/*
**********************************************************************
*   Copyright (c) 2000, International Business Machines
*   Corporation and others.  All Rights Reserved.
**********************************************************************
*   Date        Name        Description
*   01/17/2000  aliu        Ported from Java.
**********************************************************************
*/
#include "unicode/hangjamo.h"
#include "unicode/rep.h"
#include "unicode/unifilt.h"
#include "unicode/unicode.h"

// These constants are from the Unicode book's algorithm.

#define SBase   (0xAC00)
#define LBase   (0x1100)
#define VBase   (0x1161)
#define TBase   (0x11A7)
#define LCount  (19)
#define VCount  (21)
#define TCount  (28)
#define NCount  (VCount * TCount)   // 588
#define SCount  (LCount * NCount)   // 11172

/**
 * ID for this transliterator.
 */
const char* HangulJamoTransliterator::_ID = "Hangul-Jamo";

/**
 * Constructs a transliterator.
 */
HangulJamoTransliterator::HangulJamoTransliterator(UnicodeFilter* adoptedFilter) :
    Transliterator(_ID, adoptedFilter) {
}

/**
 * Copy constructor.
 */
HangulJamoTransliterator::HangulJamoTransliterator(const HangulJamoTransliterator& o) :
    Transliterator(o) {
}

/**
 * Assignment operator.
 */
HangulJamoTransliterator& HangulJamoTransliterator::operator=(
                                             const HangulJamoTransliterator& o) {
    Transliterator::operator=(o);
    return *this;
}

/**
 * Transliterator API.
 */
Transliterator* HangulJamoTransliterator::clone(void) const {
    return new HangulJamoTransliterator(*this);
}

/**
 * Implements {@link Transliterator#handleTransliterate}.
 */
void HangulJamoTransliterator::handleTransliterate(Replaceable& text, UTransPosition& offsets,
                                                   UBool isIncremental) const {
    int32_t cursor = offsets.start;
    int32_t limit = offsets.limit;

    UnicodeString replacement;
    while (cursor < limit) {
        UChar c = filteredCharAt(text, cursor);
        if (decomposeHangul(c, replacement)) {
            text.handleReplaceBetween(cursor, cursor+1, replacement);
            int32_t len = replacement.length();
            cursor += len; // skip over replacement
            limit += len - 1; // fix up limit
            offsets.contextLimit += len - 1; // fix up limit
        } else {
            ++cursor;
        }
    }

    offsets.contextLimit += limit - offsets.limit;
    offsets.limit = limit;
    offsets.start = cursor;
}

UBool HangulJamoTransliterator::decomposeHangul(UChar s, UnicodeString& result) {
    int32_t SIndex = s - SBase;
    if (0 > SIndex || SIndex >= SCount) {
        return FALSE;
    }
    int32_t L = LBase + SIndex / NCount;
    int32_t V = VBase + (SIndex % NCount) / TCount;
    int32_t T = TBase + SIndex % TCount;
    result.truncate(0);
    result.append((UChar)L);
    result.append((UChar)V);
    if (T != TBase) {
        result.append((UChar)T);
    }
    return TRUE;
}