module-navigation-tool/Editor/Toolbar/Tools/ToolBuildTargetPicker.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using JetBrains.Annotations;
using UnityEditor;
using UnityEngine;
using UTools = UnityEditor.Tools;

namespace Module.NavigationTool.Editor.Toolbar
{
    [UsedImplicitly]
    internal sealed class ToolBuildTargetPicker : AbstractToolbarDrawer
    {
        public override bool Visible => ToolbarBuildSettings.IsBuildEnabled;
        public override bool Enabled => !Application.isPlaying;
        public override EToolbarPlacement Placement => EToolbarPlacement.Left;
        public override int Priority => (int)EToolbarPriority.Low;
        
        private static bool IS_DIRTY = true;
        private static int[] HASHES = new int[0];
        private static BuildTargetGroup[] GROUPS = new BuildTargetGroup[0];
        private static BuildTarget[] TARGETS = new BuildTarget[0];
        private static GUIContent[] TARGET_LIST = new GUIContent[0];
        private static int SELECTED_INDEX = -1;

        private static void Initialize()
        {
            if (!IS_DIRTY)
                return;

            BuildTarget target = EditorUserBuildSettings.activeBuildTarget;
            BuildTargetGroup group = BuildPipeline.GetBuildTargetGroup(target);

            PopulateBuildTargetList();
            SELECTED_INDEX = Array.IndexOf(HASHES, GetHashCode(group, target));
            IS_DIRTY = false;
        }
        
        public override void Update()
        {
            Initialize();
        }

        protected override void Draw(Rect rect)
        {
            BuildTarget target = EditorUserBuildSettings.activeBuildTarget;
            BuildTargetGroup group = BuildPipeline.GetBuildTargetGroup(target);
            GUIContent content = SELECTED_INDEX != -1 ? GetButtonContent(group) : GUIContent.none;
            
            if (GUI.Button(rect, content, styles.buttonNoPadding))
            {
                // Note: Do not discard the parameters: userData and options, since they throw an error in 2019, if there are two of them
                EditorUtility.DisplayCustomMenu(rect, TARGET_LIST, SELECTED_INDEX, (userData, options, selected) =>
                {
                    if (selected != -1 && selected != SELECTED_INDEX)
                        SetBuildTargetTo(selected);
                }, null);
            }
        }
        
        public override float CalculateWidth()
        {
            return 40.0f;
        }
        
        private static void SetBuildTargetTo(int index)
        {
            if (index < 0)
                return;

            BuildTargetGroup group = GROUPS[index];
            BuildTarget target = TARGETS[index];

            if (!EditorUserBuildSettings.SwitchActiveBuildTarget(@group, target))
                return;

            IS_DIRTY = true;
            SELECTED_INDEX = index;
        }

        private static void PopulateBuildTargetList()
        {
            var hashes = new List<int>();
            var groups = new List<BuildTargetGroup>();
            var targets = new List<BuildTarget>();
            var contentList = new List<GUIContent>();
            
            Type type = typeof(BuildTarget);
            Array values = Enum.GetValues(type);

            for (var i = 0; i < values.Length; i++)
            {
                var target = (BuildTarget)values.GetValue(i);
                BuildTargetGroup group = BuildPipeline.GetBuildTargetGroup(target);

                if (target < 0 || !BuildPipeline.IsBuildTargetSupported(group, target))
                    continue;
                if (!IsValid(type, target))
                    continue;
                
                hashes.Add(GetHashCode(group, target));
                groups.Add(group);
                targets.Add(target);
                contentList.Add(new GUIContent(ObjectNames.NicifyVariableName(target.ToString())));
            }

            HASHES = hashes.ToArray();
            GROUPS = groups.ToArray();
            TARGETS = targets.ToArray();
            TARGET_LIST = contentList.ToArray();
        }
        
        private static bool IsValid(Type type, BuildTarget target)
        {
            MemberInfo[] members = type.GetMember(target.ToString(), BindingFlags.Public | BindingFlags.Static);

            if (members.Length == 0)
                return false;
            
            for (var j = 0; j < members.Length; j++)
            {
                if (members[j].GetCustomAttribute<ObsoleteAttribute>() == null)
                    return true;
            }

            return false;
        }

        private static GUIContent GetButtonContent(BuildTargetGroup group)
        {
            var name = $"BuildSettings.{group}.Small";
            
            if (group == BuildTargetGroup.WSA)
                name = "BuildSettings.Metro.Small";

            return EditorGUIUtility.IconContent(name);
        }
        
        private static int GetHashCode(BuildTargetGroup group, BuildTarget target)
        {
            return ((int)group << 16) + (int)target;
        }
    }
}