Refactor code structure for improved readability and maintainability

lib/recommendation-context.tsx

@@ -0,0 +1,125 @@
+"use client"
+
+import { createContext, ReactNode, useCallback, useContext, useEffect, useState } from "react"
+import { useAuth } from "@/lib/auth-context"
+
+type UserRecommendedNovel = {
+  id: string
+  title: string
+  slug: string
+  authorName: string
+  coverUrl: string | null
+  status: string
+  totalChapters: number
+}
+
+type UserRecommendationItem = {
+  id: string
+  novelId: string
+  createdAt: string | null
+  novel: UserRecommendedNovel
+}
+
+type RecommendationContextType = {
+  recommendations: UserRecommendationItem[]
+  isRecommended: (novelId: string) => boolean
+  toggleRecommendation: (novelId: string) => Promise<{ status: "added" | "removed" | "exists" }>
+}
+
+const RecommendationContext = createContext<RecommendationContextType | undefined>(undefined)
+
+export function RecommendationProvider({ children }: { children: ReactNode }) {
+  const { user } = useAuth()
+  const [recommendations, setRecommendations] = useState<UserRecommendationItem[]>([])
+
+  const fetchRecommendations = useCallback(async () => {
+    if (!user) {
+      setRecommendations([])
+      return
+    }
+
+    try {
+      const res = await fetch("/api/user/recommendations")
+      if (!res.ok) {
+        setRecommendations([])
+        return
+      }
+
+      const data = await res.json()
+      setRecommendations(Array.isArray(data) ? data : [])
+    } catch (error) {
+      console.error("Failed to fetch recommendations", error)
+    }
+  }, [user])
+
+  useEffect(() => {
+    fetchRecommendations()
+  }, [fetchRecommendations])
+
+  const isRecommended = useCallback(
+    (novelId: string) => recommendations.some((item) => item.novelId === novelId),
+    [recommendations]
+  )
+
+  const toggleRecommendation = useCallback(
+    async (novelId: string) => {
+      if (!user) throw new Error("Unauthorized")
+      if (!novelId) throw new Error("Missing novel id")
+
+      const existed = recommendations.some((item) => item.novelId === novelId)
+
+      if (existed) {
+        const res = await fetch(`/api/user/recommendations?novelId=${encodeURIComponent(novelId)}`, {
+          method: "DELETE",
+        })
+        const data = (await res.json()) as { error?: string }
+
+        if (!res.ok) {
+          throw new Error(data.error || "Không thể bỏ đề cử")
+        }
+
+        await fetchRecommendations()
+        return { status: "removed" as const }
+      }
+
+      const res = await fetch("/api/user/recommendations", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ novelId }),
+      })
+
+      const data = (await res.json()) as { error?: string }
+
+      if (!res.ok) {
+        if (res.status === 409) {
+          await fetchRecommendations()
+          return { status: "exists" as const }
+        }
+
+        throw new Error(data.error || "Không thể đề cử truyện")
+      }
+
+      await fetchRecommendations()
+      return { status: "added" as const }
+    },
+    [fetchRecommendations, recommendations, user]
+  )
+
+  return (
+    <RecommendationContext.Provider
+      value={{
+        recommendations,
+        isRecommended,
+        toggleRecommendation,
+      }}
+    >
+      {children}
+    </RecommendationContext.Provider>
+  )
+}
+
+export function useRecommendations() {
+  const context = useContext(RecommendationContext)
+  if (!context) throw new Error("useRecommendations must be used within RecommendationProvider")
+  return context
+}