const state = {
  library: null,
  currentFolder: "",
  currentQueue: [],
  currentTrackIndex: -1,
  shuffle: false,
  loopMode: "list",
};

const audio = document.getElementById("audioPlayer");

async function fetchLibrary() {
  const response = await fetch("/api/library");
  state.library = await response.json();
  renderTree();
  renderPlaylists();
  if (!state.currentQueue.length) {
    state.currentQueue = [...state.library.all_tracks];
    renderQueue();
  }
}

function toggleButton(id, active, label) {
  const button = document.getElementById(id);
  button.classList.toggle("active", active);
  button.textContent = label;
}

function folderTracks(path, node = state.library.tree) {
  if (node.path === path) return flattenNodeTracks(node);
  for (const child of node.folders) {
    const result = folderTracks(path, child);
    if (result) return result;
  }
  return null;
}

function flattenNodeTracks(node) {
  const tracks = [...node.tracks];
  for (const child of node.folders) {
    tracks.push(...flattenNodeTracks(child));
  }
  return tracks;
}

function renderTree() {
  const container = document.getElementById("folderTree");
  container.innerHTML = "";
  container.appendChild(renderFolderNode(state.library.tree));
}

function renderFolderNode(node) {
  const wrapper = document.createElement("div");
  wrapper.className = "folder-node";

  const title = document.createElement(node.path ? "h4" : "h3");
  title.textContent = node.name;
  wrapper.appendChild(title);

  const actions = document.createElement("div");
  actions.className = "folder-actions";

  const useBtn = document.createElement("button");
  useBtn.className = "ghost-btn";
  useBtn.textContent = "设为当前目录";
  useBtn.onclick = () => {
    state.currentFolder = node.path;
    document.getElementById("folderIndicator").textContent = `当前目录：${node.path || "根目录"}`;
  };

  const playBtn = document.createElement("button");
  playBtn.className = "ghost-btn";
  playBtn.textContent = "播放此目录";
  playBtn.onclick = () => {
    const tracks = flattenNodeTracks(node);
    if (!tracks.length) return alert("该目录下没有可播放文件");
    startQueue(tracks, 0);
    state.currentFolder = node.path;
    document.getElementById("folderIndicator").textContent = `当前目录：${node.path || "根目录"}`;
  };

  actions.append(useBtn, playBtn);
  wrapper.appendChild(actions);

  node.tracks.forEach((track) => wrapper.appendChild(renderTrack(track)));
  node.folders.forEach((folder) => wrapper.appendChild(renderFolderNode(folder)));
  return wrapper;
}

function renderTrack(track) {
  const template = document.getElementById("trackItemTemplate");
  const fragment = template.content.cloneNode(true);
  fragment.querySelector(".track-name").textContent = track.name;
  fragment.querySelector(".track-path").textContent = track.path;
  fragment.querySelector(".play-btn").onclick = () => startQueue([track], 0);
  fragment.querySelector(".queue-btn").onclick = () => {
    state.currentQueue.push(track);
    renderQueue();
  };
  fragment.querySelector(".move-btn").onclick = async () => {
    const destination = prompt("移动到哪个目录？输入相对 mp3file 的目录路径", track.folder || "");
    if (destination === null) return;
    await fetch("/api/move", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ source: track.path, destination_dir: destination }),
    });
    await fetchLibrary();
  };
  return fragment;
}

function renderQueue() {
  const container = document.getElementById("queueList");
  container.innerHTML = "";
  state.currentQueue.forEach((track, index) => {
    const item = document.createElement("div");
    item.className = "track-item";
    if (index === state.currentTrackIndex) item.style.borderColor = "var(--accent)";
    item.innerHTML = `
      <div>
        <strong class="track-name">${track.name}</strong>
        <p class="track-path">${track.path}</p>
      </div>
      <div class="track-actions">
        <button class="ghost-btn">播放</button>
        <button class="ghost-btn">移除</button>
      </div>
    `;
    const [playBtn, removeBtn] = item.querySelectorAll("button");
    playBtn.onclick = () => playTrack(index);
    removeBtn.onclick = () => {
      state.currentQueue.splice(index, 1);
      if (state.currentTrackIndex >= state.currentQueue.length) {
        state.currentTrackIndex = state.currentQueue.length - 1;
      }
      renderQueue();
    };
    container.appendChild(item);
  });
}

function renderPlaylists() {
  const container = document.getElementById("playlistList");
  container.innerHTML = "";
  state.library.playlists.forEach((playlist) => {
    const item = document.createElement("div");
    item.className = "playlist-item";
    item.innerHTML = `
      <div>
        <strong>${playlist.name}</strong>
        <p>${playlist.tracks.length} 首歌曲</p>
      </div>
      <div class="track-actions">
        <button class="ghost-btn">播放</button>
        <button class="ghost-btn">覆盖</button>
        <button class="ghost-btn">删除</button>
      </div>
    `;
    const [playBtn, replaceBtn, deleteBtn] = item.querySelectorAll("button");
    playBtn.onclick = () => {
      const tracks = playlist.tracks
        .map((path) => state.library.all_tracks.find((track) => track.path === path))
        .filter(Boolean);
      startQueue(tracks, 0);
    };
    replaceBtn.onclick = async () => {
      await fetch(`/api/playlists/${playlist.id}`, {
        method: "PUT",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ tracks: state.currentQueue.map((track) => track.path) }),
      });
      await fetchLibrary();
    };
    deleteBtn.onclick = async () => {
      await fetch(`/api/playlists/${playlist.id}`, { method: "DELETE" });
      await fetchLibrary();
    };
    container.appendChild(item);
  });
}

function startQueue(tracks, index) {
  state.currentQueue = [...tracks];
  state.currentTrackIndex = index;
  renderQueue();
  playTrack(index);
}

function playTrack(index) {
  if (!state.currentQueue.length) return;
  state.currentTrackIndex = index;
  const track = state.currentQueue[index];
  audio.src = track.url;
  audio.play();
  document.getElementById("nowTitle").textContent = track.name;
  document.getElementById("nowMeta").textContent = track.path;
  renderQueue();
}

function nextTrack() {
  if (!state.currentQueue.length) return;
  if (state.loopMode === "one") {
    playTrack(state.currentTrackIndex);
    return;
  }

  if (state.shuffle) {
    const randomIndex = Math.floor(Math.random() * state.currentQueue.length);
    playTrack(randomIndex);
    return;
  }

  const nextIndex = state.currentTrackIndex + 1;
  if (nextIndex < state.currentQueue.length) {
    playTrack(nextIndex);
    return;
  }

  if (state.loopMode === "list") {
    playTrack(0);
  }
}

audio.addEventListener("ended", nextTrack);

document.getElementById("playAllBtn").onclick = () => startQueue(state.library.all_tracks, 0);
document.getElementById("playFolderBtn").onclick = () => {
  const tracks = folderTracks(state.currentFolder || "") || [];
  if (!tracks.length) return alert("当前目录没有歌曲");
  startQueue(tracks, 0);
};

document.getElementById("shuffleBtn").onclick = () => {
  state.shuffle = !state.shuffle;
  toggleButton("shuffleBtn", state.shuffle, `随机: ${state.shuffle ? "开" : "关"}`);
};

document.getElementById("loopBtn").onclick = () => {
  state.loopMode = state.loopMode === "list" ? "one" : state.loopMode === "one" ? "off" : "list";
  const labels = { list: "循环: 列表", one: "循环: 单曲", off: "循环: 关" };
  toggleButton("loopBtn", state.loopMode !== "off", labels[state.loopMode]);
};

document.getElementById("uploadBtn").onclick = async () => {
  const files = document.getElementById("uploadInput").files;
  if (!files.length) return alert("请选择文件");
  const formData = new FormData();
  Array.from(files).forEach((file) => formData.append("files", file));
  formData.append("target_dir", document.getElementById("targetDir").value.trim());
  await fetch("/api/upload", { method: "POST", body: formData });
  document.getElementById("uploadInput").value = "";
  await fetchLibrary();
};

document.getElementById("createFolderBtn").onclick = async () => {
  const path = document.getElementById("newFolderInput").value.trim();
  if (!path) return alert("请输入目录名");
  await fetch("/api/folder", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ path }),
  });
  document.getElementById("newFolderInput").value = "";
  await fetchLibrary();
};

document.getElementById("createPlaylistBtn").onclick = async () => {
  const name = document.getElementById("playlistNameInput").value.trim();
  if (!name) return alert("请输入播放列表名称");
  await fetch("/api/playlists", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ name, tracks: state.currentQueue.map((track) => track.path) }),
  });
  document.getElementById("playlistNameInput").value = "";
  await fetchLibrary();
};

document.getElementById("saveQueueBtn").onclick = () => renderQueue();

fetchLibrary();