From 879ada6be105ef25445256561ffc0ab232967496 Mon Sep 17 00:00:00 2001
From: Jamiras <32680403+Jamiras@users.noreply.github.com>
Date: Tue, 1 Oct 2024 14:29:28 -0600
Subject: [PATCH] support for unary minus (#539)

---
 Source/Parser/Expressions/ExpressionBase.cs   | 11 +++
 .../Parser/Expressions/ExpressionBaseTests.cs | 14 ++++
 .../Expressions/MathematicExpressionTests.cs  | 78 +++++++++++++++++++
 3 files changed, 103 insertions(+)

diff --git a/Source/Parser/Expressions/ExpressionBase.cs b/Source/Parser/Expressions/ExpressionBase.cs
index 506cf225..5c924571 100644
--- a/Source/Parser/Expressions/ExpressionBase.cs
+++ b/Source/Parser/Expressions/ExpressionBase.cs
@@ -170,6 +170,7 @@ private enum OperationPriority
             AddSubtract,
             MulDivMod,
             Not,
+            Negate,
             Parenthesis,
         }
 
@@ -642,6 +643,16 @@ private static ExpressionBase ParseClauseCore(PositionalTokenizer tokenizer)
                         result.Location = new TextRange(tokenStart, tokenEnd);
                         return result;
                     }
+                    else if (Char.IsLetter(tokenizer.NextChar) || tokenizer.NextChar == '(')
+                    {
+                        var next = ParseExpression(tokenizer, OperationPriority.Negate);
+                        if (next.Type == ExpressionType.Error)
+                            return next;
+
+                        var result = new MathematicExpression(new IntegerConstantExpression(0), MathematicOperation.Subtract, next);
+                        result.Location = new TextRange(tokenStart, next.Location.End);
+                        return result;
+                    }
                     return ParseError(tokenizer, "Minus without value", tokenStart.Line, tokenStart.Column);
 
                 case '{':
diff --git a/Tests/Parser/Expressions/ExpressionBaseTests.cs b/Tests/Parser/Expressions/ExpressionBaseTests.cs
index 2820e697..d237b107 100644
--- a/Tests/Parser/Expressions/ExpressionBaseTests.cs
+++ b/Tests/Parser/Expressions/ExpressionBaseTests.cs
@@ -694,5 +694,19 @@ public void TestParseLineColumnValues()
             Assert.That(expression.Location.End.Line, Is.EqualTo(7));
             Assert.That(expression.Location.End.Column, Is.EqualTo(8));
         }
+
+        [Test]
+        public void TestParseUnaryMinusVariable()
+        {
+            var tokenizer = CreateTokenizer("-a");
+            var expression = ExpressionBase.Parse(tokenizer);
+
+            Assert.That(expression, Is.InstanceOf<MathematicExpression>());
+            var mathematic = (MathematicExpression)expression;
+            Assert.That(mathematic.Left, Is.EqualTo(new IntegerConstantExpression(0)));
+            Assert.That(mathematic.Operation, Is.EqualTo(MathematicOperation.Subtract));
+            Assert.That(mathematic.Right, Is.InstanceOf<VariableExpression>());
+            Assert.That(((VariableExpression)mathematic.Right).Name, Is.EqualTo("a"));
+        }
     }
 }
diff --git a/Tests/Parser/Expressions/MathematicExpressionTests.cs b/Tests/Parser/Expressions/MathematicExpressionTests.cs
index de28b4a9..de739a21 100644
--- a/Tests/Parser/Expressions/MathematicExpressionTests.cs
+++ b/Tests/Parser/Expressions/MathematicExpressionTests.cs
@@ -425,5 +425,83 @@ public void TestCombining(string input, string expected)
             result.AppendString(builder);
             Assert.That(builder.ToString(), Is.EqualTo(expected));
         }
+
+        [Test]
+        public void TestUnaryMinusVariable()
+        {
+            var scope = AchievementScriptTests.Evaluate(
+                "a = 8\n" +
+                "b = -a"
+            );
+
+            var b = scope.GetVariable("b");
+            Assert.That(b, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)b).Value, Is.EqualTo(-8));
+        }
+
+        [Test]
+        public void TestUnaryMinusAddition()
+        {
+            var scope = AchievementScriptTests.Evaluate(
+                "a = 8\n" +
+                "b = -a + 2"
+            );
+
+            var b = scope.GetVariable("b");
+            Assert.That(b, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)b).Value, Is.EqualTo(-6));
+        }
+
+        [Test]
+        public void TestUnaryMinusMultiplication()
+        {
+            var scope = AchievementScriptTests.Evaluate(
+                "a = 8\n" +
+                "b = -a * 2"
+            );
+
+            var b = scope.GetVariable("b");
+            Assert.That(b, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)b).Value, Is.EqualTo(-16));
+        }
+
+        [Test]
+        public void TestUnaryMinusParenthesis()
+        {
+            var scope = AchievementScriptTests.Evaluate(
+                "a = 8\n" +
+                "b = -(a + 2)"
+            );
+
+            var b = scope.GetVariable("b");
+            Assert.That(b, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)b).Value, Is.EqualTo(-10));
+        }
+
+        [Test]
+        public void TestUnaryMinusArrayValue()
+        {
+            var scope = AchievementScriptTests.Evaluate(
+                "a = [8]\n" +
+                "b = -a[0]"
+            );
+
+            var b = scope.GetVariable("b");
+            Assert.That(b, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)b).Value, Is.EqualTo(-8));
+        }
+
+        [Test]
+        public void TestUnaryMinusFunctionCall()
+        {
+            var scope = AchievementScriptTests.Evaluate(
+                "function a(n) => n\n" +
+                "b = -a(8)"
+            );
+
+            var b = scope.GetVariable("b");
+            Assert.That(b, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)b).Value, Is.EqualTo(-8));
+        }
     }
 }