fix(medusa): calculate sales channel availability correctly for variants (#10448)

* fix: calculate inventory quantities based on sales channel and locations

* Update packages/medusa/src/api/utils/middlewares/products/variant-inventory-quantity.ts

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

* Update packages/medusa/src/api/utils/middlewares/products/variant-inventory-quantity.ts

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

* Update packages/core/core-flows/src/product/steps/get-variant-availability.ts

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

* fix: crk

---------

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

packages/core/utils/src/product/get-variant-availability.ts

@@ -0,0 +1,178 @@
+import { RemoteQueryFunction } from "@medusajs/types"
+
+/**
+ * Computes the varaint availability for a list of variants in a given sales channel
+ *
+ * The availability algorithm works as follows:
+ * 1. For each variant, we retrieve its inventory items.
+ * 2. We calculate the available quantity for each inventory item, considering only the stock locations associated with the given sales channel.
+ * 3. For each inventory item, we calculate the maximum deliverable quantity by dividing the available quantity by the quantity required for the variant.
+ * 4. We take the minimum of these maximum deliverable quantities across all inventory items for the variant.
+ * 5. This minimum value represents the overall availability of the variant in the given sales channel.
+ *
+ * The algorithm takes into account:
+ * - Variant inventory items: The inventory records associated with each variant.
+ * - Required quantities: The quantity of each inventory item required to fulfill one unit of the variant.
+ * - Sales channels: The specific sales channel for which we're calculating availability.
+ * - Stock locations: The inventory locations associated with the sales channel.
+ *
+ * @param query - The Query function
+ * @param data - An object containing the variant ids and the sales channel id to compute the availability for
+ * @returns an object containing the variant ids and their availability
+ */
+export async function getVariantAvailability(
+  query: Omit<RemoteQueryFunction, symbol>,
+  data: VariantAvailabilityData
+): Promise<{
+  [variant_id: string]: {
+    availability: number
+    sales_channel_id: string
+  }
+}> {
+  const { variantInventoriesMap, locationIds } = await getDataForComputation(
+    query,
+    data
+  )
+
+  return data.variant_ids.reduce((acc, variantId) => {
+    const variantInventoryItems = variantInventoriesMap.get(variantId) || []
+    acc[variantId] = {
+      availability: computeVariantAvailability(
+        variantInventoryItems,
+        locationIds,
+        { requireChannelCheck: true }
+      ),
+      sales_channel_id: data.sales_channel_id,
+    }
+    return acc
+  }, {})
+}
+
+type TotalVariantAvailabilityData = {
+  variant_ids: string[]
+}
+
+/**
+ * Computes the total availability for a list of variants across all stock locations
+ *
+ * @param query - The Query function
+ * @param data - An object containing the variant ids to compute the availability for
+ * @returns the total availability for the given variants
+ */
+export async function getTotalVariantAvailability(
+  query: Omit<RemoteQueryFunction, symbol>,
+  data: TotalVariantAvailabilityData
+): Promise<{
+  [variant_id: string]: {
+    availability: number
+  }
+}> {
+  const { variantInventoriesMap, locationIds } = await getDataForComputation(
+    query,
+    data
+  )
+
+  return data.variant_ids.reduce((acc, variantId) => {
+    const variantInventoryItems = variantInventoriesMap.get(variantId) || []
+    acc[variantId] = {
+      availability: computeVariantAvailability(
+        variantInventoryItems,
+        locationIds,
+        { requireChannelCheck: false }
+      ),
+    }
+    return acc
+  }, {})
+}
+
+interface VariantItems {
+  variant_id: string
+  required_quantity: number
+  variant: {
+    manage_inventory: boolean
+    allow_backorder: boolean
+  }
+  inventory: {
+    location_levels: {
+      location_id: string
+      available_quantity: number
+    }[]
+  }
+}
+
+const computeVariantAvailability = (
+  variantInventoryItems: VariantItems[],
+  channelLocationsSet: Set<string>,
+  { requireChannelCheck } = { requireChannelCheck: true }
+) => {
+  const inventoryQuantities: number[] = []
+
+  for (const link of variantInventoryItems) {
+    const requiredQuantity = link.required_quantity
+    const availableQuantity = (link.inventory?.location_levels || []).reduce(
+      (sum, level) => {
+        if (
+          requireChannelCheck &&
+          !channelLocationsSet.has(level.location_id)
+        ) {
+          return sum
+        }
+
+        return sum + (level?.available_quantity || 0)
+      },
+      0
+    )
+
+    // This will give us the maximum deliverable quantities for each inventory item
+    const maxInventoryQuantity = Math.floor(
+      availableQuantity / requiredQuantity
+    )
+
+    inventoryQuantities.push(maxInventoryQuantity)
+  }
+
+  return inventoryQuantities.length ? Math.min(...inventoryQuantities) : 0
+}
+
+type VariantAvailabilityData = {
+  variant_ids: string[]
+  sales_channel_id: string
+}
+
+const getDataForComputation = async (
+  query: Omit<RemoteQueryFunction, symbol>,
+  data: { variant_ids: string[]; sales_channel_id?: string }
+) => {
+  const { data: variantInventoryItems } = await query.graph({
+    entity: "product_variant_inventory_items",
+    fields: [
+      "variant_id",
+      "required_quantity",
+      "variant.manage_inventory",
+      "variant.allow_backorder",
+      "inventory.*",
+      "inventory.location_levels.*",
+    ],
+    filters: { variant_id: data.variant_ids },
+  })
+
+  const variantInventoriesMap = new Map()
+  variantInventoryItems.forEach((link) => {
+    const array = variantInventoriesMap.get(link.variant_id) || []
+    array.push(link)
+    variantInventoriesMap.set(link.variant_id, array)
+  })
+
+  const locationIds = new Set<string>()
+  if (data.sales_channel_id) {
+    const { data: channelLocations } = await query.graph({
+      entity: "sales_channel_locations",
+      fields: ["stock_location_id"],
+      filters: { sales_channel_id: data.sales_channel_id },
+    })
+
+    channelLocations.forEach((loc) => locationIds.add(loc.stock_location_id))
+  }
+
+  return { variantInventoriesMap, locationIds }
+}

packages/core/utils/src/product/index.ts

@@ -6,3 +6,4 @@ export enum ProductStatus {
 }
 
 export * from "./events"
+export * from "./get-variant-availability"