feat(SW-717) make reduce more understandable

components/HotelReservation/SelectRate/HotelInfoCard/NoRoomsAlert.tsx

@@ -6,6 +6,7 @@ import { getIntl } from "@/i18n"
 import { safeTry } from "@/utils/safeTry"
 
 import { generateChildrenString } from "../../utils"
+import { combineRoomAvailabilities } from "./utils"
 
 import styles from "./NoRoomsAlert.module.css"
 
@@ -51,23 +52,9 @@ export async function NoRoomsAlert({
 
   const roomsAvailabilityResults = await Promise.all(roomsAvailabilityPromises)
 
-  const roomsAvailability = roomsAvailabilityResults.reduce<
+  const roomsAvailability = combineRoomAvailabilities({
-    (typeof roomsAvailabilityResults)[0][0]
+    availabilityResults: roomsAvailabilityResults,
-  >((acc, [result, error]) => {
+  })
-    if (error) {
-      console.error("[RoomsContainer] unable to fetch room availability")
-      return acc
-    }
-    if (!acc) return result
-    if (!result) return acc
-    return {
-      ...result,
-      roomConfigurations: [
-        ...acc.roomConfigurations,
-        ...result.roomConfigurations,
-      ],
-    }
-  }, null)
 
   if (!roomsAvailability) {
     return null

components/HotelReservation/SelectRate/HotelInfoCard/utils.ts

@@ -0,0 +1,23 @@
+import type { RoomsAvailability } from "@/server/routers/hotels/output"
+
+export function combineRoomAvailabilities({
+  availabilityResults,
+}: {
+  availabilityResults: Array<[RoomsAvailability | undefined | null, unknown]>
+}): RoomsAvailability | null {
+  return availabilityResults.reduce<RoomsAvailability | null>(
+    (combinedResult, [currentResult, error]) => {
+      if (error || !currentResult) return combinedResult
+      if (!combinedResult) return currentResult
+
+      return {
+        ...currentResult,
+        roomConfigurations: [
+          ...combinedResult.roomConfigurations,
+          ...currentResult.roomConfigurations,
+        ],
+      }
+    },
+    null
+  )
+}

components/HotelReservation/SelectRate/Rooms/utils.ts

@@ -8,12 +8,17 @@ import type { RoomConfiguration } from "@/types/trpc/routers/hotel/roomAvailabil
 export function filterDuplicateRoomTypesByLowestPrice(
   roomConfigurations: RoomConfiguration[]
 ): RoomConfiguration[] {
-  const roomTypeCount = roomConfigurations.reduce(
+  const roomTypeCount = roomConfigurations.reduce<Record<string, number>>(
-    (acc, room) => {
+    (roomTypeTally, currentRoom) => {
-      acc[room.roomType] = (acc[room.roomType] || 0) + 1
+      const currentRoomType = currentRoom.roomType
-      return acc
+      const currentCount = roomTypeTally[currentRoomType] || 0
+
+      return {
+        ...roomTypeTally,
+        [currentRoomType]: currentCount + 1,
+      }
     },
-    {} as Record<string, number>
+    {}
   )
 
   const duplicateRoomTypes = new Set(