Initial commit

Assets/_Project/Scripts/Code/InteractionLayer/Interactors/SnapSystem.cs

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+using System.Collections.Generic;
+using UnityEngine;
+
+/// <summary>
+/// Handles socket proximity detection, highlighting, and closest-socket tracking.
+///
+/// Key fixes vs previous version:
+///   1. Searches from col.transform.ROOT — so if OverlapSphere hits a child mesh
+///      collider, we still find SocketPoints that are siblings of that mesh.
+///   2. Uses QueryTriggerInteraction.Collide — socket colliders are usually triggers;
+///      without this flag the overlap silently finds nothing when
+///      Physics.queriesHitTriggers is false in Project Settings.
+///   3. Deduplicates across colliders that share a root, so a multi-collider block
+///      doesn't add its sockets multiple times.
+/// </summary>
+public class SnapSystem : MonoBehaviour
+{
+    private static SnapSystem instance;
+    public static SnapSystem getInstance() => instance;
+
+    [SerializeField] private float socketDetectionRadius = 0.5f;
+
+    private readonly List<SocketPoint> nearbySockets = new List<SocketPoint>();
+    private readonly HashSet<Transform> visitedRoots = new HashSet<Transform>();
+    private SocketPoint closestSocket;
+
+    private void Awake()
+    {
+        if (instance == null) instance = this;
+        else Destroy(gameObject);
+    }
+
+    // -------------------------------------------------------------------------
+    // Public API
+    // -------------------------------------------------------------------------
+
+    /// <summary>
+    /// Re-scans for sockets around <paramref name="detectionPoint"/>.
+    /// Call every frame while a ghost is being dragged.
+    /// </summary>
+    /// <param name="detectionPoint">
+    ///     World-space ray hit point on the world surface — NOT the ghost's own position.
+    /// </param>
+    /// <param name="ghostRoot">
+    ///     The ghost's root transform. Sockets belonging to this hierarchy are ignored.
+    /// </param>
+    public void UpdateSockets(Vector3 detectionPoint, Transform ghostRoot)
+    {
+        ClearHighlights();
+        nearbySockets.Clear();
+        visitedRoots.Clear();
+        closestSocket = null;
+
+        // QueryTriggerInteraction.Collide ensures trigger colliders (typical for sockets) are found
+        Collider[] colliders = Physics.OverlapSphere(detectionPoint, socketDetectionRadius,
+            Physics.AllLayers, QueryTriggerInteraction.Collide);
+
+        foreach (Collider col in colliders)
+        {
+            Transform root = col.transform.root;
+
+            // Skip anything that belongs to the held ghost
+            if (ghostRoot != null && root == ghostRoot) continue;
+
+            // Don't process the same block twice (it may have multiple colliders)
+            if (visitedRoots.Contains(root)) continue;
+            visitedRoots.Add(root);
+
+            // Search from root so we find ALL SocketPoints on the block,
+            // regardless of which child collider was hit by the overlap.
+            foreach (SocketPoint socket in root.GetComponentsInChildren<SocketPoint>())
+            {
+                if (socket.IsOccupied()) continue;
+
+                nearbySockets.Add(socket);
+                socket.Highlight(HighlightState.Compatible);
+
+                Debug.Log($"[SnappingSystem] Found socket: {socket.name} on {root.name}");
+            }
+        }
+
+        if (nearbySockets.Count > 0)
+        {
+            closestSocket = FindClosest(detectionPoint, nearbySockets);
+            closestSocket?.Highlight(HighlightState.Active);
+            Debug.Log($"[SnappingSystem] Closest socket: {closestSocket?.name}");
+        }
+    }
+
+    /// <summary>Resets all highlight states without clearing the list.</summary>
+    public void ClearHighlights()
+    {
+        foreach (SocketPoint socket in nearbySockets)
+            if (socket != null)
+                socket.Highlight(HighlightState.Default);
+    }
+
+    /// <summary>Full reset — clears highlights and all cached data.</summary>
+    public void Clear()
+    {
+        ClearHighlights();
+        nearbySockets.Clear();
+        visitedRoots.Clear();
+        closestSocket = null;
+    }
+
+    public List<SocketPoint> GetNearbySockets() => nearbySockets;
+    public SocketPoint GetClosestSocket() => closestSocket;
+
+    // -------------------------------------------------------------------------
+    // Private helpers
+    // -------------------------------------------------------------------------
+
+    private static SocketPoint FindClosest(Vector3 position, List<SocketPoint> sockets)
+    {
+        SocketPoint closest = null;
+        float minDist = float.MaxValue;
+
+        foreach (SocketPoint socket in sockets)
+        {
+            float dist = Vector3.Distance(position, socket.GetTransform().position);
+            if (dist < minDist)
+            {
+                minDist = dist;
+                closest = socket;
+            }
+        }
+        return closest;
+    }
+}