using System;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Reflection;
using JetBrains.Annotations;
using UnityEngine.UIElements;

// ReSharper disable once CheckNamespace
namespace UnityEditor
{
    [PublicAPI]
    [SuppressMessage("ReSharper", "InconsistentNaming")]
    [SuppressMessage("ReSharper", "StringLiteralTypo")]
    [SuppressMessage("ReSharper", "CommentTypo")]
    public static class EditorWindowExtensions
    {
        /// <summary>
        ///     Loads the visual tree.
        ///     <para>
        ///         This method loads the visual tree and associated style sheet using default Unity conventions,
        ///         that is, UXML and USS files are expected to be located next to this instance script asset.
        ///     </para>
        ///     <para>
        ///         Declared instance fields that derive from <see cref="VisualElement" /> will be assigned
        ///         the matching element instance found when searching the visual tree.
        ///     </para>
        /// </summary>
        /// <param name="window">
        ///     Source window.
        /// </param>
        /// <exception cref="ArgumentNullException">
        ///     <paramref name="window" /> is <c>null</c>.
        /// </exception>
        /// <exception cref="FileNotFoundException">
        ///     Associated UMXL or USS file could not be found.
        /// </exception>
        /// <exception cref="InvalidOperationException">
        ///     A declared instance field deriving from <see cref="VisualElement" /> could not be found in the visual tree.
        /// </exception>
        public static void LoadVisualTree([NotNull] this EditorWindow window)
        {
            if (window == null)
                throw new ArgumentNullException(nameof(window));

            var script = MonoScript.FromScriptableObject(window);
            var path = AssetDatabase.GetAssetPath(script);

            var xml = Path.ChangeExtension(path, "uxml");
            var css = Path.ChangeExtension(path, "uss");

            var asset = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(xml);
            if (asset == null)
                throw new FileNotFoundException("Associated UXML file could not be found.");

            var sheet = AssetDatabase.LoadAssetAtPath<StyleSheet>(css);
            if (sheet == null)
                throw new FileNotFoundException("Associated USS file could not be found.");

            var tree = asset.CloneTree();
            tree.styleSheets.Add(sheet);

            window.rootVisualElement.Clear();
            window.rootVisualElement.Add(tree);

            var fields = window
                .GetType()
                .GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.DeclaredOnly)
                .Where(s => typeof(VisualElement).IsAssignableFrom(s.FieldType))
                .ToArray();

            foreach (var field in fields)
            {
                var name = field.Name;
                var type = field.FieldType;

                var element = tree.Q(name);
                if (element == null)
                    throw new InvalidOperationException($"Element '{name}' of type '{type}' could not be found in visual tree.");

                field.SetValue(window, element);
            }
        }
    }
}