// Assets/_Project/Scripts/UI/HUDController.cs
using System.Collections;
using UnityEngine;
using UnityEngine.UIElements;
using TD.Gameplay;
using TD.Towers;
using TD.UI.Minimap;

namespace TD.UI
{
    /// <summary>
    /// Drives the in-match HUD. Requires a UIDocument on the same GameObject.
    /// Wires gold display, tower command grid, tooltip, rejection messages,
    /// and minimap RenderTexture to their UI Toolkit counterparts.
    /// </summary>
    [RequireComponent(typeof(UIDocument))]
    public class HUDController : MonoBehaviour
    {
        // ----- Inspector --------------------------------------------------

        [Header("Scene References")]
        [Tooltip("The local client's TowerPlacementController.")]
        [SerializeField] private TowerPlacementController placementController;

        [Tooltip("The TowerPlacementManager NetworkObject in the scene.")]
        [SerializeField] private TowerPlacementManager placementManager;

        [Tooltip("The local client's CameraController. Used by the minimap for click-to-jump " +
                 "and drag-to-pan.")]
        [SerializeField] private CameraController cameraController;

        [Header("Settings")]
        [SerializeField] private float rejectionMessageDuration = 2.5f;

        // ----- Cached UI element references -------------------------------

        private Label goldLabel;
        private Label waveLabel;
        private Label portraitName;
        private VisualElement commandGrid;
        private Label ttTitle;
        private Label ttDesc;
        private Label ttStats;
        private Label ttCost;
        private Label rejectionLabel;

        // ----- State ------------------------------------------------------

        private Coroutine rejectionFadeCoroutine;
        private bool gridPopulated;
        private bool uiInitialized;
        private MinimapView minimapView;
        private IPanel myPanel;   // tracked separately so OnDestroy only clears the static if it still points at us

        // ----- Static hit-test probe --------------------------------------

        // Set when InitializeUI succeeds; cleared on OnDestroy. Non-UI systems (camera,
        // input handlers) can query IsPointerOverInteractiveHud without taking a direct
        // reference to HUDController.
        private static IPanel s_hudPanel;

        /// <summary>
        /// True if <paramref name="screenMousePos"/> falls over an interactive (non-ignore)
        /// HUD element. Non-UI systems that consume mouse input (camera scroll-zoom, edge-pan)
        /// should gate their handling on this so a cursor over the minimap, command grid, or
        /// any other interactive HUD region doesn't drive both the HUD and the world at once.
        /// </summary>
        /// <remarks>
        /// Convention: <paramref name="screenMousePos"/> uses Unity Input System screen coords
        /// (origin bottom-left, y up). Returns false before the HUD has initialized; safe to
        /// call from any system at any time.
        /// </remarks>
        public static bool IsPointerOverInteractiveHud(Vector2 screenMousePos)
        {
            if (s_hudPanel == null) return false;

            // Coord convention rabbit hole:
            //   - Screen mouse position: origin bottom-left, y up (Unity Input System).
            //   - UI Toolkit panel coords: origin top-left, y down.
            //
            // RuntimePanelUtils.ScreenToPanel converts the SCALE (e.g., reference resolution
            // vs. actual resolution) but does NOT flip Y. We flip manually using the visual
            // tree's height so the result works regardless of PanelSettings scale mode.
            //
            // Subtle: visualTree.worldBound height may be 0 for one frame on the very first
            // layout pass. The caller (CameraController) checks the result against "is over
            // interactive HUD"; a one-frame false positive (camera zooms when it shouldn't)
            // is harmless and self-corrects the next frame.
            Vector2 scaled = RuntimePanelUtils.ScreenToPanel(s_hudPanel, screenMousePos);
            float panelHeight = s_hudPanel.visualTree.worldBound.height;
            Vector2 panelPos = new Vector2(scaled.x, panelHeight - scaled.y);

            // panel.Pick returns null when the topmost element under the point has
            // PickingMode.Ignore (or there's no element there at all). Non-null means an
            // interactive HUD element is under the cursor.
            return s_hudPanel.Pick(panelPos) != null;
        }

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

        private void Start()
        {
            // UIDocument creates its panel in OnEnable, which runs after all
            // Awake() calls. Accessing rootVisualElement in Awake() is too early.
            // Start() is safe because all OnEnable() calls have completed by then.
            InitializeUI();
            TryPopulateCommandGrid();
        }

        private void InitializeUI()
        {
            var doc = GetComponent<UIDocument>();
            if (doc == null)
            {
                Debug.LogError("[HUDController] No UIDocument component found.");
                return;
            }

            var root = doc.rootVisualElement;
            if (root == null)
            {
                Debug.LogError("[HUDController] rootVisualElement is null. " +
                               "Check that Panel Settings and Source Asset are assigned.");
                return;
            }

            // Cache element references — log a warning for any that are missing
            // so UXML/USS mismatches surface immediately.
            goldLabel      = Require<Label>(root, "gold-label");
            waveLabel      = Require<Label>(root, "wave-label");
            portraitName   = Require<Label>(root, "portrait-name");
            commandGrid    = Require<VisualElement>(root, "command-grid");
            ttTitle        = Require<Label>(root, "tt-title");
            ttDesc         = Require<Label>(root, "tt-desc");
            ttStats        = Require<Label>(root, "tt-stats");
            ttCost         = Require<Label>(root, "tt-cost");
            rejectionLabel = Require<Label>(root, "rejection-label");

            // Map area and its transparent ancestors must not consume pointer
            // events so clicks reach the 3D scene underneath.
            SetPickIgnore(root, "hud-root");
            SetPickIgnore(root, "main-area");
            SetPickIgnore(root, "map-area");
            if (rejectionLabel != null)
                rejectionLabel.pickingMode = PickingMode.Ignore;

            // Upgrade/sell have no backing system yet.
            SetEnabled(root, "upgrade-btn", false);
            SetEnabled(root, "sell-btn",    false);

            // Minimap. The MinimapView owns the two sub-elements (terrain + entity overlay)
            // and drives them; we just hand it the host container and the camera controller.
            // Bake is deferred until LevelLoader is ready — view tries each frame in Tick().
            var minimapContainer = root.Q<VisualElement>("minimap");
            if (minimapContainer != null)
            {
                if (cameraController == null)
                    Debug.LogWarning("[HUDController] cameraController not assigned. " +
                                     "Click-to-jump and drag-to-pan on the minimap will be disabled.");
                minimapView = new MinimapView(minimapContainer, cameraController);
            }

            // Publish the panel so non-UI systems can query "is pointer over the HUD".
            // Stored on `myPanel` too so OnDestroy only clears the static if it still
            // points at this instance (defensive against re-creation overlap).
            myPanel = root.panel;
            s_hudPanel = myPanel;

            uiInitialized = true;
        }

        private void OnEnable()
        {
            TowerPlacementController.OnRejectionMessageReady += ShowRejectionMessage;
        }

        private void OnDisable()
        {
            TowerPlacementController.OnRejectionMessageReady -= ShowRejectionMessage;
        }

        private void Update()
        {
            if (!uiInitialized) return;

            if (!gridPopulated)
                TryPopulateCommandGrid();

            RefreshGoldDisplay();
            minimapView?.Tick();
        }

        private void OnDestroy()
        {
            minimapView?.Dispose();
            minimapView = null;

            if (s_hudPanel != null && s_hudPanel == myPanel)
                s_hudPanel = null;
            myPanel = null;
        }

        // ----- Gold display -----------------------------------------------

        private void RefreshGoldDisplay()
        {
            if (goldLabel == null) return;
            var gm = PlayerGoldManager.Local;
            goldLabel.text = gm != null ? $"{gm.CurrentGold:N0} g" : "-- g";
        }

        // ----- Command grid -----------------------------------------------

        private void TryPopulateCommandGrid()
        {
            if (commandGrid == null) return;

            if (placementManager == null)
                placementManager = TowerPlacementManager.Instance;

            if (placementManager == null) return;   // not spawned yet — retry next frame

            commandGrid.Clear();

            const int COLS = 4;
            const int ROWS = 3;
            const int MAX  = COLS * ROWS;

            var defs = new System.Collections.Generic.List<(TowerDefinition def, int typeId)>();
            foreach (var entry in placementManager.GetAvailableDefinitions())
            {
                defs.Add(entry);
                if (defs.Count >= MAX) break;
            }

            for (int row = 0; row < ROWS; row++)
            {
                var rowEl = new VisualElement();
                rowEl.AddToClassList("cmd-row");

                for (int col = 0; col < COLS; col++)
                {
                    int index = row * COLS + col;
                    VisualElement btn = index < defs.Count
                        ? CreateTowerButton(defs[index].def, defs[index].typeId)
                        : CreateEmptySlot();
                    rowEl.Add(btn);
                }

                commandGrid.Add(rowEl);
            }

            gridPopulated = true;
        }

        private VisualElement CreateTowerButton(TowerDefinition def, int typeId)
        {
            var btn = new Button(() =>
            {
                if (placementController != null)
                    placementController.BeginPlacement(def, typeId);
                else
                    Debug.LogWarning("[HUDController] No TowerPlacementController assigned.");
            });

            btn.AddToClassList("cmd-btn");

            // Icon placeholder — swap for background-image on btn when art exists.
            var iconPlaceholder = new VisualElement();
            iconPlaceholder.AddToClassList("cmd-icon-placeholder");
            iconPlaceholder.pickingMode = PickingMode.Ignore;

            var costLabel = new Label($"{def.GoldCost}g");
            costLabel.AddToClassList("cmd-cost");
            costLabel.pickingMode = PickingMode.Ignore;

            btn.Add(iconPlaceholder);
            btn.Add(costLabel);

            btn.RegisterCallback<MouseEnterEvent>(_ => ShowTooltip(def));
            btn.RegisterCallback<MouseLeaveEvent>(_ => ClearTooltip());

            return btn;
        }

        private static VisualElement CreateEmptySlot()
        {
            var slot = new VisualElement();
            slot.AddToClassList("cmd-btn");
            slot.AddToClassList("empty-slot");
            slot.pickingMode = PickingMode.Ignore;
            return slot;
        }

        // ----- Portrait / selection context ----------------------------------

        /// <summary>
        /// Called by the selection system when a unit is selected or deselected.
        /// Pass null or empty to clear (nothing selected).
        /// </summary>
        public void SetSelectedUnitName(string unitName)
        {
            if (portraitName == null) return;
            portraitName.text = string.IsNullOrEmpty(unitName) ? "" : unitName;
        }

        // ----- Tooltip ----------------------------------------------------

        private void ShowTooltip(TowerDefinition def)
        {
            if (ttTitle == null) return;

            ttTitle.text = def.DisplayName;
            ttDesc.text  = def.Description ?? "";

            if (def.Damage > 0 || def.Range > 0)
            {
                ttStats.text = $"DMG: {def.Damage}  ·  Range: {def.Range:0}";
                if (def.FireRate > 0)
                    ttStats.text += $"\nFire rate: {def.FireRate:0.0}/s";
                if (def.SlowFactor < 1f)
                    ttStats.text += $"\nSlow: {(1f - def.SlowFactor) * 100f:0}%";
            }
            else
            {
                ttStats.text = "(stats pending)";
            }

            int sellValue = Mathf.RoundToInt(def.GoldCost * 0.7f);
            ttCost.text = $"Cost: {def.GoldCost}g  ·  Sell: {sellValue}g";
        }

        private void ClearTooltip()
        {
            if (ttTitle == null) return;
            ttTitle.text = "";
            ttDesc.text  = "";
            ttStats.text = "";
            ttCost.text  = "";
        }

        // ----- Rejection messages -----------------------------------------

        private void ShowRejectionMessage(string message)
        {
            if (rejectionLabel == null) return;

            rejectionLabel.text = message;
            rejectionLabel.style.display = DisplayStyle.Flex;

            if (rejectionFadeCoroutine != null)
                StopCoroutine(rejectionFadeCoroutine);

            rejectionFadeCoroutine = StartCoroutine(HideRejectionAfterDelay());
        }

        private IEnumerator HideRejectionAfterDelay()
        {
            yield return new WaitForSeconds(rejectionMessageDuration);
            if (rejectionLabel != null)
                rejectionLabel.style.display = DisplayStyle.None;
            rejectionFadeCoroutine = null;
        }

        // ----- Helpers ----------------------------------------------------

        private static T Require<T>(VisualElement root, string name) where T : VisualElement
        {
            var el = root.Q<T>(name);
            if (el == null)
                Debug.LogWarning($"[HUDController] Element not found: '{name}' ({typeof(T).Name}). " +
                                 $"Check that the name matches the UXML.");
            return el;
        }

        private static void SetPickIgnore(VisualElement root, string name)
        {
            var el = root.Q<VisualElement>(name);
            if (el != null) el.pickingMode = PickingMode.Ignore;
        }

        private static void SetEnabled(VisualElement root, string name, bool enabled)
        {
            var el = root.Q<Button>(name);
            if (el != null) el.SetEnabled(enabled);
        }
    }
}