Parser with first tests; ICommand as abstraction

Src/AjLang.Tests/Compiler/ParserTests.cs

@@ -3,68 +3,28 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using AjLang.Compiler;
+using AjLang.Expressions;
 
 namespace AjLang.Tests.Compiler
 {
-    /// <summary>
-    /// Summary description for ParserTests
-    /// </summary>
     [TestClass]
     public class ParserTests
     {
-        public ParserTests()
+        [TestMethod]
+        public void ParseInteger()
         {
-            //
-            // TODO: Add constructor logic here
-            //
-        }
+            Parser parser = new Parser("123");
+            IExpression expr = parser.ParseExpression();
 
-        private TestContext testContextInstance;
+            Assert.IsNotNull(expr);
+            Assert.IsInstanceOfType(expr, typeof(ConstantExpression));
 
-        /// <summary>
-        ///Gets or sets the test context which provides
-        ///information about and functionality for the current test run.
-        ///</summary>
-        public TestContext TestContext
-        {
-            get
-            {
-                return testContextInstance;
-            }
-            set
-            {
-                testContextInstance = value;
-            }
-        }
+            ConstantExpression cexpr = (ConstantExpression)expr;
 
-        #region Additional test attributes
-        //
-        // You can use the following additional attributes as you write your tests:
-        //
-        // Use ClassInitialize to run code before running the first test in the class
-        // [ClassInitialize()]
-        // public static void MyClassInitialize(TestContext testContext) { }
-        //
-        // Use ClassCleanup to run code after all tests in a class have run
-        // [ClassCleanup()]
-        // public static void MyClassCleanup() { }
-        //
-        // Use TestInitialize to run code before running each test 
-        // [TestInitialize()]
-        // public void MyTestInitialize() { }
-        //
-        // Use TestCleanup to run code after each test has run
-        // [TestCleanup()]
-        // public void MyTestCleanup() { }
-        //
-        #endregion
+            Assert.AreEqual(123, cexpr.Evaluate(null));
 
-        [TestMethod]
-        public void TestMethod1()
-        {
-            //
-            // TODO: Add test logic	here
-            //
+            Assert.IsNull(parser.ParseExpression());
         }
     }
 }

Src/AjLang/AjLang.csproj

@@ -45,9 +45,12 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Commands\ICommand.cs" />
     <Compile Include="Commands\SetVariableCommand.cs" />
+    <Compile Include="Compiler\ParserException.cs" />
     <Compile Include="Compiler\Lexer.cs" />
     <Compile Include="Compiler\LexerException.cs" />
+    <Compile Include="Compiler\Parser.cs" />
     <Compile Include="Compiler\Token.cs" />
     <Compile Include="Compiler\TokenType.cs" />
     <Compile Include="Context.cs" />

Src/AjLang/Commands/ICommand.cs

@@ -0,0 +1,8 @@
+
+namespace AjLang.Commands
+{
+    public interface ICommand
+    {
+        void Execute(Context context);
+    }
+}

Src/AjLang/Commands/SetVariableCommand.cs

@@ -7,7 +7,7 @@
 
     using AjLang.Expressions;
 
-    public class SetVariableCommand
+    public class SetVariableCommand : ICommand
     {
         private string name;
         private IExpression expression;

Src/AjLang/Compiler/Parser.cs

@@ -0,0 +1,45 @@
+namespace AjLang.Compiler
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Text;
+    using AjLang.Expressions;
+    using System.Globalization;
+
+    public class Parser
+    {
+        private Lexer lexer;
+
+        public Parser(string text)
+            : this(new Lexer(text))
+        {
+        }
+
+        public Parser(Lexer lexer)
+        {
+            this.lexer = lexer;
+        }
+
+        public IExpression ParseExpression()
+        {
+            Token token = this.NextToken();
+
+            if (token == null)
+                return null;
+
+            switch (token.Type)
+            {
+                case TokenType.Integer:
+                    return new ConstantExpression(int.Parse(token.Value, CultureInfo.InvariantCulture));
+            }
+
+            throw new ParserException(string.Format("Unexpected '{0}'", token.Value));
+        }
+
+        private Token NextToken()
+        {
+            return this.lexer.NextToken();
+        }
+    }
+}

Src/AjLang/Compiler/ParserException.cs

@@ -0,0 +1,15 @@
+namespace AjLang.Compiler
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Text;
+
+    public class ParserException : Exception
+    {
+        public ParserException(string msg)
+            : base(msg)
+        {
+        }
+    }
+}