# CASL Mongoose

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This package integrates [CASL] and [MongoDB]. In other words, it allows to fetch records based on CASL rules from MongoDB and answer questions like: "Which records can be read?" or "Which records can be updated?".

## Installation

```sh
npm install @casl/mongoose @casl/ability
# or
yarn add @casl/mongoose @casl/ability
# or
pnpm add @casl/mongoose @casl/ability
```

## Usage

`@casl/mongoose` can be integrated not only with [mongoose] but also with any [MongoDB] JS driver thanks to new `accessibleBy` helper function.

### `accessibleBy` helper

This neat helper function allows to convert ability rules to MongoDB query and fetch only accessible records from the database. It can be used with mongoose or [MongoDB adapter][mongo-adapter]:


#### MongoDB adapter

```js
const { accessibleBy } = require('@casl/mongoose');
const { MongoClient } = require('mongodb');
const ability = require('./ability');

async function main() {
  const db = await MongoClient.connect('mongodb://localhost:27017/blog');
  let posts;

  try {
    posts = await db.collection('posts').find(accessibleBy(ability, 'update').ofType('Post'));
  } finally {
    db.close();
  }

  console.log(posts);
}
```

This can also be combined with other conditions with help of `$and` operator:

```js
posts = await db.collection('posts').find({
  $and: [
    accessibleBy(ability, 'update').ofType('Post'),
    { public: true }
  ]
});
```

**Important!**: never use spread operator (i.e., `...`) to combine conditions provided by `accessibleBy` with something else because you may accidentally overwrite properties that restrict access to particular records:

```js
// returns { authorId: 1 }
const permissionRestrictedConditions = accessibleBy(ability, 'update').ofType('Post');

// DANGER DO NOT DO THIS (see above use $and)
const query = {
  // This is bad and potentially wrong code
  ...permissionRestrictedConditions,
  authorId: 2
};
```

In the case above, we overwrote `authorId` property and basically allowed non-authorized access to posts of author with `id = 2`

If there are no permissions defined for particular action/subjectType, `accessibleBy` will return `{ $expr: { $eq: [0, 1] } }` and when it's sent to MongoDB, database will return an empty result set.

#### Mongoose


```js
const Post = require('./Post') // mongoose model
const ability = require('./ability') // defines Ability instance

async function main() {
  const accessiblePosts = await Post.find(accessibleBy(ability).ofType('Post'));
  console.log(accessiblePosts);
}
```

Historically, `@casl/mongoose` was intended for super easy integration with [mongoose] but now we re-orient it to be more MongoDB specific package due to complexity working with mongoose types in TS.

### Accessible Records plugin

This plugin is deprecated, the recommended way is to use [`accessibleBy` helper function](#accessibleBy-helper).

`accessibleRecordsPlugin` is a plugin which adds `accessibleBy` method to query and static methods of mongoose models. We can add this plugin globally:

```js
const { accessibleRecordsPlugin } = require('@casl/mongoose');
const mongoose = require('mongoose');

mongoose.plugin(accessibleRecordsPlugin);
```

> Make sure to add the plugin before calling `mongoose.model(...)` method. Mongoose won't add global plugins to models that where created before calling `mongoose.plugin()`.

or to a particular model:

```js @{data-filename="Post.js"}
const mongoose = require('mongoose')
const { accessibleRecordsPlugin } = require('@casl/mongoose')

const Post = new mongoose.Schema({
  title: String,
  author: String
})

Post.plugin(accessibleRecordsPlugin)

module.exports = mongoose.model('Post', Post)
```

Afterwards, we can fetch accessible records using `accessibleBy` method on `Post`:

```js
const Post = require('./Post')
const ability = require('./ability') // defines Ability instance

async function main() {
  const accessiblePosts = await Post.accessibleBy(ability);
  console.log(accessiblePosts);
}
```

> See [CASL guide](https://casl.js.org/v5/en/guide/intro) to learn how to define abilities

or on existing query instance:

```js
const Post = require('./Post');
const ability = require('./ability');

async function main() {
  const accessiblePosts = await Post.find({ status: 'draft' })
    .accessibleBy(ability)
    .select('title');
  console.log(accessiblePosts);
}
```

`accessibleBy` returns an instance of `mongoose.Query` and that means you can chain it with any `mongoose.Query`'s method (e.g., `select`, `limit`, `sort`). By default, `accessibleBy` constructs a query based on the list of rules for `read` action but we can change this by providing the 2nd optional argument:

```js
const Post = require('./Post');
const ability = require('./ability');

async function main() {
  const postsThatCanBeUpdated = await Post.accessibleBy(ability, 'update');
  console.log(postsThatCanBeUpdated);
}
```

> `accessibleBy` is built on top of `rulesToQuery` function from `@casl/ability/extra`. Read [Ability to database query](https://casl.js.org/v5/en/advanced/ability-to-database-query) to get insights of how it works.

In case user doesn’t have permission to do a particular action, CASL will throw `ForbiddenError` and will not send request to MongoDB. It also adds `__forbiddenByCasl__: 1` condition for additional safety.

For example, lets find all posts which user can delete (we haven’t defined abilities for delete):

```js
const { defineAbility } = require('@casl/ability');
const mongoose = require('mongoose');
const Post = require('./Post');

mongoose.set('debug', true);

const ability = defineAbility(can => can('read', 'Post', { private: false }));

async function main() {
  try {
    const posts = await Post.accessibleBy(ability, 'delete');
  } catch (error) {
    console.log(error) // ForbiddenError;
  }
}
```

We can also use the resulting conditions in [aggregation pipeline](https://mongoosejs.com/docs/api.html#aggregate_Aggregate):

```js
const Post = require('./Post');
const ability = require('./ability');

async function main() {
  const query = Post.accessibleBy(ability)
    .where({ status: 'draft' })
    .getQuery();
  const result = await Post.aggregate([
    {
      $match: {
        $and: [
          query,
          // other aggregate conditions
        ]
      }
    },
    // other pipelines here
  ]);
  console.log(result);
}
```

or in [mapReduce](https://mongoosejs.com/docs/api.html#model_Model.mapReduce):

```js
const Post = require('./Post');
const ability = require('./ability');

async function main() {
  const query = Post.accessibleBy(ability)
    .where({ status: 'draft' })
    .getQuery();
  const result = await Post.mapReduce({
    query: {
      $and: [
        query,
        // other conditions
      ]
    },
    map: () => emit(this.title, 1);
    reduce: (_, items) => items.length;
  });
  console.log(result);
}
```

### accessibleFieldsBy

`accessibleFieldsBy` allows retrieving accessible fields for a subject type or a concrete subject instance:

```ts
import { accessibleFieldsBy } from '@casl/mongoose';
import { Post } from './models';

accessibleFieldsBy(ability).ofType('Post') // returns accessible fields for Post model
accessibleFieldsBy(ability).ofType(Post) // also possible to pass class if classes are used for rule definition
accessibleFieldsBy(ability).of(new Post()) // returns accessible fields for Post model
```

This helper can be used directly when we need to send only accessible part of a model in response:

```js
const pick = require('lodash/pick');
const { accessibleFieldsBy } = require('@casl/mongoose');
const Post = require('./Post');

app.get('/api/posts/:id', async (req, res) => {
  const post = await Post.accessibleBy(ability).findByPk(req.params.id);
  res.send(pick(post, accessibleFieldsBy(ability).of(post)));
});
```

When called with a model type, `accessibleFieldsBy` does not take instance conditions into account. It follows the same [checking logic](https://casl.js.org/v5/en/guide/intro#checking-logic) as `Ability`'s `can` method. Let's see an example to recap:

```js
const { defineAbility } = require('@casl/ability');
const Post = require('./Post');

const ability = defineAbility((can) => {
  can('read', 'Post', ['title'], { private: true });
  can('read', 'Post', ['title', 'description'], { private: false });
});
const post = new Post({ private: true, title: 'Private post' });

accessibleFieldsBy(ability).ofType(Post); // ['title', 'description']
accessibleFieldsBy(ability).of(post); // ['title']
```

As you can see, model-level access returns all fields that can be read for all posts. At the same time, instance-level access returns fields that can be read from this particular `post` instance. That's why there is usually no much sense, except reducing traffic between app and database, to pass the result of model-level access into `mongoose.Query`'s `select` method because eventually you will need to call `accessibleFieldsBy` on every instance.

This helper is pre-configured to get all fields from `Model.schema.paths`. If this is not desired, define your own custom helper:

```ts
import { AnyMongoAbility, Generics } from "@casl/ability";
import { AccessibleFields, GetSubjectTypeAllFieldsExtractor } from "@casl/ability/extra";
import mongoose from 'mongoose';

const getSubjectTypeAllFieldsExtractor: GetSubjectTypeAllFieldsExtractor = (type) => {
  /** custom implementation of returning all fields */
};

export function accessibleFieldsBy<T extends AnyMongoAbility>(
  ability: T,
  action: Parameters<T['rulesFor']>[0] = 'read'
): AccessibleFields<Extract<Generics<T>['abilities'], unknown[]>[1]> {
  return new AccessibleFields(ability, action, getSubjectTypeAllFieldsExtractor);
}
```

## TypeScript support in mongoose

The package is written in TypeScript, this makes it easier to work with plugins and helpers because IDE provides useful hints. Let's see it in action!

Suppose we have `Post` entity which can be described as:

```ts
import mongoose from 'mongoose';

export interface Post extends mongoose.Document {
  title: string
  content: string
  published: boolean
}

const PostSchema = new mongoose.Schema<Post>({
  title: String,
  content: String,
  published: Boolean
});

export const Post = mongoose.model('Post', PostSchema);
```

To extend `Post` model with `accessibleBy` method it's enough to include the corresponding plugin (either globally or locally in `Post`) and use corresponding `Model` type. So, let's change the example, so it includes `accessibleRecordsPlugin`:

```ts
import { accessibleRecordsPlugin, AccessibleRecordModel } from '@casl/mongoose';

// all previous code, except last line

PostSchema.plugin(accessibleRecordsPlugin);

export const Post = mongoose.model<Post, AccessibleRecordModel<Post>>('Post', PostSchema);

// Now we can safely use `Post.accessibleBy` method.
Post.accessibleBy(/* parameters */)
Post.where(/* parameters */).accessibleBy(/* parameters */);
```

`accessibleFieldsBy` does not require mongoose-specific types. You can use it directly with models or documents:

```ts
import { accessibleFieldsBy } from '@casl/mongoose';

accessibleFieldsBy(ability).ofType(Post);

const post = new Post();
accessibleFieldsBy(ability).of(post);
```

If you want model or document instance methods similar to the removed plugin, create a small app-level wrapper around `accessibleFieldsBy` that fits your own typings and field exposure rules.

## Want to help?

Want to file a bug, contribute some code, or improve documentation? Excellent! Read up on guidelines for [contributing].

If you'd like to help us sustain our community and project, consider [to become a financial contributor on Open Collective](https://opencollective.com/casljs/contribute)

> See [Support CASL](https://casl.js.org/v5/en/support-casljs) for details

## License

[MIT License](http://www.opensource.org/licenses/MIT)

[contributing]: https://github.com/stalniy/casl/blob/master/CONTRIBUTING.md
[mongoose]: http://mongoosejs.com/
[mongo-adapter]: https://mongodb.github.io/node-mongodb-native/
[CASL]: https://github.com/stalniy/casl
[MongoDB]: https://www.mongodb.com/