// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
* Copyright (C) 2010-2014, International Business Machines
* Corporation and others.  All Rights Reserved.
*******************************************************************************
* utf16collationiterator.h
*
* created on: 2010oct27
* created by: Markus W. Scherer
*/

#ifndef __UTF16COLLATIONITERATOR_H__
#define __UTF16COLLATIONITERATOR_H__

#include "unicode/utypes.h"

#if !UCONFIG_NO_COLLATION

#include "cmemory.h"
#include "collation.h"
#include "collationdata.h"
#include "collationiterator.h"
#include "normalizer2impl.h"

U_NAMESPACE_BEGIN

/**
 * UTF-16 collation element and character iterator.
 * Handles normalized UTF-16 text inline, with length or NUL-terminated.
 * Unnormalized text is handled by a subclass.
 */
class U_I18N_API UTF16CollationIterator : public CollationIterator {
public:
    UTF16CollationIterator(const CollationData *d, UBool numeric,
                           const char16_t *s, const char16_t *p, const char16_t *lim)
            : CollationIterator(d, numeric),
              start(s), pos(p), limit(lim) {}

    UTF16CollationIterator(const UTF16CollationIterator &other, const char16_t *newText);

    virtual ~UTF16CollationIterator();

    virtual bool operator==(const CollationIterator &other) const override;

    virtual void resetToOffset(int32_t newOffset) override;

    virtual int32_t getOffset() const override;

    void setText(const char16_t *s, const char16_t *lim) {
        reset();
        start = pos = s;
        limit = lim;
    }

    virtual UChar32 nextCodePoint(UErrorCode &errorCode) override;

    virtual UChar32 previousCodePoint(UErrorCode &errorCode) override;

protected:
    // Copy constructor only for subclasses which set the pointers.
    UTF16CollationIterator(const UTF16CollationIterator &other)
            : CollationIterator(other),
              start(nullptr), pos(nullptr), limit(nullptr) {}

    virtual uint32_t handleNextCE32(UChar32 &c, UErrorCode &errorCode) override;

    virtual char16_t handleGetTrailSurrogate() override;

    virtual UBool foundNULTerminator() override;

    virtual void forwardNumCodePoints(int32_t num, UErrorCode &errorCode) override;

    virtual void backwardNumCodePoints(int32_t num, UErrorCode &errorCode) override;

    // UTF-16 string pointers.
    // limit can be nullptr for NUL-terminated strings.
    const char16_t *start, *pos, *limit;
};

/**
 * Incrementally checks the input text for FCD and normalizes where necessary.
 */
class U_I18N_API FCDUTF16CollationIterator : public UTF16CollationIterator {
public:
    FCDUTF16CollationIterator(const CollationData *data, UBool numeric,
                              const char16_t *s, const char16_t *p, const char16_t *lim)
            : UTF16CollationIterator(data, numeric, s, p, lim),
              rawStart(s), segmentStart(p), segmentLimit(nullptr), rawLimit(lim),
              nfcImpl(data->nfcImpl),
              checkDir(1) {}

    FCDUTF16CollationIterator(const FCDUTF16CollationIterator &other, const char16_t *newText);

    virtual ~FCDUTF16CollationIterator();

    virtual bool operator==(const CollationIterator &other) const override;

    virtual void resetToOffset(int32_t newOffset) override;

    virtual int32_t getOffset() const override;

    virtual UChar32 nextCodePoint(UErrorCode &errorCode) override;

    virtual UChar32 previousCodePoint(UErrorCode &errorCode) override;

protected:
    virtual uint32_t handleNextCE32(UChar32 &c, UErrorCode &errorCode) override;

    virtual UBool foundNULTerminator() override;

    virtual void forwardNumCodePoints(int32_t num, UErrorCode &errorCode) override;

    virtual void backwardNumCodePoints(int32_t num, UErrorCode &errorCode) override;

private:
    /**
     * Switches to forward checking if possible.
     * To be called when checkDir < 0 || (checkDir == 0 && pos == limit).
     * Returns with checkDir > 0 || (checkDir == 0 && pos != limit).
     */
    void switchToForward();

    /**
     * Extend the FCD text segment forward or normalize around pos.
     * To be called when checkDir > 0 && pos != limit.
     * @return true if success, checkDir == 0 and pos != limit
     */
    UBool nextSegment(UErrorCode &errorCode);

    /**
     * Switches to backward checking.
     * To be called when checkDir > 0 || (checkDir == 0 && pos == start).
     * Returns with checkDir < 0 || (checkDir == 0 && pos != start).
     */
    void switchToBackward();

    /**
     * Extend the FCD text segment backward or normalize around pos.
     * To be called when checkDir < 0 && pos != start.
     * @return true if success, checkDir == 0 and pos != start
     */
    UBool previousSegment(UErrorCode &errorCode);

    UBool normalize(const char16_t *from, const char16_t *to, UErrorCode &errorCode);

    // Text pointers: The input text is [rawStart, rawLimit[
    // where rawLimit can be nullptr for NUL-terminated text.
    //
    // checkDir > 0:
    //
    // The input text [segmentStart..pos[ passes the FCD check.
    // Moving forward checks incrementally.
    // segmentLimit is undefined. limit == rawLimit.
    //
    // checkDir < 0:
    // The input text [pos..segmentLimit[ passes the FCD check.
    // Moving backward checks incrementally.
    // segmentStart is undefined, start == rawStart.
    //
    // checkDir == 0:
    //
    // The input text [segmentStart..segmentLimit[ is being processed.
    // These pointers are at FCD boundaries.
    // Either this text segment already passes the FCD check
    // and segmentStart==start<=pos<=limit==segmentLimit,
    // or the current segment had to be normalized so that
    // [segmentStart..segmentLimit[ turned into the normalized string,
    // corresponding to normalized.getBuffer()==start<=pos<=limit==start+normalized.length().
    const char16_t *rawStart;
    const char16_t *segmentStart;
    const char16_t *segmentLimit;
    // rawLimit==nullptr for a NUL-terminated string.
    const char16_t *rawLimit;

    const Normalizer2Impl &nfcImpl;
    UnicodeString normalized;
    // Direction of incremental FCD check. See comments before rawStart.
    int8_t checkDir;
};

U_NAMESPACE_END

#endif  // !UCONFIG_NO_COLLATION
#endif  // __UTF16COLLATIONITERATOR_H__