(Feat) Add build cost

Assets/GAME/Script/UI/CrosshairManager.cs

@@ -1,7 +1,9 @@
+using System.Collections.Generic;
 using DG.Tweening;
 using TMPro;
 using UnityEngine;
 using UnityEngine.UI;
+using Ashwild.Building;
 using Ashwild.Interaction;
 using Ashwild.Player;
 
@@ -39,6 +41,18 @@ namespace Ashwild.UI
         /// </summary>
         [SerializeField] private TMP_Text promptLabel;
 
+        [Header("Build Cost")]
+        /// <summary>
+        /// Container the per-resource cost entries are parented under while a build is being placed.
+        /// Its own layout (e.g. a HorizontalLayoutGroup) arranges them.
+        /// </summary>
+        [SerializeField] private RectTransform costHolder;
+
+        /// <summary>
+        /// Prefab instantiated once per cost line (icon + amount) into the holder. Pooled and reused.
+        /// </summary>
+        [SerializeField] private BuildCostEntryUI costEntryPrefab;
+
         [Header("States")]
         /// <summary>
         /// Look used when nothing is hovered (the plain dot).
@@ -101,6 +115,18 @@ namespace Ashwild.UI
         /// </summary>
         private string currentPrompt;
 
+        /// <summary>
+        /// True while a build's cost is displayed: the prompt label is suppressed and the holder takes
+        /// over, so a hovered interactable's prompt never fights the cost readout mid-placement.
+        /// </summary>
+        private bool isShowingCost;
+
+        /// <summary>
+        /// The instantiated cost entries, pooled and reused across placements — activated up to the
+        /// current cost's line count and hidden beyond it.
+        /// </summary>
+        private readonly List<BuildCostEntryUI> costEntries = new List<BuildCostEntryUI>();
+
         #endregion
 
         #region Unity Lifecycle
@@ -126,6 +152,7 @@ namespace Ashwild.UI
         private void OnEnable()
         {
             PlayerEvents.InteractableHoverChanged += HandleHoverChanged;
+            PlayerEvents.BuildCostChanged += HandleBuildCostChanged;
             ApplyState(idleState, isHover: false, animated: false);
             SetLabel(null, animated: false);
         }
@@ -136,6 +163,7 @@ namespace Ashwild.UI
         private void OnDisable()
         {
             PlayerEvents.InteractableHoverChanged -= HandleHoverChanged;
+            PlayerEvents.BuildCostChanged -= HandleBuildCostChanged;
         }
 
         /// <summary>
@@ -151,7 +179,7 @@ namespace Ashwild.UI
             if (prompt != currentPrompt)
             {
                 currentPrompt = prompt;
-                SetLabel(prompt, animated: true);
+                if (!isShowingCost) SetLabel(prompt, animated: true);
             }
         }
 
@@ -180,7 +208,24 @@ namespace Ashwild.UI
             currentPrompt = hovering ? target.InteractionPrompt : null;
 
             ApplyState(hovering ? hoverState : idleState, hovering, animated: true);
-            SetLabel(currentPrompt, animated: true);
+            if (!isShowingCost) SetLabel(currentPrompt, animated: true);
+        }
+
+        /// <summary>
+        /// Shows the active build's cost (hiding the prompt label and filling the holder) while placing,
+        /// or clears it and restores the normal prompt when the list is null/empty (placement ended).
+        /// </summary>
+        private void HandleBuildCostChanged(IReadOnlyList<BuildCostView> cost)
+        {
+            if (cost == null || cost.Count == 0)
+            {
+                ClearCost();
+                return;
+            }
+
+            isShowingCost = true;
+            SetLabel(null, animated: true);
+            PopulateCost(cost);
         }
 
         #endregion
@@ -243,6 +288,55 @@ namespace Ashwild.UI
                 a => promptLabel.alpha = a, target, labelFadeDuration);
         }
 
+        /// <summary>
+        /// Fills the holder with one entry per cost line, reusing pooled entries and only instantiating
+        /// when the current build needs more lines than any previous one. Entries beyond this build's
+        /// count are hidden. Logs and no-ops when the holder or prefab reference is missing.
+        /// </summary>
+        private void PopulateCost(IReadOnlyList<BuildCostView> cost)
+        {
+            if (costHolder == null || costEntryPrefab == null)
+            {
+                Debug.LogError("[CrosshairManager] Cost holder or entry prefab not assigned — cannot show the build cost.", this);
+                return;
+            }
+
+            for (int i = 0; i < cost.Count; i++)
+            {
+                BuildCostEntryUI entry;
+                if (i < costEntries.Count)
+                {
+                    entry = costEntries[i];
+                }
+                else
+                {
+                    entry = Instantiate(costEntryPrefab, costHolder);
+                    costEntries.Add(entry);
+                }
+
+                entry.gameObject.SetActive(true);
+                entry.Set(cost[i].Icon, cost[i].Owned, cost[i].Amount, cost[i].Affordable);
+            }
+
+            for (int i = cost.Count; i < costEntries.Count; i++)
+                if (costEntries[i] != null) costEntries[i].gameObject.SetActive(false);
+        }
+
+        /// <summary>
+        /// Hides every cost entry and restores the prompt for whatever is currently hovered. No-op when
+        /// no cost is being shown.
+        /// </summary>
+        private void ClearCost()
+        {
+            if (!isShowingCost) return;
+            isShowingCost = false;
+
+            for (int i = 0; i < costEntries.Count; i++)
+                if (costEntries[i] != null) costEntries[i].gameObject.SetActive(false);
+
+            SetLabel(currentPrompt, animated: true);
+        }
+
         /// <summary>
         /// Kills every cached tween so none survive a disable/destroy.
         /// </summary>