using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEditor.SceneManagement;
using UnityEngine;

namespace Ashwild.EditorTools
{
    /// <summary>
    /// The Scene Finder — a lightweight editor window that lists every scene in the project, filters
    /// them by a search box, and lets you pin the ones you use most as favourites so you never hunt
    /// through the Project window again. Favourites are keyed by asset GUID (so they survive renames
    /// and moves) and persisted per-machine in EditorPrefs, which means the pinned set follows the
    /// user's PC rather than living in the repo. Each row can open the scene (single or additive) or
    /// ping it in the Project window.
    /// </summary>
    public class SceneFinderWindow : EditorWindow
    {
        #region Constants

        /// <summary>
        /// EditorPrefs key holding the favourite scene GUIDs joined by ';'. Per-user, per-machine — the
        /// favourites are a personal shortcut list, deliberately not shared through the project.
        /// </summary>
        private const string FavoritesKey = "Ashwild.SceneFinder.Favorites";

        #endregion

        #region State

        private readonly List<SceneEntry> allScenes = new List<SceneEntry>();
        private readonly HashSet<string> favoriteGuids = new HashSet<string>();

        private string search = string.Empty;
        private Vector2 scroll;
        private bool showFavoritesOnly;

        private GUIStyle pathStyle;
        private GUIStyle sectionStyle;

        #endregion

        #region Types

        /// <summary>
        /// A single discovered scene: its GUID (stable key), display name and project-relative path.
        /// </summary>
        private struct SceneEntry
        {
            public string Guid;
            public string Name;
            public string Path;
        }

        #endregion

        #region Menu

        /// <summary>
        /// Opens (or focuses) the Scene Finder window.
        /// </summary>
        [MenuItem("Tools/Scene Finder")]
        public static void Open()
        {
            SceneFinderWindow window = GetWindow<SceneFinderWindow>();
            window.titleContent = new GUIContent("Scene Finder", EditorGUIUtility.IconContent("SceneAsset Icon").image);
            window.minSize = new Vector2(340, 300);
        }

        #endregion

        #region Window Lifecycle

        /// <summary>
        /// Loads the persisted favourites and scans the project for scenes when the window appears.
        /// </summary>
        private void OnEnable()
        {
            LoadFavorites();
            RefreshScenes();
        }

        #endregion

        #region Scene Discovery

        /// <summary>
        /// Rebuilds the scene list from the AssetDatabase, sorted by name. Called on open and whenever
        /// the user hits Refresh so newly created or deleted scenes are reflected.
        /// </summary>
        private void RefreshScenes()
        {
            allScenes.Clear();

            foreach (string guid in AssetDatabase.FindAssets("t:Scene"))
            {
                string path = AssetDatabase.GUIDToAssetPath(guid);
                if (string.IsNullOrEmpty(path)) continue;

                allScenes.Add(new SceneEntry
                {
                    Guid = guid,
                    Name = System.IO.Path.GetFileNameWithoutExtension(path),
                    Path = path
                });
            }

            allScenes.Sort((a, b) => string.Compare(a.Name, b.Name, System.StringComparison.OrdinalIgnoreCase));
        }

        #endregion

        #region Favorites Persistence

        /// <summary>
        /// Reads the favourite GUID set from EditorPrefs into memory.
        /// </summary>
        private void LoadFavorites()
        {
            favoriteGuids.Clear();
            string raw = EditorPrefs.GetString(FavoritesKey, string.Empty);
            if (string.IsNullOrEmpty(raw)) return;

            foreach (string guid in raw.Split(';'))
                if (!string.IsNullOrEmpty(guid)) favoriteGuids.Add(guid);
        }

        /// <summary>
        /// Writes the current favourite GUID set back to EditorPrefs so it survives domain reloads and
        /// editor restarts on this machine.
        /// </summary>
        private void SaveFavorites()
        {
            EditorPrefs.SetString(FavoritesKey, string.Join(";", favoriteGuids));
        }

        /// <summary>
        /// Pins or unpins a scene and persists the change immediately.
        /// </summary>
        private void ToggleFavorite(string guid)
        {
            if (!favoriteGuids.Remove(guid)) favoriteGuids.Add(guid);
            SaveFavorites();
        }

        #endregion

        #region GUI

        /// <summary>
        /// Draws the toolbar and the favourites + all-scenes lists.
        /// </summary>
        private void OnGUI()
        {
            EnsureStyles();
            DrawToolbar();

            scroll = EditorGUILayout.BeginScrollView(scroll);

            List<SceneEntry> filtered = Filter();
            List<SceneEntry> favorites = filtered.Where(s => favoriteGuids.Contains(s.Guid)).ToList();

            if (favorites.Count > 0)
            {
                DrawSectionHeader($"★ Favorites ({favorites.Count})");
                foreach (SceneEntry entry in favorites) DrawRow(entry);
                GUILayout.Space(6);
            }

            if (!showFavoritesOnly)
            {
                List<SceneEntry> rest = filtered.Where(s => !favoriteGuids.Contains(s.Guid)).ToList();
                DrawSectionHeader($"All Scenes ({rest.Count})");

                if (rest.Count == 0 && favorites.Count == 0)
                    EditorGUILayout.HelpBox("No scene matches the search.", MessageType.Info);

                foreach (SceneEntry entry in rest) DrawRow(entry);
            }

            EditorGUILayout.EndScrollView();
        }

        /// <summary>
        /// Draws the top toolbar: search field with a clear button, a favourites-only toggle and refresh.
        /// </summary>
        private void DrawToolbar()
        {
            EditorGUILayout.BeginHorizontal(EditorStyles.toolbar);

            search = GUILayout.TextField(search, EditorStyles.toolbarSearchField, GUILayout.MinWidth(80));
            if (GUILayout.Button("✕", EditorStyles.toolbarButton, GUILayout.Width(22)))
            {
                search = string.Empty;
                GUI.FocusControl(null);
            }

            showFavoritesOnly = GUILayout.Toggle(showFavoritesOnly, "★ Only", EditorStyles.toolbarButton, GUILayout.Width(50));

            if (GUILayout.Button("Refresh", EditorStyles.toolbarButton, GUILayout.Width(60)))
                RefreshScenes();

            EditorGUILayout.EndHorizontal();
        }

        /// <summary>
        /// Draws a single scene row: the pin toggle, its name and dimmed path, and the open/ping actions.
        /// </summary>
        private void DrawRow(SceneEntry entry)
        {
            EditorGUILayout.BeginHorizontal(EditorStyles.helpBox);

            bool isFav = favoriteGuids.Contains(entry.Guid);
            bool newFav = GUILayout.Toggle(isFav, isFav ? "★" : "☆", EditorStyles.label, GUILayout.Width(20));
            if (newFav != isFav) ToggleFavorite(entry.Guid);

            EditorGUILayout.BeginVertical();
            EditorGUILayout.LabelField(entry.Name, EditorStyles.boldLabel);
            EditorGUILayout.LabelField(entry.Path, pathStyle);
            EditorGUILayout.EndVertical();

            if (GUILayout.Button(new GUIContent("Open", "Open this scene (replaces the current one)"), GUILayout.Width(46)))
                OpenScene(entry.Path, OpenSceneMode.Single);

            if (GUILayout.Button(new GUIContent("+", "Open additively alongside the current scene(s)"), GUILayout.Width(24)))
                OpenScene(entry.Path, OpenSceneMode.Additive);

            if (GUILayout.Button(new GUIContent("◎", "Ping in the Project window"), GUILayout.Width(24)))
                PingScene(entry.Path);

            EditorGUILayout.EndHorizontal();
        }

        /// <summary>
        /// Draws a small section separator label.
        /// </summary>
        private void DrawSectionHeader(string title)
        {
            GUILayout.Label(title, sectionStyle);
        }

        #endregion

        #region Actions

        /// <summary>
        /// Opens a scene, prompting to save any unsaved changes first (single mode only). Guards the
        /// missing-scene case with a clear log so a stale favourite fails loudly rather than silently.
        /// </summary>
        private void OpenScene(string path, OpenSceneMode mode)
        {
            if (!System.IO.File.Exists(path))
            {
                Debug.LogError($"[SceneFinder] Scene not found at '{path}' — it may have been moved or deleted.");
                RefreshScenes();
                return;
            }

            if (mode == OpenSceneMode.Single &&
                !EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo())
                return;

            EditorSceneManager.OpenScene(path, mode);
        }

        /// <summary>
        /// Selects and pings the scene asset in the Project window.
        /// </summary>
        private void PingScene(string path)
        {
            SceneAsset asset = AssetDatabase.LoadAssetAtPath<SceneAsset>(path);
            if (asset == null) return;

            Selection.activeObject = asset;
            EditorGUIUtility.PingObject(asset);
        }

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Returns the scenes matching the current search text (case-insensitive, matched against both
        /// name and path). An empty search returns everything.
        /// </summary>
        private List<SceneEntry> Filter()
        {
            if (string.IsNullOrWhiteSpace(search)) return allScenes;

            string needle = search.Trim().ToLowerInvariant();
            return allScenes.Where(s =>
                s.Name.ToLowerInvariant().Contains(needle) ||
                s.Path.ToLowerInvariant().Contains(needle)).ToList();
        }

        /// <summary>
        /// Lazily builds the cached GUI styles once the skin is available (styles can't be created in
        /// OnEnable because the editor skin isn't ready yet).
        /// </summary>
        private void EnsureStyles()
        {
            if (pathStyle == null)
            {
                pathStyle = new GUIStyle(EditorStyles.miniLabel) { wordWrap = false };
                pathStyle.normal.textColor = new Color(0.55f, 0.55f, 0.55f);
            }

            if (sectionStyle == null)
            {
                sectionStyle = new GUIStyle(EditorStyles.boldLabel) { margin = new RectOffset(4, 4, 6, 2) };
            }
        }

        #endregion
    }
}