Implement API for working with graph-like relations

Sources/Directory.Build.props

@@ -14,7 +14,7 @@
     <PropertyGroup>
         <RepositoryUrl>https://github.com/kysect/Kysect.CommonLib</RepositoryUrl>
         <PackageProjectUrl>https://github.com/kysect/Kysect.CommonLib</PackageProjectUrl>
-        <Version>0.1.16</Version>
+        <Version>0.1.17</Version>
     </PropertyGroup>
 
     <!-- Code configuration -->

Sources/Kysect.CommonLib/Graphs/GraphBuildResult.cs

@@ -0,0 +1,20 @@
+namespace Kysect.CommonLib.Graphs;
+
+public class GraphBuildResult<TKey, T> where TKey : notnull
+{
+    public GraphBuildResult(IReadOnlyCollection<GraphNode<TKey, T>> roots)
+    {
+        Roots = roots;
+    }
+
+    public IReadOnlyCollection<GraphNode<TKey, T>> Roots { get; }
+
+    public GraphNode<TKey, T> GetValue(TKey id)
+    {
+        GraphNode<TKey, T>? found = Roots
+            .Select(root => root.Find(id))
+            .FirstOrDefault(value => value is not null);
+
+        return found ?? throw new ArgumentException($"Work item with id {id} was not found");
+    }
+}

Sources/Kysect.CommonLib/Graphs/GraphBuilder.cs

@@ -0,0 +1,52 @@
+using Kysect.CommonLib.BaseTypes.Extensions;
+
+namespace Kysect.CommonLib.Graphs;
+
+public static class GraphBuilder
+{
+    public static GraphBuildResult<TKey, T> Build<TKey, T>(
+        IReadOnlyCollection<TKey> nodes,
+        IReadOnlyCollection<GraphLink<TKey>> links,
+        GraphValueResolver<TKey, T> resolver)
+        where TKey : notnull
+    {
+        nodes.ThrowIfNull();
+        links.ThrowIfNull();
+        resolver.ThrowIfNull();
+
+        var targetNodes = new HashSet<TKey>(links.Select(l => l.To));
+
+        var rootNodes = nodes
+            .Where(l => !targetNodes.Contains(l))
+            .ToList();
+
+        ILookup<TKey, TKey> nodeLinks = links.ToLookup(l => l.From, l => l.To);
+
+        var result = new List<GraphNode<TKey, T>>();
+
+        foreach (TKey rootNode in rootNodes)
+            result.Add(BuildNode(rootNode, nodeLinks, resolver));
+
+        return new GraphBuildResult<TKey, T>(result);
+    }
+
+    private static GraphNode<TKey, T> BuildNode<TKey, T>(TKey id, ILookup<TKey, TKey> nodeLinks, IGraphValueResolver<TKey, T> resolver) where TKey : notnull
+    {
+        IReadOnlyCollection<GraphNode<TKey, T>> children = nodeLinks.Contains(id)
+            ? BuildChildren(nodeLinks[id], nodeLinks, resolver)
+            : Array.Empty<GraphNode<TKey, T>>();
+
+        return new GraphNode<TKey, T>(id, resolver.Resolve(id), children);
+    }
+
+    private static IReadOnlyCollection<GraphNode<TKey, T>> BuildChildren<TKey, T>(
+        IEnumerable<TKey> identifiers,
+        ILookup<TKey, TKey> nodeLinks,
+        IGraphValueResolver<TKey, T> resolver)
+        where TKey : notnull
+    {
+        return identifiers
+            .Select(childId => BuildNode(childId, nodeLinks, resolver))
+            .ToList();
+    }
+}

Sources/Kysect.CommonLib/Graphs/GraphLink.cs

@@ -0,0 +1,12 @@
+using System.Diagnostics.Contracts;
+
+namespace Kysect.CommonLib.Graphs;
+
+public record struct GraphLink<TKey>(TKey From, TKey To)
+{
+    [Pure]
+    public readonly GraphLink<TKey> Reversed()
+    {
+        return new GraphLink<TKey>(From: To, To: From);
+    }
+}

Sources/Kysect.CommonLib/Graphs/GraphNode.cs

@@ -0,0 +1,40 @@
+namespace Kysect.CommonLib.Graphs;
+
+public class GraphNode<TKey, T> where TKey : notnull
+{
+    public TKey Id { get; }
+    public T Value { get; }
+    public IReadOnlyCollection<GraphNode<TKey, T>> DirectChildren { get; }
+
+    public GraphNode(TKey id, T value, IReadOnlyCollection<GraphNode<TKey, T>> directChildren)
+    {
+        Id = id;
+        Value = value;
+        DirectChildren = directChildren;
+    }
+
+    public IEnumerable<GraphNode<TKey, T>> EnumerateChildren()
+    {
+        if (!DirectChildren.Any())
+            return Array.Empty<GraphNode<TKey, T>>();
+
+        return DirectChildren
+            .Concat(DirectChildren.SelectMany(c => c.EnumerateChildren()))
+            .ToList();
+    }
+
+    public GraphNode<TKey, T>? Find(TKey id)
+    {
+        if (Id.Equals(id))
+            return this;
+
+        return DirectChildren
+            .Select(node => node.Find(id))
+            .FirstOrDefault(founded => founded is not null);
+    }
+
+    public override string ToString()
+    {
+        return $"Node {Value}, Direct children count: {DirectChildren.Count}";
+    }
+}

Sources/Kysect.CommonLib/Graphs/GraphPath.cs

@@ -0,0 +1,21 @@
+namespace Kysect.CommonLib.Graphs;
+
+public class GraphPath<T>
+{
+    public GraphPath(IReadOnlyCollection<T> elements)
+    {
+        Elements = elements;
+    }
+
+    public static GraphPath<T> Empty { get; } = new GraphPath<T>(Array.Empty<T>());
+
+    public IReadOnlyCollection<T> Elements { get; }
+
+    public GraphPath<T> AppendToStart(T value)
+    {
+        var result = new List<T>();
+        result.Add(value);
+        result.AddRange(Elements);
+        return new GraphPath<T>(result);
+    }
+}

Sources/Kysect.CommonLib/Graphs/GraphValueResolver.cs

@@ -0,0 +1,19 @@
+namespace Kysect.CommonLib.Graphs;
+
+public class GraphValueResolver<TKey, T> : IGraphValueResolver<TKey, T>
+{
+    private readonly Dictionary<TKey, T> _map;
+
+    public GraphValueResolver(IReadOnlyCollection<T> values, Func<T, TKey> selector)
+    {
+        _map = values.ToDictionary(selector, v => v);
+    }
+
+    public T Resolve(TKey id)
+    {
+        if (_map.TryGetValue(id, out T? result))
+            return result;
+
+        throw new ArgumentException($"Graph node with id {id} was not found");
+    }
+}

Sources/Kysect.CommonLib/Graphs/GraphValueResolverCreator.cs

@@ -0,0 +1,9 @@
+namespace Kysect.CommonLib.Graphs;
+
+public static class GraphValueResolverCreator
+{
+    public static GraphValueResolver<TKey, T> Create<TKey, T>(IReadOnlyCollection<T> values, Func<T, TKey> selector)
+    {
+        return new GraphValueResolver<TKey, T>(values, selector);
+    }
+}

Sources/Kysect.CommonLib/Graphs/IGraphValueResolver.cs

@@ -0,0 +1,6 @@
+namespace Kysect.CommonLib.Graphs;
+
+public interface IGraphValueResolver<TKey, T>
+{
+    T Resolve(TKey id);
+}