import Rule from 'graphql-rule';

Rule.create({
  // [REQUIRED] Unique rule model name.
  // Used for child field type specification.
  name: string = null,
  
  // Base class for newly created and returned rule model class.
  // Base class must extend {Model} from 'graphql-rule'.
  base: ?class = class<Model>,
  
  // Define dynamic property getters.
  // Can be accessed via `model.$props.propName`
  // Each property is lazily initialized upon the first access and cached for performance.
  // Useful for something expensive to calculate and is accessed over and over by multiple fields.
  props: {
    [propName: string]: (model: Model) => any,
  } = {},
  
  // Define default rule for fields in this model.
  defaultRule: {
    // `preRead` is checked before accessing or calling a field.
    // Useful for failing fast before accessing field that can be expensive to calculate such as field that initiates network calls
    // If `false` or `preRead(model, key)` returns falsy value, the access to field will fail immediately.
    // [default=true]
    preRead: boolean | (model: Model, key: string) => boolean | Promise<boolean>,
    
    // `read` is checked after accessing or calling a field.
    // Useful for passing/failing based on the field value.
    // If `false` or `read(model, key, value)` returns falsy value, the access to field will fail immediately.
    // [default=true]
    read: boolean | (model: Model, key: string, value: any) => boolean | Promise<boolean>,
    
    // `readFail` is used when either `preRead` or `read` returns falsy value.
    // If it is not a function, it is used as a final value for the failed field.
    // If it is function, the returend value is used as a final value for the failed field.
    // It can throw an error, if throwing an error is a desired upon unauthorized access to a field.
    // [default=null]
    readFail: any | (model: Model, key: string, value: ?any) => any,
  } = {preRead: true, read: true, readFail: null},
  
  // Define access rule for fields in this model.
  rules: {
    [fieldName: string]: {
      // See `defaultRule.preRead`
      preRead,
      
      // See `defaultRule.read`
      read,
      
      // See `defaultRule.readFail`
      readFail,
      
      // If specified, field value will be wrapped as an instance of the specified Model class.
      type: string | class<Model> = null,
      
      // Whether the field returns a list of Model instances.
      // Used together with `type` above.
      list: boolean = false,
      
      // Filter function for list.
      // Used together with `list` above.
      readListItem: (listItem: FieldModel, model: Model, key: string, list: [FieldModel]) => boolean
      
      // Whether the field is a function method.
      method: boolean = false,
      
      // Whether to cached the final value for the field.
      // Only applied if `method: false` above.
      cache: boolean = true,
    },
  },
  
  // Interfaces to inherit static and prototype properties and methods from.
  // Useful if you have common props / field rules / etc.
  interfaces: [class<Model>] = [],
})

import Rule from 'graphql-rule';

// create access control model for your data
const Model = Rule.create({
  // name for this access model
  name: 'Model',

  // define access rules
  rules: {
    // allow access to `public` property.
    public: true,

    secret: {
      // disallow access to `secret` property.
      read: false,

      // throw an error when read is disallowed.
      readFail: () => { throw new Error('Access denied'); },
    },

    conditional: {
      // access raw data via `$data`.
      // conditionally allow access if `conditional` <= 3.
      read: (model) => model.$data.conditional <= 3,

      readFail: (model) => { throw new Error(`${model.$data.conditional} > 3`); },
    },
  },
});


// create a wrapped instance of your data.
const securedData = new Model({
  public: 'public data',
  secret: 'something secret',
  conditional: 5,
});

securedData.public // 'public data'

securedData.secret // throws Error('Access denied').

securedData.conditional // throws Error('5 > 3').


// same access model for different data.
const securedData2 = new Model({conditional: 1});

securedData2.conditional // 1 since 1 < 3.

// set default `readFail`
Rule.config({
  readFail: () => { throw new Error('Access denied'); },
});

const UserRule = Rule.create({
  name: 'User',

  // props are lazily initialized and cached once initialized.
  // accessible via `model.$props`.
  props: {
    isAdmin: (model) => model.$context.admin,

    isAuthenticated: (model) => Boolean(model.$context.userId),

    isOwner: (model) => model.$data.id === model.$context.userId,
  },

  rules: {
    // Everyone can read `id`.
    id: true,

    email: {
      // allow access by admin or owner.
      read: (model) => model.$props.isAdmin || model.$props.isOwner,

      // returns null when read denied.
      readFail: null,
    },

    // No one can read `password`.
    password: false,

    profile: {
      // Use `Profile` Rule for `profile`.
      type: 'Profile',

      // allow access by all authenticated users
      read: (model) => model.$props.isAuthenticated,

      readFail: () => { throw new Error('Login Required'); },
    },
  },
});

const ProfileRule = Rule.create({
  name: 'Profile',

  rules: {
    name: true,

    phone: {
      // Access `UserRule` instance via `$parent`.
      read: (model) => model.$parent.$props.isAdmin || model.$parent.$props.isOwner,

      readFail: () => { throw new Error('Not authorized!'); },
    },
  },
});


const session = {
  userId: 'session_user_id',
  admin: false,
};

const userData = {
  id: 'user_id',
  email: '[email protected]',
  password: 'secret',
  profile: {
    name: 'John Doe',
    phone: '123-456-7890',
  },
};

// pass `session` as a second param to make it available as `$context`.
const user = new UserRule(userData, session);

user.id // 'user_id'

user.email // `null` since not admin nor owner.

user.password // throws Error('Access denied').

user.profile // `ProfileRule` instance. accessible since authenticated.

user.profile.name // 'John Doe'

user.profile.phone // throws Error('Not authorized!') since not admin nor owner.

// Use `UserRule` and `ProfileRule` from the above example.

const ProfileType = new GraphQLObjectType({
  name: 'Profile',
  fields: {
    name: { type: GraphQLString },
    phone: { type: GraphQLString },
  }
});

const UserType = new GraphQLObjectType({
  name: 'User',
  fields: {
    id: { type: GraphQLID },
    email: { type: GraphQLString },
    password: { type: GraphQLString },
    profile: { type: ProfileType },
  }
});

const schema = new GraphQLSchema({
  query: new GraphQLObjectType({
    name: 'Query',
    fields: {
      user: {
        type: UserType,
        args: {
          id: { type: GraphQLID }
        },
        resolve: (_, args, session) => {
          // `context` is passed as the third parameter of `resolve` function.
          // pass the `context` as the second parameter of `UserRule`.
          // Now your data is secured by predefined rules!
          return database.getUser(args.id).then((user) => new UserRule(user, session));
        },
      }
    }
  })
});

app.use('/graphql', graphqlHTTP((request) => ({
  schema: schema,
  // pass session data as `context`.
  // becomes available as third parameter in field `resolve` functions.
  context: request.session,
})));

// Define Mongoose schemas.
const UserModel = mongoose.model('User', new mongoose.Schema({
  email: String,
  password: String,
  profile: {
    type: ObjectId,
    ref: 'Profile',
  },
}));

const ProfileModel = mongoose.model('Profile', new mongoose.Schema({
  name: String,
  phone: String,
}));


// Define access rules.
const UserRule = Rule.create({
  name: 'User',
  props: {
    isAdmin: (model) => model.$context.admin,
    isOwner: (model) => model.$data.id === model.$context.userId,
  },
  rules: {
    id: true,
    email: {
      preRead: (model) => model.$props.isAdmin || model.$props.isOwner,
      readFail: () => { throw new Error('Unauthorized'); },
    },
    password: false,
    profile: {
      type: 'Profile',
      preRead: true,
    },
  },
});

const ProfileRule = Rule.create({
  name: 'Profile',
  rules: {
    name: true,
    phone: {
      preRead: (model) => model.$parent.$props.isAdmin || model.$parent.$props.isOwner,
      readFail: () => null,
    },
  },
});


// Define GraphQL Types.
const ProfileType = new GraphQLObjectType({
  name: 'Profile',
  fields: {
    name: { type: GraphQLString },
    phone: { type: GraphQLString },
  }
});

const UserType = new GraphQLObjectType({
  name: 'User',
  fields: {
    id: { type: GraphQLID },
    email: { type: GraphQLString },
    password: { type: GraphQLString },
    profile: { type: ProfileType },
  }
});


// Define GraphQL Queries.
const schema = new GraphQLSchema({
  query: new GraphQLObjectType({
    name: 'Query',
    fields: {
      user: {
        type: UserType,
        args: {
          id: { type: GraphQLID }
        },
        resolve: async (_, {id}, sessionContext) => {
          const userId = new ObjectId(id);
          const user = await UserModel.findById(userId).populate('profile').exec();
          const securedUser = new UserRule(user, sessionContext);
          return securedUser;
        },
      }
    }
  })
});


// Express GraphQL middleware.
app.use('/graphql', graphqlHTTP((request) => ({
  schema: schema,
  context: request.session,
})));