LazySequenceTest

LazySequenceTest.playground

import UIKit

struct NewHashtagFeed {
  let components: [Component]

  init(components: [Component]) {
    self.components = components
  }
}

extension NewHashtagFeed {
  enum Component {
    case threeGrid(HashtagFeedThreeGridComponent)
  }
}

extension NewHashtagFeed.Component {
  func asThreeGrid() -> HashtagFeedThreeGridComponent? {
    switch self {
    case let .threeGrid(grid):
      return grid
    }
  }
}

struct Style: Hashable {
  let id: Int

  init(id: Int) {
    self.id = id
  }
}

struct NewHashtagFeedViewSection: Equatable {
  enum Identity: Hashable {
    case activityIndicator
    case content
  }

  var identity: Identity
  var items: [Item]
}

extension NewHashtagFeedViewSection {
  enum Item: Hashable {
    case styleTile(Style)
  }
}

struct HashtagFeedThreeGridComponent {
  var row: Int
  var items: [Item]

  init(row: Int, items: [HashtagFeedThreeGridComponent.Item]) {
    self.row = row
    self.items = items
  }

  enum Item {
    case threeGridStyleCard(Style)
  }
}

extension HashtagFeedThreeGridComponent.Item {
  public func asStyle() -> Style? {
    switch self {
    case let .threeGridStyleCard(style):
      return style
    }
  }
}

private func lazyStyleTileSectionItems(feed: NewHashtagFeed) -> [NewHashtagFeedViewSection.Item] {
  return feed.components
    .lazy
    .compactMap { feedComponent -> HashtagFeedThreeGridComponent? in
      print("feedComponent.asThreeGrid()")
      return feedComponent.asThreeGrid()
    }
    .flatMap { threeGridComponent -> [HashtagFeedThreeGridComponent.Item] in
      print("threeGridComponent.row: \(threeGridComponent.row)")
      return threeGridComponent.items
    }
    .compactMap { item -> Style? in
      print("item.asStyle(\(String(describing: item.asStyle()?.id)))")
      return item.asStyle()
    }
    .map { style -> NewHashtagFeedViewSection.Item in
      print(".styleTile(\(style.id))")
      return .styleTile(style)
    }
}

private func styleTileSectionItems(feed: NewHashtagFeed) -> [NewHashtagFeedViewSection.Item] {
  return feed.components
    .compactMap { feedComponent -> HashtagFeedThreeGridComponent? in
      print("feedComponent.asThreeGrid()")
      return feedComponent.asThreeGrid()
    }
    .flatMap { threeGridComponent -> [HashtagFeedThreeGridComponent.Item] in
      print("threeGridComponent.row: \(threeGridComponent.row)")
      return threeGridComponent.items
    }
    .compactMap { item -> Style? in
      print("item.asStyle(\(String(describing: item.asStyle()?.id)))")
      return item.asStyle()
    }
    .map { style -> NewHashtagFeedViewSection.Item in
      print(".styleTile(\(style.id))")
      return .styleTile(style)
    }
}

private func optimizedStyleTileSectionItems(feed: NewHashtagFeed) -> [NewHashtagFeedViewSection.Item] {
  return feed.components
    .flatMap { feedComponent -> [NewHashtagFeedViewSection.Item] in
      let threeGridComponent = feedComponent.asThreeGrid()
      print("threeGridComponent.row: \(String(describing: threeGridComponent?.row))")
      let styles = threeGridComponent?.items.compactMap { item -> Style? in
        print("item.asStyle(\(String(describing: item.asStyle()?.id)))")
        return item.asStyle()
      }
      let sectionItems = styles?.compactMap { style -> NewHashtagFeedViewSection.Item in
        print(".styleTile(\(style.id))")
        return NewHashtagFeedViewSection.Item.styleTile(style)
      }
      return sectionItems ?? []
    }
}

private func optimized2StyleTileSectionItems(feed: NewHashtagFeed) -> [NewHashtagFeedViewSection.Item] {
  var sectionItems: [NewHashtagFeedViewSection.Item] = []
  for component in feed.components {
    guard let threeGridComponent = component.asThreeGrid() else { continue }
    let flattedComponentItems = threeGridComponent.items.compactMap { $0 }
    let styles = flattedComponentItems.compactMap { $0.asStyle() }
    styles.forEach { sectionItems.append(NewHashtagFeedViewSection.Item.styleTile($0)) }
  }
  return sectionItems
}

let feed = NewHashtagFeed(components: [
  NewHashtagFeed.Component.threeGrid(HashtagFeedThreeGridComponent(row: 0, items: [
    .threeGridStyleCard(Style(id: 1)),
    .threeGridStyleCard(Style(id: 2)),
    .threeGridStyleCard(Style(id: 3)),
  ])),
  NewHashtagFeed.Component.threeGrid(HashtagFeedThreeGridComponent(row: 1, items: [
    .threeGridStyleCard(Style(id: 4)),
    .threeGridStyleCard(Style(id: 5)),
    .threeGridStyleCard(Style(id: 6)),
  ])),
  NewHashtagFeed.Component.threeGrid(HashtagFeedThreeGridComponent(row: 2, items: [
    .threeGridStyleCard(Style(id: 7)),
    .threeGridStyleCard(Style(id: 8)),
    .threeGridStyleCard(Style(id: 9)),
  ])),
])

let lazySectionItems = lazyStyleTileSectionItems(feed: feed)
let optimizedSectionItems = optimizedStyleTileSectionItems(feed: feed)
let optimized2SectionItems = optimized2StyleTileSectionItems(feed: feed)
let sectionItems = styleTileSectionItems(feed: feed)

print(lazySectionItems)
print(optimizedSectionItems)
print(optimized2SectionItems)
print(sectionItems)