import { onBeforeUnmount, watch, type Ref, isRef, unref, computed } from 'vue'
import { useNuxtApp, useHead } from '#imports'

// 按 className 维度追踪各锁的引用计数，解决多组件使用不同 className 并发锁定时的类名泄漏问题
const lockCounts = new Map<string, number>()

export const usePageScrollLock = (
  isLocked: Ref<boolean> | boolean,
  options?: { className?: string }
) => {
  const nuxtApp = useNuxtApp()
  // 由于 $lenis 是从 client 插件中注入的，SSR 期间可能为 undefined
  // 而且在 setup 期间解构可能拿不到最新的值，我们改为在函数内部动态获取

  const lockClassName = options?.className ?? 'is-home-intro-active'

  // SSR 和 CSR 都支持：自动将 class 注入到 HTML 标签上
  // 多实例调用时 Unhead 会合并各自的 class 值
  useHead({
    htmlAttrs: {
      class: computed(() => unref(isLocked) ? lockClassName : ''),
      lang: 'zh-CN',
    },
  })

  let currentlyLocked = false

  const updateLock = (locked: boolean) => {
    // 防止重复触发相同状态
    if (locked === currentlyLocked) return
    currentlyLocked = locked

    // Lenis 控制仅在客户端有效，不需要依赖 $lenis 立即存在
    if (import.meta.client) {
      if (locked) {
        const prevCount = lockCounts.get(lockClassName) ?? 0
        lockCounts.set(lockClassName, prevCount + 1)

        // 该 className 首次被锁定时，添加对应类名
        if (prevCount === 0) {
          document.documentElement.classList.add(lockClassName)
        }

        // 所有 className 的锁计数总和为 1 时（即全局第一个锁），停止 Lenis 并滚到顶部
        const totalLocks = Array.from(lockCounts.values()).reduce((sum, c) => sum + c, 0)
        if (totalLocks === 1) {
          const lenisInstance = nuxtApp.$lenis
          if (lenisInstance) {
            lenisInstance.scrollTo(0, { immediate: true })
            lenisInstance.stop()
          }
        }
      } else {
        const prevCount = lockCounts.get(lockClassName) ?? 0
        const newCount = Math.max(0, prevCount - 1)
        lockCounts.set(lockClassName, newCount)

        // 该 className 的锁计数归零时，移除对应类名
        if (newCount === 0) {
          document.documentElement.classList.remove(lockClassName)
        }

        // 所有 className 的锁计数总和为 0 时（即全局最后一个锁释放），重启 Lenis
        const totalLocks = Array.from(lockCounts.values()).reduce((sum, c) => sum + c, 0)
        if (totalLocks === 0) {
          const lenisInstance = nuxtApp.$lenis
          if (lenisInstance) {
            lenisInstance.start()
          }
        }
      }
    }
  }

  // 监听 Ref 变化，或立即处理 boolean 值
  if (isRef(isLocked)) {
    watch(isLocked, updateLock, { immediate: true })
  } else {
    updateLock(isLocked)
  }

  // 组件卸载时安全释放当前持有的锁
  onBeforeUnmount(() => {
    if (currentlyLocked) {
      updateLock(false)
    }
  })
}