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x/oak/middleware.ts

A middleware framework for handling HTTP with Deno 🐿️ 🦕
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// Copyright 2018-2022 the oak authors. All rights reserved. MIT license.
// deno-lint-ignore-file
import type { State } from "./application.ts";import type { 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<unknown>): Promise<unknown> | unknown;}
/** 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, next?: () => Promise<unknown>) => Promise<unknown> { return function composedMiddleware( context: T, next?: () => Promise<unknown>, ): Promise<unknown> { let index = -1;
async function dispatch(i: number): Promise<void> { if (i <= index) { throw 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; } await fn(context, dispatch.bind(null, i + 1)); }
return dispatch(0); };}