Add browser extension gRPC bridge

browser/extension/content.js

@@ -0,0 +1,69 @@
+function isVisibleInput(input) {
+  if (!(input instanceof HTMLInputElement)) {
+    return false;
+  }
+  if (input.disabled || input.readOnly) {
+    return false;
+  }
+  const style = window.getComputedStyle(input);
+  if (style.display === "none" || style.visibility === "hidden") {
+    return false;
+  }
+  return input.offsetParent !== null || style.position === "fixed";
+}
+
+function dispatchFillEvents(input) {
+  input.dispatchEvent(new Event("input", { bubbles: true }));
+  input.dispatchEvent(new Event("change", { bubbles: true }));
+}
+
+function findPasswordInput() {
+  return Array.from(document.querySelectorAll('input[type="password"]')).find(isVisibleInput) || null;
+}
+
+function findUsernameInput(passwordInput) {
+  const form = passwordInput?.form || null;
+  const scope = form || document;
+  const candidates = Array.from(scope.querySelectorAll('input[type="text"], input[type="email"], input:not([type])'))
+    .filter(isVisibleInput);
+  if (passwordInput) {
+    const sameForm = candidates.find((input) => input.form === passwordInput.form);
+    if (sameForm) {
+      return sameForm;
+    }
+  }
+  return candidates[0] || null;
+}
+
+function fillCredential(credential) {
+  const passwordInput = findPasswordInput();
+  const usernameInput = findUsernameInput(passwordInput);
+
+  if (usernameInput && credential.username) {
+    usernameInput.focus();
+    usernameInput.value = credential.username;
+    dispatchFillEvents(usernameInput);
+  }
+  if (passwordInput && credential.password) {
+    passwordInput.focus();
+    passwordInput.value = credential.password;
+    dispatchFillEvents(passwordInput);
+  }
+
+  if (!usernameInput && !passwordInput) {
+    return { ok: false, error: "No fillable username or password fields were found." };
+  }
+  return { ok: true };
+}
+
+(globalThis.browser ?? globalThis.chrome).runtime.onMessage.addListener((message, _sender, sendResponse) => {
+  if (message?.type !== "keepassgo-fill-credential") {
+    return false;
+  }
+  try {
+    sendResponse(fillCredential(message.credential || {}));
+  } catch (error) {
+    sendResponse({ ok: false, error: error instanceof Error ? error.message : String(error) });
+  }
+  return false;
+});