// frontend/composables/usePreload.js
// Vue 3 组合式 API：包装 core.get()，暴露响应式 state { data, loading, error, refresh }

import { ref, getCurrentInstance, onBeforeUnmount, watch } from 'vue'
import { get, refresh as coreRefresh, abortRequest } from '@/utils/preloadApi/core'

/**
 * @param {string|Ref<string>} key - 逻辑 key
 * @param {object|Ref<object>} [params] - 请求参数
 * @returns {{ data: Ref, loading: Ref, error: Ref, refresh: Function }}
 *
 * @example
 *   const { data, loading, error, refresh } = usePreload('asset.detail', { id: 123 })
 *   // With reactive params:
 *   const { data, loading, error } = usePreload('asset.detail', () => ({ id: route.params.id }))
 */
export function usePreload(key, params) {
	// 校验上下文
	if (!getCurrentInstance()) {
		console.warn('[preload] usePreload must be called in setup()')
	}

	const data = ref(null)
	const loading = ref(true)
	const error = ref(null)

	let mounted = true
	let fetchVersion = 0

	/**
	 * 执行获取（不阻塞 setup）
	 * @param {boolean} [force=false] - 跳过 TTL 缓存
	 */
	function doFetch(force = false) {
		// 先清理上一轮 in-flight 请求
		abortRequest(key, params)

		const version = ++fetchVersion
		loading.value = true
		error.value = null

		// 用 .then() 异步更新 data，不阻塞 setup
		const promise = force
			? coreRefresh(key, params, true)
			: get(key, params)

		promise
			.then((result) => {
				if (!mounted || version !== fetchVersion) return
				data.value = result
				loading.value = false
			})
			.catch((err) => {
				if (!mounted || version !== fetchVersion) return
				error.value = err
				loading.value = false
			})

		return promise
	}

	// 监听 params 变化（key 通常是静态字符串，params 动态时传入 getter）
	// 普通值包装为 getter 确保 Vue watch source 合法
	const resolvedParams = typeof params === 'function' ? params : () => params
	watch(
		resolvedParams,
		() => {
			if (mounted) doFetch()
		},
		{ deep: true }
	)

	// 初始加载
	doFetch()

	// 组件卸载时清理
	onBeforeUnmount(() => {
		mounted = false
		abortRequest(key, params)
	})

	/**
	 * 手动刷新
	 * @param {boolean} [force=false] - 跳过 TTL
	 */
	function refresh(force = false) {
		return doFetch(force)
	}

	return { data, loading, error, refresh }
}