/* Companion Buttons — the tile.

   Shows the Companion buttons this tile was given, from any pages, as
   Companion draws them and as large as the tile allows. One button fills the
   tile; several share it in whatever grid makes each one biggest. Every
   picture is live: the server forwards each redraw (a status button turning
   red, a tally lighting up).

   Choosing: the grid icon in the title bar turns the tile into the Companion
   page named by the gear's Page, laid out as it is in Companion. A click on
   a button adds it to the tile (it gets a numbered ring, the order it will
   show in) or takes it out. Change the gear's Page to pick from another page
   — what is already chosen stays. The icon again shows the chosen buttons.

   Each choice is kept as the button's id and its page/row/column; the
   server follows whichever still holds, and the tile saves back what it
   resolved to, so a moved button or a re-imported page keeps showing. */

const GRID_SVG = '<svg viewBox="0 0 16 16" width="13" height="13" fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="round"><rect x="2" y="2" width="5" height="5" rx="1"/><rect x="9" y="2" width="5" height="5" rx="1"/><rect x="2" y="9" width="5" height="5" rx="1"/><rect x="9" y="9" width="5" height="5" rx="1"/></svg>';

const GAP_PX = 6;
const CAPTION_PX = 18;
const PAGES_RETRY_MS = 5000;
const ID_RE = /^bank:[A-Za-z0-9_-]{1,64}$/;
const PAGE_RE = /^[A-Za-z0-9_-]{1,64}$/;
const MAX_BUTTONS = 64;

/** "bank:QOPCkIuUp5U9" → "QOPCkIuUp5U9": what the server's URLs carry. */
const urlId = (id) => id.slice(5);

/** A chosen button as the server's stream path names it: page.row.column.id */
const spotKey = (s) => `${s.page}.${s.row}.${s.column}.${urlId(s.id)}`;

function validSpot(s) {
  return Boolean(s) && typeof s === 'object' && ID_RE.test(String(s.id))
    && Number.isInteger(s.page) && s.page >= 1 && s.page <= 9999
    && Number.isInteger(s.row) && Math.abs(s.row) <= 999
    && Number.isInteger(s.column) && Math.abs(s.column) <= 999;
}

function el(tag, className, text) {
  const node = document.createElement(tag);
  if (className) node.className = className;
  if (text !== undefined) node.textContent = text;
  return node;
}

/** The column count that makes `n` square cells biggest inside w × h. */
function bestGrid(n, w, h, captionPx) {
  let best = { cols: 1, size: 0 };
  for (let cols = 1; cols <= n; cols += 1) {
    const rows = Math.ceil(n / cols);
    const byWidth = (w - GAP_PX * (cols - 1)) / cols;
    const byHeight = (h - GAP_PX * (rows - 1)) / rows - captionPx;
    const size = Math.floor(Math.min(byWidth, byHeight));
    if (size > best.size) best = { cols, size };
  }
  return best;
}

export default function create({ root, moduleApi }) {
  const prefs = () => moduleApi.instanceSettings || {};
  const chosen = () => (Array.isArray(prefs().buttons) ? prefs().buttons.filter(validSpot).slice(0, MAX_BUTTONS) : []);
  const save = (spots) => moduleApi.saveInstanceSettings({
    buttons: spots.map(({ id, page, row, column }) => ({ id, page, row, column })),
  });
  const imageUrl = (id) => `/api/modules/${encodeURIComponent(moduleApi.id)}/image/${urlId(id)}`;

  // Choosing survives the remount a gear change causes (picking from another
  // Page), so it is kept per tile for this browser tab, not in the closure.
  const choosingKey = `companion-buttons:choosing:${moduleApi.instanceId}`;
  const readChoosing = () => {
    try {
      return sessionStorage.getItem(choosingKey) === '1';
    } catch {
      return false;
    }
  };
  const writeChoosing = (on) => {
    try {
      if (on) sessionStorage.setItem(choosingKey, '1');
      else sessionStorage.removeItem(choosingKey);
    } catch {
      /* private window: choosing just ends on the next remount */
    }
  };

  const data = new Map();    // spot key → the server's latest word on it
  let stream = null;         // one stream for every button on the tile
  let streamPath = '';
  let lost = false;
  let choosing = false;
  let cells = [];            // one { cell, face, img, note, caption } per chosen button, in order
  let view = null;
  let banner = null;
  let chooser = null;        // the page being chosen from, while choosing
  let pages = [];
  let pagesTimer = null;
  let pagesToken = 0;
  let pickButton = null;
  let observer = null;
  let stopped = false;

  /* ── live buttons ─────────────────────────────────────────────────── */

  function onButton(msg) {
    const index = chosen().findIndex((s) => spotKey(s) === msg.key);
    if (index < 0) return;
    data.set(msg.key, msg);
    lost = false;
    paintCell(index);
    applyStatus();
    adopt(index, msg);
  }

  function syncStream() {
    const keys = chosen().map(spotKey);
    const path = keys.length ? keys.join('/') : '';
    if (path === streamPath) return;
    if (stream) stream.close();
    stream = null;
    streamPath = path;
    lost = false;
    for (const key of [...data.keys()]) if (!keys.includes(key)) data.delete(key);
    if (!path) return;
    stream = moduleApi.sse(`/stream/${path}`, {
      // The dashboard may already carry this stream (another tile showing the
      // same buttons, or this tile before a remount); then nothing is re-sent
      // on its own, so ask for what it sent on connect.
      async open() {
        try {
          const res = await moduleApi.fetch(`/state/${path}`);
          if (!res.ok || path !== streamPath) return;
          const snap = await res.json();
          if (path !== streamPath || stopped) return;
          for (const msg of snap.buttons || []) if (msg.seen || !data.has(msg.key)) onButton(msg);
        } catch {
          /* the stream itself catches up on the next redraw */
        }
      },
      events: {
        button(e) {
          try {
            onButton(JSON.parse(e.data));
          } catch {
            /* not JSON */
          }
        },
      },
      error() {
        lost = true;
        applyStatus();
      },
    });
  }

  /** Save what the server resolved a button to — a new id after a re-import, a new place after a move. */
  function adopt(index, msg) {
    const where = msg.location;
    if (!msg.controlId || !where) return;
    const spots = chosen();
    const s = spots[index];
    if (s.id === msg.controlId && s.page === where.page && s.row === where.row && s.column === where.column) return;
    if (spots.some((o, i) => i !== index && o.id === msg.controlId)) return; // already shown here
    spots[index] = { id: msg.controlId, page: where.page, row: where.row, column: where.column };
    data.set(spotKey(spots[index]), msg); // keep the picture up while the stream is re-made
    save(spots);
    syncStream();
  }

  function applyStatus() {
    const spots = chosen();
    if (choosing && !spots.length) return; // choosing reports Companion's state itself
    if (!spots.length) return moduleApi.setStatus('ok', 'No buttons chosen');
    if (lost) return showOffline('Lost the connection to ProdDash');
    const list = spots.map((s) => data.get(spotKey(s)));
    const bad = list.find((d) => d && d.status === 'error');
    if (bad) return showOffline(bad.message || 'Companion is not reachable');
    setBanner('');
    if (list.some((d) => !d || d.status !== 'ok' || !d.seen)) {
      const waiting = list.find((d) => d && d.status !== 'ok');
      return moduleApi.setStatus('connecting', waiting ? waiting.message : 'Waiting for Companion');
    }
    const missing = list.filter((d) => !d.image).length;
    if (missing) {
      return moduleApi.setStatus('connecting', `${missing} of ${list.length} button${list.length === 1 ? ' is' : 's are'} no longer in Companion`);
    }
    const msg = list[0].message || 'Companion';
    return moduleApi.setStatus('ok', list.length > 1 ? `${msg} · ${list.length} buttons` : msg);
  }

  function showOffline(message) {
    setBanner('Companion offline');
    moduleApi.setStatus('error', message);
  }

  function setBanner(text) {
    if (!banner || banner.textContent === text) return;
    banner.hidden = !text;
    banner.textContent = text;
    if (view) view.classList.toggle('is-offline', Boolean(text));
    layout(); // the banner takes room from the buttons
  }

  /* ── the chosen buttons ───────────────────────────────────────────── */

  function buildView() {
    root.textContent = '';
    cells = [];
    chooser = null;
    const spots = chosen();
    const wrap = el('div', 'cb-root');
    banner = el('div', 'cb-banner');
    banner.hidden = true;
    wrap.append(banner);

    if (!spots.length) {
      view = null;
      wrap.append(el('div', 'cb-empty', 'No buttons chosen'));
      root.append(wrap);
      return;
    }

    view = el('div', 'cb-grid');
    view.classList.toggle('has-captions', prefs().captions === true);
    spots.forEach((s, index) => {
      const cell = el('div', 'cb-cell');
      const face = el('div', 'cb-face is-waiting');
      const img = el('img', 'cb-img');
      img.alt = '';
      img.draggable = false;
      img.hidden = true;
      const note = el('div', 'cb-note');
      face.append(img, note);
      const caption = el('div', 'cb-caption');
      cell.append(face, caption);
      view.append(cell);
      cells.push({ cell, face, img, note, caption });
      paintCell(index);
    });
    wrap.append(view);
    root.append(wrap);
    layout();
  }

  function paintCell(index) {
    const c = cells[index];
    const s = chosen()[index];
    if (!c || !s) return;
    const d = data.get(spotKey(s));
    const where = d && d.location;
    const image = d && d.image;
    if (image) {
      if (c.img.getAttribute('src') !== image) c.img.src = image;
      c.img.hidden = false;
      c.note.textContent = '';
    } else {
      c.img.hidden = true;
      c.note.textContent = d && d.seen ? 'Not in Companion' : '';
    }
    c.face.classList.toggle('is-waiting', !d || !d.seen);
    c.face.classList.toggle('is-missing', Boolean(d && d.seen && !image));
    c.caption.textContent = where ? where.pageName : '';
    const title = where ? `${where.pageName} · ${where.page}/${where.row}/${where.column}` : '';
    c.cell.title = title;
    c.img.alt = title;
  }

  function layout() {
    if (!view || !cells.length) return;
    const captionPx = prefs().captions === true ? CAPTION_PX : 0;
    const { cols, size } = bestGrid(cells.length, view.clientWidth, view.clientHeight, captionPx);
    view.style.setProperty('--cb-cols', String(cols));
    view.style.setProperty('--cb-size', `${Math.max(16, size)}px`);
  }

  /* ── choosing ─────────────────────────────────────────────────────── */

  function setChoosing(on) {
    choosing = on;
    writeChoosing(on);
    pickButton?.classList.toggle('active', on);
    if (on) {
      openChooser();
    } else {
      clearTimeout(pagesTimer);
      pagesToken += 1;
      syncStream();
      buildView();
      applyStatus();
    }
  }

  function openChooser() {
    root.textContent = '';
    cells = [];
    view = null;
    banner = null;
    chooser = el('div', 'cb-chooser');
    root.append(chooser);
    loadPages();
  }

  async function loadPages() {
    const token = ++pagesToken;
    clearTimeout(pagesTimer);
    let reply = null;
    try {
      const res = await moduleApi.fetch('/pages');
      reply = await res.json();
      if (!res.ok) throw new Error(reply.error || `ProdDash answered ${res.status}`);
    } catch (err) {
      reply = { status: 'error', message: err.message || 'ProdDash is not answering', pages: [] };
    }
    if (stopped || !chooser || token !== pagesToken) return;
    pages = Array.isArray(reply.pages) ? reply.pages : [];
    moduleApi.setStatus(reply.status === 'ok' ? 'ok' : reply.status === 'connecting' ? 'connecting' : 'error', reply.message || '');
    if (!pages.length) {
      chooser.textContent = '';
      chooser.append(el('div', 'cb-empty', reply.status === 'ok' ? 'Companion has no pages' : reply.message || 'Companion is not reachable'));
      pagesTimer = setTimeout(loadPages, PAGES_RETRY_MS);
      return;
    }
    drawChooser();
  }

  /** The page the gear names; else the page of the first chosen button, or the first page with buttons — saved, so the gear shows it. */
  function chooserPage() {
    const wanted = String(prefs().page || '');
    const named = PAGE_RE.test(wanted) && pages.find((p) => p.id === wanted);
    if (named) return named;
    const first = chosen()[0];
    const fallback = (first && pages.find((p) => p.number === first.page))
      || pages.find((p) => p.buttons.length)
      || pages[0];
    moduleApi.saveInstanceSettings({ page: fallback.id });
    return fallback;
  }

  function drawChooser() {
    const page = chooserPage();
    chooser.textContent = '';
    if (!page.buttons.length) {
      chooser.append(el('div', 'cb-empty', `${page.name} has no buttons`));
      return;
    }
    // Companion's grid may start below zero; lay the page out from its own corner.
    const rows = page.buttons.map((b) => b.row);
    const cols = page.buttons.map((b) => b.column);
    const minRow = Math.min(0, ...rows);
    const minCol = Math.min(0, ...cols);
    const grid = el('div', 'cb-pick-grid');
    grid.style.setProperty('--cb-pick-cols', String(Math.max(...cols) - minCol + 1));
    for (const b of page.buttons) {
      const key = el('button', 'cb-pick-key');
      key.type = 'button';
      key.dataset.id = b.controlId;
      key.style.gridRow = String(b.row - minRow + 1);
      key.style.gridColumn = String(b.column - minCol + 1);
      key.title = `${page.name} · ${page.number}/${b.row}/${b.column}`;
      const img = el('img', 'cb-pick-img');
      img.alt = key.title;
      img.draggable = false;
      img.src = imageUrl(b.controlId);
      img.addEventListener('error', () => img.classList.add('is-broken'));
      key.append(img, el('span', 'cb-pick-badge'));
      key.addEventListener('click', () => toggle({ id: b.controlId, page: page.number, row: b.row, column: b.column }));
      grid.append(key);
    }
    chooser.append(grid);
    markPicked();
  }

  function toggle(spot) {
    const spots = chosen();
    const at = spots.findIndex((s) => s.id === spot.id);
    if (at >= 0) spots.splice(at, 1);
    else if (spots.length < MAX_BUTTONS) spots.push(spot);
    save(spots);
    markPicked();
  }

  function markPicked() {
    if (!chooser) return;
    const ids = chosen().map((s) => s.id);
    for (const key of chooser.querySelectorAll('.cb-pick-key')) {
      const at = ids.indexOf(key.dataset.id);
      key.classList.toggle('is-picked', at >= 0);
      key.querySelector('.cb-pick-badge').textContent = at >= 0 ? String(at + 1) : '';
    }
  }

  /* ── lifecycle ────────────────────────────────────────────────────── */

  return {
    start() {
      stopped = false;
      moduleApi.setStatus('connecting', 'Connecting');
      pickButton = moduleApi.header.addButton({
        icon: GRID_SVG,
        title: 'Choose buttons',
        onClick: () => setChoosing(!choosing),
      });
      observer = new ResizeObserver(() => layout());
      observer.observe(root);
      syncStream();
      // A new tile, or one that was choosing before a gear change, goes (back) to choosing.
      setChoosing(readChoosing() || !chosen().length);
    },

    stop() {
      stopped = true;
      clearTimeout(pagesTimer);
      pagesToken += 1;
      if (stream) stream.close();
      stream = null;
      streamPath = '';
      data.clear();
      if (observer) observer.disconnect();
      observer = null;
      chooser = null;
      view = null;
      cells = [];
      root.textContent = '';
    },
  };
}