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https://github.com/kalidasmuthusamy/rails-api-response-builder

API Response Builder for Rails API app
https://github.com/kalidasmuthusamy/rails-api-response-builder

api-wrapper rails-gem rails5-api ruby ruby-on-rails serializer

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API Response Builder for Rails API app

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# Api::ResponseBuilder

Module to build response object for Rails 5 API Applications.
Depends on `active_model_serializers` gem.

Pass a valid / invalid ActiveRecord object or an instance of ActiveRecord::Relation and get response object in following structure.

Properties | Description
------------ | -------------
status | 'failure' (or) 'success'
body | Serialized Object
messages | Error Description (if any)
status_code | HTTP Status Code

## Example

```ruby
#app/controllers/api/v1/application_controller.rb
module Api
module V1
class ApplicationController < ActionController::API

def serializer_responder(resource, config = {})
response = ::Api::ResponseBuilder::Main.new(resource, config, params).response
render json: response, status: response[:status_code]
end

end
end
end

# app/serializers/v1/user_serializer.rb
module V1
# Serializer for User model
class UserSerializer < ::ActiveModel::Serializer
attributes :id,
:firstname,
:lastname,
:phone_number,
:email
end
end

# app/controllers/api/v1/users_controller.rb
module Api
module V1
# Defines endpoints for CRUD operations on user model
class UsersController < ::Api::V1::ApplicationController

def index
users = User.all
serializer_responder(users, serializer: ::V1::UserSerializer)
end

end
end
end

```

Response Object for API endpoint `/api/v1/users` will be

```json
{
"status": "success",
"body" :
[
{
"id": 1,
"firstname": "Kalidas",
"lastname": "M",
"phone_number": "+919876543210",
"email": "kalidasm610@gmail.com"
},
{
"id": 2,
"firstname": "Dass",
"lastname": "Mk",
"phone_number": "+919876543211",
"email": ""
}
],
"status_code": "ok"
}
```

## Installation

Add this line to your application's Gemfile:

```ruby
gem 'api-response_builder'
```

And then execute:

$ bundle

Or install it yourself as:

$ gem install api-response_builder

## Usage

#### ApplicationController - Setup
By taking advantage of Ruby's inheritance and Rails's app structure, few instance methods in application controller can be used to handle all scenarios for rendering json response across entire application.

```ruby
module Api
module V1
class ApplicationController < ActionController::API
# action callbacks

# Global Exception Handler for Api Exceptions and StandardError
rescue_from ::Api::Exception, StandardError do |e|
handle_api_exception(e)
end

# Global exception handlers for ActiveRecord Exceptions
rescue_from ::ActiveRecord::RecordNotFound, with: :render_record_not_found
rescue_from ::ActiveRecord::RecordInvalid, with: :render_record_invalid
rescue_from ::ActiveRecord::RecordNotDestroyed, with: :render_forbidden

# Public methods
def handle_api_exception(e)
response = ::Api::ResponseBuilder::Main.new(e, {}, params).response
render json: response, status: response[:status_code]
end

def render_record_not_found
handle_api_exception ::Api::Exception.new(
::Api::Exception.record_not_found
)
end

def render_internal_server_error
handle_api_exception ::Api::Exception.new(
::Api::Exception.internal_server_error
)
end

def render_record_invalid(e)
# If exception message is not included in arguments, locale message
# (if present) for record invalid exception will be returned in resp
exception_message = e.record.errors.full_messages
exception = ::Api::Exception.new(
::Api::Exception.record_invalid, exception_message
)
handle_api_exception(exception)
end

def render_forbidden
handle_api_exception ::Api::Exception.new(
::Api::Exception.forbidden_resource
)
end

def serializer_responder(resource, config = {})
response = ::Api::ResponseBuilder::Main.new(resource, config, params).response
# response object also contains corresponding http status code under the key :status_code
# Including `Http Status Code` as part of API response is generally considered as good practice
# If all your api responses should have `200 OK` as status code, omit status key in render method
# Rails, by default, set status code as `200 OK`
render json: response, status: response[:status_code]
end
end
end
end

```

#### Passing Additional Information to Response

In some cases, meta information may be passed along with response. For example, passing total count of resources for pagination.

In order to pass meta info, include `:meta` key-value pair in config object passed to `::Api::ResponseBuilder::Main`.
It will be reflected in response object under `meta` key

Note:
* config[:serializer] should be `ActiveModel::Serializer` class (if serializer is not passed, it will serialize entire object)
* `config[:meta]` will accept only hash

```ruby
# app/controllers/api/v1/users_controller.rb
def index
users = User.all

config = {}
config[:serializer] = UserSerializer
config[:meta] = { total_count: users.count }
serializer_responder(users, config)
end

# simple way
serializer_responder(users, { serializer: UserSerializer, meta: { total_count: users.count } })
```

##### Response

```json
{
"status": "success",
"body" :
[
{
"id": 1,
"firstname": "Kalidas",
"lastname": "M",
"phone_number": "+919876543210",
"email": "kalidasm610@gmail.com"
},
{
"id": 2,
"firstname": "Dass",
"lastname": "Mk",
"phone_number": "+919876543211",
"email": ""
}
],
"status_code": "ok",
"meta": {
"total_count": 2
}
}
```

#### API Exceptions

Following exceptions are handled by this gem as there are the most commonly used.

EXCEPTION | HTTP Status Code
------------ | -------------
INTERNAL_SERVER_ERROR | :internal_server_error (500)
RECORD_NOT_FOUND | :not_found (404)
RECORD_INVALID | ::unprocessable_entity (422)
RECORD_NOT_DESTROYED | :forbidden (403)
FORBIDDEN_RESOURCE | :forbidden (403)
UNAUTHORIZED_ACCESS | :unauthorized (401)

For detailed information, feel free to dive into the [Code](https://github.com/kalidasm/rails-api-response-builder/blob/master/lib/api/exception.rb)

##### Error Messages for API Exceptions

All the error messages are internalized using `Rails Internationalization (I18n) API`.

Exceptional messages are mapped under I18n locales (`en.api_response.messages.#{key}`).

Key represents lower-cased version of exception names listed above.

Example :

```yml
en:
api_response:
messages:
internal_server_error: "Internal server error."
record_not_found: "The resource you are looking for does not exist."
record_invalid: "Validation Failed"
record_not_destroyed: "Failed to delete the resource"
forbidden_resource: "You don't have sufficient privileges to perform this operation"
unauthorized_access: "You are not authorized to perform this operation"
```

##### Raising API Exception inside controller actions

```ruby
class CreditsController < ApplicationController
before_action :authorize_user, only: :update

def update
@credit.update(credit_params)
end

private

def authorize_user
return if user_authorized?

# Will be handled by rescue_from methods in application controller
raise ::Api::Exception.new(
::Api::Exception.unauthorized_access
)
end
end
```

Response would be

```json
{
"status": "failure",
"messages": {
"errors": ["You are not authorized to perform this operation"]
},
"status_code": "unprocessable_entity",
"meta": {}
}
```

If you want to override the default error message in a specific scenario,

```ruby
private

def authorize_user
return if user_authorized?

raise ::Api::Exception.new(
::Api::Exception.unauthorized_access, "Looks like you are not authorized to update credit score"
)
end
```
```json
{
"status": "failure",
"messages": {
"errors": ["Looks like you are not authorized to update credit score"]
},
"status_code": "unprocessable_entity",
"meta": {}
}
```

#### Response Status - Failure / Success

Response Object contains a key named `status`. It will have only any one of following types
* failure
* success

Status will be `failure` when
* Resource has any errors
* Resource is an instance of `::Api::Exception`
* StandardError is raised

Status will be `success` when
* Resource do not have any errors
* Resource is *not* an instance of `::Api::Exception`
* No Exception been raised

## Development

After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).

## Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/kalidasm/api-response_builder.

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).