offscreen.js

// offscreen.js
console.log("[Offscreen] Document loaded and script running.");

// Check if the current context has access to the clipboard API.
// While execCommand is the primary method here, it's good practice to be aware.
if (navigator.clipboard) {
  console.log("[Offscreen] Clipboard API is available.");
} else {
  console.warn("[Offscreen] Clipboard API is *not* available. Relying on execCommand.");
}

// Listen for messages from the service worker (background.js)
chrome.runtime.onMessage.addListener(handleMessages);

function handleMessages(message, sender, sendResponse) {
  console.log("[Offscreen] Received message:", message);

  // Check if the message is intended for this offscreen document
  // (Good practice if you might have multiple offscreen documents later)
  if (message.target !== 'offscreen') {
    console.log("[Offscreen] Message not targeted for offscreen. Ignoring.");
    return false; // Indicate message not handled
  }

  // Handle specific actions based on the message
  switch (message.action) {
    case 'copyToClipboard':
      copyTextToClipboard(message.data, sendResponse);
      break;
    // Add other cases here if the offscreen document needs more capabilities
    default:
      console.warn(`[Offscreen] Unrecognized action received: ${message.action}`);
      sendResponse({ success: false, error: 'Unrecognized action' });
  }

  // Crucially, return true to indicate that sendResponse will be called asynchronously
  // (even though execCommand is synchronous, this prevents the message channel from closing prematurely)
  return true;
}

// Function to perform the actual copy operation
function copyTextToClipboard(text, sendResponse) {
  const textArea = document.getElementById('clipboardHelper');
  if (!textArea) {
      console.error("[Offscreen] Clipboard helper textarea not found!");
      sendResponse({ success: false, error: 'Offscreen document setup error.' });
      return;
  }

  // Set the text in the helper textarea
  textArea.value = text;
  // Select the text
  textArea.select();

  try {
    // Execute the copy command
    // Note: document.execCommand() is technically deprecated but is currently
    // the most reliable way to copy from an offscreen document in MV3.
    const success = document.execCommand('copy');

    if (success) {
      console.log("[Offscreen] Text successfully copied to clipboard:", text);
      sendResponse({ success: true });
    } else {
      console.error("[Offscreen] document.execCommand('copy') returned false.");
      sendResponse({ success: false, error: 'Copy command failed.' });
    }
  } catch (err) {
    console.error("[Offscreen] Error during document.execCommand('copy'):", err);
    sendResponse({ success: false, error: err.message || 'Exception during copy.' });
  }

  // Optional: Clear the textarea after copying to avoid lingering data
  textArea.value = '';
}

console.log("[Offscreen] Message listener attached.");