From ccad8db591129f5a9effb6469b477bb5c23ee229 Mon Sep 17 00:00:00 2001
From: Jake Mannens <jake@asger.xyz>
Date: Wed, 20 Sep 2023 11:45:46 +1000
Subject: Completed initial filter functionality

---
 Principal.cs                |  7 ++---
 Services/SecurityService.cs | 70 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 70 insertions(+), 7 deletions(-)

diff --git a/Principal.cs b/Principal.cs
index d736bf2..18b82d0 100644
--- a/Principal.cs
+++ b/Principal.cs
@@ -4,13 +4,12 @@ namespace HyperBooru;
 
 [Index(nameof(Name))]
 public class HBPrincipal : HBObject {
-    public string Name { get; set; }
+    public string            Name     { get; set; }
+    public List<Group>       MemberOf { get; set; }
 }
 
 public class User : HBPrincipal {
     public string PasswordHash { get; set; }
 }
 
-public class Group : HBPrincipal {
-    public List<HBPrincipal> Members { get; set; }
-}
\ No newline at end of file
+public class Group : HBPrincipal {}
\ No newline at end of file
diff --git a/Services/SecurityService.cs b/Services/SecurityService.cs
index 9695254..c8dafd5 100644
--- a/Services/SecurityService.cs
+++ b/Services/SecurityService.cs
@@ -1,11 +1,13 @@
 using Microsoft.EntityFrameworkCore;
+using System.Data;
 
 namespace HyperBooru.Services;
 
 public class SecurityService {
     private IDbContextFactory<HBContext> dbFactory;
 
-    private Acl[] acls;
+    private Group[]       groups;
+    private Acl[]         acls;
 
     public SecurityService(IDbContextFactory<HBContext> dbFactory) {
         this.dbFactory = dbFactory;
@@ -14,16 +16,78 @@ public class SecurityService {
 
     public void Reload() {
         using var db = dbFactory.CreateDbContext();
+
+        groups = db.Groups
+            .Include(g => g.MemberOf)
+            .ToArray();
+
         acls = db.Acls
             .Include(a => a.Rules)
             .ThenInclude(r => r.Principal)
             .ToArray();
     }
 
-    public IEnumerable<HBObject> Filter(IEnumerable<HBObject> objects, ulong permissions) {
+    public IEnumerable<HBObject> Filter(
+        IEnumerable<HBObject> objects,
+        HBPrincipal principal,
+        ulong permissions) {
+
         foreach(var obj in objects) {
+            var perms = GetPermissions(obj.Acl, principal);
+            if((perms & permissions) == permissions)
+                yield return obj;
+        }
+    }
+
+    public IEnumerable<HBObject> Filter<T>(
+        IEnumerable<HBObject> objects,
+        HBPrincipal principal,
+        T permissions) where T : Enum =>
+        Filter(objects, principal, permissions);
+
+    private ulong GetPermissions(Acl? acl, HBPrincipal principal) {
+        if(acl is null)
+            return ulong.MaxValue;
+
+        bool hasAllowRules = acl.Rules
+            .Any(r => r.Action == AclRuleAction.Allow);
+
+        ulong permissions = hasAllowRules ? 0 : ulong.MaxValue;
+
+        var principals = GetGroupMemberShip(principal)
+            .Cast<HBPrincipal>()
+            .Concat(new[] { principal })
+            .ToArray();
+
+        acl.Rules.IntersectBy(principals, r => r.Principal);
+
+        foreach(var rule in acl.Rules) {
+            if(!principals.Contains(rule.Principal))
+                continue;
+
+            if(rule.Action == AclRuleAction.Allow)
+                permissions |= rule.Permissions;
+            else
+                permissions &= ~rule.Permissions;
+        }
+
+        return permissions;
+    }
+
+    private List<Group> GetGroupMemberShip(HBPrincipal principal) {
+        var groups = principal.MemberOf.ToList();
+
+        while(true) {
+            var toAdd = this.groups
+                .Where(g => !groups.Contains(g))
+                .ToArray();
+
+            if(toAdd.Count() == 0)
+                break;
+
+            groups.AddRange(toAdd);
         }
 
-        return Enumerable.Empty<HBObject>();
+        return groups;
     }
 }
-- 
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