// <copyright file="FacetClassifier.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under BUSL-1.1.
// </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;
    }
}