Graphql - universal permission guards

Question

I am trying to implement permission guards in a graphql backend using apollo server. The following code works:

Resolvers

const Notification = require('../../database/models/notifications');
const Task = require('../../database/models/tasks');

notification: combineResolvers(isNotificationOwner, async (_, { id }) => {
  try {
    const notification = await Notification.findById(id);
    return notification;
  } catch (error) {
    throw error;
  }
})

task: combineResolvers(isTaskOwner, async (_, { id }) => {
  try {
    const task = await Task.findById(id);
    return task;
  } catch (error) {
    throw error;
  }
})

Resolver Middleware (permission guards)

const Notification = require('../../database/models/notifications');
const Task = require('../../database/models/tasks');

// userId is the id of the logged in user retrieved from the context
module.exports.isNotificationOwner = async (_, { id }, { userId }) => {
  try {
    const notification = await Notification.findById(id);
    if (notification.user.toString() !== userId) {
      throw new ForbiddenError('You are not the owner');
    }
    return skip;
  } catch (error) {
    throw error;
  }
}

module.exports.isTaskOwner = async (_, { id }, { userId }) => {
  try {
    const task = await Task.findById(id);
    if (task.user.toString() !== userId) {
      throw new ForbiddenError('You are not the owner');
    }
    return skip;
  } catch (error) {
    throw error;
  }
}

Going on like this will create a lot of duplicate code and does not feel very DRY. Therefore, I am trying to create a more universal solution, to no evail so far.

---

What I tried:

Resolvers

const Notification = require('../../database/models/notifications');
const Task = require('../../database/models/tasks');

notification: combineResolvers(isOwner, async (_, { id }) => {
  try {
    const notification = await Notification.findById(id);
    return notification;
  } catch (error) {
    throw error;
  }
})

task: combineResolvers(isOwner, async (_, { id }) => {
  try {
    const task = await Task.findById(id);
    return task;
  } catch (error) {
    throw error;
  }
})

Resolver Middleware

const Notification = require('../../database/models/notifications');
const Task = require('../../database/models/tasks');

module.exports.isOwner = async (_, { id, collection }, { userId }) => {
  try {
    const document = await collection.findById(id);
    if (document.user.toString() !== userId) {
      throw new ForbiddenError('You are not the owner');
    }

    return skip;
  } catch (error) {
    throw error;
  }
}

I am unable to pass a collection name as an argument to the middleware resolver.

I would be tremendously thankful for any kind of help!

Answer 1

Based off your code, it seems like you're looking for making isOwner a higher-order function, so that you can pass in the collection, and it returns the curried method.

module.exports.isOwner = (collection) => {
  return async (_, { id }, { userId }) => {
    try {
      const document = await collection.findById(id);
      if (document.user.toString() !== userId) {
        throw new ForbiddenError('You are not the owner');
      }

      return skip;
    } catch (error) {
      throw error;
    }
  }
}

Usage:

const resolvers = {
  Query: {
    task: combineResolvers(isOwner(Task), async (_, { id }) => {
      try {
        const task = await Task.findById(id);
        return task;
      } catch (error) {
        throw error;
      }
    })
  },
};