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src/__Libraries/StellaOps.Facet/FacetClassifier.cs

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+// <copyright file="FacetClassifier.cs" company="StellaOps">
+// Copyright (c) StellaOps. Licensed under AGPL-3.0-or-later.
+// </copyright>
+
+namespace StellaOps.Facet;
+
+/// <summary>
+/// Classifies files into facets based on selectors.
+/// </summary>
+public sealed class FacetClassifier
+{
+    private readonly List<(IFacet Facet, GlobMatcher Matcher)> _facetMatchers;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="FacetClassifier"/> class.
+    /// </summary>
+    /// <param name="facets">Facets to classify against (will be sorted by priority).</param>
+    public FacetClassifier(IEnumerable<IFacet> facets)
+    {
+        ArgumentNullException.ThrowIfNull(facets);
+
+        // Sort by priority (lowest first = highest priority)
+        _facetMatchers = facets
+            .OrderBy(f => f.Priority)
+            .Select(f => (f, GlobMatcher.ForFacet(f)))
+            .ToList();
+    }
+
+    /// <summary>
+    /// Creates a classifier using built-in facets.
+    /// </summary>
+    public static FacetClassifier Default { get; } = new(BuiltInFacets.All);
+
+    /// <summary>
+    /// Classify a file path to a facet.
+    /// </summary>
+    /// <param name="path">The file path to classify.</param>
+    /// <returns>The matching facet or null if no match.</returns>
+    public IFacet? Classify(string path)
+    {
+        ArgumentNullException.ThrowIfNull(path);
+
+        // First matching facet wins (ordered by priority)
+        foreach (var (facet, matcher) in _facetMatchers)
+        {
+            if (matcher.IsMatch(path))
+            {
+                return facet;
+            }
+        }
+
+        return null;
+    }
+
+    /// <summary>
+    /// Classify a file and return the facet ID.
+    /// </summary>
+    /// <param name="path">The file path to classify.</param>
+    /// <returns>The facet ID or null if no match.</returns>
+    public string? ClassifyToId(string path)
+        => Classify(path)?.FacetId;
+
+    /// <summary>
+    /// Classify multiple files efficiently.
+    /// </summary>
+    /// <param name="paths">The file paths to classify.</param>
+    /// <returns>Dictionary from facet ID to matched paths.</returns>
+    public Dictionary<string, List<string>> ClassifyMany(IEnumerable<string> paths)
+    {
+        ArgumentNullException.ThrowIfNull(paths);
+
+        var result = new Dictionary<string, List<string>>();
+
+        foreach (var path in paths)
+        {
+            var facet = Classify(path);
+            if (facet is not null)
+            {
+                if (!result.TryGetValue(facet.FacetId, out var list))
+                {
+                    list = [];
+                    result[facet.FacetId] = list;
+                }
+
+                list.Add(path);
+            }
+        }
+
+        return result;
+    }
+}