fakewebapp2.js

// web framework

function webapp() {
  return {
    handlers: {},
    addRoute(route, fn){
      this.handlers[route] = fn;
    },
    exec(route, params){
      const handler = this.handlers[route];
      if (!handler) {
        return {status: 404, body: `route not found: ${route}`}
      }
      return new Promise((resolve) => {
        handler(params, {send: ({status, body}) => {
          status = status || 200;
          body = body || "OK"
          resolve({status, body});
        }}).catch(err => {
          console.error(`[REQUEST ERROR] - ${route} with params ${params}`, err)
          resolve({status: 500, body: "unknown error"})
        })
      })
    }
  }
}

function sleep(ms) {
  // async pause, for dramatic purposes
  return new Promise((r) => setTimeout(r, ms));
}


// backend services

const services = {
  loadFooFromDatabase(id) {
    return sleep(300).then(() => {
      return {id, name: "foo"};
    })
  },
  saveFooToStorage(foo, filename) {
    return sleep(300).then(() => {
      const fooData = {id: foo.id, Name: foo.Name, size: foo.Name.length};
      console.log(`storage pretend save: ${JSON.stringify(fooData)}`)
      const storageId = parseInt(Math.random() * 1E10);
      return storageId;
    })
  },
  scheduleFooTransfer(storageId) {
    return sleep(300).then(() => {
      console.log(`fake pubsub call with storageId ${storageId}`)
      const messageId = parseInt(Math.random() * 1E10);
      return messageId
    })
  }
}

// my app

const myapp = webapp();

myapp.addRoute('/save/foo3', savefoo3)

function savefoo3(params, res) {
  const {id} = params;
  return services.loadFooFromDatabase(id).then(foo => {
    return services.saveFooToStorage(foo, `/path/to/foo/${foo.id}`)
  }).then(storageId => {
    return services.scheduleFooTransfer(storageId)
  }).then(messageId => {
    console.log(`finished processing foo ${id}. MessageID = ${messageId}`)
    res.send({status: 200, body: `OK - foo processed ${id}`})
  })
}


module.exports = myapp


// let r3;
// myapp.exec('/save/foo3', {id: 3}).then(r => {r3 = r})