perf: memoize generic list derived data and folder grouping

1 files changed, 44 insertions, 0 deletions

diff --git a/Sora/Views/Shared/FolderHierarchy.swift b/Sora/Views/Shared/FolderHierarchy.swift
new file mode 100644
index 0000000..99c4f8e
--- /dev/null
+++ b/Sora/Views/Shared/FolderHierarchy.swift
@@ -0,0 +1,44 @@
+import Foundation
+
+struct FolderHierarchy {
+  private let foldersByIdentifier: [UUID: SettingsFolder]
+  private let folderNames: Set<String>
+  private let nestedFoldersByTopLevelName: [String: [SettingsFolder]]
+  let rootFolders: [SettingsFolder]
+
+  var sortedTopLevelNames: [String] {
+    nestedFoldersByTopLevelName.keys.sorted()
+  }
+
+  init(folders: [SettingsFolder]) {
+    foldersByIdentifier = Dictionary(uniqueKeysWithValues: folders.map { ($0.id, $0) })
+    folderNames = Set(folders.map(\.name))
+
+    var rootFolders: [SettingsFolder] = []
+    var nestedFoldersByTopLevelName: [String: [SettingsFolder]] = [:]
+
+    for folder in folders {
+      guard let topLevelName = folder.topLevelName else {
+        rootFolders.append(folder)
+        continue
+      }
+
+      nestedFoldersByTopLevelName[topLevelName, default: []].append(folder)
+    }
+
+    self.rootFolders = rootFolders
+    self.nestedFoldersByTopLevelName = nestedFoldersByTopLevelName
+  }
+
+  func folder(for identifier: UUID) -> SettingsFolder? {
+    foldersByIdentifier[identifier]
+  }
+
+  func folders(forTopLevelName topLevelName: String) -> [SettingsFolder] {
+    nestedFoldersByTopLevelName[topLevelName] ?? []
+  }
+
+  func hasTopLevelUncategorized(forTopLevelName topLevelName: String) -> Bool {
+    folderNames.contains(topLevelName)
+  }
+}