OrderOptimizer

The OrderOptimizer gem helps to optimize orders when the goods are offered in different pack sizes and in different discount levels.

Imagine a product can be ordered in different pack sizes and each pack size has a different price per unit. For example like this:

Pack size	Price per Unit
1000	3.90
100	4.00
10	6.00
1	9.00

In this example, it is quite obvious that it is cheaper buying one 10-pack instead of nine 1-packs when you need 9 units (because the 10-pack costs 60.00 but nine 1-packs would cost 81.00).

But what would be the cheapest combination when you need 946 units? Or 947?

The OrderOptimizer answers this kind of question in a performant way.

Installation

Add this line to your application's Gemfile:

gem 'order_optimizer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install order_optimizer

Usage

# Initialize the optimizer with a catalog
order_optimizer = OrderOptimizer.new(
  '1-pack' => { quantity: 1, price_per_unit: 9 },
  '10-pack' => { quantity: 10, price_per_unit: 6 },
  '100-pack' => { quantity: 100, price_per_unit: 4 },
  '1000-pack' => { quantity: 1000, price_per_unit: 3.9 }
)

# Pick the cheapers possible order for the required quantity
cheapest_order_for_946_units = order_optimizer.cheapest_order(required_qty: 946)
cheapest_order_for_946_units.quantity # =>  946
cheapest_order_for_946_units.total    # => 3894.00
cheapest_order_for_946_units.skus     # => { '100-pack' => 9, '10-pack' => 4, '1-pack' => 6 }

cheapest_order_for_947_units = order_optimizer.cheapest_order(required_qty: 947)
cheapest_order_for_947_units.quantity # => 1_000
cheapest_order_for_947_units.total    # => 3_900.00
cheapest_order_for_947_units.skus     # => { '1000-pack' => 1 }

You can also optimize your order for exact order amounts

# Initialize the optimize with a catalog
order_optimizer = OrderOptimizer.new(
  '1-pack' => { quantity: 1, price_per_unit: 9 },
  '10-pack' => { quantity: 10, price_per_unit: 5 },
)

# Pick the cheapest order that includes the exact required quantity
cheapest_exact_order_for_58_units = order_optimizer.cheapest_exact_order(required_qty: 56)
cheapest_exact_order_for_58_units.quantity # => 58
cheapest_exact_order_for_58_units.total # => 322
cheapest_exact_order_for_58_units.skus # => { '10-pack' => 5, '1-pack' => 8 }

It is possible to define discount prices with a minimum quantity:

order_optimizer = OrderOptimizer.new(
  '1-pack' => { quantity: 1, price_per_unit: 9 },
  '10-discount' => { quantity: 1, min_quantity: 10, price_per_unit: 8 },
  '20-pack' => { quantity: 20, price_per_unit: 7 }
)

order_optimizer.cheapest_order(required_qty: 8).skus
#=> { '1-pack' => 8 }

order_optimizer.cheapest_order(required_qty: 9).skus
#=> { '10-discount' => 10 }

order_optimizer.cheapest_order(required_qty: 17).skus
#=> { '10-discount' => 17 }

order_optimizer.cheapest_order(required_qty: 18).skus
#=> { '20-pack' => 1 }

order_optimizer.cheapest_order(required_qty: 21).skus
#=> { '20-pack' => 1, '1-pack' => 1 }

order_optimizer.cheapest_order(required_qty: 29).skus
#=> { '20-pack' => 1, '10-discount' => 10 }

It is also possible to define discount prices with a maximum quantity:

order_optimizer = OrderOptimizer.new(
  '1-pack' => { quantity: 1, price_per_unit: 9 },
  '10-pack' => { quantity: 10, price_per_unit: 8, max_quantity: 20 },
)

order_optimizer.cheapest_order(required_qty: 30).skus
#=> { '10-pack' => 2, '1-pack' => 10 }

If you're just interested in all possible order combinations:

# Initialize the optimize with a catalog
order_optimizer = OrderOptimizer.new(
  '1-pack' => { quantity: 1, price_per_unit: 9 },
  '10-pack' => { quantity: 10, price_per_unit: 5 },
)

order_optimizer.possible_orders(required_qty: 11).size
#=> 3
order_optimizer.possible_orders(required_qty: 10).map(&:skus)
#=> [{"10-pack"=>1, "1-pack"=>1}, {"1-pack"=>11}, {"10-pack"=>2}]

Development

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

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/zaikio/order_optimizer. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

Make your changes and submit a pull request for them
Make sure to update CHANGELOG.md

To release a new version of the gem:

Update the version in lib/order_optimizer/version.rb
Update CHANGELOG.md to include the new version and its release date
Commit and push your changes
Create a new release on GitHub
CircleCI will build the Gem package and push it Rubygems for you

License

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

Code of Conduct

Everyone interacting in the OrderOptimizer project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.