#if UGX_BRIDGE || UNITY_EDITOR
using System;
using System.Collections.Generic;
using System.IO;
using Uigenx.Protocol;

namespace Uigenx.Bridge
{
    /// <summary>
    /// Re-opens screens after the editor reimported their assets. The runtime cannot parse UXML or
    /// USS text itself, so the daemon writes the files, the importer reimports them, and this
    /// handler rebuilds whatever is on screen. Anything it cannot match is reported as an error
    /// rather than silently ignored.
    /// </summary>
    public sealed class UgxHotReloadHandler : IDisposable
    {
        readonly UgxBridgeClient _client;
        readonly List<string> _reloaded = new List<string>(4);
        readonly List<string> _errors = new List<string>(4);

        public UgxHotReloadHandler(UgxBridgeClient client)
        {
            _client = client ?? throw new ArgumentNullException(nameof(client));
            client.Register(UgxMessageTypes.HotReloadRequest, OnRequest);
        }

        public void Dispose() => _client.Unregister(UgxMessageTypes.HotReloadRequest);

        void OnRequest(UgxEnvelope envelope)
        {
            var body = envelope.BodyAs<UgxHotReloadRequest>();
            _reloaded.Clear();
            _errors.Clear();

            var manager = UgxScreenManager.Instance;
            var registry = UgxScreenRegistry.Active;

            foreach (var file in body.Files)
            {
                var key = ScreenKeyFor(file.Path);
                if (registry == null || key == null || !registry.TryGet(key, out _))
                {
                    _errors.Add(file.Path + ": no screen matches this file, nothing to reload");
                    continue;
                }
                if (manager == null || !manager.IsOpen(key))
                {
                    // Not an error: the next open picks up the reimported asset.
                    _reloaded.Add(key);
                    continue;
                }

                // Re-open on the layer it was on, not the registry default: a modal pushed onto
                // Overlay must not come back above everything on Modal.
                var layer = LayerOf(manager, key);
                manager.Close(key);
                if (manager.Push(key, layer) != null) _reloaded.Add(key);
                else _errors.Add(key + ": could not be re-opened");
            }

            _client.Send(UgxMessageTypes.HotReloadResult, new UgxHotReloadResult
            {
                RequestId = body.RequestId,
                Reloaded = new List<string>(_reloaded),
                Errors = new List<string>(_errors),
            }, re: envelope.Id);
        }

        static UgxLayer? LayerOf(UgxScreenManager manager, string key)
        {
            var stack = manager.Stack;
            for (int i = stack.Count - 1; i >= 0; i--)
                if (stack[i].Key == key) return stack[i].Layer;
            return null;
        }

        /// <summary>`.../Screens/Hud/Hud.uxml` becomes `Hud`. Null when the path has no file name.</summary>
        public static string ScreenKeyFor(string path)
        {
            if (string.IsNullOrEmpty(path)) return null;
            var name = Path.GetFileNameWithoutExtension(path);
            return string.IsNullOrEmpty(name) ? null : name;
        }
    }
}
#endif