// POS app — catalog, cart, payment, offline queue, slip generation.
// All server access goes through /api/v1/pos/* via window.posFetch
// (see pos-config.js) — this app never talks to PocketBase directly.
(function(){
'use strict';

const CACHE = 'pos-v1';
const LS_CART = 'pos.cart';
const LS_QUEUE = 'pos.queue';

// ---------------- state ----------------
const state = {
  products: [],
  productsById: new Map(),
  categories: [],
  activeCat: 'all',
  search: '',
  // id -> {hay, squish, words}. Built by PosSearch.buildIndex on every
  // catalog load (both the IndexedDB and the network path) so the
  // per-keystroke filter only does `indexOf`, never normalisation.
  searchIndex: new Map(),
  cart: new Map(),        // id -> {p, qty}
  customer: null,
  paymentMethod: null,
  cashGiven: 0,
  // Discount: { kind: "amount" | "percent" | "none", input: number }
  // The "input" is the raw number the cashier typed (e.g. 10 for
  // "10% off" or 50 for "R50 off"). The server resolves it to a
  // rand value and applies it to the gross total post-VAT.
  discount: { kind: 'none', input: 0 },
  letterhead: null,
  // How many rows of the current filter are rendered. The full catalog
  // is several hundred items; painting them all makes the till sluggish
  // and buries the stock staff actually reach for.
  limit: 0
};

// Rows rendered per chunk. The catalog arrives newest-first, so the
// default view is effectively "recently added".
const PAGE = 50;

// ---------------- IndexedDB ----------------
const DB_NAME='pos', DB_VER=1, STORE_PRODUCTS='products', STORE_QUEUE='queue';
let dbPromise = null;
function openDB(){
  if(dbPromise) return dbPromise;
  dbPromise = new Promise((res,rej)=>{
    const req = indexedDB.open(DB_NAME, DB_VER);
    req.onupgradeneeded = e => {
      const db = e.target.result;
      if(!db.objectStoreNames.contains(STORE_PRODUCTS)) db.createObjectStore(STORE_PRODUCTS,{keyPath:'id'});
      if(!db.objectStoreNames.contains(STORE_QUEUE)) db.createObjectStore(STORE_QUEUE,{keyPath:'localId'});
    };
    req.onsuccess = e => res(e.target.result);
    req.onerror = e => rej(e.target.error);
  });
  return dbPromise;
}
async function dbPut(store, val){
  const db = await openDB();
  return new Promise((res,rej)=>{
    const tx = db.transaction(store,'readwrite');
    tx.objectStore(store).put(val);
    tx.oncomplete = ()=>res();
    tx.onerror = e=>rej(e.target.error);
  });
}
async function dbAll(store){
  const db = await openDB();
  return new Promise((res,rej)=>{
    const tx = db.transaction(store,'readonly');
    const req = tx.objectStore(store).getAll();
    req.onsuccess = ()=>res(req.result||[]);
    req.onerror = e=>rej(e.target.error);
  });
}
async function dbDel(store, key){
  const db = await openDB();
  return new Promise((res,rej)=>{
    const tx = db.transaction(store,'readwrite');
    tx.objectStore(store).delete(key);
    tx.oncomplete = ()=>res();
    tx.onerror = e=>rej(e.target.error);
  });
}

// ---------------- formatting ----------------
const fmt = n => 'R ' + (Number(n)||0).toLocaleString('en-ZA',{minimumFractionDigits:2,maximumFractionDigits:2});
const fmtN = n => (Number(n)||0).toLocaleString('en-ZA',{minimumFractionDigits:2,maximumFractionDigits:2});
const uid = ()=> 'loc_' + Date.now().toString(36) + '_' + Math.random().toString(36).slice(2,8);

// ---------------- catalog loading ----------------
/**
 * Adopt a catalog array: wire up the id map, rebuild the search index,
 * then repaint. Called from BOTH load paths — the IndexedDB cache and the
 * network refresh — because a till that booted offline has no index yet
 * and would otherwise filter against an empty one.
 */
function adoptCatalog(list){
  state.products = list;
  state.productsById = new Map(list.map(p=>[p.id,p]));
  // See filteredProducts() — an empty index is inert there via fallbackSearch.
  state.searchIndex = window.PosSearch ? window.PosSearch.buildIndex(list) : new Map();
  buildCategories();
  render();
}

async function loadProducts(){
  // Try IDB first
  try{
    const cached = await dbAll(STORE_PRODUCTS);
    if(cached.length){
      adoptCatalog(cached);
    }
  }catch{}
  // Then network refresh — single call, the API route returns the
  // full active catalog (no pagination needed at this catalog size).
  try{
    const r = await window.posFetch('/catalog');
    if(!r.ok) throw new Error('catalog returned ' + r.status);
    const j = await r.json();
    const all = (j.items || []).map(p => ({
      ...p,
      description: p.description || p.name,
    }));
    adoptCatalog(all);
    for(const p of all) await dbPut(STORE_PRODUCTS, p);
  }catch(e){
    console.warn('Network load failed', e);
    if(!state.products.length){
      const el = document.getElementById('empty');
      el.innerHTML = '<h3>Offline</h3><p>No cached catalog. Reconnect and reload.</p>';
    }
  }
}

async function loadLetterhead(){
  // Fetch + cache the active letterhead via letterhead-config.js.
  // On a fresh till, this auto-picks Westcott Group (the only
  // letterhead the POS uses per the 2026-09-04 operator decision).
  // The fetched row drives:
  //   - state.letterhead.*  → shown on the on-screen receipt
  //   - state.letterhead.vat_percent → cart VAT math (replaces the
  //     hardcoded 15% so a 0% letterhead shows no VAT line)
  //   - sale.letterhead.* → attached to the saved sale, consumed by
  //     receipt.html, epos-print.js (buildEposXml), and the
  //     history-reprint redirect.
  try{
    const item = await window.PosLetterhead.ensureActive();
    state.letterhead = item;
  }catch(e){
    console.warn('Letterhead load failed; receipt will fall back to "WFSALES POS"', e);
    state.letterhead = null;
  }
}

function buildCategories(){
  const set = new Map();
  for(const p of state.products){
    if(!p.category) continue;
    set.set(p.category, (set.get(p.category)||0)+1);
  }
  state.categories = Array.from(set.entries()).sort((a,b)=>b[1]-a[1]);

  // Label on the trigger
  const lbl = document.getElementById('catLabel');
  const cnt = document.getElementById('catCount');
  lbl.textContent = state.activeCat === 'all' ? 'All categories' : state.activeCat;
  cnt.textContent = state.products.length + ' products';

  // Menu items
  const head = document.getElementById('catMenuItems');
  const total = state.products.length;
  const totalUncategorized = state.products.filter(p => !p.category).length;
  head.innerHTML =
    `<button class="cat-item ${state.activeCat==='all'?'active':''}" data-cat="all" role="option">
       <span class="nm">All categories</span><span class="ct">${total}</span>
     </button>` +
    (totalUncategorized ? `<button class="cat-item ${state.activeCat==='__uncat'?'active':''}" data-cat="__uncat" role="option">
       <span class="nm">Uncategorised</span><span class="ct">${totalUncategorized}</span>
     </button>` : '') +
    state.categories.map(([c,n])=>`<button class="cat-item ${state.activeCat===c?'active':''}" data-cat="${escapeAttr(c)}" role="option">
       <span class="nm">${escapeHTML(c)}</span><span class="ct">${n}</span>
     </button>`).join('');

  head.querySelectorAll('.cat-item').forEach(b=>{
    b.addEventListener('click', ()=>{
      const v = b.dataset.cat;
      state.activeCat = v === '__uncat' ? '__uncat' : v;
      closeCatMenu();
      buildCategories();
      resetPaging();
      render();
    });
  });
}

function openCatMenu(){
  const menu = document.getElementById('catMenu');
  const back = document.getElementById('catBackdrop');
  const trigger = document.getElementById('catTrigger');
  // Position menu below the trigger
  const r = trigger.getBoundingClientRect();
  menu.style.top = (r.bottom + 6) + 'px';
  menu.hidden = false;
  back.hidden = false;
  trigger.setAttribute('aria-expanded','true');
}
function closeCatMenu(){
  const menu = document.getElementById('catMenu');
  const back = document.getElementById('catBackdrop');
  const trigger = document.getElementById('catTrigger');
  menu.hidden = true;
  back.hidden = true;
  trigger.setAttribute('aria-expanded','false');
}

function filteredProducts(){
  // Category first — it's a plain equality test and prunes most of the
  // catalog before any string work happens.
  let list = state.products;
  if(state.activeCat==='__uncat'){
    list = list.filter(p=>!p.category);
  } else if(state.activeCat!=='all'){
    list = list.filter(p=>p.category===state.activeCat);
  }
  // …then rank by text. PosSearch owns the tiers; an empty query returns
  // the list untouched, which keeps the default "recently added" view.
  //
  // The fallback is for a half-updated till: pos.html loads pos-search.js
  // ahead of this file, but a service worker can still be serving a stale
  // mix of the two. A blank catalog is a shop that cannot sell anything, so
  // degrade to the old substring filter rather than throwing. Only reachable
  // on a skewed cache — both files ship together.
  if(!window.PosSearch) return fallbackSearch(list);
  return window.PosSearch.search(list, state.searchIndex, state.search);
}

/** The pre-2026-10-06 filter: case-insensitive substring over sku + description. */
function fallbackSearch(list){
  const q = state.search.trim().toLowerCase();
  if(!q) return list;
  return list.filter(p=>
    (p.sku||'').toLowerCase().includes(q)
    || (p.description||'').toLowerCase().includes(q));
}

/** Call whenever the filter changes, so a new result set starts at the top. */
function resetPaging(){
  state.limit = PAGE;
}

function render(){
  const list = filteredProducts();
  const cat = document.getElementById('catalog');
  if(!list.length){
    cat.innerHTML = '<div class="empty"><h3>No matches</h3><p>Try a different search or category.</p></div>';
    return;
  }
  if(!state.limit) state.limit = PAGE;
  const shown = list.slice(0, state.limit);
  const more = list.length - shown.length;
  // Keep the scroll position across re-renders (adding to the cart calls
  // render()), otherwise the till jumps back to the top on every tap.
  const scrollTop = cat.scrollTop;

  const browsing = !state.search.trim() && state.activeCat === 'all';
  const heading = browsing ? 'Recently added' : 'Results';

  cat.innerHTML =
    `<div class="meta"><span>${heading}</span><span>${shown.length} of ${list.length}</span></div>` +
    shown.map(p=>{
    const price = p.selling_price ?? p.cost_price ?? 0;
    const inCart = state.cart.get(p.id)?.qty || 0;
    // FA icon when the category row carries one; fall back to initials
    // so an unconfigured category still renders something recognisable.
    const icon = p.category_icon
      ? `<i class="ic-fa ${escapeAttr(p.category_icon)}" aria-hidden="true"></i>`
      : initials(p.category||p.brand||'?');
    return `<button class="prod" data-id="${p.id}" data-od-id="prod-${p.id}">
      <div class="ic">${icon}</div>
      <div class="body">
        <div class="name">${escapeHTML(p.description||p.sku||'—')}</div>
        <div class="sub">${escapeHTML(p.sku||'')}${p.brand?' · '+escapeHTML(p.brand):''}${p.unit?' · '+escapeHTML(p.unit):''}${inCart?' · '+inCart+' in cart':''}</div>
      </div>
      <div class="price">${fmt(price)}<small>/${escapeHTML(p.unit||'ea')}</small></div>
    </button>`;
  }).join('') +
    (more > 0
      ? `<button class="more" id="showMore">Show ${Math.min(more, PAGE)} more <small>${more} remaining</small></button>`
      : '');

  cat.querySelectorAll('.prod').forEach(b=>{
    b.addEventListener('click', ()=>addToCart(b.dataset.id));
  });
  cat.scrollTop = scrollTop;

  const moreBtn = document.getElementById('showMore');
  if(moreBtn){
    const loadMore = ()=>{ state.limit += PAGE; render(); };
    moreBtn.addEventListener('click', loadMore);
    // Auto-load as it scrolls into view; the button stays as the fallback
    // for browsers without IntersectionObserver.
    if('IntersectionObserver' in window){
      const io = new IntersectionObserver(entries=>{
        if(entries.some(e=>e.isIntersecting)){ io.disconnect(); loadMore(); }
      }, {root: cat, rootMargin: '200px'});
      io.observe(moreBtn);
    }
  }
}

function initials(s){
  const parts = s.trim().split(/\s+/).slice(0,2);
  return parts.map(p=>p[0]||'').join('').toUpperCase().slice(0,2);
}

// ---------------- custom (ad-hoc) lines ----------------
//
// A line the cashier types by hand — "Bolt cutting" at R20 — that
// belongs on this slip and nowhere else. It is NOT a catalogue
// item: no `stock_items` row, no stock decrement, no ledger entry.
// It carries a synthetic `custom:` id purely so it can live in the
// same cart Map and flow through the same totals, slip and checkout
// path as everything else.
//
// The prefix matters: it's how the checkout payload marks the line
// `is_custom`, and it's how the cart drawer badges it so the
// cashier can see at a glance which lines are not real stock.
const CUSTOM_ID_PREFIX = 'custom:';

function addCustomItem(description, price){
  const desc = (description||'').trim();
  const amount = Number(price);
  if(!desc){ alert('Give the item a name.'); return null; }
  if(!Number.isFinite(amount) || amount <= 0){ alert('Enter a price greater than zero.'); return null; }
  const p = {
    id: CUSTOM_ID_PREFIX + uid(),
    name: desc,
    description: desc,
    sku: '',
    unit: '',
    // EX-VAT, same basis as the catalogue — VAT is added on top in
    // cartTotals(). A service the shop performs has no cost of goods.
    selling_price: amount,
    cost_price: 0,
    is_custom: true,
  };
  state.cart.set(p.id, {p, qty: 1});
  persistCart();
  render();
  paintCart();
  renderCartDrawer();
  return p;
}
function isCustomLine(p){ return !!(p && p.is_custom); }

function openCustomItem(){
  document.getElementById('customDesc').value = '';
  document.getElementById('customPrice').value = '';
  document.getElementById('customSheet').classList.add('show');
  document.getElementById('customBackdrop').classList.add('show');
  setTimeout(()=>document.getElementById('customDesc').focus(), 60);
}
function closeCustomItem(){
  document.getElementById('customSheet').classList.remove('show');
  document.getElementById('customBackdrop').classList.remove('show');
}
function saveCustomItem(){
  const desc = document.getElementById('customDesc').value;
  const price = document.getElementById('customPrice').value.replace(/[^0-9.]/g,'');
  const p = addCustomItem(desc, Number(price));
  if(p) closeCustomItem();
}

// ---------------- cart ----------------
function addToCart(id){
  const p = state.productsById.get(id);
  if(!p) return;
  const cur = state.cart.get(id);
  if(cur) cur.qty++;
  else state.cart.set(id, {p, qty:1});
  persistCart();
  render();
  paintCart();
  // tactile on the bar
  const bar = document.getElementById('cartBar');
  bar.animate([{transform:'translateY(0) scale(1)'},{transform:'translateY(-2px) scale(1.01)'},{transform:'translateY(0) scale(1)'}],{duration:200});
}
function changeQty(id, delta){
  const cur = state.cart.get(id);
  if(!cur) return;
  cur.qty += delta;
  if(cur.qty<=0) state.cart.delete(id);
  persistCart();
  render();
  paintCart();
  if(document.getElementById('cartDrawer').classList.contains('show')) renderCartDrawer();
}
function removeFromCart(id){
  state.cart.delete(id);
  persistCart();
  render();
  paintCart();
  renderCartDrawer();
}
function cartTotals(){
  let count=0, gross=0;
  for(const {p,qty} of state.cart.values()){
    count += qty;
    // Catalogue shelf price — the till never edits a line's price.
    // Prices are EX-VAT (see pos-service.ts): derived as
    // cost × markup from the supplier's ex-VAT cost, with no VAT
    // uplift. VAT is added on top below.
    const unit = lineUnitPrice({p,qty});
    gross += unit * qty;
  }
  // Discount (off the ex-VAT gross, so it's a true % off both the
  // net and the VAT on it). Percentage-only and capped at the
  // gross so the total can never go negative.
  const d = state.discount || { kind: 'none', input: 0 };
  let discountAmount = 0;
  if (d.kind === 'percent' && d.input > 0) {
    discountAmount = Math.min((gross * d.input) / 100, gross);
  }
  // The VAT rate comes from the active letterhead — each shop may
  // sit at a different rate. Falls back to the SA standard rate
  // when no letterhead has loaded yet (a fresh till on a flaky
  // network still has to be able to take money).
  const vatPct = Number(state.letterhead && state.letterhead.vat_percent);
  const pct = Number.isFinite(vatPct) && vatPct >= 0 ? vatPct : 15;
  const net = Math.max(0, gross - discountAmount);
  const vat = (net * pct) / 100;
  const total = net + vat;
  return {count, gross, discountAmount, sub: net, vat, total, vatPct: pct};
}

/**
 * Effective unit price for a cart line — always the catalogue's selling
 * price. It used to prefer a per-line override set by the long-press edit
 * sheet, but that sheet is quantity-only now, so no override can exist.
 * Kept as a named helper because the price feeds four places (line render,
 * cart totals, the sale record and the checkout payload) and they must not
 * drift apart. Returns 0 when neither price is set.
 */
function lineUnitPrice(line){
  return Number(line.p.selling_price ?? line.p.cost_price ?? 0) || 0;
}
function persistCart(){
  const arr = Array.from(state.cart.entries()).map(([id,{p,qty}])=>({id, qty, p}));
  try{ localStorage.setItem(LS_CART, JSON.stringify(arr)); }catch{}
}
function loadCart(){
  try{
    const arr = JSON.parse(localStorage.getItem(LS_CART)||'[]');
    for(const {id,p,qty} of arr) state.cart.set(id,{p,qty});
  }catch{}
}
function paintCart(){
  const t = cartTotals();
  document.getElementById('cartCount').textContent = t.count;
  document.getElementById('cartTotal').textContent = fmt(t.total);
  document.getElementById('cartBar').classList.toggle('show', t.count>0);
}

function openDrawer(){
  renderCartDrawer();
  paintDiscount();
  document.getElementById('cartDrawer').classList.add('show');
}
function closeDrawer(){
  document.getElementById('cartDrawer').classList.remove('show');
}
function renderCartDrawer(){
  const body = document.getElementById('cartLines');
  if(state.cart.size===0){
    body.innerHTML = '<div class="empty"><h3>Empty cart</h3><p>Add products from the catalog.</p></div>';
    document.getElementById('subTotal').textContent = fmt(0);
    document.getElementById('vatTotal').textContent = fmt(0);
    document.getElementById('grandTotal').textContent = fmt(0);
    document.getElementById('discountLine').hidden = true;
    return;
  }
  body.innerHTML = Array.from(state.cart.values()).map(({p,qty})=>{
    const price = lineUnitPrice({p,qty});
    const custom = isCustomLine(p);
    // Custom lines carry no SKU and no unit — badge them so the
    // cashier can see at a glance that this isn't stock, and it
    // won't show up on a stocktake or reorder list.
    const sub = custom
      ? `${fmt(price)} each · custom item`
      : `${fmt(price)} / ${escapeHTML(p.unit||'ea')} · ${escapeHTML(p.sku||'')}`;
    return `<div class="line${custom?' custom-line':''}" data-od-id="line-${p.id}" data-id="${p.id}">
      <div class="nm">${escapeHTML(p.description||p.name||p.sku)}<small>${sub}</small></div>
      <div class="qty">
        <button onclick="window.__pos.changeQty('${p.id}',-1)" aria-label="Decrease quantity">−</button>
        <button class="v" data-od-id="qty-set" onclick="window.__pos.openEditLine('${p.id}')" aria-label="Set quantity for ${escapeAttr(p.description||p.sku||'item')}">${qty}</button>
        <button onclick="window.__pos.changeQty('${p.id}',1)" aria-label="Increase quantity">+</button>
      </div>
      <div class="pr">${fmt(price*qty)}</div>
      <button class="rm" onclick="window.__pos.removeFromCart('${p.id}')" aria-label="Remove">
        <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M6 6l12 12M18 6L6 18"/></svg>
      </button>
    </div>`;
  }).join('');
  const t = cartTotals();
  document.getElementById('subTotal').textContent = fmt(t.sub);
  document.getElementById('vatTotal').textContent = fmt(t.vat);
  document.getElementById('grandTotal').textContent = fmt(t.total);
  // The VAT line label follows the letterhead's rate rather than
  // hardcoding 15%, so a shop at a different rate doesn't print a
  // wrong label over the right number.
  const vatLabel = document.getElementById('vatLabel');
  if (vatLabel) vatLabel.textContent = t.vatPct > 0 ? `VAT ${t.vatPct}%` : 'VAT';
  // Discount line: shown only when a discount is actually
  // applied. The server re-derives the resolved rand value at
  // commit time, so this number is a preview only.
  const dl = document.getElementById('discountLine');
  if (t.discountAmount > 0) {
    dl.hidden = false;
    const d = state.discount || {};
    const pctLabel = d.kind === 'percent' && d.input ? ` (${d.input}%)` : '';
    document.getElementById('discountLineAmount').textContent =
      `− ${fmt(t.discountAmount)}${pctLabel} ex VAT`;
  } else {
    dl.hidden = true;
    // Blank the figure as well as hiding the row. A discount that has
    // been cleared must not leave its old amount sitting on screen —
    // an operator seeing "− R 98.37" under a total that no longer
    // contains it has no way to tell stale text from a live one.
    document.getElementById('discountLineAmount').textContent = '';
  }
}

// ---------------- discount ----------------
// Two fixed tiers, 20% and 40%. Deliberately not a free-typed
// field: the whole point is that every discount on every slip is
// visibly one of two known-good choices, so nobody can ring up a
// hand-typed 90% (or a random rand amount) and nobody has to guess
// afterwards whether it was deliberate.
const DISCOUNT_TIERS = [20, 40];

function paintDiscount(){
  const d = state.discount || { kind: 'none', input: 0 };
  const trig = document.getElementById('discountTrigger');
  const lbl = document.getElementById('discountTriggerLabel');
  const body = document.getElementById('discountBody');
  const hint = document.getElementById('discHint');

  const active = d.kind === 'percent' && DISCOUNT_TIERS.includes(Number(d.input))
    ? Number(d.input) : 0;

  for (const tier of DISCOUNT_TIERS){
    const btn = document.getElementById('discTier'+tier);
    if (btn) btn.classList.toggle('active', tier === active);
  }
  if (active){
    trig.classList.add('has-value');
    lbl.textContent = `Discount: ${active}%`;
    body.hidden = false;
    trig.setAttribute('aria-expanded','true');
  } else {
    trig.classList.remove('has-value');
    lbl.textContent = 'Add discount';
    body.hidden = true;
    trig.setAttribute('aria-expanded','false');
  }
  hint.textContent = 'Applied off the ex-VAT total — VAT is charged on the discounted amount.';
}
function toggleDiscount(){
  // The trigger only opens/closes the tier buttons — it never clears
  // the discount. Clearing is tapping the active tier again, so
  // there's no way to lose a discount by mis-tapping the chevron.
  const body = document.getElementById('discountBody');
  const trig = document.getElementById('discountTrigger');
  const open = body.hidden;
  // Don't let the operator dismiss the panel out from under an
  // applied discount — that would hide the reason for the total.
  if (!open && state.discount && state.discount.kind === 'percent') return;
  body.hidden = !open;
  trig.setAttribute('aria-expanded', String(open));
}
function setDiscountTier(pct){
  const tier = Number(pct);
  if(!DISCOUNT_TIERS.includes(tier)) return;
  // Tapping the active tier clears it — one control, no separate
  // "remove" affordance to forget.
  if(state.discount && state.discount.kind==='percent' && Number(state.discount.input)===tier){
    clearDiscount();
    return;
  }
  state.discount = { kind:'percent', input: tier };
  paintDiscount();
  renderCartDrawer();
}
function clearDiscount(){
  state.discount = { kind:'none', input:0 };
  paintDiscount();
  renderCartDrawer();
}
// Discounts are two fixed buttons now, so there's no free-text
// input to live-listen to.

// ---------------- long-press edit line ----------------
//
// Hold a cart line for 600ms → modal opens with qty + unit price.
// Tapping the quantity number does the same thing and is the discoverable
// route; the long-press is kept because it is the faster gesture for a
// cashier who already knows it's there.
// Common on mobile POS apps; the cashier scans/selects, then holds
// the row to fix the qty before ringing it up. Quantity only — this
// sheet has no price field. We use a 600ms threshold so a normal "I'm
// thinking about it" tap doesn't accidentally open the modal — but it's
// well under the long-press duration most users naturally apply (≈800ms).
//
// Haptic feedback (navigator.vibrate) on the trigger where the
// device supports it; visual hint via the .line-holding class so
// the operator sees something happen during the press.
const LONG_PRESS_MS = 600;
let longPressTimer = null;
let longPressTarget = null;

function clearLongPress(){
  if (longPressTimer) { clearTimeout(longPressTimer); longPressTimer = null; }
  if (longPressTarget) {
    longPressTarget.classList.remove('line-holding');
    longPressTarget = null;
  }
}
function startLongPress(el){
  clearLongPress();
  longPressTarget = el;
  el.classList.add('line-holding');
  // Best-effort haptic on the long-press fire. iOS Safari only
  // honors navigator.vibrate inside a user-gesture handler; this
  // is called from a pointerdown so the chain is intact. Android
  // Chrome respects it always.
  longPressTimer = setTimeout(()=>{
    const id = el.dataset.id;
    try { navigator.vibrate?.(12); } catch(_) {}
    if (id) openEditLine(id);
    clearLongPress();
  }, LONG_PRESS_MS);
}

document.addEventListener('pointerdown', e=>{
  const line = e.target.closest('.line[data-id]');
  if (!line) return;
  // The steppers and the quantity number are their own controls now. A
  // long-press on them used to pop the edit sheet open mid-tap, which made
  // holding "+" to ring up a bulk quantity fight the sheet. Each of them
  // does its own thing on a normal tap.
  if (e.target.closest('.qty, .rm')) return;
  startLongPress(line);
}, { passive: true });
document.addEventListener('pointerup', clearLongPress);
document.addEventListener('pointercancel', clearLongPress);
document.addEventListener('pointerleave', e=>{
  if (longPressTarget && e.target === longPressTarget) clearLongPress();
});

let editingLineId = null;
function openEditLine(id){
  const line = state.cart.get(id);
  if (!line) return;
  editingLineId = id;
  document.getElementById('editSku').textContent = line.p.sku || line.p.description || '';
  // Quantity only. This popup deliberately has no price field: the till
  // sells at the catalogue shelf price and a mis-keyed price is expensive
  // and hard to spot. Per-line price overrides were removed on request —
  // the server reads only `unit_price`, so nothing else depended on them.
  document.getElementById('editQty').value = String(line.qty);
  document.getElementById('editBackdrop').classList.add('show');
  document.getElementById('editSheet').classList.add('show');
  setTimeout(()=>document.getElementById('editQty').focus(), 60);
}
function closeEditLine(){
  editingLineId = null;
  document.getElementById('editBackdrop').classList.remove('show');
  document.getElementById('editSheet').classList.remove('show');
}
function editSave(){
  if (!editingLineId) return;
  const line = state.cart.get(editingLineId);
  if (!line) { closeEditLine(); return; }
  const qty = Number((document.getElementById('editQty').value || '').replace(/[^0-9.]/g, ''));
  const hint = document.getElementById('editHint');
  // Bad qty — show an error in the hint, keep the modal open so the
  // operator can fix it. (Previously the modal stayed open without
  // any feedback, so a cleared/0 qty field left the screen grey and
  // the operator had to long-press another line to escape.)
  if (!Number.isFinite(qty) || qty <= 0) {
    if (hint) {
      hint.textContent = 'Enter a quantity of 1 or more.';
      hint.style.color = '#c92a2a';
    }
    const qIn = document.getElementById('editQty');
    if (qIn) { qIn.focus(); qIn.select(); }
    return;
  }
  line.qty = Math.floor(qty);
  // Reset the hint to its neutral default before closing so the next
  // openEditLine() doesn't show a stale error from this round.
  if (hint) { hint.textContent = 'Type a quantity like 800, then tap Save.'; hint.style.color = ''; }
  persistCart();
  render();
  renderCartDrawer();
  closeEditLine();
}
function editRemove(){
  if (!editingLineId) return;
  const id = editingLineId;
  closeEditLine();
  removeFromCart(id);
}

// ---------------- payment ----------------
function openPayment(){
  if(state.cart.size===0) return;
  const t = cartTotals();
  state.paymentMethod = null;
  state.cashGiven = 0;
  state.customer = null;
  document.getElementById('payTotal').textContent = fmt(t.total);
  document.getElementById('paySub').textContent = fmt(t.sub);
  document.getElementById('payVat').textContent = fmt(t.vat);
  document.getElementById('dueIn').value = fmt(t.total);
  document.getElementById('givenIn').value = '';
  document.getElementById('changeOut').classList.remove('show','short');
  document.getElementById('cashBlock').classList.remove('show');
  document.getElementById('custBlock').classList.remove('show');
  document.getElementById('custPicked').classList.remove('show');
  document.getElementById('custResults').innerHTML = '';
  document.getElementById('custQ').value = '';
  document.querySelectorAll('.pay-tile').forEach(t=>t.classList.remove('selected'));
  document.getElementById('confirmBtn').disabled = true;
  buildQuickAmounts(t.total);
  document.getElementById('payDrawer').classList.add('show');
}
function closePayment(){
  document.getElementById('payDrawer').classList.remove('show');
}
function buildQuickAmounts(total){
  // Rounded suggestions above the total
  const base = Math.ceil(total/10)*10;
  const suggestions = [];
  if(base>total) suggestions.push(base);
  for(const m of [50,100,200,500,1000]){
    const v = Math.ceil(total/m)*m;
    if(v>total && !suggestions.includes(v)) suggestions.push(v);
  }
  suggestions.sort((a,b)=>a-b);
  document.getElementById('quick').innerHTML = suggestions.slice(0,5).map(v=>`<button data-v="${v}">${fmt(v)}</button>`).join('');
  document.getElementById('quick').querySelectorAll('button').forEach(b=>{
    b.addEventListener('click',()=>{
      document.getElementById('givenIn').value = fmtN(b.dataset.v);
      state.cashGiven = Number(b.dataset.v);
      paintChange();
    });
  });
}
function pickMethod(m){
  state.paymentMethod = m;
  document.querySelectorAll('.pay-tile').forEach(t=>t.classList.toggle('selected', t.dataset.meth===m));
  document.getElementById('cashBlock').classList.toggle('show', m==='cash');
  document.getElementById('custBlock').classList.toggle('show', m==='account');
  if(m!=='cash') document.getElementById('changeOut').classList.remove('show');
  if(m!=='account') document.getElementById('custPicked').classList.remove('show');
  validateConfirm();
  if(m==='cash'){
    setTimeout(()=>document.getElementById('givenIn').focus(), 250);
  } else if(m==='account'){
    setTimeout(()=>document.getElementById('custQ').focus(), 250);
  }
}
function paintChange(){
  const total = cartTotals().total;
  const given = state.cashGiven || 0;
  const change = given - total;
  const out = document.getElementById('changeOut');
  if(given<=0){ out.classList.remove('show','short'); return; }
  out.classList.add('show');
  out.classList.toggle('short', change<-0.005);
  document.getElementById('changeAmt').textContent = (change>=0?'+ ':'− ') + fmt(Math.abs(change));
  validateConfirm();
}
function validateConfirm(){
  const m = state.paymentMethod;
  const btn = document.getElementById('confirmBtn');
  if(!m){ btn.disabled = true; return; }
  if(m==='cash'){
    btn.disabled = !(state.cashGiven >= cartTotals().total - 0.005);
  } else if(m==='account'){
    btn.disabled = !state.customer;
  } else {
    btn.disabled = false;
  }
}

// ---------------- customer search ----------------
let custDebounce;
document.addEventListener('input', e=>{
  if(e.target.id!=='custQ') return;
  clearTimeout(custDebounce);
  const q = e.target.value.trim();
  custDebounce = setTimeout(()=>searchCustomers(q), 200);
});
document.addEventListener('input', e=>{
  if(e.target.id!=='givenIn') return;
  const raw = e.target.value.replace(/[^0-9.]/g,'');
  e.target.value = raw;
  state.cashGiven = Number(raw)||0;
  paintChange();
});
async function searchCustomers(q){
  const box = document.getElementById('custResults');
  if(!q){ box.innerHTML=''; return; }
  try{
    const r = await window.posFetch(`/customers?q=${encodeURIComponent(q)}`);
    const j = await r.json();
    const items = j.items || [];
    // `total` is every match before the server's display cap. Without it a
    // 52-person company would render 8 rows and read as the whole team.
    const total = Number.isFinite(j.total) ? j.total : items.length;
    if(!items.length){
      box.innerHTML = `<div class="cust-none">No match for “${escapeHTML(q)}”</div>`;
      return;
    }
    const head = total > items.length
      ? `<div class="cust-count">Showing ${items.length} of ${total} — keep typing to narrow</div>`
      : `<div class="cust-count">${total} ${total===1?'match':'matches'}</div>`;
    box.innerHTML = head + items.map(c=>`<div class="cust-row" data-id="${c.id}" data-name="${escapeAttr(c.name)}" data-company="${escapeAttr(c.company||'')}">
      <span>${escapeHTML(c.name)}</span>
      <small>${escapeHTML(c.company || '')}</small>
    </div>`).join('');
    // Scoped to .cust-row on purpose: binding every div would make the
    // count header above selectable, picking a customer with an empty id.
    box.querySelectorAll('.cust-row').forEach(d=>{
      d.addEventListener('click',()=>{
        state.customer = {id:d.dataset.id, name:d.dataset.name, company:d.dataset.company};
        const pk = document.getElementById('custPicked');
        pk.classList.add('show');
        pk.querySelector('b').textContent = d.dataset.name;
        document.getElementById('custQ').value = '';
        box.innerHTML = '';
        validateConfirm();
      });
    });
  }catch{}
}
function clearCust(){
  state.customer = null;
  document.getElementById('custPicked').classList.remove('show');
  validateConfirm();
}

// ---------------- save sale ----------------
// Minimal, self-contained error toast. `toast.error(...)` below used
// to reference a `toast` global that was never defined anywhere in
// this app (no library included, no local implementation) — every
// checkout rejection (e.g. insufficient stock) threw a
// ReferenceError instead of showing the operator anything, so the
// cart just sat there with no feedback.
function showToast(message){
  let el = document.getElementById('posToast');
  if(!el){
    el = document.createElement('div');
    el.id = 'posToast';
    el.style.cssText = 'position:fixed;left:16px;right:16px;bottom:calc(96px + env(safe-area-inset-bottom));max-width:448px;margin:0 auto;background:#c92a2a;color:#fff;padding:14px 16px;border-radius:12px;font-size:14px;font-weight:600;line-height:1.4;box-shadow:0 8px 24px rgba(0,0,0,.25);z-index:999;opacity:0;transition:opacity .15s ease';
    document.body.appendChild(el);
  }
  el.textContent = message;
  el.style.opacity = '1';
  clearTimeout(el._hideTimer);
  el._hideTimer = setTimeout(()=>{ el.style.opacity = '0'; }, 5000);
}

async function confirmSale(){
  const btn = document.getElementById('confirmBtn');
  if(btn.disabled) return;
  btn.disabled = true; btn.innerHTML = 'Saving…';
  const totals = cartTotals();
  const sub = totals.sub, vat = totals.vat, total = totals.total;

  // localId doubles as the server-side idempotency key (client_ref), so
  // a queued sale that actually landed can be retried without being
  // recorded — and stock decremented — a second time.
  const localId = uid();

  // Stash the resolved discount + the gross (pre-discount) totals
  // so the receipt and the offline-queue replay both render the
  // same numbers the cashier saw on the till. The server will
  // re-derive its own gross_* / discount_* when the sale lands
  // (it can't trust what the till says), but the till-rendered
  // receipt uses these.
  const d = state.discount || { kind: 'none', input: 0 };
  const sale = {
    localId,
    createdAt: new Date().toISOString(),
    payment: state.paymentMethod,
    cashGiven: state.cashGiven || null,
    change: state.paymentMethod==='cash' ? Math.max(0, state.cashGiven - total) : 0,
    gross: totals.gross,
    discount: { kind: d.kind, input: d.input, amount: totals.discountAmount },
    sub, vat, total,
    // Which VAT rate produced those numbers — the receipt labels
    // its VAT line from this rather than hardcoding 15%.
    vatPct: totals.vatPct,
    // Attach the active letterhead so the on-screen receipt AND
    // the printed slip can show the right shop name, address,
    // phone, VAT number, footer, and logo. receipt.html's
    // renderReceipt + epos-print.js's buildEposXml both read
    // sale.letterhead.* (and fall back to "WFSALES POS" / blank
    // if it's null, so a missing letterhead is a non-fatal
    // degradation, not a crash).
    letterhead: state.letterhead || null,
    items: Array.from(state.cart.values()).map(({p,qty})=>({
      sku: p.sku, description: p.description, unit: p.unit,
      cost_price: p.cost_price,
      selling_price: lineUnitPrice({p,qty}),
      qty, product_id: p.id,
    })),
    customer: state.customer || null,
    synced: false,
  };

  const checkoutBody = {
    items: Array.from(state.cart.values()).map(({p,qty})=>({
      stock_item_id: isCustomLine(p) ? undefined : p.id,
      is_custom: isCustomLine(p),
      qty, unit_price: lineUnitPrice({p,qty}),
      sku: p.sku, description: isCustomLine(p) ? p.description : (p.description || p.sku),
    })),
    payment_method: state.paymentMethod,
    cash_given: state.paymentMethod==='cash' ? state.cashGiven : undefined,
    customer_id: state.customer ? state.customer.id : undefined,
    client_ref: localId,
    // The server reads the VAT rate off this letterhead rather than
    // trusting a rate off the wire.
    letterhead_id: state.letterhead ? state.letterhead.id : undefined,
    discount_kind: state.discount && state.discount.kind === 'percent' ? 'percent' : undefined,
    discount_input: state.discount && state.discount.kind === 'percent' ? state.discount.input : undefined,
  };

  // Distinguish a permanent server-side rejection (insufficient
  // stock, bad input) from a transient failure (server down, network
  // blip). The former must NOT advance to the receipt page or get
  // queued for offline retry — it's a real, human-fixable problem
  // the operator needs to see. The latter is what the offline queue
  // is for.
  let serverError = null;

  try{
    const r = await window.posFetch('/checkout', {
      method:'POST', headers:{'Content-Type':'application/json'}, body: JSON.stringify(checkoutBody),
    });
    if(r.ok){
      const j = await r.json();
      sale.synced = true;
      sale.serverRef = j.sale && j.sale.id;
      // The server raises the delivery note for an `account` sale and
      // hands it back here. Carried onto the local sale so
      // receipt.html can print the A4 original instead of the old
      // 80mm thermal slip. Absent for cash / card / EFT, and absent
      // for an account sale whose DN creation failed — in which case
      // the operator is told to raise one by hand.
      if (j.deliveryNote) sale.deliveryNote = j.deliveryNote;
      if (j.deliveryNoteError) sale.deliveryNoteError = j.deliveryNoteError;
    } else {
      // The route returns JSON on every non-2xx path, so this should
      // always parse. Overselling is allowed on purpose (no stock
      // check blocks the sale) — every rejection here is a real
      // validation/server failure, not a stock shortage.
      let body = null;
      try { body = await r.json(); } catch (_) { /* not json */ }
      const msg = body && body.message ? body.message : ('server returned ' + r.status);
      serverError = { message: msg };
      throw new Error(msg);
    }
  }catch(e){
    console.warn('Sale queued for sync', e);
    try{
      await dbPut(STORE_QUEUE, {...sale, checkoutBody});
    }catch(qErr){
      console.error('IndexedDB queue failed too — saving to localStorage as fallback', qErr);
      try{
        const arr = JSON.parse(localStorage.getItem('wfsales.queue') || '[]');
        arr.push({...sale, checkoutBody});
        localStorage.setItem('wfsales.queue', JSON.stringify(arr));
      }catch(_){}
    }
  }

  // Permanent server-side rejection — stop here, do NOT navigate to
  // the receipt page, do NOT queue for retry. Show a clear error,
  // re-enable the Complete button so the operator can fix the
  // cart (remove a line, lower the qty) and try again. The cart
  // stays open.
  if (serverError) {
    showToast('Sale rejected: ' + serverError.message);
    if (btn) {
      btn.disabled = false;
      btn.innerHTML = '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M5 12l5 5 9-11"/></svg>Complete sale';
    }
    return;
  }

  // ALWAYS navigate to receipt — never leave the user stuck on "Saving…"
  try{ sessionStorage.setItem('pos.lastSale', JSON.stringify(sale)); }catch(_){}
  state.cart.clear(); persistCart(); paintCart(); render();
  closePayment();
  // Use a small delay so the drawer close animation starts before navigation
  setTimeout(()=>{ location.href = 'receipt.html?id=' + encodeURIComponent(sale.localId); }, 60);
}

// ---------------- network pill + boot ----------------
function paintNet(){
  const p = document.getElementById('netpill');
  p.textContent = navigator.onLine ? 'Online' : 'Offline';
  p.classList.toggle('off', !navigator.onLine);
}
window.addEventListener('online', ()=>{ paintNet(); flushQueue(); });
window.addEventListener('offline', paintNet);

async function flushQueue(){
  if(!navigator.onLine) return;
  const q = await dbAll(STORE_QUEUE);
  for(const s of q){
    try{
      const r = await window.posFetch('/checkout', {
        method:'POST', headers:{'Content-Type':'application/json'}, body: JSON.stringify(s.checkoutBody),
      });
      if(r.ok){
        // Safe even if this sale already landed before — the server
        // matches on client_ref and replays the original instead of
        // decrementing stock again.
        await dbDel(STORE_QUEUE, s.localId);
      } else {
        break; // stop on first failure, retry next time we come online
      }
    }catch(e){ console.warn('queue item failed', e); break; }
  }
}

// ---------------- search input + topbar scroll ----------------
document.addEventListener('input', e=>{
  if(e.target.id!=='q') return;
  state.search = e.target.value;
  resetPaging();
  render();
});
const topbar = document.getElementById('topbar');
const cat = document.getElementById('catalog');
cat.addEventListener('scroll', ()=>topbar.classList.toggle('scrolled', cat.scrollTop>4));

// ---------------- category dropdown wiring ----------------
document.getElementById('catTrigger').addEventListener('click', e=>{
  e.stopPropagation();
  const t = e.currentTarget;
  if(t.getAttribute('aria-expanded')==='true') closeCatMenu();
  else openCatMenu();
});
document.getElementById('catBackdrop').addEventListener('click', closeCatMenu);
document.addEventListener('keydown', e=>{
  if(e.key==='Escape'){
    // Edit modal takes priority over the category menu.
    if (document.getElementById('editSheet').classList.contains('show')) {
      closeEditLine();
      return;
    }
    const t = document.getElementById('catTrigger');
    if(t && t.getAttribute('aria-expanded')==='true') closeCatMenu();
  }
});

// ---------------- utils ----------------
function escapeHTML(s){ return String(s).replace(/[&<>"']/g, c=>({'&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;',"'":'&#39;'})[c]); }
function escapeAttr(s){ return escapeHTML(s).replace(/`/g,'&#96;'); }

// expose for inline handlers
window.__pos = { changeQty, removeFromCart, openDrawer, closeDrawer, openPayment, closePayment, pickMethod, confirmSale, openEditLine, addCustomItem, openCustomItem, closeCustomItem, saveCustomItem, setDiscountTier, clearDiscount, toggleDiscount };
// Also expose as bare globals so inline onclick="" in pos.html works
window.openDrawer = openDrawer;
window.closeDrawer = closeDrawer;
window.openPayment = openPayment;
window.closePayment = closePayment;
window.pickMethod = pickMethod;
window.confirmSale = confirmSale;
window.changeQty = changeQty;
window.removeFromCart = removeFromCart;
window.openEditLine = openEditLine;
// The edit-line modal could be opened but not dismissed or committed:
// its Save / Cancel / Remove buttons (and the customer "Remove" chip)
// call these from inline onclick, so they need to be global too.
window.closeEditLine = closeEditLine;
window.editSave = editSave;
window.editRemove = editRemove;
window.clearCust = clearCust;
// Discount tiers + the ad-hoc line composer are driven from inline
// onclick in pos.html, so they have to be globals too.
window.setDiscountTier = setDiscountTier;
window.toggleDiscount = toggleDiscount;
window.clearDiscount = clearDiscount;
window.addCustomItem = addCustomItem;
window.openCustomItem = openCustomItem;
window.closeCustomItem = closeCustomItem;
window.saveCustomItem = saveCustomItem;

// ---------------- boot ----------------
(async function boot(){
  paintNet();
  loadCart();
  paintCart();
  await Promise.all([loadLetterhead(), loadProducts()]);
  flushQueue();
  // register SW
  if('serviceWorker' in navigator){
    navigator.serviceWorker.register('sw.js').catch(()=>{});
  }
})();

})();