import { type Page } from 'playwright';

export async function extractOpinionPdf(page: Page): Promise<Buffer> {
  const TIMEOUT = 120_000;
  const POLL_INTERVAL = 3_000;

  console.log('[SAT Opinion Scraper] Waiting for PDF to appear...');

  let interceptedPdf: Buffer | null = null;
  page.on('response', async (response) => {
    try {
      const contentType = response.headers()['content-type'] || '';
      if (contentType.includes('application/pdf') || response.url().endsWith('.pdf')) {
        const body = await response.body();
        if (body.length > 100) {
          interceptedPdf = body;
          console.log(`[SAT Opinion Scraper] PDF intercepted via network: ${body.length} bytes`);
        }
      }
    } catch { /* response body may not be available */ }
  });

  const startTime = Date.now();

  while (Date.now() - startTime < TIMEOUT) {
    if (interceptedPdf) return interceptedPdf;

    // Strategy 1: <embed> or <object> with PDF data URI
    const embedData = await page.evaluate(() => {
      for (const el of document.querySelectorAll('embed, object')) {
        const src = el.getAttribute('src') || el.getAttribute('data') || '';
        if (src.startsWith('data:application/pdf;base64,')) return src;
      }
      return null;
    }).catch(() => null);

    if (embedData) {
      console.log('[SAT Opinion Scraper] PDF found via <embed>/<object>');
      return decodeDataUri(embedData);
    }

    // Strategy 2: Scan full HTML for base64 PDF
    const html = await page.content().catch(() => '');
    const match = html.match(/data:application\/pdf;base64,([A-Za-z0-9+/=\s]+)/);
    if (match) {
      console.log('[SAT Opinion Scraper] PDF found via page content scan');
      return decodeDataUri(`data:application/pdf;base64,${match[1]}`);
    }

    // Strategy 3: Check iframes
    for (const frame of page.frames()) {
      try {
        const frameUrl = frame.url();
        if (frameUrl.startsWith('data:application/pdf;base64,')) {
          console.log('[SAT Opinion Scraper] PDF found via iframe URL');
          return decodeDataUri(frameUrl);
        }
        const frameHtml = await frame.content();
        const frameMatch = frameHtml.match(/data:application\/pdf;base64,([A-Za-z0-9+/=\s]+)/);
        if (frameMatch) {
          console.log('[SAT Opinion Scraper] PDF found via iframe content');
          return decodeDataUri(`data:application/pdf;base64,${frameMatch[1]}`);
        }
      } catch { /* cross-origin frame */ }
    }

    // Strategy 4: Page URL itself
    if (page.url().startsWith('data:application/pdf;base64,')) {
      console.log('[SAT Opinion Scraper] PDF found via page URL');
      return decodeDataUri(page.url());
    }

    console.log(`[SAT Opinion Scraper] PDF not found, retrying in ${POLL_INTERVAL / 1000}s...`);
    await page.waitForTimeout(POLL_INTERVAL);
  }

  throw new Error(`PDF not found after ${TIMEOUT / 1000}s`);
}

function decodeDataUri(dataUri: string): Buffer {
  const prefix = 'data:application/pdf;base64,';
  const base64 = dataUri.substring(prefix.length).replace(/\s/g, '');
  return Buffer.from(base64, 'base64');
}