performify

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Service object which makes you better.

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# Performify

It's well-known practice that has been proved in many large projects to move server logic into separated service classes. This approach gives a lot of advantages, because when you are able to create object that incapsulates your logic it's much easier to develop, search, control and test. And `performify` helps you to do it in nice and easy way with minimum of pain and maximum of result.

## Installation

Add this line to your application's Gemfile:

```ruby
gem 'performify'
```

And then execute:

```
$ bundle
```

Or install it yourself as:

```
$ gem install performify
```

## Usage

How to have a deal with services:

1. Define `ApplicationService`
2. Create new service inherited from `ApplicationService`
3. Implement `execute!` method
4. Use `super` to work with db transaction and automatic success / fail workflow control
5. Use `success!` and `fail!` to control everything by hands
6. Use `on_success` / `on_fail` to define callbacks
7. Use `schema do ... end` if you want to use validations

### ApplicationService

So, first of all it's better to create `ApplicationService` class that will be used as base for all services in your project. You can put any shared logic (like, authorization, for example) here:

```ruby
class ApplicationService < Performify::Base
  def authorize!(record)
    # you can put authorization logic here and use it from inherited services
  end
end
```

This is, for example, how authorization can be implemented for `Pundit`:

```ruby
class ApplicationService < Performify::Base
  def authorize!(record, query = default_query, record_policy = nil)
    record_policy ||= policy(record)
    return if record_policy.public_send(query)

raise Pundit::NotAuthorizedError, query: query, record: record, policy: record_policy
  end

def default_query
    @default_query ||= "#{self.class.name.demodulize.underscore.to_sym}?"
  end

def policy(record)
    @policy ||= Pundit.policy!(@current_user, record)
  end
end
```

### Service: database

Now, to define new service just create new class and inherit it from `ApplicationService`:

```ruby
module Users
  class Destroy < ApplicationService
    def execute!
      # current user is already available, so feel free to use it
      # to get user's context

authorize! current_user unless force?

# block passed into super's implementation will be executed
      # in transaction, so you can do multiple data operations, and final
      # result of this block will be used to determine result of execution

super do
        if current_user.update(destroyed_at: Time.zone.now)
          current_user.comments.find_each do |c|
            s = Comments::Destroy.new(current_user, c)
            s.execute!

# it's also ok to raise ActiveRecord::Rollback, it will be handled
            # gracefully as regular execution fail

raise ActiveRecord::Rollback unless s.success?
          end
        end
      end
    end

def force?
      # additional instance variables can be passed as named args into
      # initializer and accessed in service flow

force.present?
    end
  end
end
```

Now you can create instance of your service and check result of execution:

```ruby
service = Users::Destroy.new(current_user, force: true)
service.execute!
service.success? # or service.fail?
```

### Service: HTTP API

Sometimes your service doesn't work with database, but calls some http endpoint or do some other stuff that doesn't require db transaction. In this case you can control your service flow manually:

```ruby
class Stripe::Create < ApplicationService
  attr_reader :subscription

def execute!
    # here you can go to Stripe and create subscription for the user
    begin
      @subscription = Stripe::Subscription.create(
        customer: current_user.customer_id,
        plan: selected_plan.stripe_name,
      )

# everything looks ok, success

success!
   rescue Stripe::StripeError => e
      # something went wrong, let's notify developers and say that
      # service execution has been failed

Airbrake.notify(e)
     fail!
   end
  end
end
```

### Callbacks

If you need to do something on service success / fail it is possible to define appropriate callbacks. Notice, that in case of using `super` callbacks will be executed outside of db transaction, so it's safe to send emails from there, for example.

```ruby
module Passwords
  class Update < ApplicationService
    def execute!
      authorize! current_user

super do
        current_user.update(password: password, password_confirmation: password_confirmation)
      end
    end

# you can pass method name as a callback

on_success :invalidate_sessions

# or you can pass block instead of method name

on_success { UserMailer.password_changed(current_user).deliver_later }

private def invalidate_sessions
      # you can invalidate existing user's sessions here
    end
  end
end
```

### Validation

Performify allows you to validate input arguments using [dry-validation](http://dry-rb.org/gems/dry-validation/) schemas. Validation is performed on creation of service instance. And if validation is not passed it will be impossible to call execution. Result of execution will be automatically switched to failed state.

```ruby
module Users
  class Create
    schema do
      required(:email).filled(:str?)
    end

def execute!
      # it will be impossible to call execution if provided arguments
      # did not pass validation
    end
  end
end

service = Users::Create.new(current_user, email: nil)
service.execute! # nothing happens here
service.success? # will be false because of validation
service.errors   # contains hash of errors
```

Sometimes you can have differences between validation errors and execution errors. But usually it's boring to check them separately since you just need to display final result to user. To avoid double check you can use following trick:

```ruby
module Users
  class Create
    attr_reader :user

schema do
      required(:email).filled(:str?)
    end

def execute!
      user = User.new(email: email)
      authorize! user

# Let's assume that user has additional validation of uniqueness on the
      # level of model, so in controller you need to check separately service's
      # errors and model's errors, right?

super { user.save }
    end

# So, we define on fail callback where we copy errors from model
    # to service so now in controller we can check and use only service's errors

on_fail { errors! user.errors.to_h }
  end
end

# in controller

service = Users::Create.new(current_user, email: nil)
service.execute!

if service.success?
  # respond with ok
else
  # respond with unprocessable entity and service.errors
end
```

You can get filtered inputs after success validation by accessing `inputs`.

```ruby
module Users
  class UpdateProfile < ApplicationService
    schema do
      optional(:first_name).filled(:str?)
      optional(:last_name).filled(:str?)
      optional(:login).filled(:str?)
      optional(:image)
      optional(:email).filled(format?: /\A[^ \n\r\s]+@[^ \n\r\s]+\z/i)
    end

def execute!
      super { current_user.update(inputs) }
    end

on_fail { errors!(current_user.errors) }
  end
end
```

## Initialization

Performify will dynamically define accessors for all arguments passed to service in addition to current_user:

```ruby
module Users
  class Create
    def execute!
      # it will define accessors for all arguments:
      User.new(email: email, role: role, manager: current_user)
    end
  end
end

service = Users::Create.new(current_user, email: 'mail@google.com', role: 'employee')
```

But if you use `schema` to validate parameters Performify will define accessors only for additional arguments mentioned in schema:

```ruby
module Users
  class Create
    schema do
      required(:email).filled(:str?)
      optional(:phone).filled(:str?)
    end

def execute!
      # it will define accessors for `email` and `phone`, but won't define `role`
      User.new(email: email, phone: phone, manager: current_user) # phone is nil
    end
  end
end

service = Users::Create.new(current_user, email: 'mail@google.com', role: 'manager')
```

## Development

After checking out the repo, run `bin/setup` to install dependencies. Then, run `bin/rspec 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 `bin/rake install`. To release a new version, update the version number in `version.rb`, and then run `bin/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/kimrgrey/performify.

## License

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

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