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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
*
*   Copyright (C) 2011-2014 International Business Machines
*   Corporation and others.  All Rights Reserved.
*
*******************************************************************************
*/

#ifndef INDEXCHARS_H
#define INDEXCHARS_H

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

#include "unicode/uobject.h"
#include "unicode/locid.h"
#include "unicode/unistr.h"

#if !UCONFIG_NO_COLLATION

/**
 * \file
 * \brief C++ API: Index Characters
 */

U_CDECL_BEGIN

/**
 * Constants for Alphabetic Index Label Types.
 * The form of these enum constants anticipates having a plain C API
 * for Alphabetic Indexes that will also use them.
 * @stable ICU 4.8
 */
typedef enum UAlphabeticIndexLabelType {
    /**
     *  Normal Label, typically the starting letter of the names
     *  in the bucket with this label.
     * @stable ICU 4.8
     */
    U_ALPHAINDEX_NORMAL    = 0,

    /**
     * Underflow Label.  The bucket with this label contains names
     * in scripts that sort before any of the bucket labels in this index.
     * @stable ICU 4.8
     */
    U_ALPHAINDEX_UNDERFLOW = 1,

    /**
     * Inflow Label.  The bucket with this label contains names
     * in scripts that sort between two of the bucket labels in this index.
     * Inflow labels are created when an index contains normal labels for
     * multiple scripts, and skips other scripts that sort between some of the
     * included scripts.
     * @stable ICU 4.8
     */
    U_ALPHAINDEX_INFLOW    = 2,

    /**
     * Overflow Label. The bucket with this label contains names in scripts
     * that sort after all of the bucket labels in this index.
     * @stable ICU 4.8
     */
    U_ALPHAINDEX_OVERFLOW  = 3
} UAlphabeticIndexLabelType;


struct UHashtable;
U_CDECL_END

U_NAMESPACE_BEGIN

// Forward Declarations

class BucketList;
class Collator;
class RuleBasedCollator;
class StringEnumeration;
class UnicodeSet;
class UVector;

/**
 * AlphabeticIndex supports the creation of a UI index appropriate for a given language.
 * It can support either direct use, or use with a client that doesn't support localized collation.
 * The following is an example of what an index might look like in a UI:
 * 
 * <pre>
 *  <b>... A B C D E F G H I J K L M N O P Q R S T U V W X Y Z  ...</b>
 *
 *  <b>A</b>
 *     Addison
 *     Albertson
 *     Azensky
 *  <b>B</b>
 *     Baker
 *  ...
 * </pre>
 *
 * The class can generate a list of labels for use as a UI "index", that is, a list of
 * clickable characters (or character sequences) that allow the user to see a segment
 * (bucket) of a larger "target" list. That is, each label corresponds to a bucket in
 * the target list, where everything in the bucket is greater than or equal to the character
 * (according to the locale's collation). Strings can be added to the index;
 * they will be in sorted order in the right bucket.
 * <p>
 * The class also supports having buckets for strings before the first (underflow),
 * after the last (overflow), and between scripts (inflow). For example, if the index
 * is constructed with labels for Russian and English, Greek characters would fall
 * into an inflow bucket between the other two scripts.
 * <p>
 * The AlphabeticIndex class is not intended for public subclassing.
 *
 * <p><em>Note:</em> If you expect to have a lot of ASCII or Latin characters
 * as well as characters from the user's language,
 * then it is a good idea to call addLabels(Locale::getEnglish(), status).</p>
 *
 * <h2>Direct Use</h2>
 * <p>The following shows an example of building an index directly.
 *  The "show..." methods below are just to illustrate usage.
 *
 * <pre>
 * // Create a simple index.  "Item" is assumed to be an application
 * // defined type that the application's UI and other processing knows about,
 * //  and that has a name.
 *
 * UErrorCode status = U_ZERO_ERROR;
 * AlphabeticIndex index = new AlphabeticIndex(desiredLocale, status);
 * index->addLabels(additionalLocale, status);
 * for (Item *item in some source of Items ) {
 *     index->addRecord(item->name(), item, status);
 * }
 * ...
 * // Show index at top. We could skip or gray out empty buckets
 *
 * while (index->nextBucket(status)) {
 *     if (showAll || index->getBucketRecordCount() != 0) {
 *         showLabelAtTop(UI, index->getBucketLabel());
 *     }
 * }
 *  ...
 * // Show the buckets with their contents, skipping empty buckets
 *
 * index->resetBucketIterator(status);
 * while (index->nextBucket(status)) {
 *    if (index->getBucketRecordCount() != 0) {
 *        showLabelInList(UI, index->getBucketLabel());
 *        while (index->nextRecord(status)) {
 *            showIndexedItem(UI, static_cast<Item *>(index->getRecordData()))
 * </pre>
 *
 * The caller can build different UIs using this class.
 * For example, an index character could be omitted or grayed-out
 * if its bucket is empty. Small buckets could also be combined based on size, such as:
 *
 * <pre>
 * <b>... A-F G-N O-Z ...</b>
 * </pre>
 *
 * <h2>Client Support</h2>
 * <p>Callers can also use the AlphabeticIndex::ImmutableIndex, or the AlphabeticIndex itself,
 * to support sorting on a client that doesn't support AlphabeticIndex functionality.
 *
 * <p>The ImmutableIndex is both immutable and thread-safe.
 * The corresponding AlphabeticIndex methods are not thread-safe because
 * they "lazily" build the index buckets.
 * <ul>
 * <li>ImmutableIndex.getBucket(index) provides random access to all
 *     buckets and their labels and label types.
 * <li>The AlphabeticIndex bucket iterator or ImmutableIndex.getBucket(0..getBucketCount-1)
 *     can be used to get a list of the labels,
 *     such as "...", "A", "B",..., and send that list to the client.
 * <li>When the client has a new name, it sends that name to the server.
 * The server needs to call the following methods,
 * and communicate the bucketIndex and collationKey back to the client.
 *
 * <pre>
 * int32_t bucketIndex = index.getBucketIndex(name, status);
 * const UnicodeString &label = immutableIndex.getBucket(bucketIndex)->getLabel();  // optional
 * int32_t skLength = collator.getSortKey(name, sk, skCapacity);
 * </pre>
 *
 * <li>The client would put the name (and associated information) into its bucket for bucketIndex. The sort key sk is a
 * sequence of bytes that can be compared with a binary compare, and produce the right localized result.</li>
 * </ul>
 *
 * @stable ICU 4.8
 */
class U_I18N_API AlphabeticIndex: public UObject {
public:
     /**
      * An index "bucket" with a label string and type.
      * It is referenced by getBucketIndex(),
      * and returned by ImmutableIndex.getBucket().
      *
      * The Bucket class is not intended for public subclassing.
      * @stable ICU 51
      */
     class U_I18N_API Bucket : public UObject {
     public:
        /**
         * Destructor.
         * @stable ICU 51
         */
        virtual ~Bucket();

        /**
         * Returns the label string.
         *
         * @return the label string for the bucket
         * @stable ICU 51
         */
        const UnicodeString &getLabel() const { return label_; }
        /**
         * Returns whether this bucket is a normal, underflow, overflow, or inflow bucket.
         *
         * @return the bucket label type
         * @stable ICU 51
         */
        UAlphabeticIndexLabelType getLabelType() const { return labelType_; }

     private:
        friend class AlphabeticIndex;
        friend class BucketList;

        UnicodeString label_;
        UnicodeString lowerBoundary_;
        UAlphabeticIndexLabelType labelType_;
        Bucket *displayBucket_;
        int32_t displayIndex_;
        UVector *records_;  // Records are owned by the inputList_ vector.

        Bucket(const UnicodeString &label,   // Parameter strings are copied.
               const UnicodeString &lowerBoundary,
               UAlphabeticIndexLabelType type);
     };

    /**
     * Immutable, thread-safe version of AlphabeticIndex.
     * This class provides thread-safe methods for bucketing,
     * and random access to buckets and their properties,
     * but does not offer adding records to the index.
     *
     * The ImmutableIndex class is not intended for public subclassing.
     *
     * @stable ICU 51
     */
    class U_I18N_API ImmutableIndex : public UObject {
    public:
        /**
         * Destructor.
         * @stable ICU 51
         */
        virtual ~ImmutableIndex();

        /**
         * Returns the number of index buckets and labels, including underflow/inflow/overflow.
         *
         * @return the number of index buckets
         * @stable ICU 51
         */
        int32_t getBucketCount() const;

        /**
         * Finds the index bucket for the given name and returns the number of that bucket.
         * Use getBucket() to get the bucket's properties.
         *
         * @param name the string to be sorted into an index bucket
         * @param errorCode Error code, will be set with the reason if the
         *                  operation fails.
         * @return the bucket number for the name
         * @stable ICU 51
         */
        int32_t getBucketIndex(const UnicodeString &name, UErrorCode &errorCode) const;

        /**
         * Returns the index-th bucket. Returns nullptr if the index is out of range.
         *
         * @param index bucket number
         * @return the index-th bucket
         * @stable ICU 51
         */
        const Bucket *getBucket(int32_t index) const;

    private:
        friend class AlphabeticIndex;

        ImmutableIndex(BucketList *bucketList, Collator *collatorPrimaryOnly)
                : buckets_(bucketList), collatorPrimaryOnly_(collatorPrimaryOnly) {}

        BucketList *buckets_;
        Collator *collatorPrimaryOnly_;
    };

    /**
     * Construct an AlphabeticIndex object for the specified locale.  If the locale's
     * data does not include index characters, a set of them will be
     * synthesized based on the locale's exemplar characters.  The locale
     * determines the sorting order for both the index characters and the
     * user item names appearing under each Index character.
     *
     * @param locale the desired locale.
     * @param status Error code, will be set with the reason if the construction
     *               of the AlphabeticIndex object fails.
     * @stable ICU 4.8
     */
     AlphabeticIndex(const Locale &locale, UErrorCode &status);

   /** 
     * Construct an AlphabeticIndex that uses a specific collator.
     * 
     * The index will be created with no labels; the addLabels() function must be called
     * after creation to add the desired labels to the index.
     * 
     * The index adopts the collator, and is responsible for deleting it. 
     * The caller should make no further use of the collator after creating the index.
     * 
     * @param collator The collator to use to order the contents of this index.
     * @param status Error code, will be set with the reason if the 
     *               operation fails.
     * @stable ICU 51
     */
    AlphabeticIndex(RuleBasedCollator *collator, UErrorCode &status);

    /**
     * Add Labels to this Index.  The labels are additions to those
     * that are already in the index; they do not replace the existing
     * ones.
     * @param additions The additional characters to add to the index, such as A-Z.
     * @param status Error code, will be set with the reason if the 
     *               operation fails.
     * @return this, for chaining
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &addLabels(const UnicodeSet &additions, UErrorCode &status);

    /**
     * Add the index characters from a Locale to the index.  The labels
     * are added to those that are already in the index; they do not replace the
     * existing index characters.  The collation order for this index is not
     * changed; it remains that of the locale that was originally specified
     * when creating this Index.
     *
     * @param locale The locale whose index characters are to be added.
     * @param status Error code, will be set with the reason if the 
     *               operation fails.
     * @return this, for chaining
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &addLabels(const Locale &locale, UErrorCode &status);

     /**
      * Destructor
      * @stable ICU 4.8
      */
    virtual ~AlphabeticIndex();

    /**
     * Builds an immutable, thread-safe version of this instance, without data records.
     *
     * @return an immutable index instance
     * @stable ICU 51
     */
    ImmutableIndex *buildImmutableIndex(UErrorCode &errorCode);

    /**
     * Get the Collator that establishes the ordering of the items in this index.
     * Ownership of the collator remains with the AlphabeticIndex instance.
     *
     * The returned collator is a reference to the internal collator used by this
     * index.  It may be safely used to compare the names of items or to get
     * sort keys for names.  However if any settings need to be changed,
     * or other non-const methods called, a cloned copy must be made first.
     *
     * @return The collator
     * @stable ICU 4.8
     */
    virtual const RuleBasedCollator &getCollator() const;


   /**
     * Get the default label used for abbreviated buckets *between* other index characters.
     * For example, consider the labels when Latin (X Y Z) and Greek (Α Β Γ) are used:
     *
     *     X Y Z ... Α Β Γ.
     *
     * @return inflow label
     * @stable ICU 4.8
     */
    virtual const UnicodeString &getInflowLabel() const;

   /**
     * Set the default label used for abbreviated buckets <i>between</i> other index characters.
     * An inflow label will be automatically inserted if two otherwise-adjacent label characters
     * are from different scripts, e.g. Latin and Cyrillic, and a third script, e.g. Greek,
     * sorts between the two.  The default inflow character is an ellipsis (...)
     *
     * @param inflowLabel the new Inflow label.
     * @param status Error code, will be set with the reason if the operation fails.
     * @return this
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &setInflowLabel(const UnicodeString &inflowLabel, UErrorCode &status);


   /**
     * Get the special label used for items that sort after the last normal label,
     * and that would not otherwise have an appropriate label.
     *
     * @return the overflow label
     * @stable ICU 4.8
     */
    virtual const UnicodeString &getOverflowLabel() const;


   /**
     * Set the label used for items that sort after the last normal label,
     * and that would not otherwise have an appropriate label.
     *
     * @param overflowLabel the new overflow label.
     * @param status Error code, will be set with the reason if the operation fails.
     * @return this
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &setOverflowLabel(const UnicodeString &overflowLabel, UErrorCode &status);

   /**
     * Get the special label used for items that sort before the first normal label,
     * and that would not otherwise have an appropriate label.
     *
     * @return underflow label
     * @stable ICU 4.8
     */
    virtual const UnicodeString &getUnderflowLabel() const;

   /**
     * Set the label used for items that sort before the first normal label,
     * and that would not otherwise have an appropriate label.
     *
     * @param underflowLabel the new underflow label.
     * @param status Error code, will be set with the reason if the operation fails.
     * @return this
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &setUnderflowLabel(const UnicodeString &underflowLabel, UErrorCode &status);


    /**
     * Get the limit on the number of labels permitted in the index.
     * The number does not include over, under and inflow labels.
     *
     * @return maxLabelCount maximum number of labels.
     * @stable ICU 4.8
     */
    virtual int32_t getMaxLabelCount() const;

    /**
     * Set a limit on the number of labels permitted in the index.
     * The number does not include over, under and inflow labels.
     * Currently, if the number is exceeded, then every
     * nth item is removed to bring the count down.
     * A more sophisticated mechanism may be available in the future.
     *
     * @param maxLabelCount the maximum number of labels.
     * @param status error code
     * @return This, for chaining
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &setMaxLabelCount(int32_t maxLabelCount, UErrorCode &status);


    /**
     * Add a record to the index.  Each record will be associated with an index Bucket
     *  based on the record's name.  The list of records for each bucket will be sorted
     *  based on the collation ordering of the names in the index's locale.
     *  Records with duplicate names are permitted; they will be kept in the order
     *  that they were added.
     *
     * @param name The display name for the Record.  The Record will be placed in
     *             a bucket based on this name.
     * @param data An optional pointer to user data associated with this
     *             item.  When iterating the contents of a bucket, both the
     *             data pointer the name will be available for each Record.
     * @param status  Error code, will be set with the reason if the operation fails.
     * @return        This, for chaining.
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &addRecord(const UnicodeString &name, const void *data, UErrorCode &status);

    /**
     * Remove all Records from the Index.  The set of Buckets, which define the headings under
     * which records are classified, is not altered.
     *
     * @param status  Error code, will be set with the reason if the operation fails.
     * @return        This, for chaining.
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &clearRecords(UErrorCode &status);


    /**  Get the number of labels in this index.
     *      Note: may trigger lazy index construction.
     *
     * @param status  Error code, will be set with the reason if the operation fails.
     * @return        The number of labels in this index, including any under, over or
     *                in-flow labels.
     * @stable ICU 4.8
     */
    virtual int32_t  getBucketCount(UErrorCode &status);


    /**  Get the total number of Records in this index, that is, the number
     *   of <name, data> pairs added.
     *
     * @param status  Error code, will be set with the reason if the operation fails.
     * @return        The number of records in this index, that is, the total number
     *                of (name, data) items added with addRecord().
     * @stable ICU 4.8
     */
    virtual int32_t  getRecordCount(UErrorCode &status);



    /**
     *   Given the name of a record, return the zero-based index of the Bucket
     *   in which the item should appear.  The name need not be in the index.
     *   A Record will not be added to the index by this function.
     *   Bucket numbers are zero-based, in Bucket iteration order.
     *
     * @param itemName  The name whose bucket position in the index is to be determined.
     * @param status  Error code, will be set with the reason if the operation fails.
     * @return The bucket number for this name.
     * @stable ICU 4.8
     *
     */
    virtual int32_t  getBucketIndex(const UnicodeString &itemName, UErrorCode &status);


    /**
     *   Get the zero based index of the current Bucket from an iteration
     *   over the Buckets of this index.  Return -1 if no iteration is in process.
     *   @return  the index of the current Bucket
     *   @stable ICU 4.8
     */
    virtual int32_t  getBucketIndex() const;


    /**
     *   Advance the iteration over the Buckets of this index.  Return false if
     *   there are no more Buckets.
     *
     *   @param status  Error code, will be set with the reason if the operation fails.
     *   U_ENUM_OUT_OF_SYNC_ERROR will be reported if the index is modified while
     *   an enumeration of its contents are in process.
     *
     *   @return true if success, false if at end of iteration
     *   @stable ICU 4.8
     */
    virtual UBool nextBucket(UErrorCode &status);

    /**
     *   Return the name of the Label of the current bucket from an iteration over the buckets.
     *   If the iteration is before the first Bucket (nextBucket() has not been called),
     *   or after the last, return an empty string.
     *
     *   @return the bucket label.
     *   @stable ICU 4.8
     */
    virtual const UnicodeString &getBucketLabel() const;

    /**
     *  Return the type of the label for the current Bucket (selected by the
     *  iteration over Buckets.)
     *
     * @return the label type.
     * @stable ICU 4.8
     */
    virtual UAlphabeticIndexLabelType getBucketLabelType() const;

    /**
      * Get the number of <name, data> Records in the current Bucket.
      * If the current bucket iteration position is before the first label or after the
      * last, return 0.
      *
      *  @return the number of Records.
      *  @stable ICU 4.8
      */
    virtual int32_t getBucketRecordCount() const;


    /**
     *  Reset the Bucket iteration for this index.  The next call to nextBucket()
     *  will restart the iteration at the first label.
     *
     * @param status  Error code, will be set with the reason if the operation fails.
     * @return        this, for chaining.
     * @stable ICU 4.8
     */
    virtual AlphabeticIndex &resetBucketIterator(UErrorCode &status);

    /**
     * Advance to the next record in the current Bucket.
     * When nextBucket() is called, Record iteration is reset to just before the
     * first Record in the new Bucket.
     *
     *   @param status  Error code, will be set with the reason if the operation fails.
     *   U_ENUM_OUT_OF_SYNC_ERROR will be reported if the index is modified while
     *   an enumeration of its contents are in process.
     *   @return true if successful, false when the iteration advances past the last item.
     *   @stable ICU 4.8
     */
    virtual UBool nextRecord(UErrorCode &status);

    /**
     * Get the name of the current Record.
     * Return an empty string if the Record iteration position is before first
     * or after the last.
     *
     *  @return The name of the current index item.
     *  @stable ICU 4.8
     */
    virtual const UnicodeString &getRecordName() const;


    /**
     * Return the data pointer of the Record currently being iterated over.
     * Return nullptr if the current iteration position before the first item in this Bucket,
     * or after the last.
     *
     *  @return The current Record's data pointer.
     *  @stable ICU 4.8
     */
    virtual const void *getRecordData() const;


    /**
     * Reset the Record iterator position to before the first Record in the current Bucket.
     *
     *  @return This, for chaining.
     *  @stable ICU 4.8
     */
    virtual AlphabeticIndex &resetRecordIterator();

private:
     /**
      * No Copy constructor.
      * @internal (private)
      */
     AlphabeticIndex(const AlphabeticIndex &other) = delete;

     /**
      *   No assignment.
      */
     AlphabeticIndex &operator =(const AlphabeticIndex & /*other*/) { return *this;}

    /**
     * No Equality operators.
     * @internal (private)
     */
     virtual bool operator==(const AlphabeticIndex& other) const;

    /**
     * Inequality operator.
     * @internal (private)
     */
     virtual bool operator!=(const AlphabeticIndex& other) const;

     // Common initialization, for use from all constructors.
     void init(const Locale *locale, UErrorCode &status);

    /**
     * This method is called to get the index exemplars. Normally these come from the locale directly,
     * but if they aren't available, we have to synthesize them.
     */
    void addIndexExemplars(const Locale &locale, UErrorCode &status);
    /**
     * Add Chinese index characters from the tailoring.
     */
    UBool addChineseIndexCharacters(UErrorCode &errorCode);

    UVector *firstStringsInScript(UErrorCode &status);

    static UnicodeString separated(const UnicodeString &item);

    /**
     * Determine the best labels to use.
     * This is based on the exemplars, but we also process to make sure that they are unique,
     * and sort differently, and that the overall list is small enough.
     */
    void initLabels(UVector &indexCharacters, UErrorCode &errorCode) const;
    BucketList *createBucketList(UErrorCode &errorCode) const;
    void initBuckets(UErrorCode &errorCode);
    void clearBuckets();
    void internalResetBucketIterator();

public:

    //  The Record is declared public only to allow access from
    //  implementation code written in plain C.
    //  It is not intended for public use.

#ifndef U_HIDE_INTERNAL_API
    /**
     * A (name, data) pair, to be sorted by name into one of the index buckets.
     * The user data is not used by the index implementation.
     * \cond
     * @internal
     */
    struct Record: public UMemory {
        const UnicodeString  name_;
        const void           *data_;
        Record(const UnicodeString &name, const void *data);
        ~Record();
    };
    /** \endcond */
#endif  /* U_HIDE_INTERNAL_API */

private:

    /**
     * Holds all user records before they are distributed into buckets.
     * Type of contents is (Record *)
     * @internal (private)
     */
    UVector  *inputList_;

    int32_t  labelsIterIndex_;        // Index of next item to return.
    int32_t  itemsIterIndex_;
    Bucket   *currentBucket_;         // While an iteration of the index in underway,
                                      //   point to the bucket for the current label.
                                      // nullptr when no iteration underway.

    int32_t    maxLabelCount_;        // Limit on # of labels permitted in the index.

    UnicodeSet *initialLabels_;       // Initial (unprocessed) set of Labels.  Union
                                      //   of those explicitly set by the user plus
                                      //   those from locales.  Raw values, before
                                      //   crunching into bucket labels.

    UVector *firstCharsInScripts_;    // The first character from each script,
                                      //   in collation order.

    RuleBasedCollator *collator_;
    RuleBasedCollator *collatorPrimaryOnly_;

    // Lazy evaluated: null means that we have not built yet.
    BucketList *buckets_;

    UnicodeString  inflowLabel_;
    UnicodeString  overflowLabel_;
    UnicodeString  underflowLabel_;
    UnicodeString  overflowComparisonString_;

    UnicodeString emptyString_;
};

U_NAMESPACE_END

#endif  // !UCONFIG_NO_COLLATION

#endif /* U_SHOW_CPLUSPLUS_API */

#endif
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