using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;
#if ENABLE_INPUT_SYSTEM
using UnityEngine.InputSystem;
#endif

/// <summary>
/// uGUI binding for <see cref="OnlineSessionManager"/>. Drives the server-browser canvas - Host / Refresh /
/// pick a row / Join / Disconnect plus a status line - and mirrors the manager's state through its
/// <see cref="OnlineSessionManager.Changed"/> / <see cref="OnlineSessionManager.SessionsChanged"/> events.
/// Replaces the old IMGUI browser. Lives on the browser canvas; the session logic stays on the
/// NetworkManager's <see cref="OnlineSessionManager"/>.
///
/// Selection model: Refresh fills the list with clones of <see cref="entryTemplate"/> (each a clickable row
/// showing name + player count). Clicking a row selects it; Join connects to the selected session. While
/// connected, only Disconnect is interactable.
///
/// Overlay behaviour: the panel is always shown in Main (not connected). Once a connection is up it hides;
/// in the lobby/map Esc toggles it back as a modal pause overlay (cursor freed, local gameplay suspended via
/// <see cref="GameModeManager.SetPaused"/>). On the map the Disconnect button becomes "Back to Lobby" for the
/// match authority (ends the match), while everyone else (in the lobby, or a non-authority client on the map)
/// gets a plain disconnect. Only the visual <see cref="panelRoot"/> is toggled - this binder stays alive on
/// its (always-active) canvas so it keeps reading Esc while the panel is hidden.
/// </summary>
public class OnlineSessionBrowserUI : MonoBehaviour
{
    [SerializeField] private OnlineSessionManager manager;

    [Header("Buttons")]
    [SerializeField] private Button hostButton;
    [SerializeField] private Button refreshButton;
    [SerializeField] private Button joinButton;
    [SerializeField] private Button disconnectButton;

    [Header("List")]
    [Tooltip("Content RectTransform of the session ScrollRect (rows are added here).")]
    [SerializeField] private RectTransform listContent;
    [Tooltip("A row prototype kept disabled; cloned once per session. Children named 'Name' and 'Players' carry the text.")]
    [SerializeField] private GameObject entryTemplate;

    [Header("Status")]
    [SerializeField] private TMP_Text statusLabel;

    [Header("Overlay")]
    [Tooltip("Visual container toggled by Esc while connected (the panel root). Must be a CHILD of this " +
             "binder's object so the binder keeps running - and reading Esc - while the panel is hidden.")]
    [SerializeField] private GameObject panelRoot;

    [Tooltip("Background tint of the selected row.")]
    [SerializeField] private Color selectedTint = new Color(0.26f, 0.52f, 0.96f, 1f);
    [Tooltip("Background tint of an unselected row.")]
    [SerializeField] private Color normalTint = new Color(1f, 1f, 1f, 0.05f);

    private struct Row { public string id; public Image image; public GameObject go; }
    private readonly List<Row> _rows = new List<Row>();
    private string _selectedId;

    private MatchManager _match;          // local match state (scene kind + authority); found at runtime
    private GameModeManager _gameMode;    // pause hook for the modal overlay; found at runtime
    private TMP_Text _disconnectLabel;    // disconnect button caption (relabelled to "Back to Lobby")

    private bool _open;                   // Esc-toggled visibility while connected
    private bool _connected;              // last-seen connection state (to detect transitions)
    private string _lastScene;            // last-seen active scene name (to auto-close on a scene change)
    private string _disconnectText;       // last applied caption (avoids per-frame TMP churn)

    private void Awake()
    {
        // The template is the prototype, never shown itself - layout ignores it while disabled.
        if (entryTemplate) entryTemplate.SetActive(false);

        _match = FindFirstObjectByType<MatchManager>();
        _gameMode = FindFirstObjectByType<GameModeManager>();
    }

    private void OnEnable()
    {
        if (hostButton) hostButton.onClick.AddListener(OnHost);
        if (refreshButton) refreshButton.onClick.AddListener(OnRefresh);
        if (joinButton) joinButton.onClick.AddListener(OnJoin);
        if (disconnectButton)
        {
            disconnectButton.onClick.AddListener(OnDisconnect);
            _disconnectLabel = disconnectButton.GetComponentInChildren<TMP_Text>(true);
        }

        if (manager)
        {
            manager.Changed += OnManagerChanged;
            manager.SessionsChanged += RebuildList;
        }

        _connected = manager && manager.IsConnected;
        RebuildList();
        OnManagerChanged();
        ApplyVisibility();
    }

    private void OnDisable()
    {
        if (hostButton) hostButton.onClick.RemoveListener(OnHost);
        if (refreshButton) refreshButton.onClick.RemoveListener(OnRefresh);
        if (joinButton) joinButton.onClick.RemoveListener(OnJoin);
        if (disconnectButton) disconnectButton.onClick.RemoveListener(OnDisconnect);

        if (manager)
        {
            manager.Changed -= OnManagerChanged;
            manager.SessionsChanged -= RebuildList;
        }
    }

    private void Update()
    {
        if (!manager) return;
        bool connected = manager.IsConnected;

        // Auto-close the overlay if the scene changed underneath it (a remote ended/started the match, or
        // we walked into Start Match) so it never lingers as a stale pause across a transition.
        string scene = SceneManager.GetActiveScene().name;
        if (connected && _open && _lastScene != null && scene != _lastScene)
            SetOpen(false);
        _lastScene = scene;

        if (!connected) return;                                   // Main: panel always shown, Esc ignored

        bool inLobbyOrMap = _match && (_match.IsLocalSceneLobby || _match.IsLocalSceneMap);
        if (inLobbyOrMap && EscapePressed())
            SetOpen(!_open);

        RefreshDisconnectLabel();
    }

    private void OnHost() { if (manager) manager.Host(); }
    private void OnRefresh() { if (manager) manager.Refresh(); }
    private void OnJoin() { if (manager && !string.IsNullOrEmpty(_selectedId)) manager.Join(_selectedId); }

    private void OnDisconnect()
    {
        if (!manager) return;

        // On the map, the match AUTHORITY's button means "Back to Lobby" (end the match for everyone)
        // rather than leaving the session. Everyone else - in the lobby, or a non-authority client on the
        // map - does a plain disconnect.
        if (_match && _match.IsLocalSceneMap && _match.IsLocalMatchAuthority)
        {
            _match.RequestEndMatch();
            SetOpen(false);            // heading back to the lobby; close the overlay + resume input
            return;
        }

        manager.Disconnect();
    }

    private void OnManagerChanged()
    {
        if (!manager) return;

        bool connected = manager.IsConnected;
        if (connected != _connected)
        {
            _connected = connected;
            // Connection up (hosted/joined) -> hide the panel; Esc reopens it in the lobby/map.
            // Back to Main (disconnect/shutdown) -> show it again and drop any pause.
            _open = false;
            if (!connected && _gameMode) _gameMode.SetPaused(false);
            ApplyVisibility();
        }

        if (statusLabel) statusLabel.text = manager.Status;
        UpdateButtons();
        RefreshDisconnectLabel();
    }

    private void SetOpen(bool open)
    {
        _open = open;
        ApplyVisibility();
        if (_gameMode) _gameMode.SetPaused(open);
    }

    private void ApplyVisibility()
    {
        bool show = !(manager && manager.IsConnected) || _open;
        if (panelRoot && panelRoot.activeSelf != show)
            panelRoot.SetActive(show);
    }

    private void RefreshDisconnectLabel()
    {
        if (!_disconnectLabel) return;
        bool backToLobby = _match && _match.IsLocalSceneMap && _match.IsLocalMatchAuthority;
        string text = backToLobby ? "Back to Lobby" : "Disconnect";
        if (text != _disconnectText)
        {
            _disconnectText = text;
            _disconnectLabel.text = text;
        }
    }

    private void UpdateButtons()
    {
        if (!manager) return;
        bool busy = manager.IsBusy;
        bool connected = manager.IsConnected;
        bool hasSelection = !string.IsNullOrEmpty(_selectedId);

        if (hostButton) hostButton.interactable = !busy && !connected;
        if (refreshButton) refreshButton.interactable = !busy && !connected;
        if (joinButton) joinButton.interactable = !busy && !connected && hasSelection;
        if (disconnectButton) disconnectButton.interactable = !busy && connected;
    }

    private void RebuildList()
    {
        for (int i = 0; i < _rows.Count; i++)
            if (_rows[i].go) Destroy(_rows[i].go);
        _rows.Clear();

        if (manager && entryTemplate && listContent)
        {
            var sessions = manager.Sessions;
            bool selectionStillPresent = false;

            for (int i = 0; i < sessions.Count; i++)
            {
                var s = sessions[i];
                var go = Instantiate(entryTemplate, listContent);
                go.SetActive(true);

                var nameText = FindText(go.transform, "Name");
                if (nameText) nameText.text = s.Name;

                var playersText = FindText(go.transform, "Players");
                if (playersText)
                {
                    int taken = Mathf.Max(0, s.MaxPlayers - s.AvailableSlots);
                    playersText.text = $"{taken}/{s.MaxPlayers}";
                }

                string id = s.Id;                       // capture per-row for the click closure
                var button = go.GetComponent<Button>();
                if (button) button.onClick.AddListener(() => Select(id));

                _rows.Add(new Row { id = id, image = go.GetComponent<Image>(), go = go });
                if (id == _selectedId) selectionStillPresent = true;
            }

            if (!selectionStillPresent) _selectedId = null;
        }

        ApplyTints();
        UpdateButtons();
    }

    private void Select(string id)
    {
        _selectedId = id;
        ApplyTints();
        UpdateButtons();
    }

    private void ApplyTints()
    {
        for (int i = 0; i < _rows.Count; i++)
            if (_rows[i].image)
                _rows[i].image.color = _rows[i].id == _selectedId ? selectedTint : normalTint;
    }

    private static TMP_Text FindText(Transform root, string childName)
    {
        var t = root.Find(childName);
        return t ? t.GetComponent<TMP_Text>() : null;
    }

    private static bool EscapePressed()
    {
#if ENABLE_INPUT_SYSTEM
        return Keyboard.current != null && Keyboard.current.escapeKey.wasPressedThisFrame;
#else
        return Input.GetKeyDown(KeyCode.Escape);
#endif
    }
}