/******************************************************************************
 * Copyright (C) Ultraleap, Inc. 2011-2021.                                   *
 *                                                                            *
 * Use subject to the terms of the Apache License 2.0 available at            *
 * http://www.apache.org/licenses/LICENSE-2.0, or another agreement           *
 * between Ultraleap and you, your company or other organization.             *
 ******************************************************************************/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
#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));
        }

#if UNITY_2018_3_OR_NEWER
        // Implementations Leap Motion settings using the new SettingsProvider API.
        private class LeapMotionSettingsProvider : SettingsProvider
        {
            public LeapMotionSettingsProvider(string path, SettingsScope scopes = SettingsScope.User)
            : base(path, scopes)
            { }

            public override void OnGUI(string searchContext)
            {
                DrawPreferencesGUI();
            }
        }

        [SettingsProvider]
        static SettingsProvider GetSettingsProvider()
        {
            return new LeapMotionSettingsProvider("Preferences/Leap Motion");
        }
#else
    [PreferenceItem("Leap Motion")]
#endif
        public static void DrawPreferencesGUI()
        {
            ensurePreferenceItemsLoaded();

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