Rename amount to quantity

More idiomatic naming for the order quantities.

lib/rex/matcher.rb

@@ -7,15 +7,15 @@ module Rex
       return trades if highest_buy_order.nil? || lowest_sell_order.nil?
 
       while highest_buy_order.price >= lowest_sell_order.price
-        max_amount = [highest_buy_order.remaining_amount, lowest_sell_order.remaining_amount].min
-        highest_buy_order.remaining_amount -= max_amount
-        lowest_sell_order.remaining_amount -= max_amount
+        max_quantity = [highest_buy_order.remaining_quantity, lowest_sell_order.remaining_quantity].min
+        highest_buy_order.remaining_quantity -= max_quantity
+        lowest_sell_order.remaining_quantity -= max_quantity
 
         trades << Trade.new(
           id: order_book.next_trade_id,
           buy_order: highest_buy_order,
           sell_order: lowest_sell_order,
-          amount: max_amount,
+          quantity: max_quantity,
           price: lowest_sell_order.price
         )
 

lib/rex/order.rb

@@ -5,10 +5,10 @@ module Rex
       :is_buy,
       :price,
       :user_id,
-      :amount,
+      :quantity,
       :previous_order,
       :next_order,
-      :remaining_amount
+      :remaining_quantity
     )
 
     def initialize(attrs = {})
@@ -17,15 +17,15 @@ module Rex
       @user_id = attrs[:user_id]
       @price = attrs[:price]
       @is_buy = attrs[:is_buy]
-      @amount = attrs[:amount]
-      @remaining_amount = attrs[:amount]
+      @quantity = attrs[:quantity]
+      @remaining_quantity = attrs[:quantity]
 
       @next_order = nil
       @previous_order = nil
     end
 
     def filled?
-      remaining_amount == 0
+      remaining_quantity == 0
     end
   end
 end

lib/rex/trade.rb

@@ -4,7 +4,7 @@ module Rex
       :id,
       :buy_order,
       :sell_order,
-      :amount,
+      :quantity,
       :price
     )
 
@@ -12,7 +12,7 @@ module Rex
       @id = attributes[:id]
       @buy_order = attributes[:buy_order]
       @sell_order = attributes[:sell_order]
-      @amount = attributes[:amount]
+      @quantity = attributes[:quantity]
       @price = attributes[:price]
     end
   end

spec/factories/orders.rb

@@ -6,7 +6,7 @@ FactoryBot.define do
     sequence(:user_id) { |i| i }
     sequence(:is_buy) { |i| (i % 2).zero? }
     sequence(:price) { 100 }
-    sequence(:amount) { 20 }
-    remaining_amount { amount }
+    sequence(:quantity) { 20 }
+    remaining_quantity { quantity }
   end
 end

spec/matcher_spec.rb

@@ -5,9 +5,9 @@ RSpec.describe Rex::Matcher do
 
   describe "#match" do
     let(:order_book) { Rex::OrderBook.new }
-    let(:buy_order) { build(:order, price: 100, is_buy: true, amount: 100, remaining_amount: 100) }
-    let(:cheaper_sell_order) { build(:order, price: 99, is_buy: false, amount: 50, remaining_amount: 50) }
-    let(:pricier_sell_order) { build(:order, price: 100, is_buy: false, amount: 70, remaining_amount: 70) }
+    let(:buy_order) { build(:order, price: 100, is_buy: true, quantity: 100, remaining_quantity: 100) }
+    let(:cheaper_sell_order) { build(:order, price: 99, is_buy: false, quantity: 50, remaining_quantity: 50) }
+    let(:pricier_sell_order) { build(:order, price: 100, is_buy: false, quantity: 70, remaining_quantity: 70) }
 
     context "when order book has unmatched orders" do
       before do
@@ -25,13 +25,13 @@ RSpec.describe Rex::Matcher do
         expect(trades[0].buy_order).to eq(buy_order)
         expect(trades[0].sell_order).to eq(cheaper_sell_order)
         expect(trades[0].price).to eq(99)
-        expect(trades[0].amount).to eq(50)
+        expect(trades[0].quantity).to eq(50)
 
         expect(trades[1].id).to eq(2)
         expect(trades[1].buy_order).to eq(buy_order)
         expect(trades[1].sell_order).to eq(pricier_sell_order)
         expect(trades[1].price).to eq(100)
-        expect(trades[1].amount).to eq(50)
+        expect(trades[1].quantity).to eq(50)
       end
 
       it "removes filled orders from the order book" do
@@ -39,7 +39,7 @@ RSpec.describe Rex::Matcher do
 
         expect(order_book.highest_buy_order).to eq(nil)
         expect(order_book.lowest_sell_order).to eq(pricier_sell_order)
-        expect(order_book.lowest_sell_order.remaining_amount).to eq(20)
+        expect(order_book.lowest_sell_order.remaining_quantity).to eq(20)
       end
     end
 
@@ -52,14 +52,14 @@ RSpec.describe Rex::Matcher do
     # https://stackoverflow.com/a/18524231/3200224
     # Testing a common example with a proven to be correct solution
     context "stack overflow scenario" do
-      let(:order_1) { build(:order, price: 2030, is_buy: false, amount: 100) }
-      let(:order_2) { build(:order, price: 2025, is_buy: false, amount: 100) }
-      let(:order_3) { build(:order, price: 2030, is_buy: false, amount: 200) }
-      let(:order_4) { build(:order, price: 2015, is_buy: true, amount: 100) }
-      let(:order_5) { build(:order, price: 2020, is_buy: true, amount: 200) }
-      let(:order_6) { build(:order, price: 2015, is_buy: true, amount: 200) }
+      let(:order_1) { build(:order, price: 2030, is_buy: false, quantity: 100) }
+      let(:order_2) { build(:order, price: 2025, is_buy: false, quantity: 100) }
+      let(:order_3) { build(:order, price: 2030, is_buy: false, quantity: 200) }
+      let(:order_4) { build(:order, price: 2015, is_buy: true, quantity: 100) }
+      let(:order_5) { build(:order, price: 2020, is_buy: true, quantity: 200) }
+      let(:order_6) { build(:order, price: 2015, is_buy: true, quantity: 200) }
 
-      let(:crossing_order) { build(:order, is_buy: true, amount: 250, price: 2035) }
+      let(:crossing_order) { build(:order, is_buy: true, quantity: 250, price: 2035) }
 
       before do
         order_book.add_order(order_1)
@@ -79,19 +79,19 @@ RSpec.describe Rex::Matcher do
 
         expect(trades[0].id).to eq(1)
         expect(trades[0].price).to eq(2025)
-        expect(trades[0].amount).to eq(100)
+        expect(trades[0].quantity).to eq(100)
         expect(trades[0].buy_order).to eq(crossing_order)
         expect(trades[0].sell_order).to eq(order_2)
 
         expect(trades[1].id).to eq(2)
         expect(trades[1].price).to eq(2030)
-        expect(trades[1].amount).to eq(100)
+        expect(trades[1].quantity).to eq(100)
         expect(trades[1].buy_order).to eq(crossing_order)
         expect(trades[1].sell_order).to eq(order_1)
 
         expect(trades[2].id).to eq(3)
         expect(trades[2].price).to eq(2030)
-        expect(trades[2].amount).to eq(50)
+        expect(trades[2].quantity).to eq(50)
         expect(trades[2].buy_order).to eq(crossing_order)
         expect(trades[2].sell_order).to eq(order_3)
       end

spec/order_spec.rb

@@ -4,20 +4,20 @@ RSpec.describe Rex::Order do
   describe "#filled?" do
     let(:order) do
       instance = build(:order)
-      instance.remaining_amount = remaining_amount
+      instance.remaining_quantity = remaining_quantity
       instance
     end
 
     subject { order.filled? }
 
-    context "when remaining amount is not zero" do
-      let(:remaining_amount) { 50 }
+    context "when remaining quantity is not zero" do
+      let(:remaining_quantity) { 50 }
 
       it { is_expected.to be(false) }
     end
 
-    context "when remaining amount is zero" do
-      let(:remaining_amount) { 0 }
+    context "when remaining quantity is zero" do
+      let(:remaining_quantity) { 0 }
 
       it { is_expected.to be(true) }
     end