Architecture for Pharmacy Inventory Management:

DrugPurchaseOrders are sent from a dispense location to a stock location. DrugPurchaseOrder has a one-to-many relationship with DrugInventory. When a DPO is created, it has:

State	DrugPurchaseOrder	DrugInventory location	DrugInventory status
DPO is created	received: false	Pharmacy dispensary X	requested
DPO is received	received: true	Pharmacy stock center	received
DPO is filled	received: true	Pharmacy stock center	filled
DPO is sent to Pharmacy dispensary	received: false	Pharmacy stock center	sent
DPO drugs are received by dispensary	received: true	Pharmacy dispensary X	available

Notes on filling:

-Each DrugInventory is converted to a specific batch with expiryDate, etc.

-DrugInventories are split if necessary, new DrugInventories added

-The existing batches of DrugInventories that are being used to fill are decremented as needed (the user will choose which batch to fill the purchase order with)

Other use cases:

Issuing stock to dispensary: same as last two steps above. Stock Center creates the DrugPurchaseOrder but system acts as if the dispensary requested.

State	DrugPurchaseOrder	DrugInventory location	DrugInventory status
Stock sent	received: false	Pharmacy stock center	sent
Stock received	received: true	Pharmacy dispensary Y	available

Issuing stock to outside of system/offline dispensaries: existing inventories are decremented, and DrugInventories immediately available at some location:

State	DrugPurchaseOrder	DrugInventory location	DrugInventory status
Stock Issued	received: true	Dispensary Z/Unknown Location	available