import { mkdir, writeFile } from 'node:fs/promises';
import { resolve } from 'node:path';
import { defaultOutputDir, parsePageSelection } from './parser.js';
import { pdfPageCount, renderPdfPages } from './pdf.js';
import type { PdfScreenshotArtifact, RenderedPage } from './types.js';

export async function renderPdfScreenshots(
  source: string,
  options: { pages?: string; dpi?: number; outputDir?: string } = {},
): Promise<{
  outputDir: string;
  screenshots: PdfScreenshotArtifact[];
  rendered: RenderedPage[];
}> {
  const pageCount = await pdfPageCount(source);
  const selection = parsePageSelection(options.pages, pageCount);
  if (selection.pages.length > 8) {
    throw new Error(
      `pdf_screenshot accepts at most 8 pages per call; ${selection.pages.length} were selected. Narrow pages to the relevant area.`,
    );
  }
  const rendered = await renderPdfPages(source, selection, options.dpi ?? 150);
  const outputDir = resolve(options.outputDir ?? defaultOutputDir(source), 'screenshots');
  await mkdir(outputDir, { recursive: true });
  const screenshots: PdfScreenshotArtifact[] = [];
  for (const page of rendered) {
    const path = resolve(outputDir, `page-${String(page.page).padStart(4, '0')}.png`);
    await writeFile(path, page.png);
    screenshots.push({
      page: page.page,
      width: page.width,
      height: page.height,
      path,
      bytes: page.png.byteLength,
    });
  }
  return { outputDir, screenshots, rendered };
}