hrynco-common/HrynCo.Common.Tests/TreeUtilsTests.cs

namespace HrynCo.Common.Tests;

using HrynCo.Common.Tree;
using FluentAssertions;
using Xunit;

public sealed class FakeNode : ITreeNode<Guid>
{
    public required Guid Id { get; init; }
    public Guid? ParentId { get; init; }
}

public sealed class FakeNamedNode : ITreeNode<Guid>, INameNode
{
    public required string Name { get; init; }
    public required Guid Id { get; init; }
    public Guid? ParentId { get; init; }
}

public sealed class TreeUtilsTests
{
    [Fact]
    public void CollectDescendants_ShouldReturnSelfAndAllChildren()
    {
        // Arrange
        var root = Guid.NewGuid();
        var child1 = Guid.NewGuid();
        var child2 = Guid.NewGuid();
        var nodes = new List<FakeNode>
        {
            new()
            {
                Id = root,
                ParentId = null
            },
            new()
            {
                Id = child1,
                ParentId = root
            },
            new()
            {
                Id = child2,
                ParentId = child1
            }
        };

        // Act
        var result = TreeUtils.CollectDescendants(root, nodes, Guid.Empty);

        // Assert
        result.Should().BeEquivalentTo(new[]
        {
            root, child1, child2
        });
    }

    [Fact]
    public void BuildBreadcrumb_ShouldReturnPathFromRootToNode()
    {
        // Arrange
        var root = Guid.NewGuid();
        var child = Guid.NewGuid();
        var grandchild = Guid.NewGuid();

        var map = new Dictionary<Guid, FakeNamedNode>
        {
            [root] = new()
            {
                Id = root,
                ParentId = null,
                Name = "Root"
            },
            [child] = new()
            {
                Id = child,
                ParentId = root,
                Name = "Child"
            },
            [grandchild] = new()
            {
                Id = grandchild,
                ParentId = child,
                Name = "Grandchild"
            }
        };

        // Act
        var result = TreeUtils.BuildBreadcrumb(grandchild, map);

        // Assert
        result.Should().BeEquivalentTo(new[]
        {
            new BreadcrumbNode<Guid>(root, "Root"), new BreadcrumbNode<Guid>(child, "Child"),
            new BreadcrumbNode<Guid>(grandchild, "Grandchild")
        }, options => options.WithStrictOrdering());
    }

    [Fact]
    public void CollectDescendants_ShouldReturnOnlyRootWhenThereAreNoChildren()
    {
        // Arrange
        var root = Guid.NewGuid();

        // Act
        var result = TreeUtils.CollectDescendants(root, Array.Empty<FakeNode>(), Guid.Empty);

        // Assert
        result.Should().BeEquivalentTo(new[] { root });
    }

    [Fact]
    public void CollectDescendants_ShouldHandleCyclesWithoutRepeatingNodes()
    {
        // Arrange
        var root = Guid.NewGuid();
        var child = Guid.NewGuid();
        var nodes = new List<FakeNode>
        {
            new()
            {
                Id = root,
                ParentId = child
            },
            new()
            {
                Id = child,
                ParentId = root
            }
        };

        // Act
        var result = TreeUtils.CollectDescendants(root, nodes, Guid.Empty);

        // Assert
        result.Should().BeEquivalentTo(new[] { root, child });
    }

    [Fact]
    public void BuildBreadcrumb_ShouldReturnEmptyListWhenNodeIsMissing()
    {
        // Arrange
        var map = new Dictionary<Guid, FakeNamedNode>();

        // Act
        var result = TreeUtils.BuildBreadcrumb(Guid.NewGuid(), map);

        // Assert
        result.Should().BeEmpty();
    }
}