spectre.console/src/Spectre.Console/Extensions/PanelExtensions.cs

namespace Spectre.Console;

/// <summary>
/// Contains extension methods for <see cref="Panel"/>.
/// </summary>
public static class PanelExtensions
{
    /// <summary>
    /// Sets the panel header.
    /// </summary>
    /// <param name="panel">The panel.</param>
    /// <param name="text">The header text.</param>
    /// <param name="alignment">The header alignment.</param>
    /// <returns>The same instance so that multiple calls can be chained.</returns>
    public static Panel Header(this Panel panel, string text, Justify? alignment = null)
    {
        if (panel is null)
        {
            throw new ArgumentNullException(nameof(panel));
        }

        if (text is null)
        {
            throw new ArgumentNullException(nameof(text));
        }

        alignment ??= panel.Header?.Justification;
        return Header(panel, new PanelHeader(text, alignment));
    }

    /// <summary>
    /// Sets the panel header alignment.
    /// </summary>
    /// <param name="panel">The panel.</param>
    /// <param name="alignment">The header alignment.</param>
    /// <returns>The same instance so that multiple calls can be chained.</returns>
    public static Panel HeaderAlignment(this Panel panel, Justify alignment)
    {
        if (panel is null)
        {
            throw new ArgumentNullException(nameof(panel));
        }

        if (panel.Header != null)
        {
            // Update existing style
            panel.Header.Justification = alignment;
        }
        else
        {
            // Create header
            Header(panel, string.Empty, alignment);
        }

        return panel;
    }

    /// <summary>
    /// Sets the panel header.
    /// </summary>
    /// <param name="panel">The panel.</param>
    /// <param name="header">The header to use.</param>
    /// <returns>The same instance so that multiple calls can be chained.</returns>
    public static Panel Header(this Panel panel, PanelHeader header)
    {
        if (panel is null)
        {
            throw new ArgumentNullException(nameof(panel));
        }

        panel.Header = header;
        return panel;
    }
}