repost

Gem Repost implements Redirect using POST method.

Implementation story and some details in the following article Redirect using POST in Rails.

Installation

Add this line to your application’s Gemfile:

gem 'repost'

And then execute:

$ bundle

Or install it yourself as:

$ gem install repost

What problem does it solve?

When you need to send some parameters to an endpoint which should redirect you after execution. There wouldn’t be a problem if an endpoint receives [GET], because you can just use:

redirect_to entity_url(id: @model.id, token: model.token...)

But when an endpoint receives [POST], you have to generate html form and submit it. So repost gem helps to avoid creation of additional view with html form, just use redirect_post method instead. I faced with this problem when was dealing with bank transactions. You can see the approximate scheme:

P.S. The repost gem was initially created in response to the redirection process required by Adyen 3D Secure 1, which often involved creating an HTML form and submitting it via POST.
However, with the advent of 3D Secure 2, which aims for a more integrated authentication experience, the use of such forms for POST submissions has not been encountered. 3D Secure 2 typically manages authentication data exchanges in the background, potentially eliminating the need for manual form submission.

Usage

If you use Rails, gem automatically includes helper methods to your controllers:

repost(...)

and, as an alias

redirect_post(...)

Under the hood it calls render method of current controller with html:.

Example in Rails app:

class MyController < ApplicationController
  ...
  def index
    repost(...)
  end
  ...
  # or
  def show
    redirect_post(...)
  end
end

If you use Sinatra, Roda or etc., you need to require it first somewhere in you project:

require 'repost'

Then ask senpai to generate a string with html:

Repost::Senpai.perform(...)

Example in Sinatra, Roda, etc. app:

class MyController < Sinatra::Base
  get '/' do
    Repost::Senpai.perform(...)
  end
end

Reminder:

In Rails app use repost or redirect_post method in your controller which performs ‘redirect’ when it is called.
In Sinatra, Roda, etc. app or if you need html output - call Senpai

Full example:

UPD: authenticity token is turned off by default. Use :auto or 'auto' to turn on default authenticity token from Rails. Any other string value would be treated as custom auth token value.

# plain ruby
# Repost::Senpai.perform('http://......)


# Rails
redirect_post('http://examp.io/endpoint',            # URL, looks understandable
  params: {
            a: 1,
            'b': { "c": 2 },
            d: [ 3, 4, 5 ],
            e: { f: 'string', g: [ 6, 7, 8 ] }
          },                                         # Your request body, also nested params and arrays
  options: {
    method: :post,                                   # OPTIONAL - DEFAULT is :post, but you can use others if needed
    status: :ok,                                     # OPTIONAL - DEFAULT is :ok. This is the http status that the form will be returned with.
    authenticity_token: 'auto',                      # OPTIONAL - :auto or 'auto' for Rails form_authenticity_token, string - custom token
    charset: 'Windows-1251',                         # OPTIONAL - DEFAULT is "UTF-8", corresponds for accept-charset
    form_id: 'CustomFormID',                         # OPTIONAL - DEFAULT is autogenerated
    autosubmit: false,                               # OPTIONAL - DEFAULT is true, if you want to get a confirmation for redirect
    autosubmit_nonce: '1d3n7i4ier',                  # RAILS - DEFAULT is content_security_policy_nonce, for pure Ruby - string identifier, more info - https://edgeguides.rubyonrails.org/security.html#content-security-policy
    decor: {                                         # If autosubmit is turned off or Javascript is disabled on client
      section: {                                     # ... you can decorate confirmation section and button
        classes: 'red-bg red-text',                  # OPTIONAL - <DIV> section, set classNames, separate with space
        html: '<h1>Press this button, dude!</h1>'    # OPTIONAL - Any html, which will appear before submit button
      },
      submit: {
        classes: 'button-decorated round-border',    # OPTIONAL - <Input> with type submit, set classNames, separate with space
        text: 'c0n71nue ...'                         # OPTIONAL - DEFAULT is 'Continue'
      }
    }
  }
)

Authenticity Token (Rails)

Currently you can pass the authenticity token in two ways:

Recommended:

Use options and :auto to pass the auth token. That should protect you from any implementation changes in future Rails versions
```
  redirect_post('https://exmaple.io/endpoint', options: {authenticity_token: :auto})
```

Or, it is still valid to:

use params and form_authenticity_token method directly from ActionController

  redirect_post('https://exmaple.io/endpoint', params: {authenticity_token: form_authenticity_token})

License

The gem is available as open source under the terms of the MIT License.

That’s all folks.

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