feat(inventaris): stok keluar/retur/opname + detail unit, dan edit slip payroll (port upstream)

- inventoryService: port penuh dari upstream (issueStock FIFO/SN, returnStock, adjustStock opname, serial tersedia, statistik, detail barang) + kompatibilitas fork
- schema: kolom price/supplier (stock) dan remaining_stock/recipient/reference_no (log) via migrasi aman
- admin: route stok keluar/retur/opname + API detail & serial; modal + tombol aksi di halaman inventaris; viewStock yang tadinya undefined
- payroll: updateSlip() + route /payroll/slip/:id/update

services/inventoryService.js

@@ -1,42 +1,111 @@
 /**
  * Service: Manajemen Inventaris / Gudang (Warehouse)
+ * Sistem Pelacakan Stok, Pemasukan, Pengeluaran & Sisa Stok Terintegrasi
  */
 const db = require('../config/database');
 const { logger } = require('../config/logger');
 
+// ─── DEFAULT CATEGORIES SEEDER ───────────────────────────────────────────
+function seedDefaultCategories() {
+  try {
+    const count = db.prepare('SELECT count(*) as c FROM inventory_categories').get().c;
+    if (count === 0) {
+      const defaults = [
+        ['Router & ONT', 'Modem ONT GPON/EPON, Router WiFi, Access Point, Wireless Bridge'],
+        ['Kabel & Drop Core', 'Kabel Fiber Optic Drop Core 1-2 Core, Kabel LAN UTP Cat5e/Cat6'],
+        ['Aksesoris Fiber Optic', 'Patchcord, Pigtail, Adapter SC, ODP, OTB, Roset FO, Joint Closure, Protection Sleeve'],
+        ['Aksesoris LAN & Jaringan', 'Konektor RJ45, Switch Hub, Barrel LAN, Faceplate, Modular Jack'],
+        ['Aksesoris Tiang & Outdoor', 'Klem Buaya, Span Wartel, Hook S, Stainless Band, Bracket Tiang'],
+        ['Power & Adaptor', 'Adaptor 12V 1A/2A, POE Injector, UPS Mini DC, Kabel Power']
+      ];
+      const insert = db.prepare('INSERT OR IGNORE INTO inventory_categories (name, description) VALUES (?, ?)');
+      defaults.forEach(([name, desc]) => insert.run(name, desc));
+    }
+  } catch (e) {
+    logger.error('Failed to seed default inventory categories: ' + e.message);
+  }
+}
+
 // ─── CATEGORIES ───────────────────────────────────────────────────────────
 function getAllCategories() {
-  return db.prepare('SELECT * FROM inventory_categories ORDER BY name ASC').all();
+  seedDefaultCategories();
+  return db.prepare(`
+    SELECT c.*, 
+           (SELECT count(*) FROM inventory_items i WHERE i.category_id = c.id) as item_count
+    FROM inventory_categories c 
+    ORDER BY c.name ASC
+  `).all();
 }
 
 function createCategory(data) {
   const { name, description } = data;
-  return db.prepare('INSERT INTO inventory_categories (name, description) VALUES (?, ?)').run(name, description);
+  if (!name || !name.trim()) throw new Error('Nama kategori wajib diisi');
+  return db.prepare('INSERT INTO inventory_categories (name, description) VALUES (?, ?)').run(name.trim(), description || '');
 }
 
 function updateCategory(id, data) {
   const { name, description } = data;
-  return db.prepare('UPDATE inventory_categories SET name = ?, description = ? WHERE id = ?').run(name, description, id);
+  if (!name || !name.trim()) throw new Error('Nama kategori wajib diisi');
+  return db.prepare('UPDATE inventory_categories SET name = ?, description = ? WHERE id = ?').run(name.trim(), description || '', id);
 }
 
 function deleteCategory(id) {
+  const itemsCount = db.prepare('SELECT count(*) as c FROM inventory_items WHERE category_id = ?').get(id)?.c || 0;
+  if (itemsCount > 0) {
+    throw new Error(`Tidak dapat menghapus kategori karena masih memiliki ${itemsCount} jenis barang terkait.`);
+  }
   return db.prepare('DELETE FROM inventory_categories WHERE id = ?').run(id);
 }
 
+// ─── HELPER STOCK COUNT ───────────────────────────────────────────────────
+function getItemAvailableStock(itemId) {
+  const res = db.prepare(`
+    SELECT COALESCE(SUM(quantity), 0) as total
+    FROM inventory_stock
+    WHERE item_id = ? AND status = 'available'
+  `).get(itemId);
+  return Number(res?.total || 0);
+}
+
+function getItemAssignedStock(itemId) {
+  const res = db.prepare(`
+    SELECT COALESCE(SUM(quantity), 0) as total
+    FROM inventory_stock
+    WHERE item_id = ? AND status = 'assigned'
+  `).get(itemId);
+  return Number(res?.total || 0);
+}
+
+function getItemBrokenStock(itemId) {
+  const res = db.prepare(`
+    SELECT COALESCE(SUM(quantity), 0) as total
+    FROM inventory_stock
+    WHERE item_id = ? AND status = 'broken'
+  `).get(itemId);
+  return Number(res?.total || 0);
+}
+
 // ─── ITEMS ───────────────────────────────────────────────────────────────
-function getAllItems(search = '') {
+function getAllItems(search = '', categoryId = null) {
+  seedDefaultCategories();
   let query = `
     SELECT i.*, c.name as category_name, 
-           (SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'available') as stock_available,
-           (SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'assigned') as stock_assigned
+           COALESCE((SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'available'), 0) as stock_available,
+           COALESCE((SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'assigned'), 0) as stock_assigned,
+           COALESCE((SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'broken'), 0) as stock_broken
     FROM inventory_items i
     LEFT JOIN inventory_categories c ON i.category_id = c.id
+    WHERE 1=1
   `;
   const params = [];
+  if (categoryId) {
+    query += ' AND i.category_id = ?';
+    params.push(categoryId);
+  }
   if (search) {
-    query += ' WHERE i.name LIKE ? OR i.brand LIKE ? OR i.model LIKE ?';
+    query += ' AND (i.name LIKE ? OR i.brand LIKE ? OR i.model LIKE ? OR c.name LIKE ?)';
     const s = `%${search}%`;
-    params.push(s, s, s);
+    params.push(s, s, s, s);
   }
   query += ' ORDER BY i.name ASC';
   return db.prepare(query).all(...params);
@@ -44,35 +113,495 @@ function getAllItems(search = '') {
 
 function getItemById(id) {
   return db.prepare(`
-    SELECT i.*, c.name as category_name
+    SELECT i.*, c.name as category_name,
+           COALESCE((SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'available'), 0) as stock_available,
+           COALESCE((SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'assigned'), 0) as stock_assigned,
+           COALESCE((SELECT SUM(quantity) FROM inventory_stock s WHERE s.item_id = i.id AND s.status = 'broken'), 0) as stock_broken
     FROM inventory_items i
     LEFT JOIN inventory_categories c ON i.category_id = c.id
     WHERE i.id = ?
   `).get(id);
 }
 
+function getItemDetail(id) {
+  const item = getItemById(id);
+  if (!item) return null;
+
+  const stockList = db.prepare(`
+    SELECT s.*, cust.name as customer_name, cust.pppoe_username as pppoe_user
+    FROM inventory_stock s
+    LEFT JOIN customers cust ON s.assigned_to_customer_id = cust.id
+    WHERE s.item_id = ?
+    ORDER BY CASE WHEN s.status = 'available' THEN 1 WHEN s.status = 'assigned' THEN 2 ELSE 3 END, s.created_at DESC
+  `).all(id);
+
+  const logs = db.prepare(`
+    SELECT l.*, s.serial_number
+    FROM inventory_logs l
+    LEFT JOIN inventory_stock s ON l.stock_id = s.id
+    WHERE l.item_id = ?
+    ORDER BY l.created_at DESC, l.id DESC
+    LIMIT 100
+  `).all(id);
+
+  return { item, stockList, logs };
+}
+
 function createItem(data) {
   const { category_id, name, brand, model, unit, min_stock, description } = data;
+  if (!name || !name.trim()) throw new Error('Nama barang wajib diisi');
   return db.prepare(`
     INSERT INTO inventory_items (category_id, name, brand, model, unit, min_stock, description)
     VALUES (?, ?, ?, ?, ?, ?, ?)
-  `).run(category_id, name, brand, model, unit, min_stock, description);
+  `).run(
+    category_id ? Number(category_id) : null,
+    name.trim(),
+    brand ? brand.trim() : '',
+    model ? model.trim() : '',
+    unit ? unit.trim() : 'pcs',
+    Number(min_stock) || 5,
+    description ? description.trim() : ''
+  );
 }
 
 function updateItem(id, data) {
   const { category_id, name, brand, model, unit, min_stock, description } = data;
+  if (!name || !name.trim()) throw new Error('Nama barang wajib diisi');
   return db.prepare(`
     UPDATE inventory_items 
     SET category_id = ?, name = ?, brand = ?, model = ?, unit = ?, min_stock = ?, description = ?
     WHERE id = ?
-  `).run(category_id, name, brand, model, unit, min_stock, description, id);
+  `).run(
+    category_id ? Number(category_id) : null,
+    name.trim(),
+    brand ? brand.trim() : '',
+    model ? model.trim() : '',
+    unit ? unit.trim() : 'pcs',
+    Number(min_stock) || 5,
+    description ? description.trim() : '',
+    id
+  );
 }
 
 function deleteItem(id) {
+  const stockCount = db.prepare('SELECT count(*) as c FROM inventory_stock WHERE item_id = ?').get(id)?.c || 0;
+  if (stockCount > 0) {
+    throw new Error(`Tidak dapat menghapus barang karena masih ada ${stockCount} data stok terkait. Silakan sesuaikan atau kosongkan stok terlebih dahulu.`);
+  }
   return db.prepare('DELETE FROM inventory_items WHERE id = ?').run(id);
 }
 
-// ─── STOCK ───────────────────────────────────────────────────────────────
+// ─── SERIAL NUMBERS ───────────────────────────────────────────────────────
+function getAvailableSerialNumbers(itemId) {
+  return db.prepare(`
+    SELECT id, serial_number, condition, location, note
+    FROM inventory_stock
+    WHERE item_id = ? AND status = 'available' AND serial_number IS NOT NULL AND TRIM(serial_number) != ''
+    ORDER BY serial_number ASC
+  `).all(itemId);
+}
+
+// ─── STOCK TRANSACTIONS ───────────────────────────────────────────────────
+
+/**
+ * 1. INPUT STOK MASUK (IN)
+ * Menambah stok barang dan mencatat saldo sisa stok akhir secara presisi
+ */
+function addStock(data, actor = 'Admin') {
+  const { item_id, serial_number, quantity, condition, location, price, supplier, reference_no, note } = data;
+  if (!item_id) throw new Error('Pilih barang terlebih dahulu');
+  
+  const item = getItemById(item_id);
+  if (!item) throw new Error('Data barang tidak ditemukan');
+
+  const cleanSn = serial_number ? serial_number.trim() : '';
+  const qty = cleanSn ? 1 : Math.max(1, parseInt(quantity, 10) || 1);
+
+  const run = db.transaction(() => {
+    let stockId = null;
+
+    if (cleanSn) {
+      // Cek duplikasi SN
+      const existing = db.prepare('SELECT id, status FROM inventory_stock WHERE serial_number = ?').get(cleanSn);
+      if (existing) {
+        throw new Error(`Serial Number "${cleanSn}" sudah pernah terdaftar di sistem (Status: ${existing.status})!`);
+      }
+
+      const res = db.prepare(`
+        INSERT INTO inventory_stock (item_id, serial_number, quantity, condition, location, status, price, supplier, note)
+        VALUES (?, ?, 1, ?, ?, 'available', ?, ?, ?)
+      `).run(item_id, cleanSn, condition || 'new', location || 'Gudang Utama', Number(price) || 0, supplier || '', note || '');
+      stockId = res.lastInsertRowid;
+    } else {
+      // Non-serial item
+      const res = db.prepare(`
+        INSERT INTO inventory_stock (item_id, serial_number, quantity, condition, location, status, price, supplier, note)
+        VALUES (?, NULL, ?, ?, ?, 'available', ?, ?, ?)
+      `).run(item_id, qty, condition || 'new', location || 'Gudang Utama', Number(price) || 0, supplier || '', note || '');
+      stockId = res.lastInsertRowid;
+    }
+
+    // Hitung sisa stok tersedia saat ini
+    const remainingStock = getItemAvailableStock(item_id);
+
+    // Catat log stok masuk lengkap dengan sisa stok
+    const logNote = note || (cleanSn ? `Stok Masuk SN: ${cleanSn}` : `Stok Masuk (+${qty} ${item.unit})`);
+    db.prepare(`
+      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, remaining_stock, actor, recipient, reference_no, note)
+      VALUES (?, ?, 'in', ?, ?, ?, ?, ?, ?)
+    `).run(
+      item_id,
+      stockId,
+      qty,
+      remainingStock,
+      actor || 'Admin',
+      supplier || 'Gudang Utama',
+      reference_no || '',
+      logNote
+    );
+
+    return { stockId, remainingStock };
+  });
+
+  return run();
+}
+
+/**
+ * 2. PENGELUARAN BARANG (OUT / ISSUE)
+ * Mengeluarkan barang untuk instalasi baru, perbaikan, pemakaian teknisi, atau rusak
+ * Mengurangi stok secara otomatis dan mencatat sisa stok akhir
+ */
+function issueStock(data, actor = 'Admin') {
+  const { item_id, stock_id, serial_number, quantity, type, customer_id, recipient, reference_no, note } = data;
+  if (!item_id) throw new Error('Pilih barang terlebih dahulu');
+
+  const item = getItemById(item_id);
+  if (!item) throw new Error('Data barang tidak ditemukan');
+
+  const availableStock = getItemAvailableStock(item_id);
+  if (availableStock <= 0) {
+    throw new Error(`Stok ${item.name} saat ini kosong (0 ${item.unit})!`);
+  }
+
+  const issueType = type || (customer_id ? 'assigned' : 'out'); // 'out', 'assigned', 'broken', 'loss'
+
+  const run = db.transaction(() => {
+    let stockIdTarget = stock_id ? Number(stock_id) : null;
+    let qtyToDeduct = 1;
+
+    // A. JIKA DITARGETKAN KE SERIAL NUMBER SPESIFIK ATAU STOCK_ID SPESIFIK
+    if (serial_number && !stockIdTarget) {
+      const row = db.prepare('SELECT id, status FROM inventory_stock WHERE item_id = ? AND serial_number = ?').get(item_id, serial_number.trim());
+      if (!row) throw new Error(`Serial Number "${serial_number}" tidak ditemukan untuk barang ini`);
+      if (row.status !== 'available') throw new Error(`Barang SN "${serial_number}" statusnya "${row.status}", tidak dapat dikeluarkan!`);
+      stockIdTarget = row.id;
+    }
+
+    if (stockIdTarget) {
+      const stock = db.prepare('SELECT * FROM inventory_stock WHERE id = ?').get(stockIdTarget);
+      if (!stock) throw new Error('Data unit stok tidak ditemukan');
+      if (stock.status !== 'available') throw new Error(`Unit stok ini statusnya "${stock.status}", tidak tersedia`);
+
+      const targetStatus = (customer_id || issueType === 'assigned') ? 'assigned' : (issueType === 'broken' ? 'broken' : 'out');
+      const targetCustomer = customer_id ? Number(customer_id) : null;
+
+      db.prepare(`
+        UPDATE inventory_stock 
+        SET status = ?, assigned_to_customer_id = ?, updated_at = (NOW_LOCAL())
+        WHERE id = ?
+      `).run(targetStatus, targetCustomer, stockIdTarget);
+
+      qtyToDeduct = stock.quantity || 1;
+    } else {
+      // B. BARANG NON-SERIAL / PENGURANGAN KUANTITAS (FIFO)
+      qtyToDeduct = Math.max(1, parseInt(quantity, 10) || 1);
+      if (qtyToDeduct > availableStock) {
+        throw new Error(`Stok tidak mencukupi! Tersedia di gudang: ${availableStock} ${item.unit}, diminta keluar: ${qtyToDeduct} ${item.unit}`);
+      }
+
+      // Ambil batch stok yang available terurut dari yang paling lama masuk (FIFO)
+      const batches = db.prepare(`
+        SELECT id, quantity 
+        FROM inventory_stock 
+        WHERE item_id = ? AND status = 'available'
+        ORDER BY created_at ASC, id ASC
+      `).all(item_id);
+
+      let needed = qtyToDeduct;
+      for (const b of batches) {
+        if (needed <= 0) break;
+        if (b.quantity <= needed) {
+          db.prepare("UPDATE inventory_stock SET quantity = 0, status = 'out', updated_at = (NOW_LOCAL()) WHERE id = ?").run(b.id);
+          needed -= b.quantity;
+        } else {
+          db.prepare("UPDATE inventory_stock SET quantity = quantity - ?, updated_at = (NOW_LOCAL()) WHERE id = ?").run(needed, b.id);
+          needed = 0;
+          break;
+        }
+      }
+    }
+
+    // Hitung sisa stok tersedia setelah pengeluaran
+    const remainingStock = getItemAvailableStock(item_id);
+
+    // Keterangan penerima (teknisi / pelanggan)
+    let finalRecipient = recipient ? recipient.trim() : '';
+    if (customer_id && !finalRecipient) {
+      const cust = db.prepare('SELECT name, pppoe_username as pppoe_user FROM customers WHERE id = ?').get(customer_id);
+      if (cust) finalRecipient = `Pelanggan: ${cust.name} (${cust.pppoe_user || '-'})`;
+    }
+    if (!finalRecipient) finalRecipient = 'Teknisi / Operasional';
+
+    const logNote = note || `Pengeluaran Barang (-${qtyToDeduct} ${item.unit})`;
+
+    // Catat log pengeluaran dengan sisa stok
+    db.prepare(`
+      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, remaining_stock, actor, recipient, reference_no, note)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+    `).run(
+      item_id,
+      stockIdTarget,
+      issueType,
+      -qtyToDeduct,
+      remainingStock,
+      actor || 'Admin',
+      finalRecipient,
+      reference_no || '',
+      logNote
+    );
+
+    return { qtyDeducted: qtyToDeduct, remainingStock };
+  });
+
+  return run();
+}
+
+/**
+ * 3. PENYESUAIAN STOK (STOCK OPNAME / ADJUSTMENT)
+ * Menyesuaikan data sistem dengan fisik gudang dan mencatat selisih & saldo akhir
+ */
+function adjustStock(data, actor = 'Admin') {
+  const { item_id, actual_quantity, note } = data;
+  if (!item_id) throw new Error('Pilih barang terlebih dahulu');
+  
+  const item = getItemById(item_id);
+  if (!item) throw new Error('Data barang tidak ditemukan');
+
+  const actualQty = Math.max(0, parseInt(actual_quantity, 10));
+  if (isNaN(actualQty)) throw new Error('Jumlah stok fisik harus berupa angka');
+
+  const currentAvailable = getItemAvailableStock(item_id);
+  const diff = actualQty - currentAvailable;
+
+  if (diff === 0) {
+    return { diff: 0, remainingStock: actualQty, message: 'Jumlah stok sudah sesuai, tidak ada perubahan.' };
+  }
+
+  const run = db.transaction(() => {
+    if (diff > 0) {
+      // Stok fisik lebih banyak dari sistem -> Tambah selisih ke stok
+      db.prepare(`
+        INSERT INTO inventory_stock (item_id, serial_number, quantity, condition, location, status, note)
+        VALUES (?, NULL, ?, 'new', 'Gudang Utama', 'available', ?)
+      `).run(item_id, diff, note || 'Penyesuaian Fisik (Opname)');
+    } else {
+      // Stok fisik lebih sedikit dari sistem -> Kurangi selisih dari stok yang ada
+      let neededToReduce = Math.abs(diff);
+      const batches = db.prepare(`
+        SELECT id, quantity FROM inventory_stock 
+        WHERE item_id = ? AND status = 'available'
+        ORDER BY created_at ASC, id ASC
+      `).all(item_id);
+
+      for (const b of batches) {
+        if (neededToReduce <= 0) break;
+        if (b.quantity <= neededToReduce) {
+          db.prepare("UPDATE inventory_stock SET quantity = 0, status = 'out', updated_at = (NOW_LOCAL()) WHERE id = ?").run(b.id);
+          neededToReduce -= b.quantity;
+        } else {
+          db.prepare("UPDATE inventory_stock SET quantity = quantity - ?, updated_at = (NOW_LOCAL()) WHERE id = ?").run(neededToReduce, b.id);
+          neededToReduce = 0;
+          break;
+        }
+      }
+    }
+
+    const logNote = note || `Stock Opname (Penyesuaian Fisik: ${diff > 0 ? '+' : ''}${diff} ${item.unit})`;
+
+    db.prepare(`
+      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, remaining_stock, actor, recipient, reference_no, note)
+      VALUES (?, NULL, 'adjust', ?, ?, ?, 'Stock Opname', 'OPNAME', ?)
+    `).run(
+      item_id,
+      diff,
+      actualQty,
+      actor || 'Admin',
+      logNote
+    );
+
+    return { diff, remainingStock: actualQty };
+  });
+
+  return run();
+}
+
+/**
+ * 4. PENGEMBALIAN BARANG (RETURN / COPOTAN)
+ * Barang bekas / copotan dari pelanggan atau sisa pemakaian lapangan dikembalikan ke gudang
+ */
+function returnStock(data, actor = 'Admin') {
+  const { item_id, serial_number, quantity, condition, customer_id, returned_by, note } = data;
+  if (!item_id) throw new Error('Pilih barang terlebih dahulu');
+
+  const item = getItemById(item_id);
+  if (!item) throw new Error('Data barang tidak ditemukan');
+
+  const cleanSn = serial_number ? serial_number.trim() : '';
+  const qty = cleanSn ? 1 : Math.max(1, parseInt(quantity, 10) || 1);
+  const cond = condition || 'used';
+
+  const run = db.transaction(() => {
+    let stockId = null;
+
+    if (cleanSn) {
+      const existing = db.prepare('SELECT id, status FROM inventory_stock WHERE serial_number = ?').get(cleanSn);
+      if (existing) {
+        // Kembalikan unit yang sudah ada ke gudang
+        db.prepare(`
+          UPDATE inventory_stock 
+          SET status = 'available', condition = ?, assigned_to_customer_id = NULL, location = 'Gudang Utama', updated_at = (NOW_LOCAL()), note = ?
+          WHERE id = ?
+        `).run(cond, note || 'Pengembalian / Copotan', existing.id);
+        stockId = existing.id;
+      } else {
+        const res = db.prepare(`
+          INSERT INTO inventory_stock (item_id, serial_number, quantity, condition, location, status, note)
+          VALUES (?, ?, 1, ?, 'Gudang Utama', 'available', ?)
+        `).run(item_id, cleanSn, cond, note || 'Pengembalian / Copotan');
+        stockId = res.lastInsertRowid;
+      }
+    } else {
+      const res = db.prepare(`
+        INSERT INTO inventory_stock (item_id, serial_number, quantity, condition, location, status, note)
+        VALUES (?, NULL, ?, ?, 'Gudang Utama', 'available', ?)
+      `).run(item_id, qty, cond, note || 'Pengembalian / Copotan');
+      stockId = res.lastInsertRowid;
+    }
+
+    const remainingStock = getItemAvailableStock(item_id);
+
+    let returner = returned_by ? returned_by.trim() : '';
+    if (customer_id && !returner) {
+      const cust = db.prepare('SELECT name FROM customers WHERE id = ?').get(customer_id);
+      if (cust) returner = `Copotan dari: ${cust.name}`;
+    }
+    if (!returner) returner = 'Teknisi Lapangan';
+
+    const logNote = note || (cleanSn ? `Pengembalian SN: ${cleanSn} (${cond})` : `Pengembalian (+${qty} ${item.unit})`);
+
+    db.prepare(`
+      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, remaining_stock, actor, recipient, reference_no, note)
+      VALUES (?, ?, 'return', ?, ?, ?, ?, 'RETURN', ?)
+    `).run(
+      item_id,
+      stockId,
+      qty,
+      remainingStock,
+      actor || 'Admin',
+      returner,
+      logNote
+    );
+
+    return { stockId, remainingStock };
+  });
+
+  return run();
+}
+
+/**
+ * 5. RIWAYAT PERGERAKAN STOK (INVENTORY LOGS)
+ */
+function getInventoryLogs(options = {}) {
+  if (typeof options === 'number') options = { limit: options };
+  const limit = options.limit ? parseInt(options.limit, 10) : 100;
+  const itemId = options.itemId ? Number(options.itemId) : null;
+  const type = options.type ? options.type.trim() : null;
+  const search = options.search ? options.search.trim() : null;
+
+  let query = `
+    SELECT l.*, 
+           i.name as item_name, 
+           i.unit as item_unit, 
+           i.brand as item_brand, 
+           i.model as item_model,
+           c.name as category_name, 
+           s.serial_number
+    FROM inventory_logs l
+    LEFT JOIN inventory_items i ON l.item_id = i.id
+    LEFT JOIN inventory_categories c ON i.category_id = c.id
+    LEFT JOIN inventory_stock s ON l.stock_id = s.id
+    WHERE 1=1
+  `;
+  const params = [];
+
+  if (itemId) {
+    query += ' AND l.item_id = ?';
+    params.push(itemId);
+  }
+  if (type) {
+    query += ' AND l.type = ?';
+    params.push(type);
+  }
+  if (search) {
+    query += ' AND (i.name LIKE ? OR s.serial_number LIKE ? OR l.recipient LIKE ? OR l.note LIKE ? OR l.reference_no LIKE ?)';
+    const s = `%${search}%`;
+    params.push(s, s, s, s, s);
+  }
+
+  query += ' ORDER BY l.created_at DESC, l.id DESC LIMIT ?';
+  params.push(limit);
+
+  return db.prepare(query).all(...params);
+}
+
+/**
+ * 6. STATISTIK GUDANG
+ */
+function getInventoryStats() {
+  seedDefaultCategories();
+  const totalItems = db.prepare('SELECT count(*) as c FROM inventory_items').get()?.c || 0;
+  const totalCategories = db.prepare('SELECT count(*) as c FROM inventory_categories').get()?.c || 0;
+  
+  const stockSummary = db.prepare(`
+    SELECT 
+      COALESCE(SUM(CASE WHEN status = 'available' THEN quantity ELSE 0 END), 0) as available,
+      COALESCE(SUM(CASE WHEN status = 'assigned' THEN quantity ELSE 0 END), 0) as assigned,
+      COALESCE(SUM(CASE WHEN status = 'broken' THEN quantity ELSE 0 END), 0) as broken
+    FROM inventory_stock
+  `).get();
+
+  const lowStockCount = db.prepare(`
+    SELECT count(*) as c FROM (
+      SELECT i.id
+      FROM inventory_items i
+      LEFT JOIN inventory_stock s ON s.item_id = i.id AND s.status = 'available'
+      GROUP BY i.id
+      HAVING COALESCE(SUM(s.quantity), 0) <= i.min_stock
+    )
+  `).get()?.c || 0;
+
+  return {
+    total_items: totalItems,
+    total_categories: totalCategories,
+    total_stock_available: Number(stockSummary?.available || 0),
+    total_stock_assigned: Number(stockSummary?.assigned || 0),
+    total_stock_broken: Number(stockSummary?.broken || 0),
+    low_stock_count: lowStockCount
+  };
+}
+
+
+// ─── KOMPATIBILITAS FORK ─────────────────────────────────────────────────
 function getStockByItem(itemId) {
   return db.prepare(`
     SELECT s.*, cust.name as customer_name
@@ -83,78 +612,15 @@ function getStockByItem(itemId) {
   `).all(itemId);
 }
 
-function addStock(data, actor = 'Admin') {
-  const { item_id, serial_number, quantity, condition, location, note } = data;
-  
-  const run = db.transaction(() => {
-    const result = db.prepare(`
-      INSERT INTO inventory_stock (item_id, serial_number, quantity, condition, location, note)
-      VALUES (?, ?, ?, ?, ?, ?)
-    `).run(item_id, serial_number || null, quantity, condition || 'new', location || 'Gudang Utama', note || '');
-
-    db.prepare(`
-      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, actor, note)
-      VALUES (?, ?, 'in', ?, ?, ?)
-    `).run(item_id, result.lastInsertRowid, quantity, actor, note || 'Stock Masuk');
-
-    return result;
-  });
-
-  return run();
-}
-
 function assignStockToCustomer(stockId, customerId, actor = 'Admin', note = '') {
   const stock = db.prepare('SELECT * FROM inventory_stock WHERE id = ?').get(stockId);
   if (!stock) throw new Error('Stock tidak ditemukan');
-  if (stock.status === 'assigned') throw new Error('Stock sudah terpasang di pelanggan lain');
-
-  const run = db.transaction(() => {
-    db.prepare(`
-      UPDATE inventory_stock 
-      SET status = 'assigned', assigned_to_customer_id = ?, updated_at = (NOW_LOCAL())
-      WHERE id = ?
-    `).run(customerId, stockId);
-
-    db.prepare(`
-      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, actor, note)
-      VALUES (?, ?, 'out', ?, ?, ?)
-    `).run(stock.item_id, stockId, stock.quantity, actor, note || `Terpasang ke pelanggan ID: ${customerId}`);
-  });
-
-  return run();
-}
-
-function adjustStock(stockId, newQuantity, note, actor = 'Admin') {
-  const stock = db.prepare('SELECT * FROM inventory_stock WHERE id = ?').get(stockId);
-  if (!stock) throw new Error('Stock tidak ditemukan');
-
-  const run = db.transaction(() => {
-    const diff = newQuantity - stock.quantity;
-    db.prepare('UPDATE inventory_stock SET quantity = ?, updated_at = (NOW_LOCAL()) WHERE id = ?').run(newQuantity, stockId);
-
-    db.prepare(`
-      INSERT INTO inventory_logs (item_id, stock_id, type, quantity, actor, note)
-      VALUES (?, ?, 'adjust', ?, ?, ?)
-    `).run(stock.item_id, stockId, diff, actor, note || 'Penyesuaian Stock');
-  });
-
-  return run();
-}
-
-function getInventoryLogs(limit = 100) {
-  return db.prepare(`
-    SELECT l.*, i.name as item_name, s.serial_number
-    FROM inventory_logs l
-    LEFT JOIN inventory_items i ON l.item_id = i.id
-    LEFT JOIN inventory_stock s ON l.stock_id = s.id
-    ORDER BY l.created_at DESC
-    LIMIT ?
-  `).all(limit);
+  return issueStock({ item_id: stock.item_id, stock_id: stockId, customer_id: customerId, note }, actor);
 }
 
 function getLowStockItems() {
   return db.prepare(`
-    SELECT i.*, c.name as category_name, SUM(s.quantity) as current_stock
+    SELECT i.*, c.name as category_name, COALESCE(SUM(s.quantity), 0) as current_stock
     FROM inventory_items i
     LEFT JOIN inventory_categories c ON i.category_id = c.id
     LEFT JOIN inventory_stock s ON s.item_id = i.id AND s.status = 'available'
@@ -164,8 +630,11 @@ function getLowStockItems() {
 }
 
 module.exports = {
+  seedDefaultCategories,
   getAllCategories, createCategory, updateCategory, deleteCategory,
-  getAllItems, getItemById, createItem, updateItem, deleteItem,
-  getStockByItem, addStock, assignStockToCustomer, adjustStock,
-  getInventoryLogs, getLowStockItems
+  getAllItems, getItemById, getItemDetail, createItem, updateItem, deleteItem,
+  getAvailableSerialNumbers, getItemAvailableStock, getItemAssignedStock, getItemBrokenStock,
+  addStock, issueStock, adjustStock, returnStock,
+  getInventoryLogs, getInventoryStats,
+  getStockByItem, assignStockToCustomer, getLowStockItems
 };