using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;

namespace Uigenx
{
    [Serializable]
    public sealed class UgxScreenEntry
    {
        [SerializeField] string key;
        [SerializeField] VisualTreeAsset uxml;
        [SerializeField] StyleSheet[] styles = Array.Empty<StyleSheet>();
        [SerializeField] string className;
        [SerializeField] UgxLayer layer = UgxLayer.Hud;
        [SerializeField] PanelSettings panel;

        public UgxScreenEntry()
        {
        }

        public UgxScreenEntry(string key, VisualTreeAsset uxml, string className, UgxLayer layer,
            StyleSheet[] styles = null, PanelSettings panel = null)
        {
            this.key = key;
            this.uxml = uxml;
            this.className = className;
            this.layer = layer;
            this.styles = styles ?? Array.Empty<StyleSheet>();
            this.panel = panel;
        }

        public string Key => key;
        public VisualTreeAsset Uxml => uxml;
        public StyleSheet[] Styles => styles;

        /// <summary>Full name of the generated screen class. Diagnostics only, never used to reflect.</summary>
        public string ClassName => className;

        public UgxLayer Layer => layer;

        /// <summary>Optional panel override. Null means the layer's default panel.</summary>
        public PanelSettings Panel => panel;
    }

    /// <summary>
    /// Everything the runtime needs to open a screen by key. Rebuilt by the editor after every
    /// import; never hand edited.
    /// </summary>
    [CreateAssetMenu(menuName = "UI Creator/Screen Registry", fileName = "UgxScreenRegistry")]
    public sealed class UgxScreenRegistry : ScriptableObject
    {
        /// <summary>Resources path the editor writes the registry to, so a build can always find it.</summary>
        public const string ResourcePath = "UgxScreenRegistry";

        [SerializeField] UgxScreenEntry[] entries = Array.Empty<UgxScreenEntry>();

        readonly Dictionary<string, UgxScreenEntry> _byKey = new Dictionary<string, UgxScreenEntry>(StringComparer.Ordinal);

        bool _built;

        static UgxScreenRegistry _active;

        public IReadOnlyList<UgxScreenEntry> Entries => entries;

        /// <summary>The registry the settings asset points at, or the one in Resources.</summary>
        public static UgxScreenRegistry Active
        {
            get
            {
                if (_active != null) return _active;
                var settings = UgxSettings.InstanceOrNull;
                if (settings != null && settings.ScreenRegistry != null) _active = settings.ScreenRegistry;
                if (_active == null) _active = Resources.Load<UgxScreenRegistry>(ResourcePath);
                return _active;
            }
            set => _active = value;
        }

        void OnEnable() => Rebuild();

        public void Rebuild()
        {
            _byKey.Clear();
            _built = true;
            if (entries == null) return;
            foreach (var entry in entries)
            {
                if (entry == null || string.IsNullOrEmpty(entry.Key)) continue;
                if (_byKey.ContainsKey(entry.Key))
                {
                    Debug.LogWarning("[ugx] screen registry has two entries for key '" + entry.Key +
                                     "', the first one wins", this);
                    continue;
                }
                _byKey[entry.Key] = entry;
            }
        }

        public bool TryGet(string key, out UgxScreenEntry entry)
        {
            if (!_built) Rebuild();
            entry = null;
            return !string.IsNullOrEmpty(key) && _byKey.TryGetValue(key, out entry);
        }

        public UgxScreenEntry GetOrThrow(string key)
        {
            if (TryGet(key, out var entry)) return entry;
            throw new InvalidOperationException(
                "screen '" + key + "' is not in the UI Creator screen registry. Re-export from the studio, " +
                "or rebuild the registry with Tools > UI Creator > Sync now.");
        }

        /// <summary>Replaces every entry. Editor only in practice, public so tests can build one.</summary>
        public void SetEntries(UgxScreenEntry[] value)
        {
            entries = value ?? Array.Empty<UgxScreenEntry>();
            Rebuild();
        }
    }
}