template engine

Inspectron.Epson.TemplateEngine.Tests/ExpressionEvaluatorTests.cs

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+using System.Text.Json;
+using Inspectron.Epson.TemplateEngine.DataBinding;
+
+namespace Inspectron.Epson.TemplateEngine.Tests;
+
+public class ExpressionEvaluatorTests
+{
+    private static DataContext CreateContext(string json)
+    {
+        var root = JsonDocument.Parse(json).RootElement;
+        return new DataContext(root);
+    }
+
+    [Fact]
+    public void Evaluate_SimpleProperty()
+    {
+        var ctx = CreateContext("""{"Name":"John"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("Hello John", eval.Evaluate("Hello {{Name}}"));
+    }
+
+    [Fact]
+    public void Evaluate_NestedProperty()
+    {
+        var ctx = CreateContext("""{"Person":{"Name":"Alice"}}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("Hi Alice", eval.Evaluate("Hi {{Person.Name}}"));
+    }
+
+    [Fact]
+    public void Evaluate_MissingProperty_ReturnsEmpty()
+    {
+        var ctx = CreateContext("""{"Name":"John"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("Hi ", eval.Evaluate("Hi {{Missing}}"));
+    }
+
+    [Fact]
+    public void Evaluate_NumberProperty()
+    {
+        var ctx = CreateContext("""{"Count":42}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("Count: 42", eval.Evaluate("Count: {{Count}}"));
+    }
+
+    [Fact]
+    public void Evaluate_FormatString_Decimal()
+    {
+        var ctx = CreateContext("""{"Price":9.5}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("9.50", eval.Evaluate("{{Price:F2}}"));
+    }
+
+    [Fact]
+    public void Evaluate_FormatString_DateTime()
+    {
+        var ctx = CreateContext("""{"Date":"2024-03-15T14:30:00Z"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("15-Mar-24 14:30", eval.Evaluate("{{Date:dd-MMM-yy HH:mm}}"));
+    }
+
+    [Fact]
+    public void Evaluate_MultipleExpressions()
+    {
+        var ctx = CreateContext("""{"First":"John","Last":"Doe"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("John Doe", eval.Evaluate("{{First}} {{Last}}"));
+    }
+
+    [Fact]
+    public void Evaluate_CaseInsensitivePropertyLookup()
+    {
+        var ctx = CreateContext("""{"name":"Alice"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("Alice", eval.Evaluate("{{Name}}"));
+    }
+
+    [Fact]
+    public void Evaluate_EmptyTemplate()
+    {
+        var ctx = CreateContext("""{}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("", eval.Evaluate(""));
+    }
+
+    [Fact]
+    public void Evaluate_NoExpressions()
+    {
+        var ctx = CreateContext("""{}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("plain text", eval.Evaluate("plain text"));
+    }
+
+    [Fact]
+    public void Evaluate_LoopVariable_Index()
+    {
+        var ctx = CreateContext("""{}""");
+        ctx.SetLoopVariable("$index", 3);
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.Equal("Index: 3", eval.Evaluate("Index: {{$index}}"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_TruthyString()
+    {
+        var ctx = CreateContext("""{"Name":"John"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Name"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_EmptyString_IsFalsy()
+    {
+        var ctx = CreateContext("""{"Name":""}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.False(eval.EvaluateCondition("Name"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_MissingProperty_IsFalsy()
+    {
+        var ctx = CreateContext("""{}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.False(eval.EvaluateCondition("Name"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_Negation()
+    {
+        var ctx = CreateContext("""{"Name":"John"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.False(eval.EvaluateCondition("!Name"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_Negation_Missing()
+    {
+        var ctx = CreateContext("""{}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("!Name"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_NullValue_IsFalsy()
+    {
+        var ctx = CreateContext("""{"Name":null}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.False(eval.EvaluateCondition("Name"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_Comparison_Equal()
+    {
+        var ctx = CreateContext("""{"Count":5}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Count==5"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_Comparison_NotEqual()
+    {
+        var ctx = CreateContext("""{"Count":5}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Count!=3"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_Comparison_GreaterThan()
+    {
+        var ctx = CreateContext("""{"Count":5}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Count>3"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_Comparison_StringEqual()
+    {
+        var ctx = CreateContext("""{"Status":"active"}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Status=='active'"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_LoopVariable_First()
+    {
+        var ctx = CreateContext("""{}""");
+        ctx.SetLoopVariable("$first", true);
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("$first"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_LoopVariable_NotLast()
+    {
+        var ctx = CreateContext("""{}""");
+        ctx.SetLoopVariable("$last", false);
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("!$last"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_NonEmptyArray_IsTruthy()
+    {
+        var ctx = CreateContext("""{"Items":[1,2,3]}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Items"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_EmptyArray_IsFalsy()
+    {
+        var ctx = CreateContext("""{"Items":[]}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.False(eval.EvaluateCondition("Items"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_BooleanTrue_IsTruthy()
+    {
+        var ctx = CreateContext("""{"Active":true}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.True(eval.EvaluateCondition("Active"));
+    }
+
+    [Fact]
+    public void EvaluateCondition_BooleanFalse_IsFalsy()
+    {
+        var ctx = CreateContext("""{"Active":false}""");
+        var eval = new ExpressionEvaluator(ctx);
+
+        Assert.False(eval.EvaluateCondition("Active"));
+    }
+
+    [Fact]
+    public void DataContext_ChildScope_InheritsParentVariables()
+    {
+        var ctx = CreateContext("""{}""");
+        var item = JsonDocument.Parse("""{"Name":"Pizza"}""").RootElement;
+        ctx.SetVariable("item", item);
+
+        var child = ctx.CreateChildScope();
+        var childEval = new ExpressionEvaluator(child);
+
+        Assert.Equal("Pizza", childEval.Evaluate("{{item.Name}}"));
+    }
+
+    [Fact]
+    public void DataContext_ChildScope_OverridesParentVariable()
+    {
+        var ctx = CreateContext("""{}""");
+        var item1 = JsonDocument.Parse("""{"Name":"Pizza"}""").RootElement;
+        ctx.SetVariable("item", item1);
+
+        var child = ctx.CreateChildScope();
+        var item2 = JsonDocument.Parse("""{"Name":"Pasta"}""").RootElement;
+        child.SetVariable("item", item2);
+
+        var childEval = new ExpressionEvaluator(child);
+        Assert.Equal("Pasta", childEval.Evaluate("{{item.Name}}"));
+
+        var parentEval = new ExpressionEvaluator(ctx);
+        Assert.Equal("Pizza", parentEval.Evaluate("{{item.Name}}"));
+    }
+}