ExtendedGrammar Case expression

nikoraes · Oct 8, 2024 · d34fc73 · d34fc73
1 parent c598f7a
commit d34fc73
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diff --git a/JexlNet.ExtendedGrammar/ExtendedGrammar.cs b/JexlNet.ExtendedGrammar/ExtendedGrammar.cs
@@ -202,6 +202,13 @@ public ExtendedGrammar()
             AddFunction("not", Not);
             AddFunction("$not", Not);
             AddTransform("not", Not);
+            // Case / Switch
+            AddFunction("case", Case);
+            AddFunction("$case", Case);
+            AddTransform("case", Case);
+            AddFunction("switch", Case);
+            AddFunction("$switch", Case);
+            AddTransform("switch", Case);
             // ArrayAppend
             AddFunction("append", ArrayAppend);
             AddFunction("$append", ArrayAppend);
@@ -1093,6 +1100,34 @@ public static JsonNode Not(JsonNode input)
             return null;
         }
 
+        /// <summary>
+        /// Evaluates a list of predicates and returns the first result expression whose predicate is satisfied.
+        /// </summary>
+        /// <example><code>switch(expression, case1, result1, case2, result2, ..., default)</code><code>$switch(expression, case1, result1, case2, result2, ..., default)</code><code>expression|switch(case1, result1, case2, result2, ..., default)</code></example>
+        /// <returns>The result of the first case whose predicate is satisfied, or the default value if no case is satisfied</returns>
+        public static JsonNode Case(JsonNode[] args)
+        {
+            if (args.Length < 3) return null;
+
+            JsonNode expressionResult = args[0];
+
+            for (int i = 1; i < args.Length - 1; i += 2)
+            {
+                JsonNode caseResult = args[i];
+                if (JsonNode.DeepEquals(expressionResult, caseResult))
+                {
+                    return args[i + 1];
+                }
+            }
+            // Return default
+            if (args.Length % 2 == 1)
+            {
+                return args[args.Length - 1];
+            }
+            // Return null if no default specified
+            return null;
+        }
+
         /// <summary>
         /// Returns a new array with the elements of the input array and the elements of the other array.
         /// </summary>

diff --git a/JexlNet.Test/ExtendedGrammar.cs b/JexlNet.Test/ExtendedGrammar.cs
@@ -1,5 +1,6 @@
 using System.Text.Json;
 using System.Text.Json.Nodes;
+using Xunit.Sdk;
 
 namespace JexlNet.Test;
 
@@ -257,6 +258,17 @@ public void Boolean(string expression, bool? expected)
         Assert.Equal(expected, result?.GetValue<bool>());
     }
 
+    [Theory]
+    [InlineData("2|case(1,'a',2,'b',3,'c')", "b")]
+    [InlineData("$case('bar','foo','a','bar','b','baz','c')", "b")]
+    [InlineData("'notfound'|case('bar','foo','a','bar','b','baz','c','b')", "b")]
+    public void Case(string expression, string expected)
+    {
+        var jexl = new Jexl(new ExtendedGrammar());
+        var result = jexl.Eval(expression);
+        Assert.Equal(expected, result?.ToString());
+    }
+
     [Theory]
     [InlineData("['foo', 'bar', 'baz'] | append('tek')")]
     [InlineData("['foo', 'bar'] | append(['baz','tek'])")]