import { showToast } from "./toast";

function getToken(): string {
  return localStorage.getItem("token") || "";
}

export async function generateCoverBlob(
  fileUrl: string,
  formatGroup: string,
): Promise<Blob | null> {
  try {
    const View = (await import("foliate-js/view.js")).default;
    const view = new View();

    const resp = await fetch(fileUrl, {
      headers: { Authorization: `Bearer ${getToken()}` },
    });
    if (!resp.ok) {
      showToast("Failed to fetch book file for cover generation", "error");
      return null;
    }

    const blob = await resp.blob();
    const file = new File([blob], "book", { type: blob.type });

    const pdfOptions =
      formatGroup === "fixed_layout"
        ? {
            pdf: {
              cMapUrl: "/static/vendor/pdfjs/cmaps/",
              standardFontDataUrl: "/static/vendor/pdfjs/standard_fonts/",
            },
          }
        : {};

    await view.open(file, pdfOptions);

    if (!view.book?.sections?.length) {
      showToast("Could not read book sections", "error");
      return null;
    }

    if (formatGroup === "fixed_layout") {
      const canvas = document.createElement("canvas");
      await view.renderer?.renderPage(view.book.sections[0], canvas);
      return new Promise((resolve) => {
        canvas.toBlob(
          (b) => resolve(b),
          "image/jpeg",
          0.85,
        );
      });
    }

    const coverHref = view.book.cover;
    if (coverHref) {
      const coverBlob = await coverHref.blob();
      if (coverBlob.type.startsWith("image/")) {
        return coverBlob;
      }
      return new Promise((resolve) => {
        const img = new Image();
        img.onload = () => {
          const c = document.createElement("canvas");
          c.width = img.naturalWidth;
          c.height = img.naturalHeight;
          c.getContext("2d")?.drawImage(img, 0, 0);
          c.toBlob((b) => resolve(b), "image/jpeg", 0.85);
        };
        img.onerror = () => resolve(null);
        img.src = URL.createObjectURL(coverBlob);
      });
    }

    showToast("No cover found in book file", "error");
    return null;
  } catch (e) {
    console.error("Cover generation failed:", e);
    showToast("Cover generation failed", "error");
    return null;
  }
}