using ProjectM.Simulation;
using Unity.Entities;
using UnityEngine;
using UnityEngine.UIElements;

namespace ProjectM.Client
{
    /// <summary>
    /// Drives the front-end main menu (UI Toolkit). Lives on a GameObject (with a <c>UIDocument</c>) in
    /// MainMenu.unity — build index 0. On <see cref="Awake"/> it ENSURES a default "menu" world exists (the
    /// bootstrap creates one on first boot, but on return-from-game <c>World.DisposeAllWorlds</c> left none and
    /// <c>Initialize</c> does not re-run), ensures the EventSystem, and assigns the shared PanelSettings; on
    /// enable it builds the menu. Single/Host/Join hand off to <see cref="WorldLauncher"/>.
    /// </summary>
    [RequireComponent(typeof(UIDocument))]
    public class MainMenuController : MonoBehaviour
    {
        UIDocument _doc;
        VisualElement _mainPanel;
        VisualElement _settingsPanel;
        VisualElement _howToPanel;
        TextField _ipField;
        Label _classLabel;
        bool _autoStarted;

        void Awake()
        {
            EnsureMenuWorld();
            MenuUi.EnsureEventSystem();
            _doc = GetComponent<UIDocument>();
            if (_doc.panelSettings == null)
                _doc.panelSettings = MenuUi.LoadPanelSettings();
            // The menu owns the cursor.
            UnityEngine.Cursor.lockState = CursorLockMode.None;
            UnityEngine.Cursor.visible = true;
            _autoStarted = TryAutoStartFromCommandLine();
        }

        void OnEnable()
        {
            if (_autoStarted) return; // headless CLI co-op session; don't build the menu UI
            if (_doc == null) _doc = GetComponent<UIDocument>();
            var root = _doc.rootVisualElement;
            if (root == null) return;
            root.Clear();
            BuildMain(root);
        }

        /// <summary>
        /// Dev/automation hook: a player launched with <c>-mhost</c> auto-hosts; <c>-mjoin &lt;ip&gt;</c> auto-joins
        /// (ip optional, defaults to loopback). Lets two standalone builds form a co-op session headlessly for
        /// testing — the same <see cref="WorldLauncher.StartSession"/> path the menu buttons use, no UI clicks.
        /// No effect when neither arg is present. Returns true if a session was started.
        /// </summary>
        static bool TryAutoStartFromCommandLine()
        {
            var args = System.Environment.GetCommandLineArgs();
            for (int i = 0; i < args.Length; i++)
            {
                if (args[i] == "-mhost") { WorldLauncher.StartSession(SessionMode.Host, "", false); return true; }
                if (args[i] == "-mjoin")
                {
                    string ip = (i + 1 < args.Length && !args[i + 1].StartsWith("-")) ? args[i + 1] : "127.0.0.1";
                    WorldLauncher.StartSession(SessionMode.Join, ip, false);
                    return true;
                }
            }
            return false;
        }

        static void EnsureMenuWorld()
        {
            var w = World.DefaultGameObjectInjectionWorld;
            if (w == null || !w.IsCreated)
                DefaultWorldInitialization.Initialize("MenuWorld", false);
        }

        void BuildMain(VisualElement root)
        {
            _mainPanel = MenuUi.FullScreenRoot(true);
            var card = MenuUi.Card("LANTERN");
            card.Add(MenuUi.Caption("Light is territory — co-op descent"));
            // Why the last session ended (connection watchdog / bad join address) — shown once, then cleared.
            if (!string.IsNullOrEmpty(SessionEnd.Reason))
            {
                var reason = MenuUi.Caption(SessionEnd.Reason);
                reason.style.color = new Color(1f, 0.55f, 0.35f);
                reason.style.whiteSpace = WhiteSpace.Normal;
                reason.style.maxWidth = 340;
                SessionEnd.Reason = null;
                card.Add(reason);
            }

            // Slice 2: class picker -> sets WorldLauncher.SelectedClass for the next session (Bathynaut melee / Harpooner ranged).
            _classLabel = new Label(ClassName(WorldLauncher.SelectedClass));
            _classLabel.style.unityTextAlign = TextAnchor.MiddleCenter;
            _classLabel.style.marginTop = 6; _classLabel.style.marginBottom = 2;
            card.Add(_classLabel);
            var classRow = new VisualElement();
            classRow.style.flexDirection = FlexDirection.Row;
            classRow.style.justifyContent = Justify.Center;
            classRow.Add(MenuUi.Button("Bathynaut", () => SelectClass((byte)FrameKind.Bathynaut)));
            classRow.Add(MenuUi.Button("Harpooner", () => SelectClass((byte)FrameKind.Harpooner)));
            card.Add(classRow);

            card.Add(MenuUi.Button("Single Player", () => Launch(SessionMode.Single, false)));

            if (SaveService.HasSave())
                card.Add(MenuUi.Button("Continue", () => Launch(SessionMode.Single, true)));

            card.Add(MenuUi.Button("Host Co-op (LAN)", () => Launch(SessionMode.Host, SaveService.HasSave())));

            _ipField = new TextField("Join IP") { value = "127.0.0.1" };
            _ipField.style.marginTop = 8;
            card.Add(_ipField);
            card.Add(MenuUi.Button("Join", () => Launch(SessionMode.Join, false)));

            card.Add(MenuUi.Button("Settings", ShowSettings));
            card.Add(MenuUi.Button("How to Play", ShowHowToPlay));

            // 2026-08-07 audit purge: the "Replay Tutorial" button re-armed first-run coach-marks whose system
            // DR-051 deleted — it wrote OnboardingMask/TutorialHints that nothing reads. Removed rather than left
            // as a button that visibly does nothing. The How-to-Play card above is the real reference.

            card.Add(MenuUi.Button("Quit", Quit));

            _mainPanel.Add(card);
            root.Add(_mainPanel);
        }

        void Launch(SessionMode mode, bool loadSave)
        {
            string ip = _ipField != null ? _ipField.value : "127.0.0.1";
            WorldLauncher.StartSession(mode, ip, loadSave);
        }

        void SelectClass(byte classId)
        {
            WorldLauncher.SelectedClass = classId;
            if (_classLabel != null) _classLabel.text = ClassName(classId);
        }

        static string ClassName(byte classId) => classId == (byte)FrameKind.Harpooner ? "CLASS:  Harpooner (ranged)" : "CLASS:  Bathynaut (melee)";

        void ShowSettings()
        {
            _mainPanel.style.display = DisplayStyle.None;
            _settingsPanel = SettingsScreen.Build(HideSettings);
            _doc.rootVisualElement.Add(_settingsPanel);
        }

        void HideSettings()
        {
            if (_settingsPanel != null) { _settingsPanel.RemoveFromHierarchy(); _settingsPanel = null; }
            _mainPanel.style.display = DisplayStyle.Flex;
        }

        void ShowHowToPlay()
        {
            _mainPanel.style.display = DisplayStyle.None;
            _howToPanel = HowToPlayPanel.Build(HideHowToPlay);
            _doc.rootVisualElement.Add(_howToPanel);
        }

        void HideHowToPlay()
        {
            if (_howToPanel != null) { _howToPanel.RemoveFromHierarchy(); _howToPanel = null; }
            _mainPanel.style.display = DisplayStyle.Flex;
        }

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