import puppeteer from 'puppeteer';

import { PDFDocument } from 'pdf-lib';

import * as fs from 'fs';

import * as path from 'path';

import { measureChapterPages, buildTocHtml } from './toc';

import { buildHtml } from './template';

import type { Chapter } from './chapters';

const PAGE_W = '6in';

const PAGE_H = '9in';

const MARGINS = {

top: '0.875in',

right: '0.75in',

bottom: '1in',

left: '0.875in',

const FOOTER = `

async function renderHtmlToPdfBytes(

page: Awaited<ReturnType<Awaited<ReturnType<typeof puppeteer.launch>>['newPage']>>,

html: string,

options: Parameters<typeof page.pdf>[0]

): Promise<Buffer> {

await page.setContent(html, { waitUntil: 'load' });

return page.pdf(options) as Promise<Buffer>;

export async function generatePdf(

chapters: Chapter[],

coverImagePath: string | undefined,

outputPath: string

): Promise<void> {

const outputDir = path.dirname(outputPath);

if (!fs.existsSync(outputDir)) {

fs.mkdirSync(outputDir, { recursive: true });

}

const browser = await puppeteer.launch({ headless: true });

try {

const tab = await browser.newPage();

// -- Pass 1: measure chapter positions to build TOC --

const baseHtml = buildHtml(chapters);

const tocEntries = await measureChapterPages(tab, baseHtml);

const tocHtml = buildTocHtml(tocEntries);

// -- Pass 2: final content HTML with TOC injected --

const contentHtml = buildHtml(chapters, tocHtml);

// -- Content PDF (title page + TOC + chapters, normal margins) --

const contentBytes = await renderHtmlToPdfBytes(tab, contentHtml, {

width: PAGE_W,

height: PAGE_H,

printBackground: true,

displayHeaderFooter: true,

headerTemplate: '

',

footerTemplate: FOOTER,

margin: MARGINS,

});

// -- If no cover image, write content PDF directly --

if (!coverImagePath || !fs.existsSync(coverImagePath)) {

fs.writeFileSync(outputPath, contentBytes);

return;

}

// -- Cover PDF (zero margins, no footer) --

const base64 = fs.readFileSync(coverImagePath).toString('base64');

const coverHtml = `

const coverBytes = await renderHtmlToPdfBytes(tab, coverHtml, {

width: PAGE_W,

height: PAGE_H,

printBackground: true,

displayHeaderFooter: false,

margin: { top: '0', right: '0', bottom: '0', left: '0' },

});

// -- Merge: cover (page 1) + content (remaining pages) --

const merged = await PDFDocument.create();

const coverDoc = await PDFDocument.load(coverBytes);

const [coverPage] = await merged.copyPages(coverDoc, [0]);

merged.addPage(coverPage);

const contentDoc = await PDFDocument.load(contentBytes);

const contentPages = await merged.copyPages(

contentDoc,

Array.from({ length: contentDoc.getPageCount() }, (_, i) => i)

);

contentPages.forEach((p) => merged.addPage(p));

fs.writeFileSync(outputPath, await merged.save());

} finally {

await browser.close();

}