namespace SharepointToolbox.Web.Core.Models;

/// <summary>
/// Editable node for the visual folder-structure builder. SharePoint folders
/// are limited to 4 nesting levels here, matching the CSV template (Level1..Level4).
/// </summary>
public class FolderNode
{
    public const int MaxDepth = 4;

    public string Name { get; set; } = string.Empty;
    public List<FolderNode> Children { get; } = new();

    /// <summary>Flatten the tree into one <see cref="FolderStructureRow"/> per leaf path.</summary>
    public static List<FolderStructureRow> Flatten(IEnumerable<FolderNode> roots)
    {
        var rows = new List<FolderStructureRow>();
        foreach (var root in roots)
            Walk(root, new List<string>(), rows);
        return rows;
    }

    private static void Walk(FolderNode node, List<string> ancestors, List<FolderStructureRow> rows)
    {
        var name = node.Name.Trim();
        if (string.IsNullOrEmpty(name)) return;

        var path = new List<string>(ancestors) { name };

        // Only emit a row for leaves; intermediate folders are created as ancestors of the leaf path.
        if (node.Children.Count == 0)
        {
            rows.Add(new FolderStructureRow
            {
                Level1 = path.ElementAtOrDefault(0) ?? string.Empty,
                Level2 = path.ElementAtOrDefault(1) ?? string.Empty,
                Level3 = path.ElementAtOrDefault(2) ?? string.Empty,
                Level4 = path.ElementAtOrDefault(3) ?? string.Empty,
            });
            return;
        }

        if (path.Count >= MaxDepth) return; // can't nest deeper
        foreach (var child in node.Children)
            Walk(child, path, rows);
    }
}