ScrollingEmojiView.swift

import SwiftUI

struct ScrollingEmojiView: View {
  @Environment(\.accessibilityReduceMotion) var reduceMotion
  @State private var isAnimating = false

  /*
  In Personal Best (getpersonalbest.com) I get a random emoji to represent a workout type,
  using an extension to HKWorkoutActivityType. Here I've stubbed it out with a more basic
  implementation.
  */
  func randomEmoji() -> String {
    let character: Character = "🥇🍯👨‍👨‍👦👀⭐️❤️🤓💋".randomElement()!
    return String(character)
  }

  func xOffset(forRowIndex rowIndex: Int) -> Double {
    return rowIndex % 2 == 0 ? 100 : -100
  }

  func randomEmojis() -> [[String]] {
    var previouslyChosenEmojis: Set<String> = []
    return (0...10).map { _ in
      (0...10).map { _ in
        var emoji = randomEmoji()
        while previouslyChosenEmojis.contains(emoji) {
          emoji = randomEmoji()
        }
        previouslyChosenEmojis.insert(emoji)
        return emoji
      }
    }
  }

  var body: some View {
    let chosenEmojis = emojis
    GeometryReader { geo in
      VStack {
        ForEach(0..<rows, id: \.self) { index in
          Text(chosenEmojis[index].joined(separator: "  "))
            .fixedSize(horizontal: true, vertical: false)
            .font(.title)
            .offset(x: xOffset(forRowIndex: index), y: 0)
            .padding(.vertical, 5)
            .animation(.easeInOut(duration: 20).repeatForever(autoreverses: true), value: isAnimating)
        }
      }
      .rotationEffect(.degrees(-15))
      .frame(width: geo.size.width, height: geo.size.height)
      .fixedSize()
      .clipped()
    }
    .task {
      if !reduceMotion {
        isAnimating = true
      }
    }
  }
}

struct ScrollingEmojiView_Previews: PreviewProvider {
  static var previews: some View {
    ScrollingEmojiView()
      .edgesIgnoringSafeArea(.all)
  }
}