From 1ff3fb78b9696e9b46e8d1e5c37c6e57c13cfcd6 Mon Sep 17 00:00:00 2001
From: Allan Guigou <34221163+AllanGuigou@users.noreply.github.com>
Date: Tue, 9 Dec 2025 12:32:18 -0800
Subject: [PATCH] Add case function

---
 src/Sdk/Expressions/ExpressionConstants.cs |  1 +
 src/Sdk/Expressions/ExpressionParser.cs    | 20 +++++++++++++++++---
 src/Sdk/Expressions/ParseException.cs      |  3 +++
 src/Sdk/Expressions/ParseExceptionKind.cs  |  1 +
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/Sdk/Expressions/ExpressionConstants.cs b/src/Sdk/Expressions/ExpressionConstants.cs
index df98e3869..ef544395f 100644
--- a/src/Sdk/Expressions/ExpressionConstants.cs
+++ b/src/Sdk/Expressions/ExpressionConstants.cs
@@ -10,6 +10,7 @@ namespace GitHub.Actions.Expressions
     {
         static ExpressionConstants()
         {
+            AddFunction<Case>("case", 3, Byte.MaxValue);
             AddFunction<Contains>("contains", 2, 2);
             AddFunction<EndsWith>("endsWith", 2, 2);
             AddFunction<Format>("format", 1, Byte.MaxValue);
diff --git a/src/Sdk/Expressions/ExpressionParser.cs b/src/Sdk/Expressions/ExpressionParser.cs
index 32b1fd740..9d0501476 100644
--- a/src/Sdk/Expressions/ExpressionParser.cs
+++ b/src/Sdk/Expressions/ExpressionParser.cs
@@ -17,9 +17,10 @@ namespace GitHub.Actions.Expressions
             String expression,
             ITraceWriter trace,
             IEnumerable<INamedValueInfo> namedValues,
-            IEnumerable<IFunctionInfo> functions)
+            IEnumerable<IFunctionInfo> functions,
+            Boolean allowCaseFunction = false)
         {
-            var context = new ParseContext(expression, trace, namedValues, functions);
+            var context = new ParseContext(expression, trace, namedValues, functions, allowCaseFunction: allowCaseFunction);
             context.Trace.Info($"Parsing expression: <{expression}>");
             return CreateTree(context);
         }
@@ -349,6 +350,10 @@ namespace GitHub.Actions.Expressions
             {
                 throw new ParseException(ParseExceptionKind.TooManyParameters, token: @operator, expression: context.Expression);
             }
+            else if (functionInfo.Name.Equals("case", StringComparison.OrdinalIgnoreCase) && function.Parameters.Count % 2 == 0)
+            {
+                throw new ParseException(ParseExceptionKind.EvenParameters, token: @operator, expression: context.Expression);
+            }
         }
 
         /// <summary>
@@ -411,6 +416,12 @@ namespace GitHub.Actions.Expressions
             String name,
             out IFunctionInfo functionInfo)
         {
+            if (String.Equals(name, "case", StringComparison.OrdinalIgnoreCase) && !context.AllowCaseFunction)
+            {
+                functionInfo = null;
+                return false;
+            }
+
             return ExpressionConstants.WellKnownFunctions.TryGetValue(name, out functionInfo) ||
                 context.ExtensionFunctions.TryGetValue(name, out functionInfo);
         }
@@ -418,6 +429,7 @@ namespace GitHub.Actions.Expressions
         private sealed class ParseContext
         {
             public Boolean AllowUnknownKeywords;
+            public Boolean AllowCaseFunction;
             public readonly String Expression;
             public readonly Dictionary<String, IFunctionInfo> ExtensionFunctions = new Dictionary<String, IFunctionInfo>(StringComparer.OrdinalIgnoreCase);
             public readonly Dictionary<String, INamedValueInfo> ExtensionNamedValues = new Dictionary<String, INamedValueInfo>(StringComparer.OrdinalIgnoreCase);
@@ -433,7 +445,8 @@ namespace GitHub.Actions.Expressions
                 ITraceWriter trace,
                 IEnumerable<INamedValueInfo> namedValues,
                 IEnumerable<IFunctionInfo> functions,
-                Boolean allowUnknownKeywords = false)
+                Boolean allowUnknownKeywords = false,
+                Boolean allowCaseFunction = false)
             {
                 Expression = expression ?? String.Empty;
                 if (Expression.Length > ExpressionConstants.MaxLength)
@@ -454,6 +467,7 @@ namespace GitHub.Actions.Expressions
 
                 LexicalAnalyzer = new LexicalAnalyzer(Expression);
                 AllowUnknownKeywords = allowUnknownKeywords;
+                AllowCaseFunction = allowCaseFunction;
             }
 
             private class NoOperationTraceWriter : ITraceWriter
diff --git a/src/Sdk/Expressions/ParseException.cs b/src/Sdk/Expressions/ParseException.cs
index e5f7f3fa1..9f661012a 100644
--- a/src/Sdk/Expressions/ParseException.cs
+++ b/src/Sdk/Expressions/ParseException.cs
@@ -29,6 +29,9 @@ namespace GitHub.Actions.Expressions
                 case ParseExceptionKind.TooManyParameters:
                     description = "Too many parameters supplied";
                     break;
+                case ParseExceptionKind.EvenParameters:
+                    description = "Even number of parameters supplied, requires an odd number of parameters";
+                    break;
                 case ParseExceptionKind.UnexpectedEndOfExpression:
                     description = "Unexpected end of expression";
                     break;
diff --git a/src/Sdk/Expressions/ParseExceptionKind.cs b/src/Sdk/Expressions/ParseExceptionKind.cs
index 297fe0e02..db6294b50 100644
--- a/src/Sdk/Expressions/ParseExceptionKind.cs
+++ b/src/Sdk/Expressions/ParseExceptionKind.cs
@@ -6,6 +6,7 @@ namespace GitHub.Actions.Expressions
         ExceededMaxLength,
         TooFewParameters,
         TooManyParameters,
+        EvenParameters,
         UnexpectedEndOfExpression,
         UnexpectedSymbol,
         UnrecognizedFunction,