// Assets/_Project/Scripts/UI/MainMenuController.cs
using Unity.Netcode;
using UnityEngine;
using UnityEngine.UIElements;
using TD.Net;

namespace TD.UI
{
    /// <summary>
    /// Drives the main menu UI. Requires a <see cref="UIDocument"/> on the same
    /// GameObject. Builds the UI programmatically — no UXML needed for v1.
    /// </summary>
    /// <remarks>
    /// <para><b>Buttons.</b>
    /// <list type="bullet">
    ///   <item><b>Host</b> — calls <see cref="NetworkBootstrap.StartHost"/> on
    ///         the default port, then NGO scene-loads the Lobby. Clients that
    ///         join later get pulled into whatever scene the server is in.</item>
    ///   <item><b>Join</b> — reveals IP + port fields, then calls
    ///         <see cref="NetworkBootstrap.StartClient"/>. The server will pull
    ///         the client into the current networked scene (Lobby or Match)
    ///         once the connection completes.</item>
    ///   <item><b>Quit</b> — Application.Quit (no-op in the editor).</item>
    /// </list></para>
    ///
    /// <para><b>Future Steam integration.</b> A lobby-browser panel will be
    /// added here. The Host button will create a Steam lobby instead of a
    /// direct-IP host; Join becomes "browse public lobbies" + "accept friend
    /// invite". See Project_Roadmap.md §1.7-Future Steam Lobby Migration.</para>
    /// </remarks>
    [RequireComponent(typeof(UIDocument))]
    public class MainMenuController : MonoBehaviour
    {
        // ----- Inspector --------------------------------------------------

        [Tooltip("Default port shown in the Join field and used by the Host button.")]
        [SerializeField] private ushort defaultPort = NetworkBootstrap.DefaultPort;

        [Tooltip("Default address pre-filled in the Join field for solo testing.")]
        [SerializeField] private string defaultJoinAddress = NetworkBootstrap.DefaultConnectAddress;

        // ----- Cached UI elements -----------------------------------------

        private Button        hostButton;
        private Button        joinButton;
        private Button        quitButton;
        private VisualElement joinPanel;
        private TextField     joinAddressField;
        private TextField     joinPortField;
        private Button        joinConfirmButton;
        private Button        joinCancelButton;
        private Label         statusLabel;

        // ----- Lifecycle --------------------------------------------------

        private void Start()
        {
            // UIDocument creates its panel in OnEnable, which runs after Awake.
            // Start is the safe time to access rootVisualElement.
            var doc = GetComponent<UIDocument>();
            var root = doc?.rootVisualElement;
            if (root == null)
            {
                Debug.LogError("[MainMenuController] rootVisualElement is null. " +
                               "Check the UIDocument's Panel Settings.");
                return;
            }

            BuildUI(root);
        }

        // ----- UI construction --------------------------------------------

        private void BuildUI(VisualElement root)
        {
            // Centered vertical stack on a dark background.
            root.style.flexDirection    = FlexDirection.Column;
            root.style.justifyContent   = Justify.Center;
            root.style.alignItems       = Align.Center;
            root.style.backgroundColor  = new Color(0.05f, 0.05f, 0.08f, 1f);
            // The UIDocument root needs explicit width/height to fill the screen.
            root.style.width  = Length.Percent(100);
            root.style.height = Length.Percent(100);

            // Title.
            var title = new Label("Unity Tower Defense");
            title.style.fontSize         = 48;
            title.style.color            = Color.white;
            title.style.unityFontStyleAndWeight = FontStyle.Bold;
            title.style.marginBottom     = 60;
            root.Add(title);

            // Primary button column.
            var buttonColumn = new VisualElement();
            buttonColumn.style.flexDirection = FlexDirection.Column;
            buttonColumn.style.alignItems    = Align.Center;
            root.Add(buttonColumn);

            hostButton = MakeMenuButton("Host Game", OnHostClicked);
            joinButton = MakeMenuButton("Join Game", OnJoinClicked);
            quitButton = MakeMenuButton("Quit",       OnQuitClicked);
            buttonColumn.Add(hostButton);
            buttonColumn.Add(joinButton);
            buttonColumn.Add(quitButton);

            // Join sub-panel — hidden until Join is clicked. Holds the IP+port
            // fields and the Connect / Cancel buttons.
            joinPanel = new VisualElement();
            joinPanel.style.flexDirection   = FlexDirection.Column;
            joinPanel.style.alignItems      = Align.Center;
            joinPanel.style.marginTop       = 24;
            joinPanel.style.paddingTop      = 16;
            joinPanel.style.paddingBottom   = 16;
            joinPanel.style.paddingLeft     = 24;
            joinPanel.style.paddingRight    = 24;
            joinPanel.style.backgroundColor = new Color(0f, 0f, 0f, 0.4f);
            joinPanel.style.display         = DisplayStyle.None;
            root.Add(joinPanel);

            joinAddressField = new TextField("Host address");
            joinAddressField.value           = defaultJoinAddress;
            joinAddressField.style.width     = 280;
            joinAddressField.style.color     = Color.white;
            joinPanel.Add(joinAddressField);

            joinPortField = new TextField("Port");
            joinPortField.value              = defaultPort.ToString();
            joinPortField.style.width        = 280;
            joinPortField.style.marginTop    = 8;
            joinPortField.style.color        = Color.white;
            joinPanel.Add(joinPortField);

            var joinButtons = new VisualElement();
            joinButtons.style.flexDirection = FlexDirection.Row;
            joinButtons.style.marginTop     = 12;
            joinPanel.Add(joinButtons);

            joinConfirmButton = new Button(OnJoinConfirmClicked) { text = "Connect" };
            joinConfirmButton.style.minWidth     = 120;
            joinConfirmButton.style.height       = 32;
            joinConfirmButton.style.marginRight  = 8;
            joinButtons.Add(joinConfirmButton);

            joinCancelButton = new Button(OnJoinCancelClicked) { text = "Cancel" };
            joinCancelButton.style.minWidth      = 120;
            joinCancelButton.style.height        = 32;
            joinButtons.Add(joinCancelButton);

            // Status line at the bottom for connection feedback.
            statusLabel = new Label(string.Empty);
            statusLabel.style.color       = new Color(1f, 0.6f, 0.3f);
            statusLabel.style.marginTop   = 32;
            statusLabel.style.minHeight   = 20;
            root.Add(statusLabel);
        }

        private static Button MakeMenuButton(string text, System.Action onClick)
        {
            var btn = new Button(() => onClick?.Invoke()) { text = text };
            btn.style.minWidth     = 240;
            btn.style.height       = 48;
            btn.style.fontSize     = 20;
            btn.style.marginBottom = 8;
            return btn;
        }

        // ----- Button handlers --------------------------------------------

        private void OnHostClicked()
        {
            statusLabel.text = "Starting host…";
            if (!NetworkBootstrap.StartHost(defaultPort))
            {
                statusLabel.text = "Failed to start host. Check the console.";
                return;
            }

            // After StartHost the local peer is the server + client. Trigger
            // the networked scene load to take everyone to the Lobby. NGO
            // replicates this to any future-joining clients automatically.
            NetworkBootstrap.LoadSceneAsHost(SceneNames.Lobby);
        }

        private void OnJoinClicked()
        {
            // Toggle the join sub-panel.
            joinPanel.style.display = joinPanel.style.display == DisplayStyle.None
                ? DisplayStyle.Flex
                : DisplayStyle.None;
        }

        private void OnJoinConfirmClicked()
        {
            string address = string.IsNullOrWhiteSpace(joinAddressField.value)
                ? defaultJoinAddress
                : joinAddressField.value.Trim();

            ushort port = defaultPort;
            if (!string.IsNullOrWhiteSpace(joinPortField.value)
                && ushort.TryParse(joinPortField.value.Trim(), out var parsed))
            {
                port = parsed;
            }

            statusLabel.text = $"Connecting to {address}:{port}…";
            if (!NetworkBootstrap.StartClient(address, port))
            {
                statusLabel.text = "Failed to start client. Check the console.";
                return;
            }

            // The server's NGO SceneManager will pull this client into whatever
            // scene the server is in (Lobby or Match) once the connection
            // completes. SessionFlow handles disconnect recovery.
            joinPanel.style.display = DisplayStyle.None;
        }

        private void OnJoinCancelClicked()
        {
            joinPanel.style.display = DisplayStyle.None;
            statusLabel.text = string.Empty;
        }

        private void OnQuitClicked()
        {
#if UNITY_EDITOR
            UnityEditor.EditorApplication.isPlaying = false;
#else
            Application.Quit();
#endif
        }
    }
}