/**
 * useActivityLog Hook
 *
 * 记录用户最近操作到 localStorage，最多保存 20 条。
 * 每条包含：操作描述、时间戳、图标。可用于 Header 用户菜单中的"最近操作"展示。
 *
 * 用法：
 *   const { activities, addActivity, clearActivities } = useActivityLog()
 *
 *   // 记录操作
 *   addActivity('新建问诊', '📝')
 *
 *   // 展示最近操作
 *   activities.slice(0, 5).map(a => <ActivityItem key={a.id} {...a} />)
 */

import { useState, useCallback, useEffect } from 'react'

// ================================================================
// 类型定义
// ================================================================

export interface ActivityLogEntry {
  /** 唯一标识 */
  id: string
  /** 操作描述 */
  description: string
  /** 图标（emoji 或 icon 名称） */
  icon: string
  /** 时间戳 */
  timestamp: number
}

// ================================================================
// 常量
// ================================================================

const STORAGE_KEY = 'vetcopilot_activity_log'
const MAX_ENTRIES = 20

// ================================================================
// 工具函数
// ================================================================

function loadFromStorage(): ActivityLogEntry[] {
  try {
    const raw = localStorage.getItem(STORAGE_KEY)
    if (!raw) return []
    const parsed = JSON.parse(raw)
    if (Array.isArray(parsed)) return parsed as ActivityLogEntry[]
  } catch {
    // 数据损坏，清除
  }
  return []
}

function saveToStorage(entries: ActivityLogEntry[]): void {
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(entries))
  } catch {
    // storage full or unavailable
  }
}

function generateId(): string {
  return `act_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`
}

// ================================================================
// Hook
// ================================================================

interface UseActivityLogReturn {
  /** 最近操作列表（最新在前） */
  activities: ActivityLogEntry[]
  /** 添加一条操作记录 */
  addActivity: (description: string, icon?: string) => void
  /** 清除所有记录 */
  clearActivities: () => void
}

export function useActivityLog(): UseActivityLogReturn {
  const [activities, setActivities] = useState<ActivityLogEntry[]>(loadFromStorage)

  // 初始化时从 storage 加载
  useEffect(() => {
    setActivities(loadFromStorage())
  }, [])

  const addActivity = useCallback((description: string, icon: string = '') => {
    setActivities((prev) => {
      const entry: ActivityLogEntry = {
        id: generateId(),
        description,
        icon,
        timestamp: Date.now(),
      }
      const next = [entry, ...prev].slice(0, MAX_ENTRIES)
      saveToStorage(next)
      return next
    })
  }, [])

  const clearActivities = useCallback(() => {
    setActivities([])
    localStorage.removeItem(STORAGE_KEY)
  }, [])

  return { activities, addActivity, clearActivities }
}