document.addEventListener("DOMContentLoaded", () => {
  setupMobileNavigation();
  setupScrollAnimations();
  setupProjectFiltering();
  setupContactForm();
  setupSmoothScrollClose();
});

function setupMobileNavigation() {
  const toggle = document.querySelector("[data-menu-toggle]");
  const mobileNav = document.querySelector("[data-mobile-nav]");

  if (!toggle || !mobileNav) {
    return;
  }

  const updateState = (isOpen) => {
    toggle.classList.toggle("is-open", isOpen);
    toggle.setAttribute("aria-expanded", String(isOpen));
    mobileNav.classList.toggle("is-open", isOpen);
    document.body.classList.toggle("menu-open", isOpen);
  };

  toggle.addEventListener("click", () => {
    const isOpen = toggle.getAttribute("aria-expanded") === "true";
    updateState(!isOpen);
  });

  mobileNav.querySelectorAll("a").forEach((link) => {
    link.addEventListener("click", () => updateState(false));
  });

  document.addEventListener("keydown", (event) => {
    if (event.key === "Escape") {
      updateState(false);
    }
  });

  document.addEventListener("click", (event) => {
    const clickedInsideMenu = mobileNav.contains(event.target);
    const clickedToggle = toggle.contains(event.target);

    if (!clickedInsideMenu && !clickedToggle) {
      updateState(false);
    }
  });
}

function setupSmoothScrollClose() {
  const samePageLinks = document.querySelectorAll('a[href^="#"]');

  samePageLinks.forEach((link) => {
    link.addEventListener("click", (event) => {
      const targetId = link.getAttribute("href");

      if (!targetId || targetId === "#") {
        return;
      }

      const target = document.querySelector(targetId);

      if (!target) {
        return;
      }

      event.preventDefault();
      target.scrollIntoView({ behavior: "smooth", block: "start" });
    });
  });
}

function setupScrollAnimations() {
  const animatedItems = document.querySelectorAll("[data-animate]");

  if (!animatedItems.length) {
    return;
  }

  if (!("IntersectionObserver" in window)) {
    animatedItems.forEach((item) => item.classList.add("is-visible"));
    return;
  }

  const observer = new IntersectionObserver(
    (entries, currentObserver) => {
      entries.forEach((entry) => {
        if (!entry.isIntersecting) {
          return;
        }

        entry.target.classList.add("is-visible");
        currentObserver.unobserve(entry.target);
      });
    },
    {
      threshold: 0.12,
      rootMargin: "0px 0px -40px 0px"
    }
  );

  animatedItems.forEach((item) => observer.observe(item));
}

function setupProjectFiltering() {
  const filterButtons = document.querySelectorAll("[data-filter]");
  const filterItems = document.querySelectorAll("[data-category]");

  if (!filterButtons.length || !filterItems.length) {
    return;
  }

  filterButtons.forEach((button) => {
    button.addEventListener("click", () => {
      const filterValue = button.dataset.filter;

      filterButtons.forEach((otherButton) => {
        otherButton.classList.toggle("is-active", otherButton === button);
        otherButton.setAttribute("aria-pressed", String(otherButton === button));
      });

      filterItems.forEach((item) => {
        const categories = (item.dataset.category || "").split(" ");
        const shouldShow = filterValue === "all" || categories.includes(filterValue);
        item.classList.toggle("is-hidden", !shouldShow);
      });
    });
  });
}

function setupContactForm() {
  const form = document.querySelector("[data-contact-form]");

  if (!form) {
    return;
  }

  const fields = Array.from(form.querySelectorAll("[data-required], [type='email']"));
  const status = form.querySelector("[data-form-status]");

  const validators = {
    email: (value) => /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(value)
  };

  const setFieldError = (field, message) => {
    const wrapper = field.closest(".form-field");
    const error = wrapper ? wrapper.querySelector(".form-field__error") : null;

    field.setAttribute("aria-invalid", String(Boolean(message)));

    if (wrapper) {
      wrapper.classList.toggle("is-invalid", Boolean(message));
    }

    if (error) {
      error.textContent = message || "";
    }
  };

  const validateField = (field) => {
    const rawValue = field.value.trim();
    const label = field.dataset.label || "This field";

    if (field.hasAttribute("data-required") && !rawValue) {
      setFieldError(field, `${label} is required.`);
      return false;
    }

    if (field.type === "email" && rawValue && !validators.email(rawValue)) {
      setFieldError(field, "Enter a valid email address.");
      return false;
    }

    setFieldError(field, "");
    return true;
  };

  fields.forEach((field) => {
    field.addEventListener("blur", () => validateField(field));
    field.addEventListener("input", () => {
      if (field.getAttribute("aria-invalid") === "true") {
        validateField(field);
      }
    });
  });

  form.addEventListener("submit", (event) => {
    let isValid = true;

    fields.forEach((field) => {
      if (!validateField(field)) {
        isValid = false;
      }
    });

    if (!isValid) {
      event.preventDefault();

      if (status) {
        status.textContent = "Please review the highlighted fields and try again.";
        status.classList.remove("is-success");
      }

      const firstInvalid = form.querySelector("[aria-invalid='true']");

      if (firstInvalid) {
        firstInvalid.focus();
      }

      return;
    }

    event.preventDefault();

    if (status) {
      status.textContent = "Thanks. Your message structure is validated and ready for backend integration.";
      status.classList.add("is-success");
    }

    form.reset();
    fields.forEach((field) => setFieldError(field, ""));
  });
}