[Widgets]: (complete) Fixed previous pagination issues for ActiveAppsWidget

AltWidget/Widgets/PaginationDataHolder.swift

@@ -0,0 +1,72 @@
+//
+//  PaginationViewModel.swift
+//  AltStore
+//
+//  Created by Magesh K on 09/01/25.
+//  Copyright © 2025 SideStore. All rights reserved.
+//
+
+import Foundation
+
+class PaginationDataHolder: ObservableObject {
+    
+    public static let MAX_ROWS_PER_PAGE: UInt = 3
+
+    private static var instances: [String:PaginationDataHolder] = [:]
+    
+    public static func instance(_ widgetID: String) -> PaginationDataHolder {
+        let instance = PaginationDataHolder(widgetID)
+        Self.instances[widgetID] = instance
+        return instance
+    }
+
+    public static func holder(for widgetID: String) -> PaginationDataHolder? {
+        return Self.instances[widgetID]
+    }
+    
+    private lazy var serializationQ = {
+        DispatchQueue(label: widgetID)
+    }()
+
+    public let widgetID: String
+    private var currentPageindex: UInt = 0
+    
+    private init(_ widgetID: String){
+        self.widgetID = widgetID
+    }
+    
+    deinit {
+        Self.instances.removeValue(forKey: widgetID)
+    }
+    
+    public func updateDirection(_ direction: Direction) {
+        switch(direction){
+        case .up:
+            let pageIndex = Int(currentPageindex)
+            currentPageindex = UInt(max(0, pageIndex-1))
+        case .down:
+            // upper-bounds is checked when computing targetPageIndex in getUpdatedData
+            currentPageindex+=1
+        }
+    }
+    
+    public func getUpdatedData(entries: [AppSnapshot]) -> [AppSnapshot] {
+        let count = UInt(entries.count)
+        
+        if(count == 0) { return entries }
+        
+        let availablePages = UInt(ceil(Double(entries.count) / Double(Self.MAX_ROWS_PER_PAGE)))
+        let targetPageIndex: UInt = currentPageindex < availablePages ? currentPageindex : availablePages-1
+
+        // do blocking update
+        serializationQ.sync {
+            self.currentPageindex = targetPageIndex     // preserve it
+        }
+        
+        let startIndex = targetPageIndex * Self.MAX_ROWS_PER_PAGE
+        let estimatedEndIndex = startIndex + (Self.MAX_ROWS_PER_PAGE-1)
+        let endIndex: UInt = min(count-1, estimatedEndIndex)
+        let currentPageEntries = entries[Int(startIndex) ... Int(endIndex)]
+        return Array(currentPageEntries)
+    }
+}