/**
 * exportPng.ts
 * Renders each slide to a PNG at 1080x1080 using Puppeteer.
 * Returns an array of file paths for the generated PNGs.
 */

import fs from 'fs';
import path from 'path';

import type { SlideContent } from '../schema/carouselSchema';
import type { Theme } from '../render/themes';
import { renderSlideToHtml } from '../render/renderSlides';

/**
 * Export all slides to individual PNG files.
 * Creates the outputDir/slides_preview/ subdirectory.
 *
 * @param slides     - Ordered array of SlideContent objects
 * @param theme      - Visual theme
 * @param outputDir  - Base output directory (e.g. "output/job-carousel")
 * @returns          - Array of absolute file paths to generated PNGs
 */
export async function exportToPngs(
  slides: SlideContent[],
  theme: Theme,
  outputDir: string
): Promise<string[]> {
  // Lazy-import puppeteer to avoid hard crash if not installed
  let puppeteer: typeof import('puppeteer');
  try {
    puppeteer = await import('puppeteer');
  } catch (err) {
    throw new Error(
      'Puppeteer is not installed. Run: npm install puppeteer\n' +
      'If you cannot install it, use --no-render to skip PNG/PDF export.'
    );
  }

  const previewDir = path.join(outputDir, 'slides_preview');
  fs.mkdirSync(previewDir, { recursive: true });

  const browser = await puppeteer.launch({
    headless: true,
    args: [
      '--no-sandbox',
      '--disable-setuid-sandbox',
      '--disable-dev-shm-usage',
      '--font-render-hinting=none',
    ],
  });

  const pngPaths: string[] = [];

  try {
    const page = await browser.newPage();
    await page.setViewport({ width: 1080, height: 1080, deviceScaleFactor: 2 });

    for (let i = 0; i < slides.length; i++) {
      const slide = slides[i];
      const html = renderSlideToHtml(slide, theme, i);

      // Load HTML content directly (no file write needed for rendering)
      await page.setContent(html, {
        waitUntil: 'networkidle0', // Wait for Google Fonts to load
        timeout: 30000,
      });

      // Give fonts a moment to render (belt-and-suspenders)
      await page.evaluate(() => document.fonts.ready);

      const filename = `slide_${String(i + 1).padStart(2, '0')}.png`;
      const filepath = path.join(previewDir, filename);

      await page.screenshot({
        path: filepath as `${string}.png`,
        type: 'png',
        clip: { x: 0, y: 0, width: 1080, height: 1080 },
        omitBackground: false,
      });

      pngPaths.push(filepath);
      console.log(`  ✓ Exported: ${filename}`);
    }
  } finally {
    await browser.close();
  }

  return pngPaths;
}