// routes/ppc.js
// PPC (Production Planning & Control) report — one row per OPEN Sales
// Order, pivoted so each distinct Item Code appearing in the filtered
// result set becomes its own column showing that order's still-PENDING
// (undelivered/uninvoiced — RemainingOpenQuantity) quantity for that item.
// Pulled entirely from SAP B1 Service Layer (Orders + Items +
// BusinessPartners), per explicit requirement — no direct SQL against SAP's
// own database, unlike most other report pages in this app.
// NOTE: this deliberately does NOT look at Invoices at all — an invoiced
// line has nothing left pending by definition, so it's excluded already by
// only ever reading lines with RemainingOpenQuantity > 0.
'use strict';
const express = require('express');
const router  = express.Router();
const crypto  = require('crypto');
const { verifyToken } = require('../middleware/auth');
const appSettings = require('../services/appSettingsStore');

// Lets an EXTERNAL app (no portal login) call the report routes below with a
// dedicated key instead of a JWT — header "X-API-Key: <key>" (or ?apiKey=
// query param, for tools that can't set custom headers, e.g. some Power BI/
// Excel connectors). The key is set in Admin → System Settings → "PPC
// Report" and is empty by default, meaning external access is OFF until an
// admin turns it on. A normal portal Bearer token still works exactly as
// before — this only ADDS a second way in, never removes the first.
function timingSafeEqual(a, b) {
  const bufA = Buffer.from(String(a)); const bufB = Buffer.from(String(b));
  if (bufA.length !== bufB.length) return false;
  return crypto.timingSafeEqual(bufA, bufB);
}
function verifyApiKeyOrToken(req, res, next) {
  const configured = appSettings.ppcApiKey();
  const supplied = req.headers['x-api-key'] || req.query.apiKey;
  if (configured && supplied && timingSafeEqual(supplied, configured)) {
    req.user = { username: 'ppc-external-api', role: 'api' };
    return next();
  }
  return verifyToken(req, res, next);
}

let _sapSvc = null;
function getSap(){
  if(!_sapSvc) _sapSvc = require('../services/sapServiceLayer');
  return _sapSvc;
}
const cq = (req) => req.query?.company || req.body?.company || null;

// Warehouse code -> name, cached per company for the life of the server
// (this list changes essentially never) — used to label the warehouse-wise
// stock breakdown shown on hover over a Current Stock cell.
const _warehouseNameCache = {};
async function getWarehouseNames(sap, co) {
  const key = co || '';
  if (_warehouseNameCache[key]) return _warehouseNameCache[key];
  try {
    const r = await sap.sapRequest('GET', 'Warehouses?$select=WarehouseCode,WarehouseName', null, co);
    const map = {};
    (r?.value || []).forEach(w => { map[w.WarehouseCode] = w.WarehouseName || w.WarehouseCode; });
    _warehouseNameCache[key] = map;
    return map;
  } catch (_e) { return {}; }
}

// OR-batch a set of values into a Service Layer $filter clause, e.g.
// batchFilter('ItemCode', ['A','B']) -> "(ItemCode eq 'A' or ItemCode eq 'B')".
// Chunked to keep each request's URL length sane.
// SAP Service Layer silently truncates/fails an OR'd $filter batch once it
// gets too large (confirmed live: 30-40 DocEntry conditions dropped over a
// third of results with no error — 10 was reliable). Kept conservative for
// every batched lookup below, not just the one it was caught on.
const BATCH_SIZE = 10;
function chunk(arr, size) {
  const out = [];
  for (let i = 0; i < arr.length; i += size) out.push(arr.slice(i, i + size));
  return out;
}
function orFilter(field, values) {
  return `(${values.map(v => `${field} eq '${String(v).replace(/'/g, "''")}'`).join(' or ')})`;
}

// ════════════════════════════════════════════════════════════════
//  PPC PENDING ORDER REPORT  →  GET /api/ppc/invoice-report
//  (path kept for backward compat with the already-shipped frontend build;
//  the DATA is now open Sales Orders, not Invoices — see file header.)
//  Query: company, from (YYYY-MM-DD), to (YYYY-MM-DD), itemGroup (numeric
//  ItemsGroupCode, optional), salesType ('Trade'|'Institute'|'Institute Ind', optional),
//  customerType ('DOMESTIC'|'EXPORT', optional)
// ════════════════════════════════════════════════════════════════
router.get('/invoice-report', verifyApiKeyOrToken, async (req, res) => {
  const co = cq(req);
  const { from, to, itemGroup, salesType, customerType } = req.query;

  try {
    const sap = getSap();

    // ── 1. Pull matching Sales Orders (paginated) — Date range is OPTIONAL:
    //      given, it narrows by DocDate as before; left blank, every open
    //      order shows regardless of when it was raised. Header
    //      DocumentStatus eq 'bost_Open' is always applied though — a
    //      Closed header can never have a pending line, so this is a pure
    //      efficiency filter (skips years of fully-fulfilled history)
    //      that never drops a genuinely pending line. ────────────────────
    // Customer Type is NOT filtered via U_CustomerType here — that field is
    // unreliably populated (blank on plenty of real orders). Confirmed
    // convention instead: an order counts as Domestic when U_WEB_SO_NO has a
    // value, Export when U_WEB_SO_NO_EX does — derived per-order below and
    // filtered on AFTER fetching (see customerTypeFor()).
    const filters = [`DocumentStatus eq 'bost_Open'`];
    if (from) filters.push(`DocDate ge '${from}'`);
    if (to)   filters.push(`DocDate le '${to}'`);
    if (salesType) filters.push(`U_SalesType eq '${String(salesType).replace(/'/g, "''")}'`);
    const filterStr = encodeURIComponent(filters.join(' and '));
    const select = encodeURIComponent('DocEntry,DocNum,DocDate,DocDueDate,CardCode,CardName,U_SalesType,U_CustomerType,U_WEB_SO_NO,U_WEB_SO_NO_EX,DocumentLines');

    const orders = [];
    // NOTE: no $top here on purpose — confirmed live that passing $top made
    // SAP Service Layer treat it as a TOTAL cap across the whole nextLink
    // chain (silently stopping once that many results had been returned in
    // total, each page's own $top counting DOWN — 200,180,160…), not a
    // per-page size. That silently dropped genuine older still-open orders
    // once a date range had more than 200 matches. Omitting $top lets SAP
    // use its own default page size and nextLink keeps going for as long as
    // results exist.
    let url = `Orders?$filter=${filterStr}&$select=${select}&$orderby=DocDate desc`;
    const MAX_PAGES = 500;   // safety cap — ~20/page => up to ~10,000 orders per run
    for (let page = 0; page < MAX_PAGES && url; page++) {
      const result = await sap.sapRequest('GET', url, null, co);
      orders.push(...(result?.value || []));
      url = result?.['odata.nextLink'] || result?.['@odata.nextLink'] || null;
      if (!result?.value?.length) break;
    }
    if (!orders.length) return res.json({ success: true, data: { itemCodes: [], rows: [] } });

    // ── 2. Resolve item groups + current stock for every distinct item
    //      code on these orders (group only needed for the Item Group
    //      filter). Stock is warehouse-specific, not the item's blanket
    //      QuantityOnStock across every warehouse (QA/R&D/Quarantine/etc.
    //      aren't stock actually available to ship) — confirmed live:
    //      Warehouse 1A = "FG DOMESTIC", 1B = "FG EXPORT", the only two
    //      that matter for "what can I ship a customer". Service Layer has
    //      no nested $select on ItemWarehouseInfoCollection (tried, SAP
    //      rejects it), so the full per-warehouse collection comes back and
    //      is filtered down to just those two codes here. ────────────────
    const STOCK_WAREHOUSES = { '1A': 'stock1A', '1B': 'stock1B' };
    const warehouseNames = await getWarehouseNames(sap, co);
    const allCodes = [...new Set(orders.flatMap(o => (o.DocumentLines || []).map(l => l.ItemCode).filter(Boolean)))];
    let itemMeta = {};   // ItemCode -> { name, group, stock1A, stock1B, byWarehouse }
    for (const part of chunk(allCodes, BATCH_SIZE)) {
      try {
        const r = await sap.sapRequest('GET', `Items?$filter=${encodeURIComponent(orFilter('ItemCode', part))}&$select=ItemCode,ItemName,ItemsGroupCode,ItemWarehouseInfoCollection&$top=${part.length}`, null, co);
        (r?.value || []).forEach(it => {
          const meta = { name: it.ItemName || it.ItemCode, group: it.ItemsGroupCode, stock1A: 0, stock1B: 0, byWarehouse: [] };
          (it.ItemWarehouseInfoCollection || []).forEach(w => {
            const key = STOCK_WAREHOUSES[w.WarehouseCode];
            const qty = Number(w.InStock) || 0;
            if (key) meta[key] = qty;
            // Every warehouse with nonzero stock — full breakdown for the
            // "warehouse-wise stock" hover tooltip (not just 1A/1B).
            if (qty) meta.byWarehouse.push({ code: w.WarehouseCode, name: warehouseNames[w.WarehouseCode] || w.WarehouseCode, qty });
          });
          meta.byWarehouse.sort((a, b) => a.code.localeCompare(b.code));
          itemMeta[it.ItemCode] = meta;
        });
      } catch (_e) { /* best-effort — missing metadata just falls back to code-as-name, no group filter match, 0 stock */ }
    }
    // Hard ceiling — Admin → System Settings → "PPC Report Item Groups"
    // (appSettings.ppcItemGroups()). When configured, results can NEVER
    // include a group outside that list, regardless of what's requested:
    // no itemGroup picked -> restrict to the WHOLE allowed set; itemGroup
    // picked but outside it -> empty set (matches nothing), never silently
    // widened. Mirrors routes/board.js's resolveGroupFilter().
    const allowedGroups = appSettings.ppcItemGroups().map(Number).filter(n => !isNaN(n));
    let activeGroups = null;   // null = no restriction at all
    if (allowedGroups.length) {
      activeGroups = new Set(itemGroup != null && itemGroup !== '' ? allowedGroups.filter(g => g === parseInt(itemGroup)) : allowedGroups);
    } else if (itemGroup != null && itemGroup !== '') {
      activeGroups = new Set([parseInt(itemGroup)]);
    }

    // ── 3. Resolve City for every distinct customer ─────────────────────
    const cardCodes = [...new Set(orders.map(o => o.CardCode).filter(Boolean))];
    let cityByCard = {};
    for (const part of chunk(cardCodes, BATCH_SIZE)) {
      try {
        const r = await sap.sapRequest('GET', `BusinessPartners?$filter=${encodeURIComponent(orFilter('CardCode', part))}&$select=CardCode,City&$top=${part.length}`, null, co);
        (r?.value || []).forEach(bp => { cityByCard[bp.CardCode] = bp.City || ''; });
      } catch (_e) { /* non-fatal — City just shows blank */ }
    }

    // ── 4. Build rows + the set of item-code columns actually used —
    //      ONLY lines that still have something PENDING count: SAP tracks
    //      per-line RemainingOpenQuantity (confirmed live — NOT the
    //      "OpenQuantity" property name one might expect) and LineStatus.
    //      A line that's fully delivered/invoiced has RemainingOpenQuantity
    //      0 and LineStatus bost_Closed — excluded here so a fully-filled
    //      order contributes nothing (this IS what makes it a "pending"
    //      report instead of a plain order-quantity dump). ──────────────
    // Confirmed convention: an order counts as Domestic when U_WEB_SO_NO has
    // a value, Export when U_WEB_SO_NO_EX does — takes priority over the
    // (unreliable) U_CustomerType UDF, which is only a fallback here.
    function customerTypeFor(o) {
      if (o.U_WEB_SO_NO) return 'DOMESTIC';
      if (o.U_WEB_SO_NO_EX) return 'EXPORT';
      return o.U_CustomerType || '';
    }

    const usedCodes = new Set();
    const rows = [];
    orders.forEach((o) => {
      const orderCustType = customerTypeFor(o);
      if (customerType && orderCustType !== customerType) return;   // Customer Type filter, applied post-fetch (see above)
      const qtyByItem = {};
      let any = false;
      (o.DocumentLines || []).forEach(l => {
        const code = l.ItemCode; if (!code) return;
        const pending = Number(l.RemainingOpenQuantity) || 0;
        if (pending <= 0 || l.LineStatus !== 'bost_Open') return;
        const meta = itemMeta[code];
        if (activeGroups && (!meta || !activeGroups.has(meta.group))) return;   // outside the selected/allowed Item Group(s)
        qtyByItem[code] = (qtyByItem[code] || 0) + pending;
        usedCodes.add(code);
        any = true;
      });
      if (!any) return;   // nothing left pending on this order (or Item Group filter excluded it all)
      rows.push({
        srNo: rows.length + 1,
        docEntry: o.DocEntry,
        salesOrderNo: o.DocNum,
        webSoNo: o.U_WEB_SO_NO || null,
        webSoNoEx: o.U_WEB_SO_NO_EX || null,
        cardCode: o.CardCode,
        cardName: o.CardName,
        city: cityByCard[o.CardCode] || '',
        orderType: o.U_SalesType || '',
        customerType: orderCustType,
        dispatchDate: o.DocDueDate || '',
        qtyByItem,
      });
    });

    const itemCodes = [...usedCodes].sort().map(code => ({
      code,
      name: (itemMeta[code] && itemMeta[code].name) || code,
      stock1A: (itemMeta[code] && itemMeta[code].stock1A) || 0,
      stock1B: (itemMeta[code] && itemMeta[code].stock1B) || 0,
      byWarehouse: (itemMeta[code] && itemMeta[code].byWarehouse) || [],
    }));
    res.json({ success: true, data: { itemCodes, rows } });
  } catch (err) {
    console.error('[PPC] invoice-report failed:', err.message);
    res.status(400).json({ success: false, message: err.message });
  }
});

// ════════════════════════════════════════════════════════════════
//  ITEM GROUPS FOR THE FILTER  →  GET /api/ppc/item-groups
//  Restricted to Admin → System Settings → "PPC Report Item Groups"
//  (appSettings.ppcItemGroups()) when configured — e.g. just the FG groups
//  (BB, CAPD, Equipment, …), not every raw-material/packing group SAP has.
//  Empty setting = unrestricted (every group SAP has).
// ════════════════════════════════════════════════════════════════
router.get('/item-groups', verifyApiKeyOrToken, async (req, res) => {
  const co = req.query.company || null;
  try {
    const r = await getSap().sapRequest('GET', 'ItemGroups?$select=Number,GroupName&$orderby=GroupName', null, co);
    const all = (r?.value || []).map(g => ({ code: g.Number, name: g.GroupName || String(g.Number) }));
    const allowed = appSettings.ppcItemGroups().map(Number);
    const restricted = allowed.length ? all.filter(g => allowed.includes(g.code)) : all;
    res.json({ success: true, data: restricted });
  } catch (err) { res.status(400).json({ success: false, message: err.message }); }
});

// ── UNRESTRICTED group list — for the admin settings checklist itself (an
// admin configuring the restriction must see every group to choose from).
router.get('/item-groups/all', verifyToken, async (req, res) => {
  const co = req.query.company || null;
  try {
    const r = await getSap().sapRequest('GET', 'ItemGroups?$select=Number,GroupName&$orderby=GroupName', null, co);
    res.json({ success: true, data: (r?.value || []).map(g => ({ code: g.Number, name: g.GroupName || String(g.Number) })) });
  } catch (err) { res.status(400).json({ success: false, message: err.message }); }
});

// ════════════════════════════════════════════════════════════════
//  ORDER TYPES FOR THE FILTER  →  GET /api/ppc/order-types
//  Admin → System Settings → "PPC Report" → Order Types
//  (appSettings.ppcOrderTypes()) — SAP's U_SalesType is free text, not a
//  fixed picklist, so this list is admin-maintained here instead of
//  hardcoded in ppc-report.html; a new value used in SAP just needs adding
//  here, no code change.
// ════════════════════════════════════════════════════════════════
router.get('/order-types', verifyApiKeyOrToken, async (req, res) => {
  res.json({ success: true, data: appSettings.ppcOrderTypes() });
});

module.exports = router;