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

namespace BaseGames.Core
{
    /// <summary>
    /// 轻量服务定位器。通过类型键注册/查找服务，支持接口类型注册（依赖倒置）。
    /// </summary>
    public static class ServiceLocator
    {
        private static readonly Dictionary<Type, object> _services = new();

        /// <summary>以接口类型 TInterface 注册实现 impl。</summary>
        public static void Register<TInterface>(TInterface impl)
            => _services[typeof(TInterface)] = impl;

        /// <summary>仅当尚未注册时才注册（防多场景重复注册同一服务）。</summary>
        public static void RegisterIfAbsent<TInterface>(TInterface impl)
        {
            if (!_services.ContainsKey(typeof(TInterface)))
                _services[typeof(TInterface)] = impl;
        }

        /// <summary>查找服务。未注册时抛出 InvalidOperationException。</summary>
        public static TInterface Get<TInterface>()
        {
            if (_services.TryGetValue(typeof(TInterface), out var svc) && svc is TInterface typed)
                return typed;
            throw new InvalidOperationException(
                $"[ServiceLocator] Service '{typeof(TInterface).Name}' is not registered. "
                + "Ensure GameServiceRegistrar.Awake() has run before this call.");
        }

        /// <summary>安全版 Get：未注册时返回 fallback，不报错（适用于可选服务）。</summary>
        public static TInterface GetOrDefault<TInterface>(TInterface fallback = default)
            => _services.TryGetValue(typeof(TInterface), out var svc) && svc is TInterface typed
               ? typed : fallback;

#if UNITY_EDITOR
        /// <summary>单元测试中替换服务实现。</summary>
        public static void OverrideForTest<TInterface>(TInterface mock)
            => _services[typeof(TInterface)] = mock;

        /// <summary>清空所有注册（测试用）。</summary>
        public static void Reset() => _services.Clear();
#endif
    }
}