import { connect, formatDuration } from '/shared/socket.js';
import { BACKGROUNDS, AUTO_BACKGROUND, ANIMATIONS, AUTO_ANIMATION } from '/config.js';

let state = {
  items: [],
  currentId: null,
  background: AUTO_BACKGROUND,
  animation: AUTO_ANIMATION,
  paused: false,
};
// Last playhead report, kept with its arrival time so the countdown can be
// extrapolated smoothly between the 1 Hz updates.
let progress = { id: null, currentTime: 0, at: 0 };

const list = document.getElementById('list');
const empty = document.getElementById('empty');
const errorBox = document.getElementById('error');
const statusBox = document.getElementById('status');
const backgroundBox = document.getElementById('backgrounds');
const animationBox = document.getElementById('animations');
const playPause = document.getElementById('playpause');

const socket = connect({ onMessage, onStatus });

// --- adding -------------------------------------------------------------

document.getElementById('add-form').addEventListener('submit', (event) => {
  event.preventDefault();
  const input = document.getElementById('url');
  const url = input.value.trim();
  if (!url) return;
  showError(null);
  socket.send({ type: 'add', url });
  input.value = '';
  input.focus();
});

function showError(message) {
  errorBox.textContent = message || '';
  errorBox.hidden = !message;
}

// --- rendering ----------------------------------------------------------

function render() {
  list.replaceChildren(...state.items.map(renderItem));
  empty.hidden = state.items.length > 0;
  renderTransport();
  renderTotals();
}

// --- play / pause -------------------------------------------------------

playPause.addEventListener('click', () => {
  socket.send({ type: 'setPaused', paused: !state.paused });
});

/** Mirrors the server's flag rather than toggling locally, so every phone in
 * the room agrees about what the player is doing. */
function renderTransport() {
  const paused = Boolean(state.paused);
  playPause.textContent = paused ? '▶ Play' : '⏸ Pause';
  playPause.title = paused ? 'Resume playback' : 'Pause playback';
  playPause.classList.toggle('paused', paused);
  playPause.disabled = state.items.length === 0;
}

function renderItem(item, index) {
  const li = document.createElement('li');
  li.className = 'item';
  li.dataset.id = item.id;
  li.draggable = true;
  if (item.id === state.currentId) li.classList.add('current');

  const handle = document.createElement('span');
  handle.className = 'handle';
  handle.textContent = '⠿';
  handle.setAttribute('aria-hidden', 'true');

  const position = document.createElement('span');
  position.className = 'index';
  position.textContent = item.id === state.currentId ? '▶' : String(index + 1);

  const title = document.createElement('span');
  title.className = 'title';
  title.textContent = item.title;
  title.title = item.title;

  const duration = document.createElement('span');
  duration.className = 'duration';
  duration.textContent = item.duration === null ? '–:––' : formatDuration(item.duration);

  const remove = document.createElement('button');
  remove.className = 'remove';
  remove.type = 'button';
  remove.textContent = '×';
  remove.title = 'Remove';
  remove.addEventListener('click', (event) => {
    event.stopPropagation();
    socket.send({ type: 'remove', id: item.id });
  });

  li.append(handle, position, title, duration, remove);
  li.addEventListener('click', () => socket.send({ type: 'jump', id: item.id }));
  attachDrag(li);
  return li;
}

function renderTotals() {
  let total = 0;
  let remaining = 0;
  let unknown = false;
  let passedCurrent = false;

  const currentIndex = state.items.findIndex((item) => item.id === state.currentId);

  state.items.forEach((item, index) => {
    if (item.duration === null) {
      unknown = true;
      return;
    }
    total += item.duration;

    if (currentIndex === -1) return;
    if (index === currentIndex) {
      remaining += Math.max(0, item.duration - playheadFor(item));
      passedCurrent = true;
    } else if (index > currentIndex) {
      remaining += item.duration;
    }
  });

  if (currentIndex === -1) remaining = total;
  else if (!passedCurrent) unknown = true;

  const prefix = unknown ? '≥ ' : '';
  document.getElementById('total').textContent = prefix + formatDuration(total);
  document.getElementById('remaining').textContent = prefix + formatDuration(remaining);
}

/** Playhead of the current item, extrapolated since the last report. */
function playheadFor(item) {
  if (progress.id !== item.id) return 0;
  // Paused, the playhead is standing still — extrapolating would run the
  // countdown down between reports and then jump it back on the next one.
  const elapsed = state.paused ? 0 : (Date.now() - progress.at) / 1000;
  return Math.min(progress.currentTime + elapsed, item.duration ?? Infinity);
}

// Keeps the countdown ticking between server messages.
setInterval(renderTotals, 1000);

// --- drag to reorder ----------------------------------------------------

let draggingId = null;

function attachDrag(li) {
  li.addEventListener('dragstart', (event) => {
    draggingId = li.dataset.id;
    li.classList.add('dragging');
    event.dataTransfer.effectAllowed = 'move';
    // Firefox refuses to start a drag without payload.
    event.dataTransfer.setData('text/plain', li.dataset.id);
  });

  li.addEventListener('dragend', () => {
    draggingId = null;
    li.classList.remove('dragging');
    clearDropMarkers();
  });

  li.addEventListener('dragover', (event) => {
    if (!draggingId || li.dataset.id === draggingId) return;
    event.preventDefault();
    event.dataTransfer.dropEffect = 'move';
    const box = li.getBoundingClientRect();
    const after = event.clientY > box.top + box.height / 2;
    clearDropMarkers();
    li.classList.add(after ? 'drop-after' : 'drop-before');
  });

  li.addEventListener('dragleave', () => {
    li.classList.remove('drop-before', 'drop-after');
  });

  li.addEventListener('drop', (event) => {
    if (!draggingId || li.dataset.id === draggingId) return;
    event.preventDefault();

    const box = li.getBoundingClientRect();
    const after = event.clientY > box.top + box.height / 2;

    const ids = state.items.map((item) => item.id).filter((id) => id !== draggingId);
    const target = ids.indexOf(li.dataset.id);
    ids.splice(after ? target + 1 : target, 0, draggingId);

    clearDropMarkers();
    // Apply locally so the list does not flicker back before the echo lands.
    const byId = new Map(state.items.map((item) => [item.id, item]));
    state.items = ids.map((id) => byId.get(id));
    render();

    socket.send({ type: 'reorder', ids });
  });
}

function clearDropMarkers() {
  for (const el of list.querySelectorAll('.drop-before, .drop-after')) {
    el.classList.remove('drop-before', 'drop-after');
  }
}

// --- background / animation switchers -----------------------------------

/**
 * A row of buttons that sets one field of the shared state. Returns a render
 * function that lights up whichever key the server currently reports.
 */
function buildSwitcher(box, options, type, currentKey) {
  const buttons = new Map();

  for (const [key, label] of options) {
    const button = document.createElement('button');
    button.type = 'button';
    button.textContent = label;
    button.addEventListener('click', () => socket.send({ type, key }));
    box.appendChild(button);
    buttons.set(key, button);
  }

  return function render() {
    for (const [key, button] of buttons) {
      button.classList.toggle('active', key === currentKey());
    }
  };
}

// Auto leads in both rows: it is the normal party setting, the named ones are
// for holding still on one while you look at it.
const renderBackground = buildSwitcher(
  backgroundBox,
  [
    [AUTO_BACKGROUND, 'Auto'],
    ...Object.entries(BACKGROUNDS).map(([key, { label }]) => [key, label]),
  ],
  'setBackground',
  () => state.background,
);

const renderAnimation = buildSwitcher(
  animationBox,
  [
    [AUTO_ANIMATION, 'Auto'],
    ...Object.entries(ANIMATIONS).map(([key, { label }]) => [key, label]),
  ],
  'setAnimation',
  () => state.animation,
);

// --- socket -------------------------------------------------------------

function onMessage(msg) {
  if (msg.type === 'state') {
    state = msg.state;
    render();
    renderBackground();
    renderAnimation();
  } else if (msg.type === 'progress') {
    progress = { id: msg.id, currentTime: msg.currentTime, at: Date.now() };
    renderTotals();
  } else if (msg.type === 'error') {
    showError(msg.message);
  }
}

function onStatus(status) {
  statusBox.textContent = status;
  statusBox.className = status;
}