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

// 全局模块级变量，用于记录锁定请求的次数，解决多组件并发锁定的竞态问题
let lenisLockCount = 0

export const usePageScrollLock = (isLocked: Ref<boolean> | boolean) => {
  const { $lenis } = useNuxtApp() as ReturnType<typeof useNuxtApp> & { $lenis?: Lenis }

  // SSR 和 CSR 都支持：自动将 class 注入到 HTML 标签上
  useHead({
    htmlAttrs: {
      class: computed(() => unref(isLocked) ? 'is-home-intro-active' : '')
    }
  })

  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
    if (import.meta.client) {
      if (locked) {
        lenisLockCount++
        // 只有第一个锁请求时，才真正停止 Lenis 并滚动到顶部
        if (lenisLockCount === 1) {
          document.documentElement.classList.add('is-home-intro-active')
          if ($lenis) {
            $lenis.scrollTo(0, { immediate: true })
            $lenis.stop()
          }
        }
      } else {
        lenisLockCount = Math.max(0, lenisLockCount - 1)
        // 只有当所有锁请求都释放时，才重新启动 Lenis
        if (lenisLockCount === 0) {
          document.documentElement.classList.remove('is-home-intro-active')
          if ($lenis) {
            $lenis.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(() => {
    updateLock(false)
  })
}