feature/ability to apply coupon for price

README.md

@@ -15,13 +15,13 @@ Install the gem and add to the application's Gemfile by executing:
 bundle add "monopay-ruby"
 ```
 
-If bundler is not being used to manage dependencies, install the gem by executing:
+If bundler is not being used to manage dependencies, install the gem by executing the:
 
 ```ruby
 gem install "monopay-ruby"
 ```
 
-## Usage
+## Configuration
 
 Add API token. There are two ways:
 First - add to the initializer file:
@@ -46,10 +46,32 @@ Development: [https://api.monobank.ua/](https://api.monobank.ua/)
 
 Production: [https://fop.monobank.ua/](https://fop.monobank.ua/)
 
-Just get the token and go to earn moneys! 🚀
+Just get the token and go to earn money! 🚀
+
+
+_______________________________________________________________
+
+Optional
+
+You may add a minimum value to your payment:
+
+```ruby
+# config/initializers/monopay-ruby.rb
+MonopayRuby.configure do |config|
+  config.min_price = 1
+end
+```
+* 0.01 UAH - it is a minimal valid value for Monobank:
+  - if you use 1 as an Integer it is equal to 0.01 UAH
+  - if you use BigDecimal(1) it's equal to 1 UAH
+
+The default value is 1 (0.01 UAH)
+
 
 ### Generate payment request
 
+Simple:
+
 ```ruby
 # app/controllers/payments_controller.rb
 class PaymentsController < ApplicationController
@@ -59,8 +81,8 @@ class PaymentsController < ApplicationController
       "https://example.com/payments/webhook"
     )
 
-    if payment.create(amount: 100, destination: "Payment description",)
-      # your success code processing
+    if payment.create(amount: 100, destination: "Payment description")
+      # your successful code processing
     else
       # your error code processing
       # flash[:error] = payment.error_messages
@@ -69,6 +91,34 @@ class PaymentsController < ApplicationController
 end
 ```
 
+With discount:
+
+```ruby
+# app/controllers/payments_controller.rb
+class PaymentsController < ApplicationController
+  def create
+    payment = MonopayRuby::Invoices::SimpleInvoice.new(
+      "https://example.com",
+      "https://example.com/payments/webhook"
+    )
+
+    if payment.create(amount: 100, discount: 20, discount_is_fixed: true, destination: "Payment description")
+      # your successful code processing
+    else
+      # your error code processing
+      # flash[:error] = payment.error_messages
+    end
+  end
+end
+```
+
+Options:
+- discount - is an number, which represents a % of discount if discount_is_fixed: false and an amount of discount if discount_is_fixed: true
+- discount_is_fixed - a Boolean which sets the type of discount:
+  - ```true``` fixed amount of discount will be applied, for example a coupon (use Integer or BigDecimal in ```discount``` )
+  - ```false``` discount amount will be preceded by % (use Integer in ```discount``` for correct counting of 0-100 %)
+
+
 ### Verify transaction
 
 ```ruby
@@ -80,7 +130,7 @@ class PaymentsController < ApplicationController
     webhook_validator = MonopayRuby::Webhooks::Validator.new(request)
 
     if webhook_validator.valid?
-      # your success code processing
+      # your successful code processing
     else
       # your error code processing
       # flash[:error] = webhook_validator.error_messages

lib/monopay-ruby/configuration.rb

@@ -1,7 +1,8 @@
 class MonopayRuby::Configuration
-  attr_accessor :api_token
+  attr_accessor :api_token, :min_price
 
   def initialize
-    @api_token = ENV["MONOBANK_API_TOKEN"] # note ability to use ENV variable in docs
+    @api_token = ENV["MONOBANK_API_TOKEN"]
+    @min_price = ENV["MIN_PRICE"] || 1
   end
 end

lib/monopay-ruby/invoices/simple_invoice.rb

@@ -30,11 +30,20 @@ def initialize(redirect_url: nil, webhook_url: nil)
       # @param [String] destination - additional info about payment
       # @param [String] reference - bill number or other reference
       # @return [Boolean] true if invoice was created successfully, false otherwise
-      def create(amount, destination: nil, reference: nil)
+      def create(amount:, options: {})
+        @amount = MonopayRuby::Services::ValidateValue.call(amount, DEFAULT_CURRENCY)
+        discount = options[:discount]
+        discount_is_fixed = options[:discount_is_fixed]
+        @destination = options[:destination]
+        @reference = options[:reference]
+
+        @min_amount = MonopayRuby::Services::ValidateValue.call(MonopayRuby.configuration.min_price, DEFAULT_CURRENCY, "Minimal amount")
         begin
-          @amount = convert_to_cents(amount)
-          @destination = destination
-          @reference = reference
+          if discount
+            discount = MonopayRuby::Services::ConvertAmount.call(discount, DEFAULT_CURRENCY)
+
+            @amount = MonopayRuby::Services::Discount.call(@amount, discount, discount_is_fixed, @min_amount)
+          end
 
           response = RestClient.post(API_CREATE_INVOICE_URL, request_body, headers)
           response_body = JSON.parse(response.body)
@@ -71,14 +80,6 @@ def request_body
           }
         }.to_json
       end
-
-      def convert_to_cents(amount)
-        if amount.is_a?(BigDecimal)
-          Money.from_amount(amount, DEFAULT_CURRENCY).cents
-        else
-          amount
-        end
-      end
     end
   end
 end

lib/monopay-ruby/services/base_service.rb

@@ -0,0 +1,9 @@
+module MonopayRuby
+  module Services
+    class BaseService
+      def self.call(*args)
+        new(*args).call
+      end
+    end
+  end
+end

lib/monopay-ruby/services/convert_amount.rb

@@ -0,0 +1,25 @@
+require "money"
+require "bigdecimal"
+
+module MonopayRuby
+  module Services
+    class ConvertAmount < BaseService
+      attr_reader :amount, :currency
+
+      def initialize(amount, currency)
+        @amount = amount
+        @currency = currency
+      end
+
+      def call
+        if amount.is_a?(BigDecimal)
+          Money.from_amount(amount, currency).cents
+        elsif amount.is_a?(Integer)
+          amount
+        else
+          raise TypeError, "allowed to use only a BigDecimal or Integer type"
+        end
+      end
+    end
+  end
+end

lib/monopay-ruby/services/discount.rb

@@ -0,0 +1,24 @@
+module MonopayRuby
+  module Services
+    class Discount < BaseService
+      attr_reader :amount, :discount, :discount_is_fixed, :min_amount
+
+      def initialize(amount, discount, discount_is_fixed, min_amount)
+        @amount = amount
+        @discount = discount
+        @discount_is_fixed = discount_is_fixed
+        @min_amount = min_amount
+      end
+
+      def call
+        if discount_is_fixed
+          sum = amount - discount
+        else
+          sum = amount * (1 - (discount.to_f / 100))
+        end
+
+        [sum.to_i, min_amount].max
+      end
+    end
+  end
+end

lib/monopay-ruby/services/validate_value.rb

@@ -0,0 +1,37 @@
+require "bigdecimal"
+
+module MonopayRuby
+  module Services
+    class ValidateValue < BaseService
+      attr_reader :amount, :currency, :type
+
+      def initialize(amount, currency, type='Amount')
+        @amount = amount
+        @currency = currency
+        @type = type
+      end
+
+      def call
+        if amount.is_a?(Integer) || amount.is_a?(BigDecimal)
+          if amount > 0
+            MonopayRuby::Services::ConvertAmount.call(amount, currency)
+          else
+            raise ArgumentError, "#{type} must be greater than 0"
+          end
+        else
+          raise TypeError, "#{type} is allowed to be Integer or BigDecimal, got #{amount.class}" unless amount.is_a?(Integer) || amount.is_a?(BigDecimal)
+        end
+      end
+
+      private
+
+      def name(var)
+        binding.local_variables.each do |name|
+          value = binding.local_variable_get(name)
+          return name.to_s if value == var
+        end
+        nil
+      end
+    end
+  end
+end

lib/monopay-ruby/webhooks/public_key.rb

@@ -2,7 +2,6 @@
 require "base64"
 require "json"
 
-require "pry"
 module MonopayRuby
   module Webhooks
     class PublicKey < MonopayRuby::Base