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x/oak/middleware.ts

A middleware framework for handling HTTP with Deno 🐿️ 🦕
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// Copyright 2018-2024 the oak authors. All rights reserved. MIT license.
// deno-lint-ignore-file
import type { State } from "./application.ts";import type { Context } from "./context.ts";
/** A function for chaining middleware. */export type Next = () => Promise<unknown>;
/** 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: Next): Promise<unknown> | unknown;}
/** Middleware objects allow encapsulation of middleware along with the ability * to initialize the middleware upon listen. */export interface MiddlewareObject< S extends State = Record<string, any>, T extends Context<S> = Context<S>,> { /** Optional function for delayed initialization which will be called when * the application starts listening. */ init?: () => Promise<unknown> | unknown; /** The method to be called to handle the request. */ handleRequest(context: T, next: Next): Promise<unknown> | unknown;}
/** Type that represents {@linkcode Middleware} or * {@linkcode MiddlewareObject}. */export type MiddlewareOrMiddlewareObject< S extends State = Record<string, any>, T extends Context = Context<S>,> = Middleware<S, T> | MiddlewareObject<S, T>;
/** A type guard that returns true if the value is * {@linkcode MiddlewareObject}. */export function isMiddlewareObject< S extends State = Record<string, any>, T extends Context = Context<S>,>(value: MiddlewareOrMiddlewareObject<S, T>): value is MiddlewareObject<S, T> { return value && typeof value === "object" && "handleRequest" in value;}
/** Compose multiple middleware functions into a single middleware function. */export function compose< S extends State = Record<string, any>, T extends Context = Context<S>,>( middleware: MiddlewareOrMiddlewareObject<S, T>[],): (context: T, next?: Next) => Promise<unknown> { return function composedMiddleware( context: T, next?: Next, ): 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 m: MiddlewareOrMiddlewareObject<S, T> | undefined = middleware[i]; let fn: Middleware<S, T> | undefined; if (typeof m === "function") { fn = m; } else if (m && typeof m.handleRequest === "function") { fn = (m as MiddlewareObject).handleRequest.bind(m); } if (i === middleware.length) { fn = next; } if (!fn) { return; } await fn(context, dispatch.bind(null, i + 1)); }
return dispatch(0); };}