stock management for partial shipment in laravel?

I am currently working on a project relating to a stock management system on laravel 5.6. Basically I have 3 tables in a MySQL database that I will link to my program; parts, order and receive

Parts table looks like

id  | brand    |  model    |   partcode    |  partname
1   | Apple    |  Iphone X |    ixmainpcb  |    PCB  
2   | Apple    |  Iphone X |    ixLCD      |   Main PCB 
3   | Apple    |  Iphone X |    ixcamera   |   PCB

Order table looks like

id  |part_id | orderno | orderqty | freeqty | purchaseqty | price | totalqty
1   |   1    |  O18001 |    1000  |    50   |     950     |  9500 |   1000
2   |   2    |  O18002 |    1500  |   100   |     1400    | 28000 |   1500
3   |   3    |  O18003 |    2000  |   100   |     1900    | 38000 |   2000

we have to pay price for the purchaseqty only no need to pay for the freeqty. freeqty is the scheme quantity. price is the total price amount.

Receive looks like

id  | order_id |fresh | defect | short | excess | Stock | totalreceive
1   |    1     | 600  |   100  |  300  |   0    |    5  |    700
2   |    2     | 400  |   50   |  1050 |   0    |   130 |    450
3   |    1     | 300  |   0    |   0   |   0    |   300 |    300

At first shipment order_id 1 product is received 700 pieces. It was sold to the customer and now in stock I have only 5 pieces left. At the second shipment my order_id 1 shipment has been completed by receiving the 300 pieces, so defect and short would be 0 in table and stock field will be 300 for third row.

While selling the actual problem arises.

What can I do in the following cases.

Case 1:

Suppose the customer want to buy 50 pieces product which have order_id 1. Then when I sell it the 5 should be deducted from first row and remaining 45 should be deducted from third row so that my new receive table would look like

id  | order_id |fresh | defect | short | excess | Stock | totalreceive
1   |    1     | 600  |   100  |  300  |   0    |    0  |    700
2   |    2     | 400  |   50   |  1050 |   0    |   130 |    450
3   |    1     | 300  |   0    |   0   |   0    |   255 |    300

Case 2:

Suppose the customer want to buy 5 (or less than 5) pieces product which have order_id 1. Then when I sell it from the first row so that my new receive table would look like

id  | order_id |fresh | defect | short | excess | Stock | totalreceive
1   |    1     | 600  |   100  |  300  |   0    |    0  |    700
2   |    2     | 400  |   50   |  1050 |   0    |   130 |    450
3   |    1     | 300  |   0    |   0   |   0    |   300 |    300

What is the best way\logic to handle these cases. Thanks in advance.

via Chebli Mohamed