/*
    * Copyright 2021-2022 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.driver.windows;
   
   import java.util.ArrayList;
   import java.util.HashMap;
   import java.util.List;
  import java.util.Map;
  
  import com.sun.jna.Pointer;
  import com.sun.jna.platform.DesktopWindow;
  import com.sun.jna.platform.WindowUtils;
  import com.sun.jna.platform.win32.User32;
  import com.sun.jna.platform.win32.WinDef.DWORD;
  import com.sun.jna.platform.win32.WinDef.HWND;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.jna.ByRef.CloseableIntByReference;
  import oshi.software.os.OSDesktopWindow;
  
  /**
   * Utility to query Desktop windows
   */
  @ThreadSafe
  public final class EnumWindows {
  
      private static final DWORD GW_HWNDNEXT = new DWORD(2);
  
      private EnumWindows() {
      }
  
      /**
       * Gets windows on the operating system's GUI desktop.
       *
       * @param visibleOnly Whether to restrict the list to only windows visible to the user.
       * @return A list of {@link oshi.software.os.OSDesktopWindow} objects representing the desktop windows.
       */
      public static List<OSDesktopWindow> queryDesktopWindows(boolean visibleOnly) {
          // Get the windows using JNA's implementation
          List<DesktopWindow> windows = WindowUtils.getAllWindows(true);
          // Prepare a list to return
          List<OSDesktopWindow> windowList = new ArrayList<>();
          // Populate the list
          Map<HWND, Integer> zOrderMap = new HashMap<>();
          for (DesktopWindow window : windows) {
              HWND hWnd = window.getHWND();
              if (hWnd != null) {
                  boolean visible = User32.INSTANCE.IsWindowVisible(hWnd);
                  if (!visibleOnly || visible) {
                      if (!zOrderMap.containsKey(hWnd)) {
                          updateWindowZOrderMap(hWnd, zOrderMap);
                      }
                      try (CloseableIntByReference pProcessId = new CloseableIntByReference()) {
                          User32.INSTANCE.GetWindowThreadProcessId(hWnd, pProcessId);
                          windowList.add(new OSDesktopWindow(Pointer.nativeValue(hWnd.getPointer()), window.getTitle(),
                                  window.getFilePath(), window.getLocAndSize(), pProcessId.getValue(),
                                  zOrderMap.get(hWnd), visible));
                      }
                  }
              }
          }
          return windowList;
      }
  
      private static void updateWindowZOrderMap(HWND hWnd, Map<HWND, Integer> zOrderMap) {
          if (hWnd != null) {
              int zOrder = 1;
              HWND h = new HWND(hWnd.getPointer());
              // First is highest, so decrement
              do {
                  zOrderMap.put(h, --zOrder);
              } while ((h = User32.INSTANCE.GetWindow(h, GW_HWNDNEXT)) != null);
              // now add lowest value to all
              final int offset = zOrder * -1;
              zOrderMap.replaceAll((k, v) -> v + offset);
          }
      }
  }