🛡️ Implement a Permission System

In this step we'll extend the Potato.Examples solution with a basic permission model. The goal is to restrict access to nodes in the tree using PermissionNode and ReferenceNode.

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1. 📦 Add Domain Models

Inside Potato.Examples.Domain/Entities add two new records:

ReferenceNode.cs

namespace Potato.Examples.Domain;

public record ReferenceNode(
    Guid? Id,
    Guid? ParentId,
    Guid ReferenceId
) : Node(Id, ParentId, DisplayName: null);

PermissionNode.cs

namespace Potato.Examples.Domain;

public record PermissionNode(
    Guid? Id,
    Guid? ParentId,
    Guid ReferenceId,
    bool CanRead,
    bool CanWrite,
    bool CanDelete,
    bool CanPermit,
    bool CanRevoke
) : Node(Id, ParentId)
{
    public static readonly PermissionNode NoPermissions = new(null, null, Guid.Empty, false, false, false, false, false);

    public bool MeetsRequirements(PermissionsRequirements req) =>
        (!req.Read || CanRead) &&
        (!req.Write || CanWrite) &&
        (!req.Delete || CanDelete) &&
        (!req.Permit || CanPermit) &&
        (!req.Revoke || CanRevoke);
}

Add an enum to the same folder:

PermissionsRequirements.cs

namespace Potato.Examples.Domain;

public record PermissionsRequirements(
    bool Read = false,
    bool Write = false,
    bool Delete = false,
    bool Permit = false,
    bool Revoke = false
);

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2. 🧩 Querying with Permissions

Use the helper methods in PotatoPermissionService and PotatoPermissionFilters to resolve and check permissions.

Example usage inside a query handler:

var permissions = await PotatoPermissionService.FindPermissions(tree, references, subjectNode);
var hasAccess = PotatoPermissionService.MeetsRequirements(permissions, subjectNode, new PermissionsRequirements(Read: true));

You can also filter search results:

var results = await finder.Find(
    PotatoPermissionFilters.OnlyNodesWithPermission(permissions, new PermissionsRequirements(Read: true)),
    cursor
);

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✅ Summary

You now have:

• Permission and reference nodes in your domain
• A simple requirements model
• Examples of resolving and evaluating permissions

➡️ Next: Working with S3 Files