geoctrl / weather-project

Project

Testing out my implementation

• You'll need node and yarn installed
• Run $ yarn to install the jest package (the only dependency)
• Run $ yarn test
• Within the src/controller.test.js you can change the backendResDelay variable to change how long the backend takes to respond.

Time

It took around 6 hours to complete this project.

Some thoughts

First pass at caching ranges

My first idea at solving this problem was to cache datapoints based off of time ranges. I would get a time range, convert it into a string, so I can use it as the value in my cache map (eg: '1234-5678'). Although this might work for whole date ranges, this becomes problematic for partial ranges. For example, if I had the range [1234-8999], the key '1234-5678' would be a partial match, but wouldn't help me find the rest of the ranges that might contain partial cached data.

Simplify the cache

I then realized it would be much simpler if I saved each data point in the cache with its time as the key. Since I'm already calculating all the times to find the intervals, I could iterate over this new timeList and save each piece in the cache.

No need to average/roll up datapoints

Because I'm already building the intervals of datapoints, I don't need to find or average anything. I just iterate over the intervals and grab the data from the cache. While iterating, I also find start/stop points for null values, which allows me to limit the amount of data requested from the backend.

Assumptions and thoughts

• Users can make many requests before the first request resolves, so I only resolve the most recent response - all other responses are thrown out after the backend is done (after caching the data).
• I added timestamps to each of the requests to keep track of responses. We could also use uuid's or something, but I figured this was fine for this assignment.
• I'm assuming the backend is giving the time back to me in the response (within the datapoint), so I can cache it. This is why I made the datapoint an object - assuming that was the structure.

Small bit of feedback

The API docs state that the backend should be passed into the Controller constructor, but the backend also needs to call the controller when the calls are finished. This is a circular dependency and was a bit strange to implement (see src/controller.js on lines 6-8 for my implementation).

I would probably recommend not passing the backend into the Controller, and instead using it as a dependency that resolves a promise:

const { backend } = require('./backend');

class Controller {
  setStartTime = () => {
    backend.requestTemperatureData()
      .then(this.receiveTemperatureData); 
  }

  receiveTemperatureData = () => {
    // this method will be called when the backend request resolves
  }
}