using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.Localization;
using UnityEngine.Localization.Settings;
using UnityEngine.Localization.Tables;
using UnityEngine.ResourceManagement.AsyncOperations;

namespace Ichni.Localization
{
    /// <summary>
    /// 项目运行时代码读取 Unity Localization 文本的统一入口。
    /// <para>静态 Prefab 文本仍应使用 <c>LocalizeStringEvent</c>；只有运行时生成、Yarn 命令、Story 数据等无法直接挂组件的文本才调用本服务。</para>
    /// <para>同步接口绝不强制 Addressables 完成加载：Localization 尚未就绪时直接返回 fallback，避免在场景切换或 UI 点击中制造卡顿。</para>
    /// </summary>
    public static class LocalizationTextService
    {
        private static readonly HashSet<string> ReportedFallbacks = new HashSet<string>();

        /// <summary>
        /// 在 Unity Localization 已初始化时立即解析文本；无法解析时返回调用方提供的 fallback。
        /// <para>fallback 传入 <c>null</c> 时回退显示 Key，适合开发阶段快速定位缺失条目；传入空字符串时会保留空字符串。</para>
        /// </summary>
        public static string Resolve(
            TableReference tableReference,
            string entryKey,
            string fallback = null,
            params object[] arguments)
        {
            string resolvedFallback = GetFallback(entryKey, fallback);
            if (string.IsNullOrEmpty(entryKey))
            {
                return resolvedFallback;
            }

            AsyncOperationHandle<LocalizationSettings> initializationOperation = LocalizationSettings.InitializationOperation;
            if (!initializationOperation.IsDone || initializationOperation.Status != AsyncOperationStatus.Succeeded)
            {
                ReportFallbackOnce(tableReference, entryKey, "Unity Localization 尚未完成初始化");
                return resolvedFallback;
            }

            try
            {
                string localizedText = LocalizationSettings.StringDatabase.GetLocalizedString(
                    tableReference,
                    entryKey,
                    null,
                    FallbackBehavior.UseProjectSettings,
                    arguments);
                if (!string.IsNullOrEmpty(localizedText))
                {
                    return localizedText;
                }

                ReportFallbackOnce(tableReference, entryKey, "String Table 未返回有效文本");
            }
            catch (Exception exception)
            {
                ReportFallbackOnce(tableReference, entryKey, exception.Message);
            }

            return resolvedFallback;
        }

        /// <summary>
        /// 异步解析文本。该接口只等待 Unity 官方 <see cref="LocalizationSettings.InitializationOperation"/> 和字符串加载操作，
        /// 不创建额外 Bootstrap，也不使用 <c>WaitForCompletion</c> 阻塞主线程。
        /// </summary>
        public static async Task<string> ResolveAsync(
            TableReference tableReference,
            string entryKey,
            string fallback = null,
            params object[] arguments)
        {
            string resolvedFallback = GetFallback(entryKey, fallback);
            if (string.IsNullOrEmpty(entryKey))
            {
                return resolvedFallback;
            }

            try
            {
                AsyncOperationHandle<LocalizationSettings> initializationOperation = LocalizationSettings.InitializationOperation;
                await initializationOperation.Task;
                if (initializationOperation.Status != AsyncOperationStatus.Succeeded)
                {
                    ReportFallbackOnce(tableReference, entryKey, "Unity Localization 初始化失败");
                    return resolvedFallback;
                }

                AsyncOperationHandle<string> textOperation = LocalizationSettings.StringDatabase.GetLocalizedStringAsync(
                    tableReference,
                    entryKey,
                    null,
                    FallbackBehavior.UseProjectSettings,
                    arguments);
                await textOperation.Task;
                if (textOperation.Status == AsyncOperationStatus.Succeeded && !string.IsNullOrEmpty(textOperation.Result))
                {
                    return textOperation.Result;
                }

                ReportFallbackOnce(tableReference, entryKey, "String Table 异步加载失败或未返回有效文本");
            }
            catch (Exception exception)
            {
                ReportFallbackOnce(tableReference, entryKey, exception.Message);
            }

            return resolvedFallback;
        }

        private static string GetFallback(string entryKey, string fallback)
        {
            return fallback ?? entryKey ?? string.Empty;
        }

        /// <summary>
        /// 同一 Table/Key 的回退原因只输出一次，避免 Helper、Timeline 等重复刷新 UI 时刷屏。
        /// </summary>
        private static void ReportFallbackOnce(TableReference tableReference, string entryKey, string reason)
        {
            string diagnosticKey = $"{tableReference}:{entryKey}";
            if (!ReportedFallbacks.Add(diagnosticKey))
            {
                return;
            }

            Debug.LogWarning($"[LocalizationTextService] 无法解析 '{diagnosticKey}'，将显示 fallback。原因：{reason}");
        }
    }
}