     */
    private Collator(java.text.Collator delegate) {
        this.collator = delegate;
    }

    /**
     * Create a collator with a null delegate.
     * For use by possible subclassers.  This is present since
     * the original Collator is abstract, and so, in theory
     * subclassable.  All member APIs must be overridden.
     */
    protected Collator() {
        this.collator = null;
    }

    // public data members ---------------------------------------------------

    /**
     * Strongest collator strength value. Typically used to denote differences
     * between base characters. See class documentation for more explanation.
     * @see #setStrength
     * @see #getStrength
     * @stable ICU 2.8
     */
    public final static int PRIMARY = java.text.Collator.PRIMARY;

    /**
     * Second level collator strength value.
     * Accents in the characters are considered secondary differences.
     * Other differences between letters can also be considered secondary
     * differences, depending on the language.
     * See class documentation for more explanation.
     * @see #setStrength
     * @see #getStrength
     * @stable ICU 2.8
     */
    public final static int SECONDARY = java.text.Collator.SECONDARY;

    /**
     * Third level collator strength value.
     * Upper and lower case differences in characters are distinguished at this
     * strength level. In addition, a variant of a letter differs from the base
     * form on the tertiary level.
     * See class documentation for more explanation.
     * @see #setStrength
     * @see #getStrength
     * @stable ICU 2.8
     */
    public final static int TERTIARY = java.text.Collator.TERTIARY;

    /**
     * Fourth level collator strength value.
     * When punctuation is ignored
     * <a href="http://www.icu-project.org/userguide/Collate_Concepts.html#Ignoring_Punctuation">
     * (see Ignoring Punctuations in the user guide)</a> at PRIMARY to TERTIARY
     * strength, an additional strength level can
     * be used to distinguish words with and without punctuation.
     * See class documentation for more explanation.
     * @see #setStrength
     * @see #getStrength
     * @stable ICU 2.8
     */
    public final static int QUATERNARY = java.text.Collator.IDENTICAL;

    /**
     * <p>
     * Smallest Collator strength value. When all other strengths are equal,
     * the IDENTICAL strength is used as a tiebreaker. The Unicode code point
     * values of the NFD form of each string are compared, just in case there
     * is no difference.
     * See class documentation for more explanation.
     * </p>
     * <p>
     * Note this value is different from JDK's
     * </p>
     * @stable ICU 2.8
     */
    public final static int IDENTICAL = java.text.Collator.FULL_DECOMPOSITION;

    /**
     * This is for backwards compatibility with Java APIs only.  It
     * should not be used, IDENTICAL should be used instead.  ICU's
     * collation does not support Java's FULL_DECOMPOSITION mode.
     * @stable ICU 3.4
     * @deprecated Backwards compatibility with Java only.
     */
    public final static int FULL_DECOMPOSITION = java.text.Collator.FULL_DECOMPOSITION;

    /**
     * <p>Decomposition mode value. With NO_DECOMPOSITION set, Strings
     * will not be decomposed for collation. This is the default
     * decomposition setting unless otherwise specified by the locale
     * used to create the Collator.</p>
     *
     * <p><strong>Note</strong> this value is different from the JDK's.</p>
     * @see #CANONICAL_DECOMPOSITION
     * @see #getDecomposition
     * @see #setDecomposition
     * @stable ICU 2.8
     */
    public final static int NO_DECOMPOSITION = java.text.Collator.NO_DECOMPOSITION;

    /**
     * <p>Decomposition mode value. With CANONICAL_DECOMPOSITION set,
     * characters that are canonical variants according to the Unicode standard
     * will be decomposed for collation.</p>
     *
     * <p>CANONICAL_DECOMPOSITION corresponds to Normalization Form D as
     * described in <a href="http://www.unicode.org/unicode/reports/tr15/">
     * Unicode Technical Report #15</a>.
     * </p>
     * @see #NO_DECOMPOSITION
     * @see #getDecomposition
     * @see #setDecomposition
     * @stable ICU 2.8
     */
    public final static int CANONICAL_DECOMPOSITION = java.text.Collator.CANONICAL_DECOMPOSITION;

    // public methods --------------------------------------------------------

    // public setters --------------------------------------------------------

    /**
     * <p>Sets this Collator's strength property. The strength property
     * determines the minimum level of difference considered significant
     * during comparison.</p>
     *
     * <p>The default strength for the Collator is TERTIARY, unless specified
     * otherwise by the locale used to create the Collator.</p>
     *
     * <p>See the Collator class description for an example of use.</p>
     * @param newStrength the new strength value.
     * @see #getStrength
     * @see #PRIMARY
     * @see #SECONDARY
     * @see #TERTIARY
     * @see #QUATERNARY
     * @see #IDENTICAL
     * @exception IllegalArgumentException if the new strength value is not one
     *                of PRIMARY, SECONDARY, TERTIARY, QUATERNARY or IDENTICAL.
     * @stable ICU 2.8
     */
    public void setStrength(int newStrength) {
        collator.setStrength(newStrength);
    }

    /**
     * <p>Set the decomposition mode of this Collator.  Setting this
     * decomposition property with CANONICAL_DECOMPOSITION allows the
     * Collator to handle un-normalized text properly, producing the
     * same results as if the text were normalized. If
     * NO_DECOMPOSITION is set, it is the user's responsibility to
     * insure that all text is already in the appropriate form before
     * a comparison or before getting a CollationKey. Adjusting
     * decomposition mode allows the user to select between faster and
     * more complete collation behavior.</p>
     *
     * <p>Since a great many of the world's languages do not require
     * text normalization, most locales set NO_DECOMPOSITION as the
     * default decomposition mode.</p>
     *
     * The default decompositon mode for the Collator is
     * NO_DECOMPOSITON, unless specified otherwise by the locale used
     * to create the Collator.</p>
     *
     * <p>See getDecomposition for a description of decomposition
     * mode.</p>
     *
     * @param decomposition the new decomposition mode
     * @see #getDecomposition
     * @see #NO_DECOMPOSITION
     * @see #CANONICAL_DECOMPOSITION
     * @exception IllegalArgumentException If the given value is not a valid
     *            decomposition mode.
     * @stable ICU 2.8
     */
    public void setDecomposition(int decomposition) {
        collator.setDecomposition(decomposition);
    }

    // public getters --------------------------------------------------------

    /**
     * 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) if it
     *         is created successfully. Otherwise if there is no Collator
     *         associated with the current locale, the default UCA collator
     *         will be returned.
     * @see java.util.Locale#getDefault()
     * @see #getInstance(Locale)
     * @stable ICU 2.8
     */
    public static final Collator getInstance() {
        return new Collator(java.text.Collator.getInstance());
    }

     /**
     * Gets the Collator for the desired locale.
     * @param locale the desired locale.
     * @return Collator for the desired locale if it is created successfully.
     *         Otherwise if there is no Collator
     *         associated with the current locale, a default UCA collator will
     *         be returned.
     * @see java.util.Locale
     * @see java.util.ResourceBundle
     * @see #getInstance(Locale)
     * @see #getInstance()
     * @stable ICU 3.4.3
     */
    public static final Collator getInstance(ULocale locale) {
        return getInstance(locale.toLocale());
    }

    /**
     * Gets the Collator for the desired locale.
     * @param locale the desired locale.
     * @return Collator for the desired locale if it is created successfully.
     *         Otherwise if there is no Collator
     *         associated with the current locale, a default UCA collator will
     *         be returned.
     * @see java.util.Locale
     * @see java.util.ResourceBundle
     * @see #getInstance(ULocale)
     * @see #getInstance()
     * @stable ICU 2.8
     */
    public static final Collator getInstance(Locale locale) {
        return new Collator(java.text.Collator.getInstance(locale));
    }

     /**
     * Get the set of locales, as Locale objects, for which collators
     * are installed.  Note that Locale objects do not support RFC 3066.
     * @return the list of locales in which collators are installed.
     * This list includes any that have been registered, in addition to
     * those that are installed with ICU4J.
     * @stable ICU 2.4
     */
    public static Locale[] getAvailableLocales() {
        return java.text.Collator.getAvailableLocales();
    }

    /**
     * Get the set of locales, as ULocale objects, for which collators
     * are installed.  ULocale objects support RFC 3066.
     * @return the list of locales in which collators are installed.
     * This list includes any that have been registered, in addition to
     * those that are installed with ICU4J.
     * @stable ICU 3.4.3
     */
    public static final ULocale[] getAvailableULocales() {
        Locale[] locales = java.text.Collator.getAvailableLocales();
        ULocale[] ulocales = new ULocale[locales.length];
        for (int i = 0; i < locales.length; ++i) {
            ulocales[i] = ULocale.forLocale(locales[i]);
        }
        return ulocales;
    }
 
    /**
     * Return an array of all possible keywords that are relevant to
     * collation. At this point, the only recognized keyword for this
     * service is "collation".
     * @return an array of valid collation keywords.
     * @see #getKeywordValues
     * @stable ICU 3.0
     */
    public static final String[] getKeywords() {
        return new String[0];
    }
    
    /**
     * Given a keyword, return an array of all values for
     * that keyword that are currently in use.
     * @param keyword one of the keywords returned by getKeywords.
     * @see #getKeywords
     * @stable ICU 3.0
     */
    public static final String[] getKeywordValues(String keyword) {
        return new String[0];
    }

    /**
     * <p>Returns this Collator's strength property. The strength property
     * determines the minimum level of difference considered significant.
     * </p>
     * <p>
     * See the Collator class description for more details.
     * </p>
     * @return this Collator's current strength property.
     * @see #setStrength
     * @see #PRIMARY
     * @see #SECONDARY
     * @see #TERTIARY
     * @see #QUATERNARY
     * @see #IDENTICAL
     * @stable ICU 2.8
     */
    public int getStrength() {
        return collator.getStrength();
    }

    /**
     * <p>
     * Get the decomposition mode of this Collator. Decomposition mode
     * determines how Unicode composed characters are handled.
     * </p>
     * <p>
     * See the Collator class description for more details.
     * </p>
     * @return the decomposition mode
     * @see #setDecomposition
     * @see #NO_DECOMPOSITION
     * @see #CANONICAL_DECOMPOSITION
     * @stable ICU 2.8
     */
    public int getDecomposition() {
        return collator.getDecomposition();
    }

    /**
     * <p>
     * Compares the source text String to the target text String according to
     * this Collator's rules, strength and decomposition mode.
     * 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>
     * @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 CollationKey
     * @see #getCollationKey
     * @exception NullPointerException thrown if either arguments is null.
     *            IllegalArgumentException thrown if either source or target is
     *            not of the class String.
     * @stable ICU 2.8
     */
    public int compare(Object source, Object target) {
        return collator.compare(source, target);
    }

    // public other methods -------------------------------------------------

    /**
     * Convenience method for comparing the equality of two text Strings using
     * this Collator's rules, strength and decomposition mode.
     * @param source the source string to be compared.
     * @param target the target string to be compared.
     * @return true if the strings are equal according to the collation
     *         rules, otherwise false.
     * @see #compare
     * @exception NullPointerException thrown if either arguments is null.
     * @stable ICU 2.8
     */
    public boolean equals(String source, String target) {
        return (compare(source, target) == 0);
    }

    /**
     * <p>
     * Compares the source text String to the target text String according to
     * this Collator's rules, strength and decomposition mode.
     * 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>
     * @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 CollationKey
     * @see #getCollationKey
     * @exception NullPointerException thrown if either arguments is null.
     * @stable ICU 2.8
     */
    public int compare(String source, String target) {
        return collator.compare(source, target);
    }

    /**
     * <p>
     * Transforms the String into a CollationKey suitable for efficient
     * repeated comparison.  The resulting key depends on the collator's
     * rules, strength and decomposition mode.
     * </p>
     * <p>See the CollationKey class documentation for more information.</p>
     * @param source the string to be transformed into a CollationKey.
     * @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 CollationKey
     * @see #compare(String, String)
     * @stable ICU 2.8
     */
    public CollationKey getCollationKey(String source) {
        return new CollationKey(collator.getCollationKey(source));
    }
    
    /**
     * Return a string suitable for debugging.
     * @return a string suitable for debugging
     * @stable ICU 3.4.3
     */
    public String toString() {
        return collator.toString();
    }

   /**
     * Clone the collator.
     * @return a clone of this collator.
     * @stable ICU 2.6
     */
    public Object clone() throws CloneNotSupportedException {
        return new Collator((java.text.Collator)collator.clone());
    }

    /**
     * Return true if rhs is a Collator and compares the same as this.
     * @return true if rhs equals this
     * @stable ICU 3.4.3
     */
    public boolean equals(Object rhs) {
        try {
            return collator.equals(((Collator)rhs).collator);
        }
        catch (Exception e) {
            return false;
        }
    }

    /**
     * Return a hashCode.
     * @return a hashCode
     * @stable ICU 3.4.3
     */
    public int hashCode() {
        return collator.hashCode();
    }
}