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x/oak/middleware.ts

A middleware framework for handling HTTP with Deno 🐿️ 🦕
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// Copyright 2018-2020 the oak authors. All rights reserved. MIT license.
import { State } from "./application.ts";import { Context } from "./context.ts";
/** Middleware are functions which are chained together to deal with requests. */export interface Middleware< S extends State = Record<string, any>, T extends Context = Context<S>,> { (context: T, next: () => Promise<void>): Promise<void> | void;}
/** Compose multiple middleware functions into a single middleware function. */export function compose< S extends State = Record<string, any>, T extends Context = Context<S>,>(middleware: Middleware<S, T>[]): (context: T) => Promise<void> { return function composedMiddleware(context: T, next?: () => Promise<void>) { let index = -1;
function dispatch(i: number): Promise<void> { if (i <= index) { Promise.reject(new Error("next() called multiple times.")); } index = i; let fn: Middleware<S, T> | undefined = middleware[i]; if (i === middleware.length) { fn = next; } if (!fn) { return Promise.resolve(); } try { return Promise.resolve(fn(context, dispatch.bind(null, i + 1))); } catch (err) { return Promise.reject(err); } }
return dispatch(0); };}