End of Year: preload stories

[leandroalonso]

📘 Project: #376

To provide a better experience for the users, the app preloads the next 2 stories. The assets that are preloaded are:

1. Image covers
2. Podcast colors

Those are requested if they do not exist, and they are requests only once (images by using Kingfisher and colors by using the current ColorManager).

This also changes how the StoriesView is rendered to avoid Stories being re-created hundreds of time.

To test

Playing stories without skipping to next/previous

1. Enable the endOfYear flag in FeatureFlag.swift
2. Do a fresh install of the app
3. Login to an account with a few items on Listening History
4. Use a tool like Network Link Conditioner to change the speed of your connection (to 3G, for example)
5. When the prompt appears, tap "View My 2022"
6. ✅ Leave the stories to play and check that most stuff should be ready when the stories appear

Skipping

1. Enable the endOfYear flag in FeatureFlag.swift
2. Do a fresh install of the app
3. Login to an account with a few items on Listening History
4. Use a tool like Network Link Conditioner to change the speed of your connection (to 3G, for example)
5. When the prompt appears, tap "View My 2022"
6. ✅ Quickly goes to the next story and you should be able to see that the background is opaque but once colors are downloaded it changes

Number of Stories View

A bit of context: StoriesModel had the progress property as a published one. Each time that changed, StoriesView was invalidated and re-rendered again. In turn, this caused the current story to be invalidated and re-rendered again.

In terms of allocation, this wasn't a big problem because the views are mainly structs, but the CPU usage was going up due to the view being invalidated every 0.01s.

I moved the progress to another object that is used only by the progress indicators, now the StoriesView is only invalidated when the current story changes.

To test:

1. Enable the endOfYear flag in FeatureFlag.swift
2. Run the app and make sure you're logged in to an account with a few items on Listening History
3. Run Instruments > Allocations and start recording the current Pocket Casts instance
4. Add "Story" to the "Detail Filter"
5. Check that only 1 to 2 total Story views area created

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.

[emilylaguna]

Nice work, left some comments to clean up a few items and an idea for default colors.

None of them are blockers though.