From b586bfe11efa7e71a918a3e989fb1e85009de011 Mon Sep 17 00:00:00 2001
From: ModZero <modzero@modzero.xyz>
Date: Thu, 8 Feb 2024 18:19:48 +0100
Subject: [PATCH] Test and fix the "operator after equals" case.

---
 Server/Calculator.cs           | 19 +++++++++----------
 ServerTests/CalculatorTests.cs | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/Server/Calculator.cs b/Server/Calculator.cs
index 4f78828..52eeb4a 100644
--- a/Server/Calculator.cs
+++ b/Server/Calculator.cs
@@ -44,15 +44,14 @@ public record Calculator(CalculatorState State, string LeftOperand, CalculatorOp
 
     public Calculator() : this(CalculatorState.AfterEquals, "0", null, "0") { }
 
-    public Calculator OperatorPressed(CalculatorOperator op) => this with
-    {
-        LeftOperand = State switch {
-            CalculatorState.AfterOperator or CalculatorState.AfterEquals => RightOperand,
+    public Calculator OperatorPressed(CalculatorOperator op) => new(
+        LeftOperand: State switch {
+            CalculatorState.AfterOperator or CalculatorState.AfterEquals => Display,
             CalculatorState.AfterDigit => Evaluate(),
-        },
-        Operator = op,
-        State = CalculatorState.AfterOperator,
-    };
+        }, 
+        Operator: op, 
+        RightOperand: Display, 
+        State: CalculatorState.AfterOperator);
 
     public Calculator EqualsPressed() => this with {
         LeftOperand = Evaluate(),
@@ -61,13 +60,13 @@ public record Calculator(CalculatorState State, string LeftOperand, CalculatorOp
 
     public Calculator DigitPressed(string digit) => this with {
         LeftOperand = State switch {
-            CalculatorState.AfterEquals or CalculatorState.AfterOperator => RightOperand,
+            CalculatorState.AfterEquals or CalculatorState.AfterOperator => Display,
             CalculatorState.AfterDigit => LeftOperand,
         },
         RightOperand = State switch {
             CalculatorState.AfterOperator or CalculatorState.AfterEquals => digit,
             CalculatorState.AfterDigit => RightOperand + digit,
-        },        
+        },
         State = CalculatorState.AfterDigit,
     };
 
diff --git a/ServerTests/CalculatorTests.cs b/ServerTests/CalculatorTests.cs
index 249fa11..a972c50 100644
--- a/ServerTests/CalculatorTests.cs
+++ b/ServerTests/CalculatorTests.cs
@@ -40,4 +40,19 @@ public class CalculatorTests
         calculator = calculator.EqualsPressed();
         Assert.Equal("8", calculator.Display);
     }
+
+    [Fact]
+    public void OperatorAfterEquals()
+    {
+        var calculator = new Calculator()
+            .DigitPressed("2")
+            .OperatorPressed(CalculatorOperator.Multiplication)
+            .DigitPressed("3")
+            .EqualsPressed();
+        Assert.Equal("6", calculator.Display);
+        calculator = calculator.OperatorPressed(CalculatorOperator.Addition);
+        Assert.Equal("6", calculator.Display);
+        calculator = calculator.EqualsPressed();
+        Assert.Equal("12", calculator.Display);
+    }
 }
\ No newline at end of file