spectre.console/src/Spectre.Console/Internal/Aligner.cs

using System;
using System.Collections.Generic;
using Spectre.Console.Rendering;

namespace Spectre.Console
{
    internal static class Aligner
    {
        public static string Align(string text, Justify? alignment, int maxWidth)
        {
            if (alignment == null || alignment == Justify.Left)
            {
                return text;
            }

            var width = Cell.GetCellLength(text);
            if (width >= maxWidth)
            {
                return text;
            }

            switch (alignment)
            {
                case Justify.Right:
                    {
                        var diff = maxWidth - width;
                        return new string(' ', diff) + text;
                    }

                case Justify.Center:
                    {
                        var diff = (maxWidth - width) / 2;

                        var left = new string(' ', diff);
                        var right = new string(' ', diff);

                        // Right side
                        var remainder = (maxWidth - width) % 2;
                        if (remainder != 0)
                        {
                            right += new string(' ', remainder);
                        }

                        return left + text + right;
                    }

                default:
                    throw new NotSupportedException("Unknown alignment");
            }
        }

        public static void Align<T>(RenderContext context, T segments, Justify? alignment, int maxWidth)
            where T : List<Segment>
        {
            if (alignment == null || alignment == Justify.Left)
            {
                return;
            }

            var width = Segment.CellCount(segments);
            if (width >= maxWidth)
            {
                return;
            }

            switch (alignment)
            {
                case Justify.Right:
                    {
                        var diff = maxWidth - width;
                        segments.Insert(0, Segment.Padding(diff));
                        break;
                    }

                case Justify.Center:
                    {
                        // Left side.
                        var diff = (maxWidth - width) / 2;
                        segments.Insert(0, Segment.Padding(diff));

                        // Right side
                        segments.Add(Segment.Padding(diff));
                        var remainder = (maxWidth - width) % 2;
                        if (remainder != 0)
                        {
                            segments.Add(Segment.Padding(remainder));
                        }

                        break;
                    }

                default:
                    throw new NotSupportedException("Unknown alignment");
            }
        }
    }
}