browser-tools-mcp/chrome-extension/background.js

// Listen for messages from the devtools panel
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.type === "CAPTURE_SCREENSHOT" && message.tabId) {
    // First get the server settings
    chrome.storage.local.get(["browserConnectorSettings"], (result) => {
      const settings = result.browserConnectorSettings || {
        serverHost: "localhost",
        serverPort: 3025,
      };

      // Validate server identity first
      validateServerIdentity(settings.serverHost, settings.serverPort)
        .then((isValid) => {
          if (!isValid) {
            console.error(
              "Cannot capture screenshot: Not connected to a valid browser tools server"
            );
            sendResponse({
              success: false,
              error:
                "Not connected to a valid browser tools server. Please check your connection settings.",
            });
            return;
          }

          // Continue with screenshot capture
          captureAndSendScreenshot(message, settings, sendResponse);
        })
        .catch((error) => {
          console.error("Error validating server:", error);
          sendResponse({
            success: false,
            error: "Failed to validate server identity: " + error.message,
          });
        });
    });
    return true; // Required to use sendResponse asynchronously
  }
});

// Validate server identity
async function validateServerIdentity(host, port) {
  try {
    const response = await fetch(`http://${host}:${port}/.identity`, {
      signal: AbortSignal.timeout(3000), // 3 second timeout
    });

    if (!response.ok) {
      console.error(`Invalid server response: ${response.status}`);
      return false;
    }

    const identity = await response.json();

    // Validate the server signature
    if (identity.signature !== "mcp-browser-connector-24x7") {
      console.error("Invalid server signature - not the browser tools server");
      return false;
    }

    return true;
  } catch (error) {
    console.error("Error validating server identity:", error);
    return false;
  }
}

// Function to capture and send screenshot
function captureAndSendScreenshot(message, settings, sendResponse) {
  // Get the inspected window's tab
  chrome.tabs.get(message.tabId, (tab) => {
    if (chrome.runtime.lastError) {
      console.error("Error getting tab:", chrome.runtime.lastError);
      sendResponse({
        success: false,
        error: chrome.runtime.lastError.message,
      });
      return;
    }

    // Get all windows to find the one containing our tab
    chrome.windows.getAll({ populate: true }, (windows) => {
      const targetWindow = windows.find((w) =>
        w.tabs.some((t) => t.id === message.tabId)
      );

      if (!targetWindow) {
        console.error("Could not find window containing the inspected tab");
        sendResponse({
          success: false,
          error: "Could not find window containing the inspected tab",
        });
        return;
      }

      // Capture screenshot of the window containing our tab
      chrome.tabs.captureVisibleTab(
        targetWindow.id,
        { format: "png" },
        (dataUrl) => {
          // Ignore DevTools panel capture error if it occurs
          if (
            chrome.runtime.lastError &&
            !chrome.runtime.lastError.message.includes("devtools://")
          ) {
            console.error(
              "Error capturing screenshot:",
              chrome.runtime.lastError
            );
            sendResponse({
              success: false,
              error: chrome.runtime.lastError.message,
            });
            return;
          }

          // Send screenshot data to browser connector using configured settings
          const serverUrl = `http://${settings.serverHost}:${settings.serverPort}/screenshot`;
          console.log(`Sending screenshot to ${serverUrl}`);

          fetch(serverUrl, {
            method: "POST",
            headers: {
              "Content-Type": "application/json",
            },
            body: JSON.stringify({
              data: dataUrl,
              path: message.screenshotPath,
            }),
          })
            .then((response) => response.json())
            .then((result) => {
              if (result.error) {
                console.error("Error from server:", result.error);
                sendResponse({ success: false, error: result.error });
              } else {
                console.log("Screenshot saved successfully:", result.path);
                // Send success response even if DevTools capture failed
                sendResponse({
                  success: true,
                  path: result.path,
                  title: tab.title || "Current Tab",
                });
              }
            })
            .catch((error) => {
              console.error("Error sending screenshot data:", error);
              sendResponse({
                success: false,
                error: error.message || "Failed to save screenshot",
              });
            });
        }
      );
    });
  });
}