using System;
using System.Collections.Generic;
using UnityEditor;
using UnityEditor.PackageManager;
using UnityEditor.PackageManager.Requests;
using UnityEngine;

namespace FlowScope.Editor
{
    public sealed class FlowScopeDiagnosticsWindow : EditorWindow
    {
        private const string PackageRuntimeAsmdefPath = "Packages/com.flowscope.gamecore/Runtime/FlowScope.Runtime.asmdef";
        private const string PackageAddressablesAsmdefPath = "Packages/com.flowscope.gamecore/Addressables/FlowScope.Addressables.asmdef";
        private const string AssetsRuntimeAsmdefPath = "Assets/FlowScope/Runtime/FlowScope.Runtime.asmdef";
        private const string AssetsAddressablesAsmdefPath = "Assets/FlowScope/Addressables/FlowScope.Addressables.asmdef";
        private const string AssetsMainMenuScenePath = "Assets/FlowScope/Samples/MainMenuP0/Scenes/MainMenuP0.unity";
        private const string AssetsMainMenuPanelPrefabPath = "Assets/FlowScope/Samples/MainMenuP0/Prefabs/MainMenuPanel.prefab";
        private const string AddressablesPackageName = "com.unity.addressables";

        private static readonly IReadOnlyList<AssetCheck> AssetChecks = new[]
        {
            new AssetCheck("Runtime asmdef", PackageRuntimeAsmdefPath, AssetsRuntimeAsmdefPath),
            new AssetCheck("Addressables asmdef", PackageAddressablesAsmdefPath, AssetsAddressablesAsmdefPath),
            new AssetCheck("MainMenuP0 scene", AssetsMainMenuScenePath),
            new AssetCheck("MainMenuPanel prefab", AssetsMainMenuPanelPrefabPath),
        };

        private readonly List<DiagnosticResult> _assetResults = new List<DiagnosticResult>();

        private ListRequest _packageListRequest;
        private DiagnosticResult _addressablesPackageResult = DiagnosticResult.Pending(
            "Addressables package",
            "Package status has not been refreshed.");

        private Vector2 _scrollPosition;

        [MenuItem("Tools/FlowScope/Diagnostics")]
        public static void Open()
        {
            FlowScopeDiagnosticsWindow window = GetWindow<FlowScopeDiagnosticsWindow>("FlowScope Diagnostics");
            window.minSize = new Vector2(520f, 320f);
            window.RefreshAll();
            window.Show();
        }

        private void OnEnable()
        {
            RefreshAssetChecks();
            RefreshPackageStatus();
        }

        private void OnDisable()
        {
            EditorApplication.update -= PollPackageListRequest;
        }

        private void OnGUI()
        {
            using (new EditorGUILayout.VerticalScope())
            {
                EditorGUILayout.LabelField("FlowScope Diagnostics", EditorStyles.boldLabel);
                EditorGUILayout.HelpBox("Read-only diagnostics. This window checks project state and does not create, move, delete, or repair user assets.", MessageType.Info);

                using (new EditorGUILayout.HorizontalScope())
                {
                    if (GUILayout.Button("Refresh", GUILayout.Width(96f)))
                    {
                        RefreshAll();
                    }

                    GUILayout.Label(
                        _packageListRequest != null && !_packageListRequest.IsCompleted
                            ? "Refreshing package status..."
                            : "Package status is complete or has not been requested.",
                        EditorStyles.miniLabel);
                }

                EditorGUILayout.Space();

                _scrollPosition = EditorGUILayout.BeginScrollView(_scrollPosition);
                DrawResult(_addressablesPackageResult);

                foreach (DiagnosticResult result in _assetResults)
                {
                    DrawResult(result);
                }

                EditorGUILayout.EndScrollView();
            }
        }

        private void RefreshAll()
        {
            RefreshAssetChecks();
            RefreshPackageStatus();
            Repaint();
        }

        private void RefreshAssetChecks()
        {
            _assetResults.Clear();

            foreach (AssetCheck check in AssetChecks)
            {
                string foundPath = FindExistingAssetPath(check.Paths);
                _assetResults.Add(foundPath != null
                    ? DiagnosticResult.Pass(check.Label, foundPath)
                    : DiagnosticResult.Fail(check.Label, string.Join(" or ", check.Paths)));
            }
        }

        private static string FindExistingAssetPath(IReadOnlyList<string> paths)
        {
            foreach (string path in paths)
            {
                if (AssetDatabase.LoadAssetAtPath<UnityEngine.Object>(path) != null)
                {
                    return path;
                }
            }

            return null;
        }

        private void RefreshPackageStatus()
        {
            EditorApplication.update -= PollPackageListRequest;

            _addressablesPackageResult = DiagnosticResult.Pending(
                "Addressables package",
                "Querying com.unity.addressables through Unity Package Manager.");

            _packageListRequest = Client.List(true);
            EditorApplication.update += PollPackageListRequest;
        }

        private void PollPackageListRequest()
        {
            if (_packageListRequest == null || !_packageListRequest.IsCompleted)
            {
                return;
            }

            EditorApplication.update -= PollPackageListRequest;

            if (_packageListRequest.Status == StatusCode.Success)
            {
                bool found = false;
                foreach (UnityEditor.PackageManager.PackageInfo packageInfo in _packageListRequest.Result)
                {
                    if (string.Equals(packageInfo.name, AddressablesPackageName, StringComparison.Ordinal))
                    {
                        found = true;
                        _addressablesPackageResult = DiagnosticResult.Pass(
                            "Addressables package",
                            packageInfo.name + " " + packageInfo.version);
                        break;
                    }
                }

                if (!found)
                {
                    _addressablesPackageResult = DiagnosticResult.Fail(
                        "Addressables package",
                        "com.unity.addressables was not found in the current Package Manager list.");
                }
            }
            else
            {
                string errorMessage = _packageListRequest.Error != null
                    ? _packageListRequest.Error.message
                    : "Package Manager returned an unknown error.";
                _addressablesPackageResult = DiagnosticResult.Warning("Addressables package", errorMessage);
            }

            _packageListRequest = null;
            Repaint();
        }

        private static void DrawResult(DiagnosticResult result)
        {
            MessageType messageType = ToMessageType(result.Status);

            using (new EditorGUILayout.VerticalScope(EditorStyles.helpBox))
            {
                using (new EditorGUILayout.HorizontalScope())
                {
                    GUILayout.Label(ToStatusText(result.Status), GUILayout.Width(72f));
                    EditorGUILayout.LabelField(result.Label, EditorStyles.boldLabel);
                }

                EditorGUILayout.HelpBox(result.Detail, messageType);
            }
        }

        private static MessageType ToMessageType(DiagnosticStatus status)
        {
            switch (status)
            {
                case DiagnosticStatus.Pass:
                    return MessageType.Info;
                case DiagnosticStatus.Fail:
                    return MessageType.Error;
                case DiagnosticStatus.Warning:
                    return MessageType.Warning;
                default:
                    return MessageType.None;
            }
        }

        private static string ToStatusText(DiagnosticStatus status)
        {
            switch (status)
            {
                case DiagnosticStatus.Pass:
                    return "OK";
                case DiagnosticStatus.Fail:
                    return "Missing";
                case DiagnosticStatus.Warning:
                    return "Warning";
                default:
                    return "Pending";
            }
        }

        private readonly struct AssetCheck
        {
            public AssetCheck(string label, params string[] paths)
            {
                Label = label;
                Paths = paths;
            }

            public string Label { get; }

            public IReadOnlyList<string> Paths { get; }
        }

        private readonly struct DiagnosticResult
        {
            private DiagnosticResult(DiagnosticStatus status, string label, string detail)
            {
                Status = status;
                Label = label;
                Detail = detail;
            }

            public DiagnosticStatus Status { get; }

            public string Label { get; }

            public string Detail { get; }

            public static DiagnosticResult Pass(string label, string detail)
            {
                return new DiagnosticResult(DiagnosticStatus.Pass, label, detail);
            }

            public static DiagnosticResult Fail(string label, string detail)
            {
                return new DiagnosticResult(DiagnosticStatus.Fail, label, detail);
            }

            public static DiagnosticResult Warning(string label, string detail)
            {
                return new DiagnosticResult(DiagnosticStatus.Warning, label, detail);
            }

            public static DiagnosticResult Pending(string label, string detail)
            {
                return new DiagnosticResult(DiagnosticStatus.Pending, label, detail);
            }
        }

        private enum DiagnosticStatus
        {
            Pending,
            Pass,
            Warning,
            Fail,
        }
    }
}