Avalonia/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs

using System.Collections.Generic;
using System.Linq;
using Avalonia.Data.Core;
using Avalonia.Markup.Parsers;
using Avalonia.Markup.Parsers.Nodes;
using Xunit;

namespace Avalonia.Markup.UnitTests.Parsers
{
    public class ExpressionObserverBuilderTests
    {
        [Fact]
        public void Should_Build_Single_Property()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo"));

            AssertIsProperty(result[0], "Foo");
        }

        [Fact]
        public void Should_Build_Underscored_Property()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("_Foo"));

            AssertIsProperty(result[0], "_Foo");
        }

        [Fact]
        public void Should_Build_Property_With_Digits()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("F0o"));

            AssertIsProperty(result[0], "F0o");
        }

        [Fact]
        public void Should_Build_Dot()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("."));

            Assert.Equal(1, result.Count);
            Assert.IsType<EmptyExpressionNode>(result[0]);
        }

        [Fact]
        public void Should_Build_Property_Chain()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo.Bar.Baz"));

            Assert.Equal(3, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsProperty(result[1], "Bar");
            AssertIsProperty(result[2], "Baz");
        }

        [Fact]
        public void Should_Build_Negated_Property_Chain()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("!Foo.Bar.Baz"));

            Assert.Equal(4, result.Count);
            Assert.IsType<LogicalNotNode>(result[0]);
            AssertIsProperty(result[1], "Foo");
            AssertIsProperty(result[2], "Bar");
            AssertIsProperty(result[3], "Baz");
        }

        [Fact]
        public void Should_Build_Double_Negated_Property_Chain()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("!!Foo.Bar.Baz"));

            Assert.Equal(5, result.Count);
            Assert.IsType<LogicalNotNode>(result[0]);
            Assert.IsType<LogicalNotNode>(result[1]);
            AssertIsProperty(result[2], "Foo");
            AssertIsProperty(result[3], "Bar");
            AssertIsProperty(result[4], "Baz");
        }

        [Fact]
        public void Should_Build_Indexed_Property()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo[15]"));

            Assert.Equal(2, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsIndexer(result[1], "15");
            Assert.IsType<StringIndexerNode>(result[1]);
        }

        [Fact]
        public void Should_Build_Indexed_Property_StringIndex()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo[Key]"));

            Assert.Equal(2, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsIndexer(result[1], "Key");
            Assert.IsType<StringIndexerNode>(result[1]);
        }

        [Fact]
        public void Should_Build_Multiple_Indexed_Property()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo[15,6]"));

            Assert.Equal(2, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsIndexer(result[1], "15", "6");
        }

        [Fact]
        public void Should_Build_Multiple_Indexed_Property_With_Space()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo[5, 16]"));

            Assert.Equal(2, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsIndexer(result[1], "5", "16");
        }

        [Fact]
        public void Should_Build_Consecutive_Indexers()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo[15][16]"));

            Assert.Equal(3, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsIndexer(result[1], "15");
            AssertIsIndexer(result[2], "16");
        }

        [Fact]
        public void Should_Build_Indexed_Property_In_Chain()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo.Bar[5, 6].Baz"));

            Assert.Equal(4, result.Count);
            AssertIsProperty(result[0], "Foo");
            AssertIsProperty(result[1], "Bar");
            AssertIsIndexer(result[2], "5", "6");
            AssertIsProperty(result[3], "Baz");
        }

        [Fact]
        public void Should_Build_Stream_Node()
        {
            var result = ToList(ExpressionObserverBuilder.Parse("Foo^"));

            Assert.Equal(2, result.Count);
            Assert.IsType<StreamNode>(result[1]);
        }

        private static void AssertIsProperty(ExpressionNode node, string name)
        {
            Assert.IsType<PropertyAccessorNode>(node);

            var p = (PropertyAccessorNode)node;
            Assert.Equal(name, p.PropertyName);
        }

        private static void AssertIsIndexer(ExpressionNode node, params string[] args)
        {
            Assert.IsType<StringIndexerNode>(node);

            var e = (StringIndexerNode)node;
            Assert.Equal(e.Arguments.ToArray(), args);
        }

        private static List<ExpressionNode> ToList((ExpressionNode node, SourceMode mode) parsed)
        {
            var (node, _) = parsed;
            var result = new List<ExpressionNode>();
            
            while (node != null)
            {
                result.Add(node);
                node = node.Next;
            }

            return result;
        }
    }
}