spectre.console/src/Spectre.Console/TableBorder.cs

namespace Spectre.Console;

/// <summary>
/// Represents a border.
/// </summary>
public abstract partial class TableBorder
{
    /// <summary>
    /// Gets a value indicating whether or not the border is visible.
    /// </summary>
    public virtual bool Visible { get; } = true;

    /// <summary>
    /// Gets the safe border for this border or <c>null</c> if none exist.
    /// </summary>
    public virtual TableBorder? SafeBorder { get; }

    /// <summary>
    /// Gets the string representation of a specified table border part.
    /// </summary>
    /// <param name="part">The part to get the character representation for.</param>
    /// <returns>A character representation of the specified border part.</returns>
    public abstract string GetPart(TableBorderPart part);

    /// <summary>
    /// Gets a whole column row for the specific column row part.
    /// </summary>
    /// <param name="part">The column row part.</param>
    /// <param name="widths">The column widths.</param>
    /// <param name="columns">The columns.</param>
    /// <returns>A string representing the column row.</returns>
    public virtual string GetColumnRow(TablePart part, IReadOnlyList<int> widths, IReadOnlyList<IColumn> columns)
    {
        if (widths is null)
        {
            throw new ArgumentNullException(nameof(widths));
        }

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

        var (left, center, separator, right) = GetTableParts(part);

        var builder = new StringBuilder();
        builder.Append(left);

        foreach (var (columnIndex, _, lastColumn, columnWidth) in widths.Enumerate())
        {
            var padding = columns[columnIndex].Padding;
            var centerWidth = padding.GetLeftSafe() + columnWidth + padding.GetRightSafe();
            builder.Append(center.Repeat(centerWidth));

            if (!lastColumn)
            {
                builder.Append(separator);
            }
        }

        builder.Append(right);
        return builder.ToString();
    }

    /// <summary>
    /// Gets the table parts used to render a specific table row.
    /// </summary>
    /// <param name="part">The table part.</param>
    /// <returns>The table parts used to render the specific table row.</returns>
    protected (string Left, string Center, string Separator, string Right) GetTableParts(TablePart part)
    {
        return part switch
        {
            // Top part
            TablePart.Top =>
                (GetPart(TableBorderPart.HeaderTopLeft), GetPart(TableBorderPart.HeaderTop),
                GetPart(TableBorderPart.HeaderTopSeparator), GetPart(TableBorderPart.HeaderTopRight)),

            // Separator between header and cells
            TablePart.HeaderSeparator =>
                (GetPart(TableBorderPart.HeaderBottomLeft), GetPart(TableBorderPart.HeaderBottom),
                GetPart(TableBorderPart.HeaderBottomSeparator), GetPart(TableBorderPart.HeaderBottomRight)),

            // Separator between footer and cells
            TablePart.FooterSeparator =>
                (GetPart(TableBorderPart.FooterTopLeft), GetPart(TableBorderPart.FooterTop),
                GetPart(TableBorderPart.FooterTopSeparator), GetPart(TableBorderPart.FooterTopRight)),

            // Bottom part
            TablePart.Bottom =>
                (GetPart(TableBorderPart.FooterBottomLeft), GetPart(TableBorderPart.FooterBottom),
                GetPart(TableBorderPart.FooterBottomSeparator), GetPart(TableBorderPart.FooterBottomRight)),

            // Unknown
            _ => throw new NotSupportedException("Unknown column row part"),
        };
    }
}