midori

Minimalist, monadic, typed http apps for http/express/hapi.

Usage

Install midori and add it to your package.json file:

npm install --save midori

Test out your first app:

import {get, send, listen} from 'midori';

const app = get('/', send('Hello world.'));

listen(app, 8081, () => {
  console.log('Example `midori` app started.');
});

import {apply, query, url, send} from 'midori';

const app = apply(query, url, (query, {pathname}) => {
  return send(`${pathname} - got ${query.foo}`);
})

There are plenty of other examples available in the [./examples] folder.

Async

Many midori functions (including request and error) understand how to handle promises and async functions.

Using Promise:

import {send, request} from 'midori';

const getData = () => Promise.resolve(50);

const app = request(() => {
  return getData().then((result) => {
    if (result > 5) {
      return Promise.resolve(send('Yes.'));
    }
    return Promise.resolve(send('No.'));
  });
});

Using async / await:

import {request, send} from 'midori';

const getData = () => Promise.resolve(50);

const app = request(async () => {
  const result = await getData();
  if (result > 5) {
    return send('Yes.');
  }
  return send('No.');
});

Error Handling

Just as request provides a mechanism for dealing with request flow, error provides the same for handling errors.

import {request, error, compose, halt} from 'midori';

const app = compose(
  request(() => {
    // Can also `return Promise.reject();`
    throw new Error('Help!');
  }),
  error((err) => {
    console.log(`I caught an error.`);
    return halt;
  }),
);

If you need access to the request/response during error handling you can use those functions:

import {request, error, compose} from 'midori';

const app = compose(
  request(() => {
    // Can also `return Promise.reject();`
    throw new Error('Help!');
  }),
  error((err) => {
    return request((req) => {
      console.log('There was an error at:', req.url);
      throw err;
    });
  }),
);

Testing

Testing Apps

midori includes a dedicated fetch() utility for testing apps:

import {response, next} from 'midori';
import {fetch} from 'midori/test';

const app = response((res) => {
  res.setHeader('Content-Type', 'test');
  return next;
});

it('should set the header', () => {
  return fetch(app, '/').then((res) => {
    assert(res.headers['content-type'] === 'test');
  });
});

But you can use a real HTTP server too:

import {response, listen, halt} from 'midori';
import fetch from 'node-fetch';

// Reference to HTTP server instance used in each test.
let server;
let url;

const app = response((res) => {
  res.end('Hello world');
  return halt;
});

beforeEach(done => {
  // Spin up a server and connect your app to it.
  server = listen(app, () => {
    const {port} = server.address();
    url = `http://localhost:${port}`;
    done();
  });
});

afterEach(done => {
  // Shut down the server after each test.
  server.close(done);
  server = null;
  url = null;
});

it('should return a result', () => {
  return fetch(url).then((res) => {
    assert(res.statusCode === 200);
  });
});

Testing Selectors

You can use runSelector and getSelectorImplementation to test selectors in isolation.

import {createSelector} from 'midori';
import {runSelector, getSelectorImplementation} from 'midori/test';

import mySelectorA from './mySelectorA';
import mySelectorB from './mySelectorB';

jest.mock('./mySelectorA', () => createSelector(jest.fn()));
jest.mock('./mySelectorB', () => createSelector(jest.fn()));

const mySelectorC = createSelector(
  mySelectorA,
  mySelectorB,
  (a, b) => a + b,
);


getSelectorImplementation(selectorA).mockImplementation(() => 1);
getSelectorImplementation(selectorB).mockImplementation(() => 1);

const result = runSelector(mySelectorC);
expect(result).toBe(2);

To mock request or other midori internal selectors you can:

import {request} from 'midori';
import {createMockRequest} from 'midori/test';

jest.mock('midori/request', () => {
  return createSelector(jest.fn(() => {
    return createMockRequest({
      url: '/foo',
      method: 'POST',
    });
  }));
});

If you're not using jest or just want to mock values for a single test, then runSelector also provides a factory function with which you can use to setup your mocks.

import {createSelector} from 'midori';
import {runSelector} from 'midori/test';

import mySelectorA from './mySelectorA';
import mySelectorB from './mySelectorB';

const mySelectorC = createSelector(
  mySelectorA,
  mySelectorB,
  (a, b) => a + b,
);

const result = runSelector(mySelectorC, (inst) => {
  inst.mockValue(mySelectorA, 1);
  inst.mockValue(mySelectorB, 1);
});
expect(result).toBe(2);

Advanced

Routing

The standard way of doing request dependent routing is by using match. Most frameworks allow you to only match against the request path and method, but midori makes no such compromises and you can use all kinds of predicates to determine the control flow of your application.

import {match, send, compose} from 'midori';
import {path, host} from 'midori/match';

const isFoo = path('/foo'); // Match against URL path
const isLocalhost = host(/localhost/); // Match against `Host` header

const createApp = compose(
  match(isFoo, send('Hello from foo')),
  match(isLocalhost, send('You accessed from localhost')),
);

You can also create match conjunctions using every (i.e. all predicates must be true for the match to succeed).

import {match, send, compose} from 'midori';
import {path, method, every} from 'midori/match';

// This is roughly how `get()` works internally.
const isGetFoo = every(method('GET'), path('/foo'));

const app = compose(
  match(isGetFoo, send('Hello from foo')),
);

You can also take action based on when the match fails:

import {match, send, compose} from 'midori';
import {path, host} from 'midori/match';

const isFoo = path('/foo'); // Match against URL path
const isLocalhost = host(/localhost/); // Match against `Host` header

const app = compose(
  match(isFoo, send('Hello from foo'), send('Hello not from foo')),
);

Connectors

You can connect midori to a number of other HTTP frameworks (like express, hapi).

import {send} from 'midori';

const app = send('Hello world.');

With express

Install dependencies:

npm install --save midori-express express

Create an express app and just use() your midori middleware as if it were express middleware:

import express from 'express';
import createMiddleware from 'midori-express';
import {compose} from 'midori';

const expressApp = express();

expressApp.use(createMiddleware(app));
expressApp.listen(8080);

With hapi

Install dependencies:

npm install --save midori-hapi hapi

Create a hapi app and register your midori middleware as an extension:

import {Server} from 'hapi';
import createExt from 'midori-hapi';

const server = new Server();

server.connection({port: 8080});
server.ext(createExt(app));
server.start();

Migration & Middleware Compatibility

Coming from another framework? Prefer to write your middleware handlers like you do in those other frameworks? Not a problem.

Express

The traditional callback style that express uses is compatible with midori. You can connect your express middleware as follows:

import {middleware} from 'midori';

const createMiddleware = middleware((req, res, next) => {
  req.statusCode = 201;
  next();
});

Error handlers are also supported:

import {middleware} from 'midori';

const createMiddleware = middleware((err, req, res, next) => {
  console.log('We got an error:', err);
  next(err);
});