Fix/adjust reservations correctly (#3474)

**What**
- Adjust reservations correctly according to the following heuristic: 

adjustment by addition:  (i.e. positive quantity adjustment passed to the adjustment method)
- if a reservation for the line-item in the location exists add quantity to that
- if not create a new reservation

adjustment by subtraction: 
- if a reservation with the exact quantity exists, delete it and return
- if a reservation with a greater quantity exists, subtract from it and return 
- otherwise delete from reservations until a reservation with greater quantity than the remaining is found and adjust that with the remaining quantity OR there are no more reservations

Fixes CORE-1247

integration-tests/plugins/__tests__/inventory/inventory-items/index.js

@@ -278,7 +278,7 @@ describe("Inventory Items endpoints", () => {
       })
     })
 
-    it.skip("Creates an inventory item using the api", async () => {
+    it("Creates an inventory item using the api", async () => {
       const product = await simpleProductFactory(dbConnection, {})
 
       const api = useApi()
@@ -316,20 +316,14 @@ describe("Inventory Items endpoints", () => {
       )
 
       expect(variantInventoryRes.data).toEqual({
-        variant: {
+        variant: expect.objectContaining({
           id: variantId,
           inventory: [
             expect.objectContaining({
               ...inventoryItemCreateRes.data.inventory_item,
             }),
           ],
-          sales_channel_availability: [
-            expect.objectContaining({
-              available_quantity: 0,
-              channel_name: "Default Sales Channel",
-            }),
-          ],
-        },
+        }),
       })
       expect(variantInventoryRes.status).toEqual(200)
     })

integration-tests/plugins/__tests__/inventory/order/order.js

@@ -295,7 +295,7 @@ describe("/store/carts", () => {
         )
       })
 
-      it("Adjusts reservations on successful fulfillment with reservation", async () => {
+      it("Adjusts reservation on successful fulfillment with reservation", async () => {
         const api = useApi()
 
         await prodVarInventoryService.reserveQuantity(variantId, 1, {
@@ -350,6 +350,273 @@ describe("/store/carts", () => {
         )
       })
 
+      it("Deletes multiple reservations on successful fulfillment with reservation", async () => {
+        const api = useApi()
+
+        const a = await inventoryService.updateInventoryLevel(
+          invItemId,
+          locationId,
+          { stocked_quantity: 2 }
+        )
+
+        await prodVarInventoryService.reserveQuantity(variantId, 1, {
+          locationId: locationId,
+          lineItemId: order.items[0].id,
+        })
+
+        await prodVarInventoryService.reserveQuantity(variantId, 1, {
+          locationId: locationId,
+          lineItemId: order.items[0].id,
+        })
+
+        let inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        expect(inventoryItem.data.inventory_item.location_levels[0]).toEqual(
+          expect.objectContaining({
+            stocked_quantity: 2,
+            reserved_quantity: 2,
+            available_quantity: 0,
+          })
+        )
+
+        const fulfillmentRes = await api.post(
+          `/admin/orders/${order.id}/fulfillment`,
+          {
+            items: [{ item_id: lineItemId, quantity: 2 }],
+            location_id: locationId,
+          },
+          adminHeaders
+        )
+
+        expect(fulfillmentRes.status).toBe(200)
+        expect(fulfillmentRes.data.order.fulfillment_status).toBe("fulfilled")
+
+        inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        const reservations = await api.get(
+          `/admin/reservations?inventory_item_id[]=${invItemId}`,
+          adminHeaders
+        )
+
+        expect(reservations.data.reservations.length).toBe(0)
+        expect(inventoryItem.data.inventory_item.location_levels[0]).toEqual(
+          expect.objectContaining({
+            stocked_quantity: 0,
+            reserved_quantity: 0,
+            available_quantity: 0,
+          })
+        )
+      })
+
+      it("Deletes single reservation on successful fulfillment with partial reservation", async () => {
+        const api = useApi()
+
+        await inventoryService.updateInventoryLevel(invItemId, locationId, {
+          stocked_quantity: 2,
+        })
+
+        await prodVarInventoryService.reserveQuantity(variantId, 1, {
+          locationId: locationId,
+          lineItemId: order.items[0].id,
+        })
+
+        let inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        expect(inventoryItem.data.inventory_item.location_levels[0]).toEqual(
+          expect.objectContaining({
+            stocked_quantity: 2,
+            reserved_quantity: 1,
+            available_quantity: 1,
+          })
+        )
+
+        const fulfillmentRes = await api.post(
+          `/admin/orders/${order.id}/fulfillment`,
+          {
+            items: [{ item_id: lineItemId, quantity: 2 }],
+            location_id: locationId,
+          },
+          adminHeaders
+        )
+
+        expect(fulfillmentRes.status).toBe(200)
+        expect(fulfillmentRes.data.order.fulfillment_status).toBe("fulfilled")
+
+        inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        const reservations = await api.get(
+          `/admin/reservations?inventory_item_id[]=${invItemId}`,
+          adminHeaders
+        )
+
+        expect(reservations.data.reservations.length).toBe(0)
+        expect(inventoryItem.data.inventory_item.location_levels[0]).toEqual(
+          expect.objectContaining({
+            stocked_quantity: 0,
+            reserved_quantity: 0,
+            available_quantity: 0,
+          })
+        )
+      })
+
+      it("Adjusts single reservation on successful fulfillment with over-reserved line item", async () => {
+        const api = useApi()
+
+        const a = await inventoryService.updateInventoryLevel(
+          invItemId,
+          locationId,
+          { stocked_quantity: 3 }
+        )
+
+        await prodVarInventoryService.reserveQuantity(variantId, 3, {
+          locationId: locationId,
+          lineItemId: order.items[0].id,
+        })
+
+        let inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        expect(inventoryItem.data.inventory_item.location_levels[0]).toEqual(
+          expect.objectContaining({
+            stocked_quantity: 3,
+            reserved_quantity: 3,
+            available_quantity: 0,
+          })
+        )
+
+        const fulfillmentRes = await api.post(
+          `/admin/orders/${order.id}/fulfillment`,
+          {
+            items: [{ item_id: lineItemId, quantity: 2 }],
+            location_id: locationId,
+          },
+          adminHeaders
+        )
+
+        expect(fulfillmentRes.status).toBe(200)
+        expect(fulfillmentRes.data.order.fulfillment_status).toBe("fulfilled")
+
+        inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        const reservations = await api.get(
+          `/admin/reservations?inventory_item_id[]=${invItemId}`,
+          adminHeaders
+        )
+
+        expect(reservations.data.reservations.length).toBe(1)
+        expect(reservations.data.reservations).toEqual([
+          expect.objectContaining({
+            quantity: 1,
+          }),
+        ])
+        expect(inventoryItem.data.inventory_item.location_levels[0]).toEqual(
+          expect.objectContaining({
+            stocked_quantity: 1,
+            reserved_quantity: 1,
+            available_quantity: 0,
+          })
+        )
+      })
+
+      it("Prioritizes adjusting reservations at the chosen location", async () => {
+        const api = useApi()
+
+        const sl = await stockLocationService.create({
+          name: "test-location 1",
+        })
+
+        await inventoryService.createInventoryLevel({
+          inventory_item_id: invItemId,
+          location_id: sl.id,
+          stocked_quantity: 3,
+        })
+
+        const a = await inventoryService.updateInventoryLevel(
+          invItemId,
+          locationId,
+          { stocked_quantity: 3 }
+        )
+
+        await prodVarInventoryService.reserveQuantity(variantId, 1, {
+          locationId: locationId,
+          lineItemId: order.items[0].id,
+        })
+
+        await prodVarInventoryService.reserveQuantity(variantId, 2, {
+          locationId: sl.id,
+          lineItemId: order.items[0].id,
+        })
+
+        let inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        expect(inventoryItem.data.inventory_item.location_levels).toEqual(
+          expect.arrayContaining([
+            expect.objectContaining({
+              location_id: locationId,
+              stocked_quantity: 3,
+              reserved_quantity: 1,
+              available_quantity: 2,
+            }),
+            expect.objectContaining({
+              location_id: sl.id,
+              stocked_quantity: 3,
+              reserved_quantity: 2,
+              available_quantity: 1,
+            }),
+          ])
+        )
+
+        const fulfillmentRes = await api.post(
+          `/admin/orders/${order.id}/fulfillment`,
+          {
+            items: [{ item_id: lineItemId, quantity: 2 }],
+            location_id: locationId,
+          },
+          adminHeaders
+        )
+
+        expect(fulfillmentRes.status).toBe(200)
+        expect(fulfillmentRes.data.order.fulfillment_status).toBe("fulfilled")
+
+        inventoryItem = await api.get(
+          `/admin/inventory-items/${invItemId}`,
+          adminHeaders
+        )
+
+        const reservations = await api.get(
+          `/admin/reservations?inventory_item_id[]=${invItemId}`,
+          adminHeaders
+        )
+
+        expect(reservations.data.reservations.length).toBe(1)
+        expect(reservations.data.reservations).toEqual([
+          expect.objectContaining({
+            quantity: 1,
+            location_id: sl.id,
+          }),
+        ])
+      })
+
       it("increases stocked quantity when return is received at location", async () => {
         const api = useApi()