Perfect Price

• Define your plans and features

• Use the definition to:

  • calculate the total for your billing
  • get data for the plans section of your page

Features

• Plan definitions with:

  • Name
  • Setup and monthly fees
  • Features

• Feature definitions with:

  • Custom labels for rendering
  • Limits and units
  • Metered pricing (base price per unit, volume discounts)
  • Credits handling

What it's not

• It doesn't handle your charging
• It doesn't update your models

Defining a plan

Plans are defined in config/initializers/perfect_price.rb like this:

PerfectPrice.configure do

  feature :projects,  :label => "Projects", :limit => 35
  feature :storage,   :label => "Storage",  :limit => 15, :units => "Gb"
  feature :users,     :label => "Users",    :limit => PerfectPrice::UNLIMITED
  feature :mo
  feature :mt,        :unit_price       => 0.05,
                      :bundled          => 100
                      :volume_discounts => {
                          20000   => 0.005,
                          50000   => 0.01,
                          100000  => 0.015,
                          250000  => 0.02,
                          500000  => 0.025,
                          1000000 => 0.03 }

  plan :max, :label => 'Max' do
    setup_fee    100
    monthly_fee  149
    meta         :label => "Top-of-the-line"
    
    feature      :projects => PerfectPrice::UNLIMITED
    feature      :storage  => 75
    feature      :notes    => PerfectPrice::UNLIMITED
  end

  plan :premium, :label => 'Premium' do
    setup_fee    100
    monthly_feee 99
    meta         :label => "The Sweet Spot"

    feature      :projects, :limit => 100
    feature      :storage, :limit => 30
  end

  plan :plus, :label => 'Plus' do
    setup_fee    100
    monthly_fee  49
    meta         :label => "For Small Groups"
  end

end

Calculating the total

Assuming that you have an Account model that's responsible for all account handling logic, you might want to have the process_payment call like this:

def Account.process_payment(payment)
    # Try charging with the total and return false if it didn't work
    return false unless self.subscription.charge(payment[:total])

    # Update credits
    self.credits = payment[:credits]
    save

    # Record the payment in log
    subscription_payments.create(:total => payment[:total], :details => payment[:details])
    return true
end

And here's how you use the library to calculate the total amount for initial payment:

# Initial payment
plan    = account.plan
payment = PerfectPrice.initial_payment(plan)

unless account.process_payment(payment)
    # Notification
end

When the time comes to calculate the monthly payment you do it like this:

# Then monthly
payment = PerfectPrice.monthly_payment(plan,
    :credits => { :feature_a => 100 },
    :usage   => { :feature_a => 150, :feature_b => 1 })

unless account.process_payment(payment)
    # Notification
end

In both cases the payment structure being returned contains the following:

payment.total      # X + Y
payment.details    # { 'monthy_fee' => X, 'feature_a' => Y }

When handling monthly payments, there also will be the updated credits section:

payment.credits    # { :feature_a => 0 }

It's the intention that you get the details of the calculation in the details section for your records. This way you can explain how'd you come up with the number.

The credits section contains the updated credits hash that you can put back into your account upon the successful transaction.

Snapshots

Sometimes you need to save a plan defition with all its features. The most common case is to freeze a plan for all existing subscribers, so that when you make changes to your current plans, it didn't affect billing of existing customers.

Both plans and features support this by taking a snapshot into a JSON string and restoring everything from such JSON string.

plan.to_snapshot    # { :name => 'abc', :features => { :mo => {}, ... } }

When you want to restore the plan, you do:

plan = Plan.from_snapshot(snapshot_hash)

License

perfect_price is Copyright © 2013 Aleksey Gureiev and Recess Mobile.

It is free software, and may be redistributed under the terms specified in the MIT-LICENSE file.