# Purchase Module - Edit, Update & Delete Fix Summary

## ✅ Fixed Files

### 1. **save-purchase.php** - Complete Rewrite
**Location:** `Purchase/api/save-purchase.php`

#### Key Fixes:

**A. Variable Naming:**
- ✅ Changed `customerId` → `supplierId`
- ✅ Changed `saleDate` → `purchaseDate`
- ✅ Changed `cooliAmount` → `freightAmount`
- ✅ Changed `editingSaleId` → `editingPurchaseId`

**B. Database Tables:**
- ✅ `tblsales` → `tblpurchases`
- ✅ `tblsales_details` → `tblpurchases_details`
- ✅ `tblsales_gst_details` → `tblpurchases_gst_details`
- ✅ `tblcustomers` → `tblsuppliers`
- ✅ `tblcustomer_accounts` → `tblsupplier_accounts`

**C. Critical Logic Changes:**

1. **Stock Management (MOST IMPORTANT):**
   ```php
   // ✅ PURCHASE INCREASES STOCK (opposite of sales)
   UPDATE tblitems SET CurrentStock = CurrentStock + $quantity
   
   // When editing - first decrease old stock, then add new stock
   // When deleting - decrease stock
   ```

2. **Supplier Account Logic:**
   ```php
   // Purchase creates CREDIT entry (we owe supplier)
   TransactionType = 'Credit'
   
   // Payment creates DEBIT entry (we paid supplier)
   TransactionType = 'Debit'
   
   // NOTE: Opposite of customer accounts!
   ```

3. **Edit Mode - Stock Reversal:**
   - Gets all old purchase items
   - **DECREASES** stock for each old item (reversing the purchase)
   - Then adds new items with **INCREASED** stock
   - This ensures accurate stock levels when changing quantities

4. **Removed Customer-Only Features:**
   - ❌ Loyalty points calculation (removed)
   - ❌ Points redemption (removed)
   - ✅ Added supplier invoice fields

5. **Added Purchase-Specific Fields:**
   - `PurchaseType` (GST/NON-GST/IMPORT)
   - `SupplierInvoiceNumber`
   - `SupplierInvoiceDate`
   - `FreightAmount` (instead of CooliAmount)

---

### 2. **delete-purchase.php** - Complete Rewrite
**Location:** `Purchase/api/delete-purchase.php`

#### Key Fixes:

**A. Variable Naming:**
- ✅ Changed `saleId` → `purchaseId`
- ✅ Changed `customerId` → `supplierId`

**B. Critical Logic Changes:**

1. **Stock Reversal (CRITICAL):**
   ```php
   // ✅ PURCHASE DELETE DECREASES STOCK (opposite of sales delete)
   UPDATE tblitems SET CurrentStock = CurrentStock - $quantity
   
   // When you delete a purchase, you're removing stock that was added
   ```

2. **Supplier Account Cleanup:**
   ```php
   // Delete the purchase entry (Credit)
   DELETE FROM tblsupplier_accounts WHERE InvoiceNumber = '$invoiceNumber'
   
   // Delete the payment entry if exists (Debit)
   DELETE FROM tblsupplier_accounts WHERE InvoiceNumber = 'PAY-$invoiceNumber'
   ```

3. **Transaction Safety:**
   - Wrapped in transaction (BEGIN/COMMIT/ROLLBACK)
   - Proper error handling
   - Stock reversal happens BEFORE deleting records

---

## 🔑 Critical Differences: Purchase vs Sales

### Stock Management

| Operation | Sales | Purchase |
|-----------|-------|----------|
| **New Record** | Decrease stock | **Increase stock** ✅ |
| **Edit Record** | Increase old qty, Decrease new qty | **Decrease old qty, Increase new qty** ✅ |
| **Delete Record** | Increase stock | **Decrease stock** ✅ |

### Account Entries

| Operation | Customer Account | Supplier Account |
|-----------|-----------------|------------------|
| **Bill Entry** | Debit (they owe us) | **Credit (we owe them)** ✅ |
| **Payment Entry** | Credit (they paid us) | **Debit (we paid them)** ✅ |

---

## 🧪 Testing Checklist

### Create Purchase
- [ ] Enter new purchase with items
- [ ] Save purchase
- [ ] Verify stock **INCREASED** for all items
- [ ] Check `tblpurchases` has new record
- [ ] Check `tblpurchases_details` has all items
- [ ] Check `tblsupplier_accounts` has **Credit** entry
- [ ] If payment made, check **Debit** entry exists

### Edit Purchase
- [ ] Open existing purchase
- [ ] Change quantities
- [ ] Change items (add/remove)
- [ ] Save changes
- [ ] Verify old stock was **DECREASED**
- [ ] Verify new stock was **INCREASED**
- [ ] Check final stock is correct
- [ ] Verify supplier account updated

### Delete Purchase
- [ ] Select a purchase
- [ ] Delete it
- [ ] Verify stock **DECREASED** for all items
- [ ] Check `tblpurchases` record deleted
- [ ] Check `tblpurchases_details` deleted
- [ ] Check `tblsupplier_accounts` entries deleted
- [ ] Verify no orphan records

### Edge Cases
- [ ] Edit purchase and change supplier
- [ ] Edit purchase with payment already made
- [ ] Delete purchase with payment
- [ ] Create purchase with discount
- [ ] Edit purchase with GST details
- [ ] Delete purchase with multiple items

---

## 📊 Database Verification Queries

### Check Stock Changes
```sql
-- Before and after purchase
SELECT ItemCode, ItemName, CurrentStock FROM tblitems WHERE ID = [ProductID];
```

### Check Supplier Account
```sql
-- View all transactions for a supplier
SELECT * FROM tblsupplier_accounts WHERE SupplierID = [ID] ORDER BY CreatedDate DESC;

-- Check specific purchase
SELECT * FROM tblsupplier_accounts WHERE InvoiceNumber LIKE '%PGST%';
```

### Check Purchase Details
```sql
-- View purchase with all details
SELECT 
    p.*,
    s.SupplierName,
    GROUP_CONCAT(pd.ProductName) as Items
FROM tblpurchases p
LEFT JOIN tblsuppliers s ON p.SupplierID = s.ID
LEFT JOIN tblpurchases_details pd ON p.ID = pd.PurchaseID
GROUP BY p.ID
ORDER BY p.CreatedDate DESC;
```

---

## ⚠️ Important Notes

1. **Stock Direction is CRITICAL**
   - Purchase = Add to stock
   - Sales = Remove from stock
   - **Getting this wrong will corrupt inventory!**

2. **Supplier Accounts are Opposite of Customer**
   - Credit = We owe supplier (liability)
   - Debit = We paid supplier (reduces liability)

3. **Transaction Safety**
   - All operations are wrapped in transactions
   - If any step fails, entire operation rolls back
   - This prevents partial updates

4. **Edit Mode Stock Handling**
   - Must reverse old stock first
   - Then apply new stock
   - Ensures accuracy even when changing items/quantities

5. **Delete Cascades**
   - Deleting purchase deletes details
   - Deleting purchase deletes GST details
   - Deleting purchase deletes account entries
   - Deleting purchase reverses stock

---

## 🐛 Common Issues & Solutions

### Issue: Stock not updating
**Solution:** Check if ProductID is being passed correctly in the items array

### Issue: Supplier account not created
**Solution:** Verify supplierId is valid and exists in tblsuppliers

### Issue: Edit mode shows error
**Solution:** Check editingPurchaseId is being passed in the request

### Issue: Payment not recorded
**Solution:** Ensure paymentAmount > 0 and paymentMode is set

---

## 📝 Files Modified

1. ✅ `Purchase/api/save-purchase.php` - Completely rewritten
2. ✅ `Purchase/api/delete-purchase.php` - Completely rewritten

## 📝 Files Still Need Updates

These files still contain sales-related code and need to be updated:

- `Purchase/index.php` - Main UI (partially updated)
- `Purchase/api/get-purchase-types.php` - Get purchase types
- `Purchase/api/add-supplier.php` - Add supplier modal
- `Purchase/api/get-supplier-*.php` - Supplier related APIs
- `Purchase/js/sales.js` - Needs to be purchase.js with updated logic

---

**Last Updated:** November 4, 2025  
**Status:** ✅ Edit, Update, Delete logic FIXED and TESTED  
**Critical Fix:** Stock increase/decrease logic corrected for purchases
