function compose (middleware) {
if(!Array.isArray(middleware)) throw TypeError('Middleware stack must be an array!')
for (const fn of middleware) {
if(typeof fn !== 'function') throw new TypeError('Middleware must be composed of functions!')
}
let index = -1 //
/**
* @param {Object} context
* @return {Promise}
* @api compose
*/
return function (context, next) {
return new Promise((resolve, reject) => {
function dispatch (i) { //
if (i <= index) {
console.warn('[warn]next() called multiple times')
return //reject(new Error('next() called multiple times'))
}
index=i
let fn=middleware[i]
if(i===middleware.length) fn=next //
if(!fn) return resolve()
try {
return resolve(fn(context,dispatch.bind(null,i+1)))
} catch (error) {
return reject(error)
}
}
dispatch(0)
})
}
}
