// Per-letterhead slip layout: which blocks print, in what order,
// enabled or not, with what custom text. Single source of truth for
// the editor (slip-layout.html), its live preview, and both print
// transports (epos-print.js's XML builders, receipt.html's ESC/POS
// builders) — all three must resolve the same way or the editor
// would silently not apply to whichever transport a till is using.
window.PosSlipLayout = (function () {
  'use strict';

  // Blocks that can be reordered but never disabled — a slip missing
  // these stops being a valid record of the transaction (e.g. a
  // receipt with no total).
  const REQUIRED = {
    sale: ['items', 'totals'],
    delivery: ['items', 'totals'],
    cashup: ['payment_breakdown', 'grand_total'],
  };

  const LABELS = {
    header_title: 'Header title',
    logo: 'Logo',
    business_info: 'Business info',
    date_slip: 'Date & slip number',
    customer: 'Customer',
    items: 'Item list',
    totals: 'Totals & VAT',
    payment: 'Payment & change',
    footer: 'Footer message',
    date: 'Date',
    signature: 'Signature line',
    shift_date: 'Shift & date',
    payment_breakdown: 'Payment breakdown',
    grand_total: 'Grand total',
    cash_reconciliation: 'Cash reconciliation',
    denominations: 'Denominations counted',
  };

  // Matches what each builder actually prints today (verified by
  // reading buildEposXml/buildEposDeliveryXml/buildEposCashupXml and
  // their Bluetooth ESC/POS equivalents) — this formalizes existing
  // content into blocks, it doesn't add anything new. Notably,
  // delivery notes don't print business info today (only a title),
  // and cash-up's title line becomes its own header_title block for
  // consistency with the other two slip types.
  const DEFAULTS = {
    sale: [
      { id: 'logo', enabled: true },
      { id: 'header_title', enabled: true, text: null },
      { id: 'business_info', enabled: true },
      { id: 'date_slip', enabled: true },
      { id: 'customer', enabled: true },
      { id: 'items', enabled: true },
      { id: 'totals', enabled: true },
      { id: 'payment', enabled: true },
      { id: 'footer', enabled: true, text: null },
    ],
    delivery: [
      { id: 'logo', enabled: true },
      { id: 'header_title', enabled: true, text: null },
      { id: 'business_info', enabled: true },
      { id: 'customer', enabled: true },
      { id: 'date', enabled: true },
      { id: 'items', enabled: true },
      { id: 'totals', enabled: true },
      { id: 'signature', enabled: true },
    ],
    cashup: [
      { id: 'logo', enabled: true },
      { id: 'header_title', enabled: true, text: null },
      { id: 'business_info', enabled: true },
      { id: 'shift_date', enabled: true },
      { id: 'payment_breakdown', enabled: true },
      { id: 'grand_total', enabled: true },
      { id: 'cash_reconciliation', enabled: true },
      { id: 'denominations', enabled: true },
      { id: 'footer', enabled: true, text: null },
    ],
  };

  const DEFAULT_SHOW_PRICING = true;
  const DEFAULT_HEADER_TITLE = 'WFSALES POS';

  function isRequired(slipType, blockId) {
    return (REQUIRED[slipType] || []).includes(blockId);
  }

  function labelFor(blockId) {
    return LABELS[blockId] || blockId;
  }

  // Merge saved blocks with the default catalog: saved order/enabled/
  // text wins. Any default block missing from `saved` (first time
  // this slip type has been customized, or a new block id shipped
  // after the letterhead's layout was last saved) is appended so
  // nothing silently disappears. Unknown/retired ids in `saved` are
  // dropped. Required blocks are forced enabled regardless of what
  // was saved, defensively.
  function resolveBlocks(slipType, saved) {
    const defaults = DEFAULTS[slipType] || [];
    const normalize = function (b) {
      return {
        id: b.id,
        enabled: isRequired(slipType, b.id) ? true : !!b.enabled,
        text: b.text != null ? b.text : null,
      };
    };
    if (!Array.isArray(saved) || !saved.length) {
      return defaults.map(function (b) { return normalize(b); });
    }
    // Start from the saved order, dropping ids we no longer ship.
    const result = saved
      .filter(function (b) { return defaults.some(function (d) { return d.id === b.id; }); })
      .map(function (b) { return Object.assign({}, b); });
    const present = {};
    result.forEach(function (b) { present[b.id] = true; });
    // A block shipped after this letterhead last saved its layout has
    // to be slotted in at its intended spot — appending to the end
    // would drop e.g. a newly added logo/business_info block below the
    // signature line. Anchor each missing block just after the nearest
    // preceding default that IS present, so the operator's own
    // reordering is preserved.
    defaults.forEach(function (def, defIdx) {
      if (present[def.id]) return;
      let insertAt = 0;
      for (let i = defIdx - 1; i >= 0; i--) {
        const pos = result.findIndex(function (b) { return b.id === defaults[i].id; });
        if (pos !== -1) { insertAt = pos + 1; break; }
      }
      result.splice(insertAt, 0, Object.assign({}, def));
      present[def.id] = true;
    });
    return result.map(function (b) { return normalize(b); });
  }

  // -------- cache (till-local, mirrors letterhead-config.js) --------

  function cacheKey(letterheadId) { return 'pos.slipLayout.' + letterheadId; }

  function getCached(letterheadId) {
    try { return JSON.parse(localStorage.getItem(cacheKey(letterheadId)) || 'null'); } catch (e) { return null; }
  }

  function setCached(letterheadId, layout) {
    try { localStorage.setItem(cacheKey(letterheadId), JSON.stringify(layout)); } catch (e) { /* quota or disabled */ }
  }

  // -------- network --------

  async function fetchLayout(letterheadId) {
    const r = await window.posFetch('/slip-layout/' + encodeURIComponent(letterheadId));
    if (!r.ok) throw new Error('slip-layout fetch returned ' + r.status);
    const j = await r.json();
    if (j.layout) setCached(letterheadId, j.layout);
    return j.layout; // null when nothing saved yet
  }

  async function saveLayout(letterheadId, input) {
    const r = await window.posFetch('/slip-layout/' + encodeURIComponent(letterheadId), {
      method: 'PUT',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(input),
    });
    if (!r.ok) throw new Error('slip-layout save returned ' + r.status);
    const j = await r.json();
    if (j.layout) setCached(letterheadId, j.layout);
    return j.layout;
  }

  // -------- print-time helpers --------
  // Printing must never block on a settings-sync failure: use the
  // cached layout if we have one (refreshing it in the background for
  // next time), else the hardcoded defaults.

  function getBlocksForPrint(letterheadId, slipType) {
    const cached = letterheadId ? getCached(letterheadId) : null;
    if (letterheadId) {
      fetchLayout(letterheadId).catch(function () { /* keep cached/defaults on failure */ });
    }
    const saved = cached ? cached[slipType + '_blocks'] : null;
    return resolveBlocks(slipType, saved);
  }

  function getShowPricingForPrint(letterheadId) {
    const cached = letterheadId ? getCached(letterheadId) : null;
    return cached && cached.delivery_show_pricing != null ? !!cached.delivery_show_pricing : DEFAULT_SHOW_PRICING;
  }

  return {
    DEFAULTS: DEFAULTS,
    DEFAULT_SHOW_PRICING: DEFAULT_SHOW_PRICING,
    DEFAULT_HEADER_TITLE: DEFAULT_HEADER_TITLE,
    isRequired: isRequired,
    labelFor: labelFor,
    resolveBlocks: resolveBlocks,
    getCached: getCached,
    setCached: setCached,
    fetchLayout: fetchLayout,
    saveLayout: saveLayout,
    getBlocksForPrint: getBlocksForPrint,
    getShowPricingForPrint: getShowPricingForPrint,
  };
})();