stocks change

The order-placement stock check (read available qty, then insert an "out"
deduction) had no row lock, so two concurrent orders for the same product
could both pass the availability check before either committed its
deduction, overselling the item. Locks each ordered product's
productlocations row with SELECT ... FOR UPDATE up front, in a fixed
(productid, locationid) order across all items so overlapping concurrent
orders contend for locks in the same sequence instead of deadlocking.

models/product.go

@@ -124,6 +124,11 @@ type Locationproducts struct {
 	Productcombo      int     `json:"productcombo" gorm:"default:0"`
 	Variants          int     `json:"variants" gorm:"default:0"`
 	Quantity          int     `json:"quantity"`
+	// Price is the per-store selling price from productlocations.price — the one
+	// CreateProductLocation upserts. Read-only here: it comes from the joined
+	// productlocations row, not from products. Without it a store could set a
+	// price and never read it back, so the UI always showed the master price.
+	Price       float64 `json:"price" gorm:"->"`
 	Retailprice float64 `json:"retailprice,omitempty"`
 	Diffprice   float64 `json:"diffprice,omitempty"`
 	Diffpercent float64 `json:"diffpercent,omitempty"`

repositories/orderRepository.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"log"
 	"nearle/models"
+	"sort"
 	"strings"
 	"time"
 
@@ -1130,6 +1131,49 @@ func (r *orderRepository) CreateOrder(data models.Orders) (models.Orders, error)
 		locID = data.Applocationid
 	}
 
+	// 🛠️ Step 0: Lock every (tenantid, locationid, productid) row this order
+	// touches before checking availability. Without this, two concurrent
+	// orders for the same product can both read "stock available" before
+	// either commits its deduction, oversell the item, and drive stock
+	// negative. Locking productlocations — the row the stock computation is
+	// already keyed against — serializes conflicting orders instead.
+	//
+	// Locks are acquired in a fixed (productid, locationid) order so that
+	// two orders sharing overlapping products always contend for them in
+	// the same sequence, avoiding a lock-ordering deadlock between the two
+	// transactions (as opposed to just making each individually block).
+	type lockTarget struct {
+		productid  int
+		locationid int
+	}
+	seen := make(map[lockTarget]bool)
+	locks := make([]lockTarget, 0, len(data.Items))
+	for _, item := range data.Items {
+		itemLocID := item.Locationid
+		if itemLocID == 0 {
+			itemLocID = locID
+		}
+		lt := lockTarget{productid: item.Productid, locationid: itemLocID}
+		if !seen[lt] {
+			seen[lt] = true
+			locks = append(locks, lt)
+		}
+	}
+	sort.Slice(locks, func(a, b int) bool {
+		if locks[a].productid != locks[b].productid {
+			return locks[a].productid < locks[b].productid
+		}
+		return locks[a].locationid < locks[b].locationid
+	})
+	for _, lt := range locks {
+		var locked int
+		lockQuery := `SELECT productlocationid FROM productlocations WHERE tenantid = ? AND locationid = ? AND productid = ? FOR UPDATE`
+		if err := tx.Raw(lockQuery, data.Tenantid, lt.locationid, lt.productid).Scan(&locked).Error; err != nil {
+			tx.Rollback()
+			return models.Orders{}, fmt.Errorf("failed to lock stock for product %d: %w", lt.productid, err)
+		}
+	}
+
 	// 🛠️ Step 1: Pre-validate stock availability for all items before placing order
 	for _, item := range data.Items {
 		itemLocID := item.Locationid

repositories/productRepository.go

@@ -405,7 +405,11 @@ func (r *productRepository) GetLocationProducts(tenantID, locationID, subcategor
 
 	params := []interface{}{tenantID, locationID}
 
-	query := `SELECT a.*, b.productlocationid, b.status,
+	// b.price is the per-store selling price. It has to be selected explicitly:
+	// a.* only covers products (whose price column is retailprice, the master
+	// price), so without this the catalogue could never read back a price set
+	// for this outlet via CreateProductLocation.
+	query := `SELECT a.*, b.productlocationid, b.status, b.price,
 			  COALESCE(SUM(CASE WHEN UPPER(c.stocktype) = 'IN' THEN c.quantity ELSE 0 END), 0) AS total_in,
     		  COALESCE(SUM(CASE WHEN UPPER(c.stocktype) = 'OUT' THEN c.quantity ELSE 0 END), 0) AS total_out,
     		  COALESCE(SUM(CASE WHEN UPPER(c.stocktype) = 'IN' THEN c.quantity ELSE 0 END) - 
@@ -427,7 +431,7 @@ func (r *productRepository) GetLocationProducts(tenantID, locationID, subcategor
 
 	query += ` GROUP BY a.productid, a.productname, a.productimage, a.categoryid, a.subcategoryid,
 			 a.productunit, a.productcost, a.taxpercent, a.taxamount, a.retailprice,
-			 b.tenantid, b.locationid, b.productlocationid, b.status
+			 b.tenantid, b.locationid, b.productlocationid, b.status, b.price
 			 ORDER BY a.productid DESC LIMIT ? OFFSET ?`
 
 	params = append(params, pagesize, offset)