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;
});