using System.Collections.Generic;
using System.IO;
using TMPro;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class SongSelectManager : MonoBehaviour
{
    [Header("탭 버튼")]
    [SerializeField] private Button tabAllBtn;
    [SerializeField] private Button tabOwnedBtn;
    [SerializeField] private Color  tabActiveColor   = Color.white;
    [SerializeField] private Color  tabInactiveColor = new Color(0.6f, 0.6f, 0.6f);

    [Header("카드 목록")]
    [SerializeField] private Transform  cardContainer;
    [SerializeField] private GameObject songCardPrefab;

    [Header("연결")]
    [SerializeField] private SongDetailPanel detailPanel;
    [SerializeField] private DownloadManager downloadManager;

    [Header("상태 오버레이")]
    [SerializeField] private GameObject loadingOverlay;
    [SerializeField] private GameObject errorOverlay;
    [SerializeField] private TMP_Text   errorText;

    private static string CachePath =>
        Path.Combine(Application.persistentDataPath, "songs_cache.json");

    private List<SongInfo> allSongs     = new List<SongInfo>();
    private bool           showingOwned = false;

    // ── Unity ────────────────────────────────────────────────

    private void Start()
    {
        tabAllBtn.onClick.AddListener(() => SwitchTab(false));
        tabOwnedBtn.onClick.AddListener(() => SwitchTab(true));

        detailPanel.gameObject.SetActive(false);
        SetTabVisual(false);
        FetchSongs();
    }

    // ── 탭 전환 ──────────────────────────────────────────────

    private void SwitchTab(bool owned)
    {
        showingOwned = owned;
        SetTabVisual(owned);
        RefreshCards();
    }

    private void SetTabVisual(bool owned)
    {
        tabAllBtn.image.color   = owned ? tabInactiveColor : tabActiveColor;
        tabOwnedBtn.image.color = owned ? tabActiveColor   : tabInactiveColor;
    }

    // ── 데이터 로드 ───────────────────────────────────────────

    private void FetchSongs()
    {
        loadingOverlay.SetActive(true);
        errorOverlay.SetActive(false);

        downloadManager.FetchSongsList(
            onSuccess: list =>
            {
                allSongs = list.songs;
                SaveCache(list);
                SongLibrary.Instance.ValidateWithFileSystem(downloadManager, list.songs);
                loadingOverlay.SetActive(false);
                RefreshCards();
            },
            onError: _ =>
            {
                SongsList cached = LoadCache();
                loadingOverlay.SetActive(false);

                if (cached != null)
                {
                    allSongs = cached.songs;
                    RefreshCards();
                }
                else
                {
                    errorOverlay.SetActive(true);
                    errorText.text = "서버 연결 실패\n인터넷 연결을 확인해주세요";
                }
            });
    }

    // ── 카드 갱신 ────────────────────────────────────────────

    public void RefreshCards()
    {
        foreach (Transform child in cardContainer)
            Destroy(child.gameObject);

        List<SongInfo> songs = showingOwned
            ? allSongs.FindAll(s => SongLibrary.Instance.IsSongDownloaded(s.id))
            : allSongs;

        foreach (SongInfo song in songs)
        {
            bool        downloaded = SongLibrary.Instance.IsSongDownloaded(song.id);
            GameObject  obj        = Instantiate(songCardPrefab, cardContainer);
            SongInfo    captured   = song;
            obj.GetComponent<SongCard>().Setup(song, downloaded, () => OnCardClicked(captured));
        }
    }

    private void OnCardClicked(SongInfo song)
    {
        detailPanel.gameObject.SetActive(true);
        detailPanel.Show(song, downloadManager, this);
    }

    // ── 로컬 캐시 (오프라인 폴백) ─────────────────────────────

    private static void SaveCache(SongsList list)
    {
        try { File.WriteAllText(CachePath, JsonUtility.ToJson(list, true)); }
        catch { }
    }

    private static SongsList LoadCache()
    {
        if (!File.Exists(CachePath)) return null;
        try { return JsonUtility.FromJson<SongsList>(File.ReadAllText(CachePath)); }
        catch { return null; }
    }
}