forked from akai/readest
Huang Xin
454 lines
14 KiB
TypeScript
454 lines
14 KiB
TypeScript
import { getBaseFilename } from './book';
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import { partialMD5 } from './md5';
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interface Metadata {
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bookTitle: string;
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author: string;
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language: string;
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identifier: string;
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}
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interface Chapter {
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title: string;
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content: string;
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}
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interface Txt2EpubOptions {
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file: File;
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author?: string;
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language?: string;
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}
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interface ExtractChapterOptions {
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linesBetweenSegments: number;
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fallbackParagraphsPerChapter: number;
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}
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interface ConversionResult {
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file: File;
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bookTitle: string;
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chapterCount: number;
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language: string;
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}
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const zipWriteOptions = {
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lastAccessDate: new Date(0),
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lastModDate: new Date(0),
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};
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const escapeXml = (str: string) => {
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if (!str) return '';
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return str
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.replace(/&/g, '&')
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.replace(/</g, '<')
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.replace(/>/g, '>')
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.replace(/"/g, '"')
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.replace(/'/g, ''');
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};
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export class TxtToEpubConverter {
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public async convert(options: Txt2EpubOptions): Promise<ConversionResult> {
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const { file: txtFile, author: providedAuthor, language: providedLanguage } = options;
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const fileContent = await txtFile.arrayBuffer();
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const detectedEncoding = this.detectEncoding(fileContent) || 'utf-8';
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const decoder = new TextDecoder(detectedEncoding);
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const txtContent = decoder.decode(fileContent).trim();
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const bookTitle = this.extractBookTitle(getBaseFilename(txtFile.name));
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const fileName = `${bookTitle}.epub`;
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const fileHeader = txtContent.slice(0, 1024);
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const authorMatch =
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fileHeader.match(/[【\[]?作者[】\]]?[:：\s]\s*(.+)\r?\n/) ||
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fileHeader.match(/[【\[]?\s*(.+)\s+著\s*[】\]]?\r?\n/);
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let matchedAuthor = authorMatch ? authorMatch[1]!.trim() : providedAuthor || '';
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try {
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matchedAuthor = matchedAuthor.replace(/^[\p{P}\p{S}]+|[\p{P}\p{S}]+$/gu, '');
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} catch {}
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const author = matchedAuthor || providedAuthor || '';
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const language = providedLanguage || this.detectLanguage(fileHeader);
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const identifier = await partialMD5(txtFile);
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const metadata = { bookTitle, author, language, identifier };
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let chapters: Chapter[] = [];
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for (let i = 8; i >= 6; i--) {
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chapters = this.extractChapters(txtContent, metadata, {
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linesBetweenSegments: i,
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fallbackParagraphsPerChapter: 100,
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});
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if (chapters.length === 0) {
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throw new Error('No chapters detected.');
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} else if (chapters.length > 1) {
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break;
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}
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}
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const blob = await this.createEpub(chapters, metadata);
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return {
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file: new File([blob], fileName),
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bookTitle,
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chapterCount: chapters.length,
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language,
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};
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}
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private extractChapters(
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txtContent: string,
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metadata: Metadata,
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option: ExtractChapterOptions,
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): Chapter[] {
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const { language } = metadata;
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const { linesBetweenSegments, fallbackParagraphsPerChapter } = option;
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const segmentRegex = new RegExp(`(?:\\r?\\n){${linesBetweenSegments},}|-{8,}\r?\n`);
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const chapterRegexps: RegExp[] = [];
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if (language === 'zh') {
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chapterRegexps.push(
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new RegExp(
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String.raw`(?:^|\n)\s*` +
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'(' +
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[
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String.raw`第[零〇一二三四五六七八九十0-9][零〇一二三四五六七八九十百千万0-9]*(?:[章卷节回讲篇封])(?:[：:、 \(\)0-9]*[^\n-]{0,24})(?!\S)`,
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String.raw`(?:楔子|前言|简介|引言|序言|序章|总论|概论)(?:[：: ][^\n-]{0,24})?(?!\S)`,
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].join('|') +
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')',
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'gu',
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),
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);
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chapterRegexps.push(
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new RegExp(
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String.raw`(?:^|\n)\s*` +
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'(' +
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[
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String.raw`[一二三四五六七八九十][零〇一二三四五六七八九十百千万]?[：:、 ][^\n-]{0,24}(?=\n|$)`,
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String.raw`[0-9]+[^\n]{0,16}(?=\n|$)`,
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].join('|') +
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')',
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'gu',
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),
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);
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} else {
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chapterRegexps.push(
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/(?:^|\n|\s)(?:(Chapter|Part)\s+(\d+|[IVXLCDM]+)(?:[:.\-–—]?\s+[^\n]*)?|(?:Prologue|Epilogue|Introduction|Foreword)(?:[:.\-–—]?\s+[^\n]*)?)(?=\s|$)/gi,
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);
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}
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const formatSegment = (segment: string): string => {
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segment = escapeXml(segment);
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return segment
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.replace(/-{8,}|_{8,}/g, '\n')
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.split(/\n+/)
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.map((line) => line.trim())
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.filter((line) => line)
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.join('</p><p>');
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};
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const joinAroundUndefined = (arr: (string | undefined)[]) =>
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arr.reduce<string[]>((acc, curr, i, src) => {
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if (
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curr === undefined &&
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i > 0 &&
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i < src.length - 1 &&
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src[i - 1] !== undefined &&
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src[i + 1] !== undefined
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) {
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acc[acc.length - 1] += src[i + 1]!;
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return acc;
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}
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if (curr !== undefined && (i === 0 || src[i - 1] !== undefined)) {
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acc.push(curr);
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}
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return acc;
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}, []);
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const isGoodMatches = (matches: string[], maxLength: number = 100000): boolean => {
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const meaningfulParts = matches.filter((part) => part.trim().length > 0);
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if (meaningfulParts.length <= 1) return false;
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const hasLongParts = meaningfulParts.some((part) => part.length > maxLength);
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return !hasLongParts;
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};
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const chapters: Chapter[] = [];
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const segments = txtContent.split(segmentRegex);
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for (const segment of segments) {
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const trimmedSegment = segment.replace(/<!--.*?-->/g, '').trim();
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if (!trimmedSegment) continue;
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const segmentChapters = [];
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let matches: string[] = [];
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for (const chapterRegex of chapterRegexps) {
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const tryMatches = trimmedSegment.split(chapterRegex);
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if (isGoodMatches(tryMatches)) {
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matches = joinAroundUndefined(tryMatches);
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break;
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}
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}
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if (matches.length === 0 && fallbackParagraphsPerChapter > 0) {
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const paragraphs = trimmedSegment.split(/\n+/);
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const totalParagraphs = paragraphs.length;
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for (let i = 0; i < totalParagraphs; i += fallbackParagraphsPerChapter) {
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const chunks = paragraphs.slice(i, i + fallbackParagraphsPerChapter);
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const formattedSegment = formatSegment(chunks.join('\n'));
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const title = `${chapters.length + 1}`;
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const content = `<h2>${title}</h2><p>${formattedSegment}</p>`;
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chapters.push({ title, content });
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}
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continue;
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}
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for (let j = 1; j < matches.length; j += 2) {
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const title = matches[j]?.trim() || '';
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const content = matches[j + 1]?.trim() || '';
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let isVolume = false;
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if (language === 'zh') {
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isVolume = /第[零〇一二三四五六七八九十百千万0-9]+卷/.test(title);
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} else {
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isVolume = /\b(Part|Volume|Book)\b/i.test(title);
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}
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const headTitle = isVolume ? `<h1>${title}</h1>` : `<h2>${title}</h2>`;
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const formattedSegment = formatSegment(content);
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segmentChapters.push({
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title: escapeXml(title),
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content: `${headTitle}<p>${formattedSegment}</p>`,
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});
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}
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if (matches[0] && matches[0].trim()) {
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const initialContent = matches[0].trim();
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const firstLine = initialContent.split('\n')[0]!.trim();
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const segmentTitle =
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(firstLine.length > 16 ? initialContent.split(/[\n\s\p{P}]/u)[0]!.trim() : firstLine) ||
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initialContent.slice(0, 16);
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const formattedSegment = formatSegment(initialContent);
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segmentChapters.unshift({
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title: escapeXml(segmentTitle),
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content: `<h3></h3><p>${formattedSegment}</p>`,
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});
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}
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chapters.push(...segmentChapters);
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}
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return chapters;
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}
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private async createEpub(chapters: Chapter[], metadata: Metadata): Promise<Blob> {
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const { BlobWriter, TextReader, ZipWriter } = await import('@zip.js/zip.js');
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const { bookTitle, author, language, identifier } = metadata;
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const zipWriter = new ZipWriter(new BlobWriter('application/epub+zip'), {
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extendedTimestamp: false,
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});
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await zipWriter.add('mimetype', new TextReader('application/epub+zip'), zipWriteOptions);
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// Add META-INF/container.xml
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const containerXml = `<?xml version="1.0" encoding="UTF-8"?>
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<container xmlns="urn:oasis:names:tc:opendocument:xmlns:container" version="1.0">
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<rootfiles>
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<rootfile full-path="content.opf" media-type="application/oebps-package+xml"/>
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</rootfiles>
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</container>`.trim();
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await zipWriter.add('META-INF/container.xml', new TextReader(containerXml), zipWriteOptions);
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// Create navigation points for TOC
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const navPoints = chapters
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.map((chapter, index) => {
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const id = `chapter${index + 1}`;
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const playOrder = index + 1;
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return `
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<navPoint id="navPoint-${id}" playOrder="${playOrder}">
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<navLabel>
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<text>${chapter.title}</text>
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</navLabel>
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<content src="./OEBPS/${id}.xhtml" />
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</navPoint>
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`.trim();
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})
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.join('\n');
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// Add NCX file (table of contents)
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const tocNcx = `<?xml version="1.0" encoding="UTF-8"?>
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<ncx xmlns="http://www.daisy.org/z3986/2005/ncx/" version="2005-1">
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<head>
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<meta name="dtb:uid" content="book-id" />
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<meta name="dtb:depth" content="1" />
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<meta name="dtb:totalPageCount" content="0" />
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<meta name="dtb:maxPageNumber" content="0" />
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</head>
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<docTitle>
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<text>${escapeXml(bookTitle)}</text>
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</docTitle>
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<docAuthor>
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<text>${escapeXml(author)}</text>
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</docAuthor>
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<navMap>
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${navPoints}
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</navMap>
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</ncx>`.trim();
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await zipWriter.add('toc.ncx', new TextReader(tocNcx), zipWriteOptions);
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// Create manifest and spine items
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const manifest = chapters
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.map(
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(_, index) => `
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<item id="chap${index + 1}" href="OEBPS/chapter${index + 1}.xhtml" media-type="application/xhtml+xml"/>
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`,
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)
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.join('\n')
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.trim();
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const spine = chapters
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.map(
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(_, index) => `
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<itemref idref="chap${index + 1}"/>`,
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)
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.join('\n')
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.trim();
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// Add CSS stylesheet
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const css = `
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body { line-height: 1.6; font-size: 1em; font-family: 'Arial', sans-serif; text-align: justify; }
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p { text-indent: 2em; margin: 0; }
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`;
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await zipWriter.add('style.css', new TextReader(css), zipWriteOptions);
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// Add chapter files
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for (let i = 0; i < chapters.length; i++) {
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const chapter = chapters[i]!;
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const chapterContent = `<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="zh">
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<head>
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<title>${chapter.title}</title>
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<link rel="stylesheet" type="text/css" href="../style.css"/>
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</head>
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<body>${chapter.content}</body>
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</html>`.trim();
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await zipWriter.add(
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`OEBPS/chapter${i + 1}.xhtml`,
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new TextReader(chapterContent),
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zipWriteOptions,
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);
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}
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const tocManifest = `<item id="ncx" href="toc.ncx" media-type="application/x-dtbncx+xml"/>`;
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// Add content.opf file
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const contentOpf = `<?xml version="1.0" encoding="UTF-8"?>
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<package xmlns="http://www.idpf.org/2007/opf" unique-identifier="book-id" version="2.0">
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<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
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<dc:title>${escapeXml(bookTitle)}</dc:title>
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<dc:language>${language}</dc:language>
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<dc:creator>${escapeXml(author)}</dc:creator>
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<dc:identifier id="book-id">${identifier}</dc:identifier>
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</metadata>
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<manifest>
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${manifest}
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${tocManifest}
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</manifest>
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<spine toc="ncx">
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${spine}
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</spine>
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</package>`.trim();
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await zipWriter.add('content.opf', new TextReader(contentOpf), zipWriteOptions);
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return await zipWriter.close();
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}
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private detectEncoding(buffer: ArrayBuffer): string | undefined {
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try {
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new TextDecoder('utf-8', { fatal: true }).decode(buffer);
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return 'utf-8';
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} catch {
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// If UTF-8 decoding fails, try to detect other encodings
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}
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const headerBytes = new Uint8Array(buffer.slice(0, 4));
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if (headerBytes[0] === 0xff && headerBytes[1] === 0xfe) {
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return 'utf-16le';
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}
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if (headerBytes[0] === 0xfe && headerBytes[1] === 0xff) {
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return 'utf-16be';
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}
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if (headerBytes[0] === 0xef && headerBytes[1] === 0xbb && headerBytes[2] === 0xbf) {
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return 'utf-8';
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}
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// Analyze a sample of the content to guess between common East Asian encodings
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// If the content has a high ratio of bytes in the 0x80-0xFF range, it's likely GBK/GB18030
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const sample = new Uint8Array(buffer.slice(0, Math.min(1024, buffer.byteLength)));
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let highByteCount = 0;
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for (let i = 0; i < sample.length; i++) {
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if (sample[i]! >= 0x80) {
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highByteCount++;
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}
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}
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const highByteRatio = highByteCount / sample.length;
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if (highByteRatio > 0.3) {
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return 'gbk';
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}
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if (highByteRatio > 0.1) {
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let sjisPattern = false;
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for (let i = 0; i < sample.length - 1; i++) {
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const b1 = sample[i]!;
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const b2 = sample[i + 1]!;
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if (
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((b1 >= 0x81 && b1 <= 0x9f) || (b1 >= 0xe0 && b1 <= 0xfc)) &&
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((b2 >= 0x40 && b2 <= 0x7e) || (b2 >= 0x80 && b2 <= 0xfc))
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) {
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sjisPattern = true;
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break;
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}
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}
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if (sjisPattern) {
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return 'shift-jis';
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}
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return 'gb18030';
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}
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return 'utf-8';
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}
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private detectLanguage(fileHeader: string): string {
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const sample = fileHeader;
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let chineseCount = 0;
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for (let i = 0; i < sample.length; i++) {
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const code = sample.charCodeAt(i);
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if (
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(code >= 0x4e00 && code <= 0x9fff) ||
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(code >= 0x3400 && code <= 0x4dbf) ||
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(code >= 0x20000 && code <= 0x2a6df)
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) {
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chineseCount++;
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}
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}
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if (chineseCount / sample.length > 0.05) {
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return 'zh';
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}
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return 'en';
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}
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private extractBookTitle(filename: string): string {
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const match = filename.match(/《([^》]+)》/);
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return match ? match[1]! : filename.split('.')[0]!;
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}
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}
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