`@flare-city/core` - Middleware

Overview

The Middleware type in the @flare-city/core package represents a function that can be used to perform pre-processing tasks or actions before the main route handler is executed. Middleware functions take an array of arguments, known as HandlerArgs, which includes the request object, environment variables, and the execution context.

Key Concepts

1. Middleware Function

Definition: Middleware functions are asynchronous functions that can modify or enhance the request handling process.
Signature: Middleware: (...args: HandlerArgs) => Promise<void>

2. HandlerArgs

Definition: HandlerArgs is a tuple type representing the arguments passed to a middleware function. It includes the request object, environment variables, and the execution context.
Signature: HandlerArgs<T extends RequestURLSegments = RequestURLSegments> = [Request, Env, ExecutionContext<T>]

How to Use

1. Creating a Middleware

import { Middleware, HandlerArgs } from "@flare-city/core";
 
/**
 * Example Middleware: Log Request Information
 */
const logRequestInfo: Middleware = async (request, env, context) => {
  console.log(`Request Method: ${req.method}`);
  console.log(`Request URL: ${req.url}`);
  console.log(`Environment: ${env.NODE_ENV}`);
};

2. Using Middleware in a Route

import { Middleware } from "@flare-city/core";
import { Route } from "@flare-city/core";
 
const myRoute = new Route({ basePath: "/api" });
 
const myMiddleware: Middleware = async (request, env, context) => {
  // Your middleware logic here
};
 
myRoute.register({
  path: "/example",
  method: "GET",
  middleware: [myMiddleware],
  handler: async (req, env, context, res) => {
    // Your route logic here
  },
});

3. Using Middleware in an App

import { App } from "@flare-city/core";
import { Middleware } from "@flare-city/core";
 
const myApp = new App("MyApp");
 
const myMiddleware: Middleware = async (request, env, context) => {
  // Your middleware logic here
};
 
myApp.addMiddleware(myMiddleware);
 
const myRoute = new Route({ basePath: "/api", middleware: [myMiddleware] });
 
myApp.addRoute(myRoute);
 
const response = myApp.run(request, env, context);

Example

Add prisma client to execution context

The following example demonstrates a middleware function, middlewarePrisma, that adds a Prisma client to the execution context. This middleware can be used to provide database access to route handlers.

import { Middleware } from "@flare-city/core";
import { createPrismaClient } from "./createPrismaClient";
import { log } from "../logger";
 
/**
 * Middleware to add the Prisma client to the execution
 * context of the request
 */
export const middlewarePrisma: Middleware = async (request, env, context) => {
  log.setName("Middleware:Prisma");
 
  log.info("Middleware: Creating PrismaClient and adding to context...");
  const prisma = createPrismaClient(env);
  context.prisma = prisma;
  log.info("Middleware: Creating PrismaClient and adding to context... done.");
};

Conclusion

The Middleware type in the @flare-city/core package provides a powerful mechanism for customizing the request-handling flow. By creating and using middleware functions, developers can inject additional logic, such as logging, authentication, or database connections, into their routes and applications.

Route @flare-city/logger

@flare-city/core - Middleware