The middleware-hook from koajs

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Example of accessing application context inside of reducer

Must have lost my mind because I cannot figure out how to do this.

I'd really appreciate if someone could chime in on how to accomplish accessing the koa req context inside of the reducer function. I need to attach meta data to the state property.

Eg: for a simplified version of koajs/timer

// SimpleTimer.js
const middlewareHook = require('koa-middleware-hook');

module.exports = SimpleTimer;

function SimpleTimer() {
  var hook = middlewareHook(marker, reducer);

  return function timer(generator) {
    return hook(generator);
  };
}

function marker() {
  return new Date();
}

function reducer(name, topStart, topEnd, bottomStart, bottomEnd) {
  let top = topEnd - topStart;
  let bottom = 0;

  if (bottomStart && bottomEnd) {
    bottom = bottomEnd - bottomStart;
  }

  // access the context here to attach properties to state
  (this.state.metrics = (this.state.metrics || [])).push({
    name: name,
    duration: top + bottom
  });
}

// eg: index.js

let timer = require('./SimpleTimer')();

app.use(function *entryPoint(next) {
  yield next;
  console.log(this.state.metrics); // ==>  [{ name: 'foo', duration: 250 }]
});

app.use(timer(function *foo(next) {
  yield wait(250);
}));


// ... ala koajs/timer ...
function wait (ms) {
  return function (done) {
    setTimeout(done, ms)
  }
}

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