chore: finalise performance optimisation batch and metrics

1 files changed, 50 insertions, 4 deletions

diff --git a/Sora/Views/FavoritesView.swift b/Sora/Views/FavoritesView.swift
index 12f1bc0..04ecd24 100644
--- a/Sora/Views/FavoritesView.swift
+++ b/Sora/Views/FavoritesView.swift
@@ -25,6 +25,9 @@ struct FavoritesView: View {  // swiftlint:disable:this type_body_length
   @State private var displayedFavorites: [SettingsFavoritePost] = []
   @State private var displayedPosts: [BooruPost] = []
   @State private var displayedColumnsData: [[SettingsFavoritePost]] = []
+  @State private var shuffleOrderByIdentifier: [UUID: Int] = [:]
+  @State private var shuffleSourceIdentifiers: [UUID] = []
+  @State private var shouldRefreshShuffleOrder = true
 
   private func refreshFolderHierarchy() {
     folderHierarchy = FolderHierarchy(folders: settings.folders)
@@ -61,7 +64,7 @@ struct FavoritesView: View {  // swiftlint:disable:this type_body_length
     }
   }
 
-  private func sortedFavorites(from unsortedFavorites: [SettingsFavoritePost])
+  private func orderedFavorites(from unsortedFavorites: [SettingsFavoritePost])
     -> [SettingsFavoritePost]
   {
     unsortedFavorites.sorted { leftFavorite, rightFavorite in
@@ -76,8 +79,40 @@ struct FavoritesView: View {  // swiftlint:disable:this type_body_length
         return leftFavorite.visitedCount > rightFavorite.visitedCount
 
       case .shuffle:
-        return Bool.random()
+        return leftFavorite.date > rightFavorite.date
+      }
+    }
+  }
+
+  private func refreshShuffleOrder(for favoritesToShuffle: [SettingsFavoritePost]) {
+    let currentIdentifiers = favoritesToShuffle.map(\.id)
+
+    if shouldRefreshShuffleOrder || shuffleSourceIdentifiers != currentIdentifiers {
+      var refreshedShuffleOrderByIdentifier: [UUID: Int] = [:]
+      let shuffledIdentifiers = currentIdentifiers.shuffled()
+
+      for (identifierIndex, identifier) in shuffledIdentifiers.enumerated() {
+        refreshedShuffleOrderByIdentifier[identifier] = identifierIndex
+      }
+
+      shuffleOrderByIdentifier = refreshedShuffleOrderByIdentifier
+      shuffleSourceIdentifiers = currentIdentifiers
+      shouldRefreshShuffleOrder = false
+    }
+  }
+
+  private func shuffledFavorites(from favoritesToShuffle: [SettingsFavoritePost])
+    -> [SettingsFavoritePost]
+  {
+    favoritesToShuffle.sorted { leftFavorite, rightFavorite in
+      let leftIndex = shuffleOrderByIdentifier[leftFavorite.id] ?? Int.max
+      let rightIndex = shuffleOrderByIdentifier[rightFavorite.id] ?? Int.max
+
+      if leftIndex != rightIndex {
+        return leftIndex < rightIndex
       }
+
+      return leftFavorite.id.uuidString < rightFavorite.id.uuidString
     }
   }
 
@@ -93,7 +128,7 @@ struct FavoritesView: View {  // swiftlint:disable:this type_body_length
 
   private func refreshDisplayedFavorites() {
     let normalizedSearchText = searchText.lowercased()
-    let filteredFavorites = settings.favorites.filter { favorite in
+    let matchingFavorites = settings.favorites.filter { favorite in
       let matchesSearch =
         normalizedSearchText.isEmpty
         || favorite.tags
@@ -106,7 +141,14 @@ struct FavoritesView: View {  // swiftlint:disable:this type_body_length
 
       return matchesSelectedCollection(for: favorite) && matchesSearch && matchesProvider
     }
-    let sortedFavorites = sortedFavorites(from: filteredFavorites)
+    let sortedFavorites: [SettingsFavoritePost]
+
+    if sort == .shuffle {
+      refreshShuffleOrder(for: matchingFavorites)
+      sortedFavorites = shuffledFavorites(from: matchingFavorites)
+    } else {
+      sortedFavorites = orderedFavorites(from: matchingFavorites)
+    }
 
     displayedFavorites = sortedFavorites
     displayedPosts = sortedFavorites.map { $0.toBooruPost() }
@@ -365,6 +407,10 @@ struct FavoritesView: View {  // swiftlint:disable:this type_body_length
       refreshDisplayedFavorites()
     }
     .onChange(of: sort) {
+      if sort == .shuffle {
+        shouldRefreshShuffleOrder = true
+      }
+
       refreshDisplayedFavorites()
     }
     .onChange(of: settings.folders) {