let cpdfLoaded = false;

function loadCpdf(cpdfUrl) {
  if (cpdfLoaded) return Promise.resolve();

  return new Promise((resolve, reject) => {
    if (typeof coherentpdf !== 'undefined') {
      cpdfLoaded = true;
      resolve();
      return;
    }

    try {
      self.importScripts(cpdfUrl);
      cpdfLoaded = true;
      resolve();
    } catch (error) {
      reject(new Error('Failed to load CoherentPDF: ' + error.message));
    }
  });
}

function getAttachmentsFromPDFInWorker(fileBuffer, fileName) {
  try {
    const uint8Array = new Uint8Array(fileBuffer);

    let pdf;
    try {
      pdf = coherentpdf.fromMemory(uint8Array, '');
    } catch (error) {
      self.postMessage({
        status: 'error',
        message: `Failed to load PDF: ${fileName}. Error: ${error.message || error}`,
      });
      return;
    }

    coherentpdf.startGetAttachments(pdf);
    const attachmentCount = coherentpdf.numberGetAttachments();

    if (attachmentCount === 0) {
      self.postMessage({
        status: 'success',
        attachments: [],
        fileName: fileName,
      });
      coherentpdf.deletePdf(pdf);
      return;
    }

    const attachments = [];
    for (let i = 0; i < attachmentCount; i++) {
      try {
        const name = coherentpdf.getAttachmentName(i);
        const page = coherentpdf.getAttachmentPage(i);
        const attachmentData = coherentpdf.getAttachmentData(i);

        const dataArray = new Uint8Array(attachmentData);
        const buffer = dataArray.buffer.slice(
          dataArray.byteOffset,
          dataArray.byteOffset + dataArray.byteLength
        );

        attachments.push({
          index: i,
          name: String(name),
          page: Number(page),
          data: buffer,
        });
      } catch (error) {
        console.warn(`Failed to get attachment ${i} from ${fileName}:`, error);
      }
    }

    coherentpdf.endGetAttachments();
    coherentpdf.deletePdf(pdf);

    const response = {
      status: 'success',
      attachments: attachments,
      fileName: fileName,
    };

    const transferBuffers = attachments.map((att) => att.data);
    self.postMessage(response, transferBuffers);
  } catch (error) {
    self.postMessage({
      status: 'error',
      message:
        error instanceof Error
          ? error.message
          : 'Unknown error occurred during attachment listing.',
    });
  }
}

function editAttachmentsInPDFInWorker(
  fileBuffer,
  fileName,
  attachmentsToRemove
) {
  try {
    const uint8Array = new Uint8Array(fileBuffer);

    let pdf;
    try {
      pdf = coherentpdf.fromMemory(uint8Array, '');
    } catch (error) {
      self.postMessage({
        status: 'error',
        message: `Failed to load PDF: ${fileName}. Error: ${error.message || error}`,
      });
      return;
    }

    if (attachmentsToRemove && attachmentsToRemove.length > 0) {
      coherentpdf.startGetAttachments(pdf);
      const attachmentCount = coherentpdf.numberGetAttachments();
      const attachmentsToKeep = [];

      for (let i = 0; i < attachmentCount; i++) {
        if (!attachmentsToRemove.includes(i)) {
          const name = coherentpdf.getAttachmentName(i);
          const page = coherentpdf.getAttachmentPage(i);
          const data = coherentpdf.getAttachmentData(i);

          const dataCopy = new Uint8Array(data.length);
          dataCopy.set(new Uint8Array(data));

          attachmentsToKeep.push({
            name: String(name),
            page: Number(page),
            data: dataCopy,
          });
        }
      }

      coherentpdf.endGetAttachments();

      coherentpdf.removeAttachedFiles(pdf);

      for (const attachment of attachmentsToKeep) {
        if (attachment.page === 0) {
          coherentpdf.attachFileFromMemory(
            attachment.data,
            attachment.name,
            pdf
          );
        } else {
          coherentpdf.attachFileToPageFromMemory(
            attachment.data,
            attachment.name,
            pdf,
            attachment.page
          );
        }
      }
    }

    const modifiedBytes = coherentpdf.toMemory(pdf, false, true);
    coherentpdf.deletePdf(pdf);

    const buffer = modifiedBytes.buffer.slice(
      modifiedBytes.byteOffset,
      modifiedBytes.byteOffset + modifiedBytes.byteLength
    );

    const response = {
      status: 'success',
      modifiedPDF: buffer,
      fileName: fileName,
    };

    self.postMessage(response, [response.modifiedPDF]);
  } catch (error) {
    self.postMessage({
      status: 'error',
      message:
        error instanceof Error
          ? error.message
          : 'Unknown error occurred during attachment editing.',
    });
  }
}

self.onmessage = async function (e) {
  const { cpdfUrl } = e.data;

  if (!cpdfUrl) {
    self.postMessage({
      status: 'error',
      message:
        'CoherentPDF URL not provided. Please configure it in WASM Settings.',
    });
    return;
  }

  try {
    await loadCpdf(cpdfUrl);
  } catch (error) {
    self.postMessage({
      status: 'error',
      message: error.message,
    });
    return;
  }

  if (e.data.command === 'get-attachments') {
    getAttachmentsFromPDFInWorker(e.data.fileBuffer, e.data.fileName);
  } else if (e.data.command === 'edit-attachments') {
    editAttachmentsInPDFInWorker(
      e.data.fileBuffer,
      e.data.fileName,
      e.data.attachmentsToRemove
    );
  }
};