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/*
 * Copyright (C) 2016  Alex Yatskov <alex@foosoft.net>
 * Author: Alex Yatskov <alex@foosoft.net>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


function jpIsKanji(c) {
    const code = c.charCodeAt(0);
    return code >= 0x4e00 && code < 0x9fb0 || code >= 0x3400 && code < 0x4dc0;
}

function jpIsKana(c) {
    return wanakana.isKana(c);
}

function jpKatakanaToHiragana(text) {
    let result = '';
    for (const c of text) {
        if (wanakana.isKatakana(c)) {
            result += wanakana.toHiragana(c);
        } else {
            result += c;
        }
    }

    return result;
}

function distributeFurigana(word, reading) {
    reading = reading || wanakana.toHiragana(word);
    function span(str, pred) {
        let i = 0;
        while (i < str.length && pred(str[i])) {
            i++;
        }
        return [str.substring(0, i), str.substring(i)];
    }
    const isKanji = c => jpIsKanji(c) ||
        c === '\u3005'; /* kurikaeshi */
    const isKana = c => jpIsKana(c) ||
        c === '\u30fc'; /* chouonpu */
    function parse(word) {
        const res = [];
        while (word.length > 0) {
            const c = word.charAt(0);
            if (isKana(c)) {
                const [text, rest] = span(word, isKana);
                res.push({ type: 'kana', text });
                word = rest;
            } else if (isKanji(c)) {
                const [text, rest] = span(word, isKanji);
                res.push({ type: 'kanji', text });
                word = rest;
            } else return null;
        }
        return res;
    }

    const fallback = () => [{ text: word, furigana: reading }];
    const parts = parse(word);
    if (!parts) return fallback();
    let parti = 0;
    let readingi = 0;
    const res = [];
    let current = null;
    function backtrack() {
        parti--;
        const prev = res.pop();
        current = prev.furigana;
    }
    while (parti < parts.length) {
        const part = parts[parti];
        switch (part.type) {
            case 'kana':
                if (reading.startsWith(wanakana.toHiragana(part.text), readingi)) {
                    if (parti === parts.length - 1 && readingi !== reading.length - part.text.length) {
                        backtrack();
                    } else {
                        readingi += part.text.length;
                        res.push({ text: part.text });
                        parti++;
                    }
                } else backtrack();
                break;
            case 'kanji':
                current = current || '';
                if (parti === parts.length - 1) {
                    // last part, consume all
                    current += reading.substring(readingi);
                } else {
                    const nextText = parts[parti + 1].text;
                    const end = reading.indexOf(nextText, readingi + 1); // consume at least one character
                    if (end === -1) {
                        return fallback();
                    }
                    current += reading.substring(readingi, end);
                    readingi = end;
                }
                res.push({ text: part.text, furigana: current });
                current = null;
                parti++;
        }
    }
    return res;
}