Move Access & AccessReader to shared. (#5798)

* git mv

* Move Access Component & system.

- Name space changes
- Rename AccessReader to AccessReaderComponent
- Also need an abstract TryGetSlot function for SharedInventoryComponent

* better TryGetSlot

* Ah yes, tests exist.

Content.Shared/Access/Systems/AccessReaderSystem.cs

@@ -0,0 +1,117 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using Content.Shared.Access.Components;
+using Content.Shared.Hands.Components;
+using Content.Shared.Inventory;
+using Content.Shared.Item;
+using Content.Shared.PDA;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.Access.Systems
+{
+    public class AccessReaderSystem : EntitySystem
+    {
+        [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
+
+        public override void Initialize()
+        {
+            base.Initialize();
+            SubscribeLocalEvent<AccessReaderComponent, ComponentInit>(OnInit);
+        }
+
+        private void OnInit(EntityUid uid, AccessReaderComponent reader, ComponentInit args)
+        {
+            var allTags = reader.AccessLists.SelectMany(c => c).Union(reader.DenyTags);
+            foreach (var level in allTags)
+            {
+                if (!_prototypeManager.HasIndex<AccessLevelPrototype>(level))
+                {
+                    Logger.ErrorS("access", $"Invalid access level: {level}");
+                }
+            }
+        }
+
+        /// <summary>
+        /// Searches an <see cref="AccessComponent"/> in the entity itself, in its active hand or in its ID slot.
+        /// Then compares the found access with the configured access lists to see if it is allowed.
+        /// </summary>
+        /// <remarks>
+        ///     If no access is found, an empty set is used instead.
+        /// </remarks>
+        /// <param name="entity">The entity to be searched for access.</param>
+        public bool IsAllowed(AccessReaderComponent reader, EntityUid entity)
+        {
+            var tags = FindAccessTags(entity);
+            return IsAllowed(reader, tags);
+        }
+
+        public bool IsAllowed(AccessReaderComponent reader, ICollection<string> accessTags)
+        {
+            if (reader.DenyTags.Overlaps(accessTags))
+            {
+                // Sec owned by cargo.
+                return false;
+            }
+
+            return !reader.Enabled || reader.AccessLists.Count == 0 || reader.AccessLists.Any(a => a.IsSubsetOf(accessTags));
+        }
+
+        public ICollection<string> FindAccessTags(EntityUid uid)
+        {
+            // check entity itself
+            if (FindAccessTagsItem(uid, out var tags))
+                return tags;
+
+            // maybe access component inside its hands?
+            if (EntityManager.TryGetComponent(uid, out SharedHandsComponent? hands))
+            {
+                if (hands.TryGetActiveHeldEntity(out var heldItem) &&
+                    FindAccessTagsItem(heldItem, out tags))
+                {
+                    return tags;
+                }
+            }
+
+            // maybe its inside an inventory slot?
+            if (EntityManager.TryGetComponent(uid, out SharedInventoryComponent? inventoryComponent))
+            {
+                if (inventoryComponent.TryGetSlot(EquipmentSlotDefines.Slots.IDCARD, out var entity) &&
+                    FindAccessTagsItem(entity.Value, out tags)
+                )
+                {
+                    return tags;
+                }
+            }
+
+            return Array.Empty<string>();
+        }
+
+        /// <summary>
+        ///     Try to find <see cref="AccessComponent"/> on this item
+        ///     or inside this item (if it's pda)
+        /// </summary>
+        private bool FindAccessTagsItem(EntityUid uid, [NotNullWhen(true)] out HashSet<string>? tags)
+        {
+            if (EntityManager.TryGetComponent(uid, out AccessComponent? access))
+            {
+                tags = access.Tags;
+                return true;
+            }
+
+            if (EntityManager.TryGetComponent(uid, out PDAComponent? pda) &&
+                pda.ContainedID?.Owner is {Valid: true} id)
+            {
+                tags = EntityManager.GetComponent<AccessComponent>(id).Tags;
+                return true;
+            }
+
+            tags = null;
+            return false;
+        }
+    }
+}