using System;
using System.Linq;
using Yarn.Unity;

namespace Ichni.Story.Dialogue
{
    /// <summary>
    /// Yarn 选项的章节内记忆服务。
    /// <para>玩家第一次完成某组选项后，保存其 <see cref="DialogueOption.TextID"/>；再次进入同一 TextBlock 时，
    /// 若该选项仍存在且可用，则不显示选择 UI，直接返回该 Option 给 Yarn。</para>
    /// <para>记录随 Timeline 回滚快照一起恢复，因此回滚到选项之前会让玩家重新选择。</para>
    /// </summary>
    public static class StoryChoiceMemory
    {
        /// <summary>
        /// 根据来源 Block 与当前全部 Option Text ID 生成选项组 Key。
        /// Text ID 已由 Yarn 编译结果稳定生成；排序使纯显示顺序调整不会把同一组选项误认为新选项组。
        /// </summary>
        public static string CreateChoiceKey(string sourceBlockId, DialogueOption[] options)
        {
            if (string.IsNullOrWhiteSpace(sourceBlockId) || options == null || options.Length == 0 ||
                options.Any(option => option == null || string.IsNullOrWhiteSpace(option.TextID)))
            {
                return null;
            }

            string optionSignature = string.Join("|", options
                .Select(option => option.TextID)
                .OrderBy(textId => textId, StringComparer.Ordinal));
            return sourceBlockId + "::" + optionSignature;
        }

        /// <summary>
        /// 查找已保存的选项。若 Yarn 改稿后旧 Text ID 已不存在或暂时不可用，
        /// 会删除陈旧记录并回退为普通选择界面，避免自动选择错误路线。
        /// </summary>
        public static bool TryGetRememberedOption(string sourceBlockId, DialogueOption[] options,
            out DialogueOption rememberedOption)
        {
            rememberedOption = null;
            StoryTreeController treeController = StoryManager.instance?.treeController;
            StorySaveModule saveModule = GameSaveManager.instance?.StorySaveModule;
            string choiceKey = CreateChoiceKey(sourceBlockId, options);
            if (treeController == null || saveModule == null || string.IsNullOrEmpty(treeController.ActiveChapterIndex) ||
                string.IsNullOrEmpty(choiceKey))
            {
                return false;
            }

            if (!saveModule.TryGetChoice(treeController.ActiveChapterIndex, choiceKey, out StoryChoiceRecord record))
                return false;

            rememberedOption = options.FirstOrDefault(option => option != null && option.IsAvailable &&
                                                               option.TextID == record.selectedOptionTextId);
            if (rememberedOption != null)
                return true;

            saveModule.RemoveChoice(treeController.ActiveChapterIndex, choiceKey);
            return false;
        }

        /// <summary>
        /// 保存玩家首次确认的选项。调用时先捕获所属 Block 的 Marker 快照，
        /// 保证该选项及其随后写入的路线变量都能被重开流程一起回滚。
        /// </summary>
        public static void RememberChoice(string sourceBlockId, DialogueOption[] options, DialogueOption selectedOption)
        {
            StoryTreeController treeController = StoryManager.instance?.treeController;
            StorySaveModule saveModule = GameSaveManager.instance?.StorySaveModule;
            string choiceKey = CreateChoiceKey(sourceBlockId, options);
            if (treeController == null || saveModule == null || selectedOption == null ||
                string.IsNullOrEmpty(treeController.ActiveChapterIndex) || string.IsNullOrEmpty(choiceKey))
            {
                return;
            }

            StoryProgress.TryCaptureActiveBlockSnapshot();
            saveModule.SetChoice(treeController.ActiveChapterIndex, new StoryChoiceRecord
            {
                sourceBlockId = sourceBlockId,
                choiceKey = choiceKey,
                selectedOptionTextId = selectedOption.TextID
            });
        }
    }
}