import html2canvas from "html2canvas";
import { jsPDF } from "jspdf";

const fontFile = "Vazirmatn-Regular.ttf";
const fontFamily = "VazirmatnReceipt";
const pageMargin = 24;
const pdfCaptureScale = 3;
const jpegQuality = 0.94;
const ignoredReceiptControls = ".registration-copy-reference, .registration-event-details-link";
const omittedReceiptContent = `${ignoredReceiptControls}, [data-receipt-status-badge], [data-receipt-reference]`;

function toBase64(buffer: ArrayBuffer) {
  const bytes = new Uint8Array(buffer);
  let binary = "";
  for (let offset = 0; offset < bytes.length; offset += 0x8000) {
    binary += String.fromCharCode(...bytes.subarray(offset, offset + 0x8000));
  }
  return window.btoa(binary);
}

function toUtf16Hex(value: string) {
  let result = "FEFF";
  for (let index = 0; index < value.length; index += 1) {
    result += value.charCodeAt(index).toString(16).padStart(4, "0");
  }
  return result.toUpperCase();
}

async function addSelectableTextLayer(
  pdf: jsPDF,
  element: HTMLElement,
  canvas: HTMLCanvasElement,
  image: { x: number; y: number; scale: number },
) {
  const response = await fetch(`/fonts/${fontFile}`, { cache: "force-cache" });
  if (!response.ok) throw new Error("فونت رسید بارگذاری نشد.");
  const base64 = toBase64(await response.arrayBuffer());
  pdf.addFileToVFS(fontFile, base64);
  pdf.addFont(fontFile, fontFamily, "normal");
  pdf.setFont(fontFamily, "normal");
  pdf.setR2L(false);
  (pdf as unknown as { __private__: { setPdfVersion: (version: string) => void } }).__private__.setPdfVersion("1.4");

  const rootRect = element.getBoundingClientRect();
  const captureScale = canvas.width / rootRect.width;
  const walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT);
  let node: Node | null = walker.nextNode();
  const write = (pdf.internal as unknown as { write: (value: string) => void }).write;

  while (node) {
    const textNode = node as Text;
    const parent = textNode.parentElement;
    const value = textNode.nodeValue ?? "";
    if (
      parent
      && value.trim()
      && !parent.closest(`${omittedReceiptContent}, button, svg, [aria-hidden="true"]`)
      && getComputedStyle(parent).display !== "none"
      && getComputedStyle(parent).visibility !== "hidden"
    ) {
      const words = value.matchAll(/\S+/gu);
      for (const match of words) {
        const word = match[0];
        const offset = match.index;
        if (!word) continue;
        const range = document.createRange();
        range.setStart(textNode, offset);
        range.setEnd(textNode, offset + word.length);
        const rect = range.getBoundingClientRect();
        if (!rect.width || !rect.height) continue;

        const computedStyle = getComputedStyle(parent);
        const fontSize = Number.parseFloat(computedStyle.fontSize) || 14;
        const x = image.x + (rect.left - rootRect.left) * captureScale * image.scale;
        const y = image.y + (rect.bottom - rootRect.top) * captureScale * image.scale;
        const pdfFontSize = Math.max(4, fontSize * 0.75 * captureScale * image.scale);
        const following = value.slice(offset + word.length, offset + word.length + 1);
        const actualText = `${word}${following && /\s/u.test(following) ? " " : ""}`;

        // The page image keeps the original visual layout; this invisible layer preserves selectable Unicode text.
        write(`/Span << /ActualText <${toUtf16Hex(actualText)}> >> BDC`);
        pdf.setFontSize(pdfFontSize);
        pdf.text(word, x, y, { align: "left", renderingMode: "invisible" });
        write("EMC");
      }
    }
    node = walker.nextNode();
  }
}

async function prepareReceiptImage(image: HTMLImageElement) {
  const source = image.currentSrc || image.src;
  if (!source) return;

  const parsedSource = new URL(source, window.location.href);
  if (!["http:", "https:"].includes(parsedSource.protocol)) {
    await image.decode();
    return;
  }

  image.removeAttribute("srcset");
  const encodeForReceipt = async (imageBlob: Blob) => {
    if (!imageBlob.type.startsWith("image/")) throw new Error("پاسخ تصویر رویداد معتبر نیست.");
    const bitmap = await createImageBitmap(imageBlob);
    const resize = Math.min(1, 640 / Math.max(bitmap.width, bitmap.height));
    const canvas = document.createElement("canvas");
    canvas.width = Math.max(1, Math.round(bitmap.width * resize));
    canvas.height = Math.max(1, Math.round(bitmap.height * resize));
    const context = canvas.getContext("2d");
    if (!context) {
      bitmap.close();
      throw new Error("آماده‌سازی تصویر رویداد برای رسید انجام نشد.");
    }

    context.fillStyle = "#ffffff";
    context.fillRect(0, 0, canvas.width, canvas.height);
    context.drawImage(bitmap, 0, 0, canvas.width, canvas.height);
    bitmap.close();
    return canvas.toDataURL("image/jpeg", 0.88);
  };

  try {
    const response = await fetch(parsedSource.href, {
      mode: "cors",
      credentials: parsedSource.origin === window.location.origin ? "same-origin" : "omit",
    });
    if (!response.ok) throw new Error("تصویر رویداد برای رسید بارگذاری نشد.");
    image.src = await encodeForReceipt(await response.blob());
  } catch {
    if (parsedSource.origin === window.location.origin) {
      throw new Error("تصویر رویداد برای رسید بارگذاری نشد.");
    }

    const optimizedUrl = new URL("/_next/image", window.location.origin);
    optimizedUrl.searchParams.set("url", parsedSource.href);
    optimizedUrl.searchParams.set("w", "640");
    optimizedUrl.searchParams.set("q", "75");
    const response = await fetch(optimizedUrl, { credentials: "same-origin" });
    if (!response.ok) throw new Error("تصویر رویداد برای رسید بارگذاری نشد.");
    image.src = await encodeForReceipt(await response.blob());
  }

  await image.decode();
}

export async function downloadRegistrationReceipt(element: HTMLElement, fileName: string) {
  await document.fonts.ready;

  const canvas = await html2canvas(element, {
    scale: pdfCaptureScale,
    useCORS: true,
    allowTaint: false,
    backgroundColor: "#ffffff",
    onclone: async (documentClone, clonedElement) => {
      documentClone.documentElement.classList.remove("dark");
      clonedElement.querySelectorAll(omittedReceiptContent).forEach((control) => control.remove());

      const receiptHeader = clonedElement.querySelector("header");
      if (receiptHeader) {
        receiptHeader.style.alignItems = "start";
        const headerText = receiptHeader.firstElementChild as HTMLElement | null;
        if (headerText) headerText.style.alignSelf = "start";
      }

      const eventCard = clonedElement.querySelector("section h2")?.closest("section");
      if (eventCard) {
        (eventCard as HTMLElement).style.alignItems = "start";
        const eventText = eventCard.firstElementChild as HTMLElement | null;
        if (eventText) eventText.style.alignSelf = "start";
      }

      const images = Array.from(clonedElement.querySelectorAll("img"));
      await Promise.all(images.map(prepareReceiptImage));
    },
  });

  const pdf = new jsPDF({
    orientation: "portrait",
    unit: "pt",
    format: "a4",
    compress: true,
    putOnlyUsedFonts: true,
  });
  const pageWidth = pdf.internal.pageSize.getWidth();
  const pageHeight = pdf.internal.pageSize.getHeight();
  const scale = Math.min(
    (pageWidth - pageMargin * 2) / canvas.width,
    (pageHeight - pageMargin * 2) / canvas.height,
  );
  const width = canvas.width * scale;
  const height = canvas.height * scale;
  const x = (pageWidth - width) / 2;
  const y = pageMargin;
  const compressedImage = canvas.toDataURL("image/jpeg", jpegQuality);

  pdf.setFillColor(255, 255, 255);
  pdf.rect(0, 0, pageWidth, pageHeight, "F");
  pdf.addImage(compressedImage, "JPEG", x, y, width, height, undefined, "FAST");
  await addSelectableTextLayer(pdf, element, canvas, { x, y, scale });
  pdf.setProperties({ title: "رسید ثبت‌نام رویداد", subject: "رسید ثبت‌نام", creator: "سامانهٔ انجمن" });
  pdf.save(fileName);
}