Foxnouns.NET/Foxnouns.Backend/Middleware/LimitMiddleware.cs

// Copyright (C) 2023-present sam/u1f320 (vulpine.solutions)
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
using Foxnouns.Backend.Database.Models;

namespace Foxnouns.Backend.Middleware;

public class LimitMiddleware : IMiddleware
{
    public async Task InvokeAsync(HttpContext ctx, RequestDelegate next)
    {
        Endpoint? endpoint = ctx.GetEndpoint();
        LimitAttribute? attribute = endpoint?.Metadata.GetMetadata<LimitAttribute>();

        Token? token = ctx.GetToken();

        if (attribute == null)
        {
            // Check for authorize attribute
            // If it exists, and the user is deleted, throw an error.
            if (
                endpoint?.Metadata.GetMetadata<AuthorizeAttribute>() != null
                && token?.User.Deleted == true
            )
            {
                throw new ApiError.Forbidden("Deleted users cannot access this endpoint.");
            }

            await next(ctx);
            return;
        }

        if (token?.User.Deleted == true && !attribute.UsableBySuspendedUsers)
            throw new ApiError.Forbidden("Deleted users cannot access this endpoint.");

        if (attribute.RequireAdmin && token?.User.Role != UserRole.Admin)
            throw new ApiError.Forbidden("This endpoint can only be used by admins.");

        if (
            attribute.RequireModerator
            && token?.User.Role is not (UserRole.Admin or UserRole.Moderator)
        )
        {
            throw new ApiError.Forbidden("This endpoint can only be used by moderators.");
        }

        await next(ctx);
    }
}

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class LimitAttribute : Attribute
{
    public bool UsableBySuspendedUsers { get; init; }
    public bool RequireAdmin { get; init; }
    public bool RequireModerator { get; init; }
}