feat: Add visual feedback and polish (Task 15)

- Implement toast notification system for success/error messages
- Add loading states with skeleton loaders for async operations
- Create smooth CSS transitions and animations
- Enhance empty states with EmptyState component
- Add loading.tsx files for Next.js loading states
- Integrate toast notifications across all CRUD operations
- Add fade-in and scale-in animations for better UX
- Improve visual feedback for user actions

components/DeleteItemButton.tsx

@@ -4,6 +4,7 @@ import { useState } from 'react'
 import { useRouter } from 'next/navigation'
 import { deleteItem } from '@/lib/actions'
 import { Trash2 } from 'lucide-react'
+import { useToast } from './ToastContainer'
 
 interface DeleteItemButtonProps {
   itemId: string
@@ -13,6 +14,7 @@ interface DeleteItemButtonProps {
 
 export default function DeleteItemButton({ itemId, listId, variant = 'full' }: DeleteItemButtonProps) {
   const router = useRouter()
+  const { showToast } = useToast()
   const [isDeleting, setIsDeleting] = useState(false)
   const [showConfirm, setShowConfirm] = useState(false)
 
@@ -22,6 +24,7 @@ export default function DeleteItemButton({ itemId, listId, variant = 'full' }: D
     setIsDeleting(true)
     try {
       await deleteItem(itemId)
+      showToast('Task deleted successfully', 'success')
       if (listId) {
         router.push(`/list/${listId}`)
       } else {
@@ -29,6 +32,7 @@ export default function DeleteItemButton({ itemId, listId, variant = 'full' }: D
       }
     } catch (error) {
       console.error('Error deleting item:', error)
+      showToast('Failed to delete task', 'error')
       setIsDeleting(false)
       setShowConfirm(false)
     }

components/DeleteListButton.tsx

@@ -5,6 +5,7 @@ import { Trash2 } from 'lucide-react'
 import { deleteList } from '@/lib/actions'
 import { useRouter } from 'next/navigation'
 import Modal from './Modal'
+import { useToast } from './ToastContainer'
 
 interface DeleteListButtonProps {
   listId: string
@@ -20,6 +21,7 @@ export default function DeleteListButton({
   redirectAfterDelete = false 
 }: DeleteListButtonProps) {
   const router = useRouter()
+  const { showToast } = useToast()
   const [isConfirmOpen, setIsConfirmOpen] = useState(false)
   const [isDeleting, setIsDeleting] = useState(false)
 
@@ -27,6 +29,7 @@ export default function DeleteListButton({
     setIsDeleting(true)
     try {
       await deleteList(listId)
+      showToast('List deleted successfully', 'success')
       setIsConfirmOpen(false)
       if (redirectAfterDelete) {
         router.push('/')
@@ -35,7 +38,7 @@ export default function DeleteListButton({
       }
     } catch (err) {
       console.error('Failed to delete list:', err)
-      alert('Failed to delete list. Please try again.')
+      showToast('Failed to delete list', 'error')
     } finally {
       setIsDeleting(false)
     }

components/EmptyState.tsx

@@ -0,0 +1,41 @@
+'use client'
+
+import { ReactNode } from 'react'
+import { Inbox, ListTodo, Search, Filter } from 'lucide-react'
+
+interface EmptyStateProps {
+  icon?: 'inbox' | 'list' | 'search' | 'filter'
+  title: string
+  description?: string
+  action?: ReactNode
+}
+
+export default function EmptyState({ icon = 'inbox', title, description, action }: EmptyStateProps) {
+  const icons = {
+    inbox: <Inbox size={48} className="text-gray-300" />,
+    list: <ListTodo size={48} className="text-gray-300" />,
+    search: <Search size={48} className="text-gray-300" />,
+    filter: <Filter size={48} className="text-gray-300" />,
+  }
+
+  return (
+    <div className="flex flex-col items-center justify-center py-12 sm:py-16 px-4 text-center">
+      <div className="mb-4 sm:mb-6 opacity-50">
+        {icons[icon]}
+      </div>
+      <h3 className="text-lg sm:text-xl font-semibold text-gray-700 mb-2">
+        {title}
+      </h3>
+      {description && (
+        <p className="text-sm sm:text-base text-gray-500 mb-6 max-w-md">
+          {description}
+        </p>
+      )}
+      {action && (
+        <div className="mt-4">
+          {action}
+        </div>
+      )}
+    </div>
+  )
+}

components/InlineItemCreate.tsx

@@ -4,6 +4,7 @@ import { useState } from 'react'
 import { useRouter } from 'next/navigation'
 import { createItem } from '@/lib/actions'
 import { Plus } from 'lucide-react'
+import { useToast } from './ToastContainer'
 
 interface InlineItemCreateProps {
   listId: string
@@ -11,6 +12,7 @@ interface InlineItemCreateProps {
 
 export default function InlineItemCreate({ listId }: InlineItemCreateProps) {
   const router = useRouter()
+  const { showToast } = useToast()
   const [isCreating, setIsCreating] = useState(false)
   const [title, setTitle] = useState('')
   const [isSubmitting, setIsSubmitting] = useState(false)
@@ -26,11 +28,13 @@ export default function InlineItemCreate({ listId }: InlineItemCreateProps) {
 
     try {
       await createItem(listId, title.trim())
+      showToast('Task added successfully', 'success')
       setTitle('')
       setIsCreating(false)
       router.refresh()
     } catch (error) {
       console.error('Error creating item:', error)
+      showToast('Failed to add task', 'error')
     } finally {
       setIsSubmitting(false)
     }

components/ItemForm.tsx

@@ -3,6 +3,7 @@
 import { useState } from 'react'
 import { useRouter } from 'next/navigation'
 import { updateItem, createItem } from '@/lib/actions'
+import { useToast } from './ToastContainer'
 
 interface ItemFormProps {
   listId: string
@@ -20,6 +21,7 @@ interface ItemFormProps {
 
 export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps) {
   const router = useRouter()
+  const { showToast } = useToast()
   const [isSubmitting, setIsSubmitting] = useState(false)
   const [errors, setErrors] = useState<Record<string, string>>({})
 
@@ -79,14 +81,17 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           tags: data.tags,
           notes: data.notes,
         })
+        showToast('Task created successfully', 'success')
         router.push(`/list/${listId}`)
       } else if (item) {
         await updateItem(item.id, data)
+        showToast('Task updated successfully', 'success')
         router.push(`/list/${listId}/item/${item.id}`)
       }
     } catch (error) {
       console.error('Error saving item:', error)
       setErrors({ submit: 'Failed to save item. Please try again.' })
+      showToast('Failed to save task', 'error')
     } finally {
       setIsSubmitting(false)
     }

components/ListDetailView.tsx

@@ -5,6 +5,7 @@ import ItemCard from './ItemCard'
 import SearchBar from './SearchBar'
 import FilterPanel from './FilterPanel'
 import SearchResults from './SearchResults'
+import EmptyState from './EmptyState'
 import { searchItems, getItemsByFilter } from '@/lib/actions'
 import { useSearch, useFilters, useScrollPosition } from '@/hooks'
 
@@ -138,7 +139,7 @@ export default function ListDetailView({ listId, initialItems }: ListDetailViewP
         <div className="space-y-6">
           {/* Incomplete Items */}
           {incompleteItems.length > 0 && (
-            <div>
+            <div className="animate-fade-in">
               <h2 className="text-lg font-semibold text-gray-900 mb-3">
                 To Do ({incompleteItems.length})
               </h2>
@@ -152,7 +153,7 @@ export default function ListDetailView({ listId, initialItems }: ListDetailViewP
 
           {/* Completed Items */}
           {completedItems.length > 0 && (
-            <div>
+            <div className="animate-fade-in">
               <h2 className="text-lg font-semibold text-gray-500 mb-3">
                 Completed ({completedItems.length})
               </h2>
@@ -166,14 +167,15 @@ export default function ListDetailView({ listId, initialItems }: ListDetailViewP
 
           {/* Empty State */}
           {displayItems.length === 0 && (
-            <div className="text-center py-12 bg-gray-50 rounded-lg">
-              <p className="text-gray-500 text-lg mb-2">No tasks found</p>
-              <p className="text-gray-400">
-                {filters.priority || filters.completed !== null || filters.tags.length > 0
-                  ? 'Try adjusting your filters'
-                  : 'Add your first task to get started'}
-              </p>
-            </div>
+            <EmptyState
+              icon={filters.priority || filters.completed !== null || filters.tags.length > 0 ? 'filter' : 'inbox'}
+              title="No tasks found"
+              description={
+                filters.priority || filters.completed !== null || filters.tags.length > 0
+                  ? 'Try adjusting your filters to see more tasks'
+                  : 'Add your first task using the button above'
+              }
+            />
           )}
         </div>
       )}

components/ListForm.tsx

@@ -3,6 +3,7 @@
 import { useState } from 'react'
 import { createList, updateList } from '@/lib/actions'
 import { useRouter } from 'next/navigation'
+import { useToast } from './ToastContainer'
 
 interface ListFormProps {
   list?: {
@@ -27,6 +28,7 @@ const PRESET_COLORS = [
 
 export default function ListForm({ list, onCancel, onSuccess }: ListFormProps) {
   const router = useRouter()
+  const { showToast } = useToast()
   const [title, setTitle] = useState(list?.title || '')
   const [color, setColor] = useState(list?.color || PRESET_COLORS[0])
   const [isSubmitting, setIsSubmitting] = useState(false)
@@ -47,9 +49,11 @@ export default function ListForm({ list, onCancel, onSuccess }: ListFormProps) {
       if (list) {
         // Update existing list
         await updateList(list.id, { title: title.trim(), color })
+        showToast('List updated successfully', 'success')
       } else {
         // Create new list
         await createList(title.trim(), color)
+        showToast('List created successfully', 'success')
       }
       
       if (onSuccess) {
@@ -59,6 +63,7 @@ export default function ListForm({ list, onCancel, onSuccess }: ListFormProps) {
       }
     } catch (err) {
       setError('Failed to save list. Please try again.')
+      showToast('Failed to save list', 'error')
       console.error(err)
     } finally {
       setIsSubmitting(false)

components/LoadingSpinner.tsx

@@ -0,0 +1,33 @@
+'use client'
+
+interface LoadingSpinnerProps {
+  size?: 'sm' | 'md' | 'lg'
+  className?: string
+}
+
+export default function LoadingSpinner({ size = 'md', className = '' }: LoadingSpinnerProps) {
+  const sizeClasses = {
+    sm: 'w-4 h-4 border-2',
+    md: 'w-6 h-6 border-2',
+    lg: 'w-8 h-8 border-3',
+  }
+
+  return (
+    <div
+      className={`${sizeClasses[size]} border-gray-300 border-t-blue-500 rounded-full animate-spin ${className}`}
+      role="status"
+      aria-label="Loading"
+    />
+  )
+}
+
+export function LoadingOverlay({ message = 'Loading...' }: { message?: string }) {
+  return (
+    <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50 backdrop-blur-sm">
+      <div className="bg-white rounded-lg p-6 sm:p-8 shadow-xl flex flex-col items-center gap-4">
+        <LoadingSpinner size="lg" />
+        <p className="text-gray-700 font-medium text-sm sm:text-base">{message}</p>
+      </div>
+    </div>
+  )
+}

components/Modal.tsx

@@ -42,15 +42,15 @@ export default function Modal({ isOpen, onClose, title, children }: ModalProps)
   if (!isOpen) return null
 
   return (
-    <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center">
+    <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center animate-fade-in">
       {/* Backdrop */}
       <div 
-        className="absolute inset-0 bg-black bg-opacity-50 transition-opacity"
+        className="absolute inset-0 bg-black bg-opacity-50 transition-opacity backdrop-blur-sm"
         onClick={onClose}
       />
       
       {/* Modal */}
-      <div className="relative bg-white rounded-t-2xl sm:rounded-lg shadow-xl max-w-md w-full mx-0 sm:mx-4 max-h-[90vh] overflow-y-auto transform transition-transform">
+      <div className="relative bg-white rounded-t-2xl sm:rounded-lg shadow-xl max-w-md w-full mx-0 sm:mx-4 max-h-[90vh] overflow-y-auto transform transition-transform animate-scale-in">
         <div className="flex items-center justify-between p-4 sm:p-5 border-b border-gray-200 sticky top-0 bg-white z-10">
           <h2 className="text-lg sm:text-xl font-semibold text-gray-900">{title}</h2>
           <button

components/SearchResults.tsx

@@ -3,6 +3,7 @@
 import { highlightText } from '@/lib/utils'
 import Link from 'next/link'
 import { Calendar, Tag, AlertCircle } from 'lucide-react'
+import EmptyState from './EmptyState'
 
 interface SearchResultsProps {
   results: Array<{
@@ -31,10 +32,11 @@ export default function SearchResults({ results, query, onClose }: SearchResults
 
   if (results.length === 0) {
     return (
-      <div className="bg-white rounded-lg border border-gray-200 p-8 text-center">
-        <p className="text-gray-500">No tasks found matching "{query}"</p>
-        <p className="text-sm text-gray-400 mt-2">Try a different search term</p>
-      </div>
+      <EmptyState
+        icon="search"
+        title={`No tasks found matching "${query}"`}
+        description="Try a different search term or check your spelling"
+      />
     )
   }
 
@@ -45,7 +47,7 @@ export default function SearchResults({ results, query, onClose }: SearchResults
   }
 
   return (
-    <div className="space-y-2">
+    <div className="space-y-2 animate-fade-in">
       <div className="flex items-center justify-between mb-4">
         <p className="text-sm text-gray-600">
           Found {results.length} {results.length === 1 ? 'task' : 'tasks'}

components/SkeletonLoader.tsx

@@ -0,0 +1,76 @@
+'use client'
+
+interface SkeletonProps {
+  className?: string
+}
+
+export function Skeleton({ className = '' }: SkeletonProps) {
+  return (
+    <div className={`animate-pulse bg-gray-200 rounded ${className}`} />
+  )
+}
+
+export function ListCardSkeleton() {
+  return (
+    <div className="bg-white rounded-lg shadow-sm border border-gray-200 p-5 sm:p-6 min-h-[140px] sm:min-h-[160px]">
+      <div className="flex items-start justify-between mb-4 gap-2">
+        <div className="flex items-center gap-2 sm:gap-3 flex-1">
+          <Skeleton className="w-3 h-3 sm:w-4 sm:h-4 rounded-full" />
+          <Skeleton className="h-6 w-32 sm:w-40" />
+        </div>
+      </div>
+      
+      <div className="space-y-2.5 sm:space-y-3">
+        <div className="flex items-center justify-between">
+          <Skeleton className="h-4 w-24" />
+          <Skeleton className="h-4 w-8" />
+        </div>
+        <Skeleton className="h-2 sm:h-2.5 w-full rounded-full" />
+      </div>
+    </div>
+  )
+}
+
+export function ItemCardSkeleton() {
+  return (
+    <div className="bg-white rounded-lg border border-gray-200 p-4 sm:p-5">
+      <div className="flex items-start gap-3 sm:gap-4">
+        <Skeleton className="w-5 h-5 sm:w-6 sm:h-6 rounded-full flex-shrink-0 mt-0.5 sm:mt-1" />
+        
+        <div className="flex-1 min-w-0 space-y-2">
+          <Skeleton className="h-5 w-3/4" />
+          <Skeleton className="h-4 w-full" />
+          <Skeleton className="h-4 w-2/3" />
+          
+          <div className="flex flex-wrap items-center gap-1.5 sm:gap-2 mt-2">
+            <Skeleton className="h-6 w-16 rounded" />
+            <Skeleton className="h-6 w-20 rounded" />
+            <Skeleton className="h-6 w-24 rounded" />
+          </div>
+        </div>
+        
+        <Skeleton className="w-5 h-5 rounded flex-shrink-0" />
+      </div>
+    </div>
+  )
+}
+
+export function ListDetailSkeleton() {
+  return (
+    <div className="space-y-4">
+      <ItemCardSkeleton />
+      <ItemCardSkeleton />
+      <ItemCardSkeleton />
+    </div>
+  )
+}
+
+export function SearchResultsSkeleton() {
+  return (
+    <div className="space-y-3">
+      <Skeleton className="h-5 w-32" />
+      <ItemCardSkeleton />
+      <ItemCardSkeleton />
+    </div>
+  )
+}

components/Toast.tsx

@@ -0,0 +1,51 @@
+'use client'
+
+import { useEffect } from 'react'
+import { CheckCircle, XCircle, AlertCircle, X } from 'lucide-react'
+
+export type ToastType = 'success' | 'error' | 'info'
+
+interface ToastProps {
+  message: string
+  type: ToastType
+  onClose: () => void
+  duration?: number
+}
+
+export default function Toast({ message, type, onClose, duration = 3000 }: ToastProps) {
+  useEffect(() => {
+    if (duration > 0) {
+      const timer = setTimeout(onClose, duration)
+      return () => clearTimeout(timer)
+    }
+  }, [duration, onClose])
+
+  const icons = {
+    success: <CheckCircle size={20} className="flex-shrink-0" />,
+    error: <XCircle size={20} className="flex-shrink-0" />,
+    info: <AlertCircle size={20} className="flex-shrink-0" />,
+  }
+
+  const styles = {
+    success: 'bg-green-50 border-green-200 text-green-800',
+    error: 'bg-red-50 border-red-200 text-red-800',
+    info: 'bg-blue-50 border-blue-200 text-blue-800',
+  }
+
+  return (
+    <div
+      className={`flex items-center gap-3 px-4 py-3 rounded-lg border shadow-lg ${styles[type]} animate-slide-in-right`}
+      role="alert"
+    >
+      {icons[type]}
+      <p className="flex-1 text-sm font-medium">{message}</p>
+      <button
+        onClick={onClose}
+        className="text-current opacity-70 hover:opacity-100 transition-opacity tap-target-sm"
+        aria-label="Close notification"
+      >
+        <X size={18} />
+      </button>
+    </div>
+  )
+}

components/ToastContainer.tsx

@@ -0,0 +1,53 @@
+'use client'
+
+import { createContext, useContext, useState, useCallback, ReactNode } from 'react'
+import Toast, { ToastType } from './Toast'
+
+interface ToastMessage {
+  id: string
+  message: string
+  type: ToastType
+}
+
+interface ToastContextType {
+  showToast: (message: string, type: ToastType) => void
+}
+
+const ToastContext = createContext<ToastContextType | undefined>(undefined)
+
+export function useToast() {
+  const context = useContext(ToastContext)
+  if (!context) {
+    throw new Error('useToast must be used within ToastProvider')
+  }
+  return context
+}
+
+export function ToastProvider({ children }: { children: ReactNode }) {
+  const [toasts, setToasts] = useState<ToastMessage[]>([])
+
+  const showToast = useCallback((message: string, type: ToastType) => {
+    const id = Math.random().toString(36).substring(7)
+    setToasts((prev) => [...prev, { id, message, type }])
+  }, [])
+
+  const removeToast = useCallback((id: string) => {
+    setToasts((prev) => prev.filter((toast) => toast.id !== id))
+  }, [])
+
+  return (
+    <ToastContext.Provider value={{ showToast }}>
+      {children}
+      <div className="fixed top-4 right-4 z-50 flex flex-col gap-2 max-w-sm w-full px-4 sm:px-0">
+        {toasts.map((toast) => (
+          <Toast
+            key={toast.id}
+            message={toast.message}
+            type={toast.type}
+            onClose={() => removeToast(toast.id)}
+          />
+        ))}
+      </div>
+    </ToastContext.Provider>
+  )
+}

components/ToggleItemButton.tsx

@@ -3,6 +3,7 @@
 import { useState } from 'react'
 import { toggleItem } from '@/lib/actions'
 import { CheckCircle2, Circle } from 'lucide-react'
+import { useToast } from './ToastContainer'
 
 interface ToggleItemButtonProps {
   itemId: string
@@ -11,6 +12,7 @@ interface ToggleItemButtonProps {
 }
 
 export default function ToggleItemButton({ itemId, completed, variant = 'full' }: ToggleItemButtonProps) {
+  const { showToast } = useToast()
   const [isToggling, setIsToggling] = useState(false)
 
   const handleToggle = async (e: React.MouseEvent) => {
@@ -19,8 +21,10 @@ export default function ToggleItemButton({ itemId, completed, variant = 'full' }
     setIsToggling(true)
     try {
       await toggleItem(itemId)
+      showToast(completed ? 'Task marked incomplete' : 'Task completed', 'success')
     } catch (error) {
       console.error('Error toggling item:', error)
+      showToast('Failed to update task', 'error')
     } finally {
       setIsToggling(false)
     }