using System;
using System.Collections;
using System.Collections.Generic;
using Sirenix.OdinInspector;
using UnityEngine;

namespace Ichni.Menu
{
    public class MenuInformationRecorder : SerializedMonoBehaviour
    {
        public static MenuInformationRecorder instance;
        public Dictionary<ChapterSelectionUnit, SongSelectionRecord> songSelectionRecords;

        private void Awake()
        {
            if (instance == null)
            {
                instance = this;
                songSelectionRecords = new Dictionary<ChapterSelectionUnit, SongSelectionRecord>();
            }
            else
            {
                Destroy(gameObject);
            }
        }

        /// <summary>
        /// 取得当前 Chapter 的选曲缓存；缓存缺失时创建“第一首有效歌曲 + 难度位置 0”的默认记录。
        /// <para>此方法只保证缓存对象可用，不保证该歌曲或难度仍能游玩。歌曲失效与难度回退由选曲 UI 在
        /// 每次进入页面时完成，避免把运行期缓存变成持久化存档。</para>
        /// </summary>
        public bool TryGetRecordOfThisChapter(out SongSelectionRecord record)
        {
            record = null;
            ChapterSelectionUnit currentChapter = ChapterSelectionManager.instance.currentChapter;
            if (currentChapter == null || currentChapter.songs == null)
            {
                return false;
            }

            if (songSelectionRecords.TryGetValue(currentChapter, out SongSelectionRecord cachedRecord) && cachedRecord != null)
            {
                record = cachedRecord;
                return true;
            }

            SongItemData firstValidSong = currentChapter.songs.Find(song => song != null);
            if (firstValidSong == null)
            {
                return false;
            }

            record = new SongSelectionRecord(firstValidSong, 0);
            songSelectionRecords[currentChapter] = record;
            return true;
        }

        /// <summary>
        /// 将缓存修正为当前 Chapter 中实际存在的歌曲，并保留调用方提供的难度列表偏好位置。
        /// 这里只写内存缓存，玩家重启游戏后不会恢复该选择。
        /// </summary>
        public void SetRecordForChapter(ChapterSelectionUnit chapter, SongItemData song, int difficultyListIndex)
        {
            if (chapter == null || song == null)
            {
                return;
            }

            songSelectionRecords[chapter] = new SongSelectionRecord(song, difficultyListIndex);
        }
    }

    public class SongSelectionRecord
    {
        public SongItemData song;
        public int difficultyListIndex;

        /// <summary>
        /// 使用难度在歌曲列表中的位置构建缓存。
        /// 这是选曲 UI 的临时偏好，不等同于 DifficultyData.saveDifficultyId 的游戏记录稳定 ID。
        /// </summary>
        public SongSelectionRecord(SongItemData song, int difficultyListIndex)
        {
            this.song = song;
            this.difficultyListIndex = difficultyListIndex;
        }
        
        public SongSelectionRecord(SongItemData song, DifficultyData difficulty)
            : this(song, song?.difficultyDataList?.IndexOf(difficulty) ?? 0)
        {
        }
    }
}