content.js

// content script

// check if enabled
chrome.storage.local.get(["enabled"], (result) => {
  if (chrome.runtime.lastError) {
    console.error('Error getting enabled state:', chrome.runtime.lastError);
    return;
  }
  if (result.enabled !== false) {
    injectInstantPage();
  }
});

// listen for state changes
chrome.storage.onChanged.addListener((changes) => {
  if (changes.enabled) {
    if (changes.enabled.newValue !== false) {
      injectInstantPage();
    } else {
      // remove script when disabled
      const script = document.querySelector('script[data-preloadify="true"]');
      if (script) script.remove();
    }
  }
});

// inject instantpage script
function injectInstantPage() {
  // check if already injected
  if (document.querySelector('script[data-preloadify="true"]')) {
    return;
  }
  
  // wait for DOM to be ready if not already
  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', injectInstantPage, { once: true });
    return;
  }
  
  try {
    // create script element for local file
    const script = document.createElement("script");
    script.src = chrome.runtime.getURL("vendor/instantpage.min.js");
    script.type = "module";
    script.dataset.preloadify = "true";
    
    // append to doc
    const target = document.head || document.documentElement;
    if (target) {
      script.onload = function() {
        // console.log("preloadify injected");
        setupPreloadTracking();
      };
      
      script.onerror = function(event) {
        console.error("Failed to load instant.page script:", event);
        if (script.parentNode) {
          script.parentNode.removeChild(script);
        }
      };
      
      target.appendChild(script);
    } else {
      console.error("No valid target to inject script");
    }
  } catch (error) {
    console.error("Error injecting instant.page script:", error);
  }
}

// track preload activity
function setupPreloadTracking() {
  // observe for new elements being added (preloads)
  const observer = new MutationObserver((mutations) => {
    mutations.forEach((mutation) => {
      mutation.addedNodes.forEach((node) => {
        if (node.nodeType === Node.ELEMENT_NODE) {
          // track speculation rules (modern browsers)
          if (node.tagName === 'SCRIPT' && node.type === 'speculationrules') {
            incrementPreloadCounter();
          }
          // track prefetch links (fallback)
          else if (node.tagName === 'LINK' && node.rel === 'prefetch') {
            incrementPreloadCounter();
          }
        }
      });
    });
  });
  
  observer.observe(document.head, { childList: true });
}

function incrementPreloadCounter() {
  chrome.storage.local.get(["preloadCount"], (result) => {
    if (chrome.runtime.lastError) return;
    
    const currentCount = result.preloadCount || 0;
    chrome.storage.local.set({ preloadCount: currentCount + 1 });
  });
}