let gallery;
let sentinel;
let counter;
let select;
let observer;

let offset = 0;
let loading = false;
let hasMore = true;

const urlParams = new URLSearchParams(window.location.search);

let height = urlParams.get("height") || (window.innerWidth > 1600 ? 320 : 220);
let sort = urlParams.get("sort") || "time";
let tags = urlParams.get("tags") || "";
const limit = window.innerWidth > 1600 ? 50 : 20;

function resetGallery() {
  imgviewer.resetList();
  gallery.replaceChildren();
  height = urlParams.get("height") || (window.innerWidth > 1600 ? 320 : 220);
  offset = 0;
  hasMore = true;
  loadMore();
}

async function loadMore() {
  if (loading || !hasMore) return;

  let url = `/api/files?offset=${offset}&limit=${limit}&sort=${sort}`
  observer.unobserve(sentinel);
  loading = true;

  if (tags) url += `&tags=${tags}`

  try {
    const res = await fetch(url);
    const data = await res.json();

    switch (res.status) {
      case 200:
        break;
      case 401:
        alert("Session expired");
        return;
      case 500:
        if (data.error) {
          hasMore = false;
          alert(`${data.msg}: ${data.error}`);
          return
        }
    }

    appendFiles(data.files);

    hasMore = data.offset + data.files.length < data.total;
    offset += data.files.length;
    counter.textContent = data.total;
    if (!sort) sort = data.sort;
  } catch (err) {
    console.error(err);
    hasMore = false;
  } finally {
    loading = false;

    // 加载完成下一帧重新观察，强制刷新交叉状态
    requestAnimationFrame(() => {
      observer.observe(sentinel);
    });
  }
}

function appendFiles(files) {
  imgviewer.appendFiles(files);
  const fragment = document.createDocumentFragment();

  for (const file of files) {
    const jWidth = file.width * height / file.height;
    const jPadding = file.height / file.width * 100;
    const wrapper = document.createElement("div");
    wrapper.style.width = jWidth + "px";
    wrapper.style.flexGrow = jWidth;

    const i = document.createElement("i");
    i.style.paddingBottom = jPadding + "%";
    if (sort == "size" || sort == "size-down") {
      const span = document.createElement("span");
      const p = document.createElement("p");
      p.textContent = `${file.ext} | ${file.thumbed ? "☇ " : ""}${file.size_str}`;
      span.appendChild(p);
      i.appendChild(span);
    }
    wrapper.appendChild(i);

    const imgs = document.createElement("div");
    imgs.id = "imgs";

    const img = document.createElement("img");
    img.loading = "lazy";
    img.decoding = "async";
    img.tabIndex = "0";
    if (file.thumbed) {
      img.src = `/thumbnails/${file.id_str}.jpg`;
      img.dataset.highres = `/files/${file.id_str}.${file.ext}`;
    } else {
      img.src = `/files/${file.id_str}.${file.ext}`;
    }

    let artwork = file.edges.artwork;
    img.alt = `trpic_artwork_${artwork.id}_${file.id_str}`;
    img.dataset.id_str = file.id_str;
    img.dataset.artwork_id = artwork.id;

    imgs.appendChild(img);

    if (file.thumbhash) {
      const thumb = document.createElement("img");
      thumb.id = "thumbhash";
      thumb.src = thumbHashToDataURL(file.thumbhash);
      imgs.appendChild(thumb);

      img.onload = () => {
        img.onload = null;
        thumb.style.opacity = 0;
        setInterval(() => {
          thumb.remove();
        }, 1000)
      };
    }

    wrapper.appendChild(imgs);
    imgviewer.bindClickEvents(img);
    fragment.appendChild(wrapper);
  }

  gallery.appendChild(fragment);
}

document.addEventListener("DOMContentLoaded", () => {
  gallery = document.getElementById("gallery");
  sentinel = document.getElementById("sentinel");
  counter = document.getElementById("image-count");
  select = document.getElementById('sort-select')

  select.value = sort

  select.addEventListener('change', () => {
    urlParams.set("sort", sort = select.value);
    history.replaceState(null, null, `/files?${urlParams.toString()}`);
    resetGallery()
  })

  observer = new IntersectionObserver(
    (entries) => {
      if (entries[0].isIntersecting) {
        loadMore();
      }
    },
    {
      root: null,
      rootMargin: "800px", // 提前 800px 加载
      threshold: 0,
    }
  );

  observer.observe(sentinel);
});

document.addEventListener("error", (e) => {
  let target = e.target;
  const tagName = target.tagName || "";
  const curTimes = Number(target.dataset.retryTimes) || 0;
  if (tagName.toLowerCase() === "img") {
    if (curTimes >= 5) {
      target.alt = "loading failed";
    } else {
      setTimeout(() => {
        target.dataset.retryTimes = curTimes + 1;
        target.src = target.src;
      }, 10000);
    }
  } else {
    target = null;
  }
}, true);