import { assert } from '../helpers/error'
import { isFunction } from '../helpers/isTypes'
import { AxiosRequestConfig, AxiosResponse } from './Axios'

export interface MiddlewareNext {
	(): Promise<void>
}

/**
 * 中间件上下文
 */
export interface MiddlewareContext {
	/**
	 * 请求体
	 *
	 * 同于请求配置
	 */
	req: AxiosRequestConfig
	/**
	 * 响应体
	 */
	res: null | AxiosResponse
}

/**
 * 中间件
 */
export interface MiddlewareCallback {
	(ctx: MiddlewareContext, next: MiddlewareNext): Promise<void>
}

/**
 * 中间件管理器
 */
export default class MiddlewareManager {
	/**
	 * 中间件缓存池
	 */
	#middlewares: MiddlewareCallback[] = []

	/**
	 * 注册中间件
	 *
	 * @param middleware 中间件
	 */
	use(middleware: MiddlewareCallback) {
		assert(isFunction(middleware), 'middleware 不是一个 function')
		this.#middlewares.push(middleware)
	}

	/**
	 * 创建中间件上下文
	 */
	createContext(config: AxiosRequestConfig): MiddlewareContext {
		return {
			req: config,
			res: null,
		}
	}

	/**
	 * 中间件执行器
	 *
	 * @param ctx 中间件上下文
	 * @param respond 目标函数
	 */
	run(ctx: MiddlewareContext, respond: MiddlewareCallback) {
		const middlewares = [...this.#middlewares, respond]
		async function next() {
			await middlewares.shift()!(ctx, next)
		}
		return next()
	}

	/**
	 * 强化中间件执行器
	 *
	 * @param enhancer 强化器
	 */
	enhanceRun(enhancer: MiddlewareManager['run']): MiddlewareManager['run'] {
		return (ctx, respond) => {
			return enhancer(ctx, () => this.run(ctx, respond))
		}
	}
}