/******************************************************************************
 * Copyright (C) Leap Motion, Inc. 2011-2017.                                 *
 * Leap Motion proprietary and  confidential.                                 *
 *                                                                            *
 * Use subject to the terms of the Leap Motion SDK Agreement available at     *
 * https://developer.leapmotion.com/sdk_agreement, or another agreement       *
 * between Leap Motion and you, your company or other organization.           *
 ******************************************************************************/

using System;
using System.Linq;
using System.Reflection;
using System.Collections.Generic;
#if UNITY_EDITOR
using UnityEditor;
#endif

namespace Leap.Unity {

  /// <summary>
  /// This attribute is used to add items to the Leap Motion preferences window.
  /// This allows each module to define their own preferences and still have them
  /// all show up under the same window.  
  /// 
  /// The usage is very similar to the built-in PreferenceItem attribute.  You
  /// add the attribute onto a static method that should be run whenever the 
  /// preference window is visited.  This method is a gui method and should use
  /// GuiLayout and EditorGuiLayout in order to draw the preferences.  You can
  /// specify the name of the preferences as well as an order value to specify
  /// how the preferences are ordered relative to other preferences.
  /// </summary>
  [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
  public class LeapPreferences : Attribute {
    public readonly string header;
    public readonly int order;

    public LeapPreferences(string header, int order) {
      this.header = header;
      this.order = order;
    }

#if UNITY_EDITOR
    private static List<LeapPreferenceItem> _leapPreferenceItems = null;

    private struct LeapPreferenceItem {
      public Action drawPreferenceGui;
      public LeapPreferences attribute;
    }

    private static void ensurePreferenceItemsLoaded() {
      if (_leapPreferenceItems != null) {
        return;
      }

      _leapPreferenceItems = new List<LeapPreferenceItem>();

      var assemblies = AppDomain.CurrentDomain.GetAssemblies();
      foreach (var type in assemblies.SelectMany(a => a.GetTypes())) {
        foreach (var method in type.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static)) {
          var attributes = method.GetCustomAttributes(typeof(LeapPreferences), inherit: true);
          if (attributes.Length == 0) {
            continue;
          }

          var attribute = attributes[0] as LeapPreferences;
          _leapPreferenceItems.Add(new LeapPreferenceItem() {
            drawPreferenceGui = () => {
              EditorGUILayout.LabelField(attribute.header, EditorStyles.boldLabel);
              using (new EditorGUILayout.VerticalScope(EditorStyles.helpBox)) {
                method.Invoke(null, null);
              }
              EditorGUILayout.Space();
              EditorGUILayout.Space();
              EditorGUILayout.Space();
            },
            attribute = attribute
          });
        }
      }

      _leapPreferenceItems.Sort((a, b) => a.attribute.order.CompareTo(b.attribute.order));
    }

    [PreferenceItem("Leap Motion")]
    private static void preferenceMenu() {
      ensurePreferenceItemsLoaded();

      foreach (var item in _leapPreferenceItems) {
        item.drawPreferenceGui();
      }
    }
#endif
  }
}