Hi Outlook folks 👋!

[Status: Selected for interviewing! 🎉]

I'm Robin, and first of all I'd like to thank you for letting me participate in your iOS engineer challenge. It's been a lot of fun, and honestly I've learned a lot.

A little about me

Hi 👋 ! I'm Robin. My love affair with computers started with my dad's hand-me-down IBM PC. I'm a huge swift fan (both  and Taylor), and I like to spend my free time playing Basketball and working on Open Source. When I'm not coding or wasting time on Reddit, I usually wind down with a nice game of Overwatch or NBA 2k 🎮

Installation instructions

Committing your API keys to a git repo is usually a really bad idea, and so I'm using code generation to allow us to supply our own API keys (more info on my technique here )

In order to pass in your own API keys, create a file env-vars.sh with the following content at the project directory.

export API_KEY=<YOUR API KEY HERE>

After building once, the missing file(Credentials.generated.swift should be automatically added to your project). Don't hesitate to contact me if you need help setting up 😅

Goals

Our aim in this challenge is to implement the Calendar/Agenda view as seen in the Outlook iOS app. I've tried my best to be faithful to the original design, and I've pointed out places where I've made different choices and added/removed features. There's also places where I've cut-out non essential features, but still try to articulate how I'd implement them if I had the time.

Here's a gif of the app in action:

Stuff I've improved

Dynamic Type Almost all the views in the app now support dynamic type + expanded content. From the calendar cells to the labels in the agenda view.
Attendees View now shows as many attendees as possible, not limited to 5 avatars. In addition, this view also scales with dynamic type, using the size of the "+(leftover numbers)" label as a reference.
Date limits The dates in the calendar extend to 1000 days before and after the current date. It's based on a range of offsets, and so it can be extended/contracted as necessary. I did try doing an infinite scroll with pagination, but doing it smoothly is really hard, as evidenced by apps like Fantastical handling it (notice how they stop scrolling when they need to load in more data).
Feedback Generator I've added a light impact feedback generator so that scrolling the agenda view feels like scrolling through a UIDatePicker
Under 250 lines of code Classes are decoupled for easy testability, and are generally single purpose and small.
Forecast API my Forecast API is well tested, and uses 's new Codable protocol for all operations
Tapping on the status bar takes you to the current date.

Let's look at the app

Let's divide the screen into two parts - the "Calendar" view "Agenda" view. Here's my first instinct on seeing the screen:

The Calendar View is probably a UICollectionView, where each cell is a UICollectionViewCell that displays the Day. There's a cell we have to "highlight" (premonitions, anyone? 😉) that's the top date in the Agenda view. Some key features I noticed:-
- Odd and even days have different background colors
- The first day of the month shows the month name
The Agenda View is probably a TableView, where the day title is sticky, and there can possibly be multiple events per day. The events can :-
- have titles
- (optional) have locations
- (optional) have a list of attendees
- either be All-day events (like a national holiday), or can have a start time and a duration

In addition, dragging on either view causes the other view to collapse with an animation

Styling

In order to figure out things like margins, cell sizes etc, I tried overlaying rectangles on top of screenshots (Check out the "Outlook Mobile screens for reference" sketch file in the repo). Also I used Sip to grab colors for use in the app.

For things like text sizes, I'm a heavy supporter of Dynamic type (the current Outlook app doesn't seem to support it 😕), so I matched font sizes to 's UI style guidelines from their design resources. So, a 16pt UILabel now corresponds to a UIFontTextStyle.callout.

To structure this in code, I took inspiration from Githawk, where all the styles are represented as static properties in an enum. This has 2 benefits - static properties are lazily evaluated and cached, and allows for easier namespacing too 🎉.

Architecture

For this project we're going to adopt a very standard, no-frills MVC pattern, as Dave Delong intended. We'll try our best to keep things as testable as possible while staying true to the platform.

Model

This project suggests using a static data source for events, and we're probably going to need O(1) access for each day's events. So, a dictionary probably makes most sense for us right now

// It's a var so we can set events relative to the current day
var staticEventsDataSet: [Date: [EventViewModel]] = [:]

But wait 🚨, there's a problem. Date is really a misnomer. It doesn't really represent a day in time, but rather an Instance of time. So if you added an event at 12:00 AM and another at 12:01, they'd get different keys in the dictionary 😱.

In order to fix this, we'll split a Date into DateComponents and hide things like the hour/minute/second behind a struct. (Refer to Day.swift in the project to see how it's implemented). This also lets us use DateComponents' hashValue property for the dictionary. So now our events look like

var staticEventsDataSet: [Day: [EventViewModel]] = [:]

In the future, we'd probably want to replace these static events with an actual dataSource, such as EventKit or possibly a REST API. So it makes to abstact away this information into a protocol for easy decoupling and testability.

protocol EventDataProvider {
	func loadEvents(from startDate: Date, to endDate: Date, completion: @escaping ([(Date, [EventViewModel])]) -> Void)
}

and for our static data source, we can simply create an array of (Date, [EventViewModel]) tuples and return these. Refer to StaticEventsDataProvider.swift for the implementation

Events(Presentation Model)

Note: I'm taking my definition of "Presentation Model" from Ben Sandofsky's post. In other contexts, people sometimes refer to these as "View Model"s

By themselves, EventViewModels are simply their titles, timing (either All-Day or with a start time and duration), a highlightColor to represent the color of the dot in the cell, an optional location, and an array of Attendees.

I'm not considering an event that extend across multiple days (say an event that starts today and ends tomorrow), since this is just a ViewModel. In the real world, that event would probably be deconstructed into 2 view models, one for each day it stretches across.

Views

I've made efforts to make sure all of the views work well with dynamic height + locales. Most UILabels support multiple lines of content where necessary, and content generally adapts for accessibility reasons.

Most views have a configure method, that takes in a presentation model, and configures the view accordingly. Given more time, these would be a prime target for unit testing (similar to Githawk's implementation ) since our views have multiple states/configurations where subviews are hidden/shown depending on the presentation model's properties.

Things I missed out/want to improve

Tests for the UITableViewCell bindings.
A swift 4.1 update with some niceness for the Result type like this: https://twitter.com/stephencelis/status/979394451280982016
There's some transient broken constraints initially (for some reason UITableViewCellContentView is constrained to be 0 width)
Scrolling quickly in the UITableView has a delay scrolling to the right place in the UICollectionView. I tried using layoutAttributes to get the correct offsets in the collectionView, but that didn't work quite well either.
I would love to figure out how the "Month Overlay" works (when you start dragging on the calendar view, it shows the months while blurring out the actual calendar). My first theory involved using decoration views(and there's a couple of classes in my project trying to use those), but decoration views in general aren't supposed to depend on data, so I'm not sure how'd it work
Infinite scrolling would be a nice addition, but it's also kind of a pain to implement ('s calendar app seems to work on black magic for all I know, and even fantastical's implementation seems sub par since it pauses the user scrolling to load new content)
I'd like to display the weather for each day separately per day, but that'd require a lot of wrangling with the time travel API and pagination. For now, I'm displaying the weather in the navigation controller's titleView. In addition, we'd probably have to think about which location you'd gather weather data for (the meeting? or the current user location? 🤔)
Use UIApplicationSignificantTimeChangeNotification to "re-jigger" all the dates once midnight strikes/some major time change happens

colla2me/Outlook-Assignment