const linkList = document.getElementById("linkList");
const emptyState = document.getElementById("emptyState");
const linkForm = document.getElementById("linkForm");
const urlInput = document.getElementById("urlInput");
const formError = document.getElementById("formError");
const loadingEl = document.getElementById("loading");
const scrollSentinel = document.getElementById("scrollSentinel");
const PLACEHOLDER_DATA_URI =
  "data:image/svg+xml;utf8," +
  "<svg%20width='640'%20height='360'%20viewBox='0%200%20640%20360'%20fill='none'%20" +
  "xmlns='http://www.w3.org/2000/svg'>" +
  "<rect%20width='640'%20height='360'%20fill='%23e9ecef'/>" +
  "<rect%20x='120'%20y='90'%20width='400'%20height='180'%20rx='16'%20fill='%23dee2e6'/>" +
  "<path%20d='M210%20210l60-70%2070%2080%2060-60%2090%2090H210z'%20fill='%23adb5bd'/>" +
  "<circle%20cx='260'%20cy='150'%20r='22'%20fill='%23adb5bd'/>" +
  "<text%20x='320'%20y='260'%20text-anchor='middle'%20font-size='18'%20" +
  "fill='%236c757d'%20font-family='Arial,%20sans-serif'>No%20Image</text>" +
  "</svg>";

function setLoading(isLoading) {
  if (!loadingEl) return;
  loadingEl.classList.toggle("d-none", !isLoading);
}

function extractFirstUrl(text) {
  if (!text) return "";
  const trimmed = String(text).trim();

  // 1) http/https URL
  const httpMatch = trimmed.match(/https?:\/\/[^\s<>"')\]]+/i);
  if (httpMatch && httpMatch[0]) return httpMatch[0];

  // 2) www. URL (no scheme)
  const wwwMatch = trimmed.match(/www\.[^\s<>"')\]]+/i);
  if (wwwMatch && wwwMatch[0]) return `https://${wwwMatch[0]}`;

  return "";
}

function setEmptyStateVisible(visible, message) {
  if (!emptyState) return;
  if (message) emptyState.textContent = message;
  emptyState.classList.toggle("d-none", !visible);
}

function appendLinks(links) {
  if (!links.length) return;
  setEmptyStateVisible(false);

  links.forEach((link) => {
    const col = document.createElement("div");
    col.className = "col-12 col-md-6 col-lg-4";

    const card = document.createElement("div");
    card.className = "card h-100 shadow-sm";

    const image = document.createElement("img");
    image.className = "card-img-top";
    image.alt = "미리보기 이미지";
    const needsFallback =
      !link.image || link.image === "/static/placeholder.svg";
    image.src = needsFallback ? PLACEHOLDER_DATA_URI : link.image;
    if (!needsFallback) {
      image.addEventListener("error", () => {
        if (image.dataset.fallbackApplied) {
          return;
        }
        image.dataset.fallbackApplied = "1";
        image.onerror = null;
        image.src = PLACEHOLDER_DATA_URI;
      });
    }

    const body = document.createElement("div");
    body.className = "card-body d-flex flex-column";

    const title = document.createElement("h5");
    title.className = "card-title mb-2";
    title.textContent = link.title || link.url;

    const description = document.createElement("p");
    description.className = "card-text text-secondary flex-grow-1";
    description.textContent = link.description || "설명 없음";

    const linkBtn = document.createElement("a");
    linkBtn.className = "btn btn-outline-primary btn-sm";
    linkBtn.href = link.url;
    linkBtn.target = "_blank";
    linkBtn.rel = "noopener";
    linkBtn.textContent = "원문 보기";

    body.append(title, description, linkBtn);
    card.append(image, body);
    col.appendChild(card);
    linkList.appendChild(col);
  });
}

const PAGE_SIZE = 30;
let nextOffset = 0;
let hasMore = true;
let loading = false;

function resetPagination() {
  nextOffset = 0;
  hasMore = true;
  loading = false;
  linkList.innerHTML = "";
}

async function loadNextPage() {
  if (loading || !hasMore) return;
  loading = true;
  setLoading(true);
  setEmptyStateVisible(false);

  try {
    const res = await fetch(`/links?limit=${PAGE_SIZE}&offset=${nextOffset}`);
    const data = await res.json();
    if (!res.ok) {
      const detail = data?.detail ? ` (${data.detail})` : "";
      throw new Error((data.error || "링크를 불러오지 못했습니다.") + detail);
    }

    const items = Array.isArray(data) ? data : data.items || [];
    appendLinks(items);

    if (Array.isArray(data)) {
      nextOffset += items.length;
      hasMore = items.length === PAGE_SIZE;
    } else {
      nextOffset = data.next_offset ?? nextOffset + items.length;
      hasMore = Boolean(data.has_more);
    }

    if (nextOffset === 0 && items.length === 0) {
      setEmptyStateVisible(true, "아직 저장된 링크가 없습니다.");
    }
  } catch (err) {
    if (nextOffset === 0) {
      setEmptyStateVisible(true, err.message);
    }
    hasMore = false;
  } finally {
    loading = false;
    setLoading(false);
  }
}

linkForm.addEventListener("submit", async (event) => {
  event.preventDefault();
  formError.textContent = "";

  const url = urlInput.value.trim();
  if (!url) {
    formError.textContent = "URL을 입력해주세요.";
    return;
  }

  try {
    const res = await fetch("/links", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ url }),
    });
    const data = await res.json();
    if (!res.ok) {
      const detail = data?.detail ? ` (${data.detail})` : "";
      throw new Error((data.error || "저장에 실패했습니다.") + detail);
    }

    resetPagination();
    await loadNextPage();

    const modalElement = document.getElementById("linkModal");
    const modal = bootstrap.Modal.getOrCreateInstance(modalElement);
    modal.hide();
    urlInput.value = "";
  } catch (err) {
    formError.textContent = err.message;
  }
});

if (urlInput) {
  urlInput.addEventListener("paste", (event) => {
    const text = event.clipboardData?.getData("text") ?? "";
    const extracted = extractFirstUrl(text);
    if (!extracted) return;
    event.preventDefault();
    urlInput.value = extracted;
    urlInput.dispatchEvent(new Event("input", { bubbles: true }));
  });
}

function setupInfiniteScroll() {
  if (!scrollSentinel) return;
  const observer = new IntersectionObserver(
    (entries) => {
      const entry = entries[0];
      if (entry && entry.isIntersecting) {
        loadNextPage();
      }
    },
    { root: null, rootMargin: "400px 0px", threshold: 0 }
  );
  observer.observe(scrollSentinel);
}

function init() {
  resetPagination();
  setupInfiniteScroll();
  loadNextPage();
}

if (document.readyState === "loading") {
  document.addEventListener("DOMContentLoaded", init);
} else {
  init();
}