Add Products/Quantity to Stock Management In Laravel 5.4 - laravel

Question

I'm developing Inventory System Using Laravel 5.4. I need help. I've a product table and stock table. If the user tried to add a product to stock whereby the supplier_id and product_id already exist i.e (Select quantity FROM Stocks WHERE supplier_id=1 AND product_id=1) The product should be added to the quantity column of the existing stock instead of inserting the product and quantity into another column.
i.e if Stock table has --> ProductName == Laptop; SupplierID==1; Quantity ==(50). If the user select ProductName == Laptop; AND SupplierID==1; The Quantity Coulmn should be sum to ( 50) Inserting should ONLY be when ProductName and Supplier doesn't exist in same row i.e (Select quantity FROM Stocks WHERE supplier_id=20 AND product_id=2) .
How can I use Eloquent effectively to achieve this pls
Product Table
Schema::create('products', function (Blueprint $table) {
$table->increments('id');
$table->integer('brand_id')->index()->unsigned()->nullable();
$table->string('name');
$table->string('part_number');
$table->string('serial_number');
$table->timestamps();
});
STOCK TABLE
Schema::create('stocks', function (Blueprint $table) {
$table->increments('id');
$table->integer('product_id')->index()->unsigned()->nullable();
$table->integer('category_id')->index()->unsigned()->nullable();
$table->integer('supplier_id')->index()->unsigned()->nullable();
$table->string('quantity');
$table->string('unit_price');
$table->date('purchased_date');
$table->timestamps();
$table->date('delete_at');
});
My StockController :;
public function create(Request $request)
{
$products= Product::lists('name', 'id')->all();
$categories= Category::lists('name', 'id')->all();
$suppliers= Supplier::lists('name', 'id')->all();
return view('admin.stocks.create', compact('products','categories','suppliers'));
}
public function store(Request $request)
{
Stock::create($request->all());
return redirect('/admin/stocks');
}
create.blade.php
{!! Form::open(['method'=>'POST', 'action'=> 'StocksController#store','files'=>true]) !!}
<div class="form-group">
{!! Form::label('supplier_id', 'Supplier/Vendor:') !!}
{!! Form::select('supplier_id', [''=>'Select Supplier'] + $suppliers, null, ['class'=>'form-control'])!!}
</div>
<div class="form-group">
{!! Form::label('product_id', 'Part Name:') !!}
{!! Form::select('product_id', [''=>'Select Part Name'] + $products, null, ['class'=>'form-control'])!!}
</div>
<div class="form-group">
{!! Form::label('category_id', 'Category:') !!}
{!! Form::select('category_id', [''=>'Choose Category'] + $categories, null, ['class'=>'form-control'])!!}
</div>
<div class="form-group">
{!! Form::label('quantity', 'Quantity:') !!}
{!! Form::text('quantity', null, ['class'=>'form-control'])!!}
</div>
<div class="form-group">
{!! Form::label('purchased_date', 'Purchased Date:') !!}
{!! Form::text('purchased_date', null, ['class'=>'form-control'])!!}
</div>
<div class="form-group">
{!! Form::label('unit_price', 'Unit Price (Naira):') !!}
{!! Form::text('unit_price', null, ['class'=>'form-control'])!!}
</div>
<div class="form-group">
{!! Form::submit('Add Stock', ['class'=>'btn btn-primary']) !!}
</div>
{!! Form::close() !!}
I hope someone can help me out.

Answer 1

Your store method in StockController need to be like this:
public function store(Request $request)
{
$stock = Stock::where([
['product_id', '=', $request->product_id],
['supplier_id', '=', $request->supplier_id]
])->first();
if ($stock) {
$stock->increment('quantity', $request->quantity);
} else {
Stock::create($request->all());
}
return redirect('/admin/stocks');
}
Think this will fix problem, but check what you do with unit_price and purchase_date in case of updating same row?