import { PdfFile, PdfPage } from '../types/drawing.ts'
import * as PDFJS from 'pdfjs-dist'
PDFJS.GlobalWorkerOptions.workerSrc = 'node_modules/pdfjs-dist/build/pdf.worker.mjs';

const toFile = (arrayBuffer: ArrayBuffer, fileName: string) : File => {
  const blob = new Blob([arrayBuffer], { type: "application/pdf" });
  return new File([blob], fileName, { type: "application/pdf" });
}

const toPdfFile = async (file: File): Promise<PdfFile> => {
  const data = await readPdf(file)
  const pages = await pdfToImages(data)
  return { file, pages, expanded: false }
}

const toPdfFiles = async (selectedFiles: File[]): Promise<PdfFile[]> => {
  return Promise.all(
    selectedFiles
      .filter(isPdf)
      .map(toPdfFile));
}

const inPx = (coordinate: number): string => `${coordinate}px`;

const isPdf = (file: File) => file.type.toLowerCase().includes('pdf');

/**
 * Reads the pdf file binaries
 */
const readPdf = (file: File) => {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();

    reader.onload = (e: any) => {
      const data = e.target.result

      resolve(data)
    };

    reader.onerror = (err) => {
      console.error('err', err)
      reject(err)
    };

    reader.readAsDataURL(file);
  })
}

/**
 * Converts pdf to the images
 * @param data pdf file bytes
 */
const pdfToImages = async (data: any): Promise<PdfPage[]> => {
  const images: string[] = [];
  const pdf = await PDFJS.getDocument(data).promise;
  const canvas = document.createElement("canvas");

  for (let i = 0; i < pdf.numPages; i++) {
    const page = await pdf.getPage(i + 1);
    const viewport = page.getViewport({ scale: 3 });
    const context = canvas.getContext("2d");
    canvas.height = viewport.height;
    canvas.width = viewport.width;
    await page.render({ canvasContext: context!, viewport: viewport }).promise;
    images.push(canvas.toDataURL());
  }

  return Promise.resolve(images.map((image) => {
    return {
      image,
      drawnFields: []
    }
  }))
}

export {
  toFile,
  toPdfFile,
  toPdfFiles,
  inPx
}