✨ Relationships controllers

DysonNetwork.Sphere/Account/AccountService.cs

@@ -1,8 +1,10 @@
+using Casbin;
 using Microsoft.EntityFrameworkCore;
+using NodaTime;
 
 namespace DysonNetwork.Sphere.Account;
 
-public class AccountService(AppDatabase db)
+public class AccountService(AppDatabase db, IEnforcer enforcer)
 {
     public async Task<Account?> LookupAccount(string probe)
     {
@@ -17,4 +19,144 @@ public class AccountService(AppDatabase db)
 
         return null;
     }
+
+    public async Task<bool> HasExistingRelationship(Account userA, Account userB)
+    {
+        var count = await db.AccountRelationships
+            .Where(r => (r.AccountId == userA.Id && r.AccountId == userB.Id) ||
+                        (r.AccountId == userB.Id && r.AccountId == userA.Id))
+            .CountAsync();
+        return count > 0;
+    }
+
+    public async Task<Relationship?> GetRelationship(
+        Account account,
+        Account related,
+        RelationshipStatus? status,
+        bool ignoreExpired = false
+    )
+    {
+        var now = Instant.FromDateTimeUtc(DateTime.UtcNow);
+        var queries = db.AccountRelationships
+            .Where(r => r.AccountId == account.Id && r.AccountId == related.Id);
+        if (ignoreExpired) queries = queries.Where(r => r.ExpiredAt > now);
+        if (status is not null) queries = queries.Where(r => r.Status == status);
+        var relationship = await queries.FirstOrDefaultAsync();
+        return relationship;
+    }
+
+    public async Task<Relationship> CreateRelationship(Account sender, Account target, RelationshipStatus status)
+    {
+        if (status == RelationshipStatus.Pending)
+            throw new InvalidOperationException(
+                "Cannot create relationship with pending status, use SendFriendRequest instead.");
+        if (await HasExistingRelationship(sender, target))
+            throw new InvalidOperationException("Found existing relationship between you and target user.");
+
+        var relationship = new Relationship
+        {
+            Account = sender,
+            AccountId = sender.Id,
+            Related = target,
+            RelatedId = target.Id,
+            Status = status
+        };
+
+        db.AccountRelationships.Add(relationship);
+        await db.SaveChangesAsync();
+        await ApplyRelationshipPermissions(relationship);
+
+        return relationship;
+    }
+
+    public async Task<Relationship> SendFriendRequest(Account sender, Account target)
+    {
+        if (await HasExistingRelationship(sender, target))
+            throw new InvalidOperationException("Found existing relationship between you and target user.");
+
+        var relationship = new Relationship
+        {
+            Account = sender,
+            AccountId = sender.Id,
+            Related = target,
+            RelatedId = target.Id,
+            Status = RelationshipStatus.Pending,
+            ExpiredAt = Instant.FromDateTimeUtc(DateTime.UtcNow.AddDays(7))
+        };
+
+        db.AccountRelationships.Add(relationship);
+        await db.SaveChangesAsync();
+
+        return relationship;
+    }
+
+    public async Task<Relationship> AcceptFriendRelationship(
+        Relationship relationship,
+        RelationshipStatus status = RelationshipStatus.Friends
+    )
+    {
+        if (relationship.Status == RelationshipStatus.Pending)
+            throw new ArgumentException("Cannot accept friend request by setting the new status to pending.");
+
+        // Whatever the receiver decides to apply which status to the relationship,
+        // the sender should always see the user as a friend since the sender ask for it
+        relationship.Status = RelationshipStatus.Friends;
+        relationship.ExpiredAt = null;
+        db.Update(relationship);
+
+        var relationshipBackward = new Relationship
+        {
+            Account = relationship.Related,
+            AccountId = relationship.RelatedId,
+            Related = relationship.Account,
+            RelatedId = relationship.AccountId,
+            Status = status
+        };
+        db.AccountRelationships.Add(relationshipBackward);
+
+        await db.SaveChangesAsync();
+
+        await Task.WhenAll(
+            ApplyRelationshipPermissions(relationship),
+            ApplyRelationshipPermissions(relationshipBackward)
+        );
+
+        return relationshipBackward;
+    }
+
+    public async Task<Relationship> UpdateRelationship(Account account, Account related, RelationshipStatus status)
+    {
+        var relationship = await GetRelationship(account, related, status);
+        if (relationship is null) throw new ArgumentException("There is no relationship between you and the user.");
+        if (relationship.Status == status) return relationship;
+        relationship.Status = status;
+        db.Update(relationship);
+        await db.SaveChangesAsync();
+        await ApplyRelationshipPermissions(relationship);
+        return relationship;
+    }
+
+    private async Task ApplyRelationshipPermissions(Relationship relationship)
+    {
+        // Apply the relationship permissions to casbin enforcer
+        // domain: the user
+        // status is friends: all permissions are allowed by default, expect specially specified
+        // status is blocked: all permissions are disallowed by default, expect specially specified
+        // others: use the default permissions by design
+
+        var domain = $"user:{relationship.AccountId.ToString()}";
+        var target = relationship.RelatedId.ToString();
+
+        await enforcer.DeleteRolesForUserAsync(target, domain);
+
+        string role = relationship.Status switch
+        {
+            RelationshipStatus.Friends => "friends",
+            RelationshipStatus.Blocked => "blocked",
+            _ => "default" // fallback role
+        };
+        if (role == "default") return;
+
+        await enforcer.AddRoleForUserAsync(target, role, domain);
+    }
 }