process/src/Process/Builders/ArgumentsBuilder.cs

using System.Globalization;
using System.Text;

namespace Geekeey.Extensions.Process;

/// <summary>
/// Builder that helps format command-line arguments into a string.
/// </summary>
public sealed partial class ArgumentsBuilder
{
	private static readonly IFormatProvider DefaultFormatProvider = CultureInfo.InvariantCulture;

	private readonly StringBuilder _buffer = new();

	/// <summary>
	/// Adds the specified value to the list of arguments.
	/// </summary>
	public ArgumentsBuilder Add(string value, bool escape = true)
	{
		if (_buffer.Length > 0)
			_buffer.Append(' ');

		_buffer.Append(escape ? Escape(value) : value);

		return this;
	}

	/// <summary>
	/// Adds the specified values to the list of arguments.
	/// </summary>
	public ArgumentsBuilder Add(IEnumerable<string> values, bool escape = true)
	{
		foreach (var value in values)
		{
			Add(value, escape);
		}

		return this;
	}

	/// <summary>
	/// Adds the specified value to the list of arguments.
	/// </summary>
	public ArgumentsBuilder Add(IFormattable value, IFormatProvider formatProvider, bool escape = true)
		=> Add(value.ToString(null, formatProvider), escape);

	/// <summary>
	/// Adds the specified value to the list of arguments.
	/// The value is converted to string using invariant culture.
	/// </summary>
	public ArgumentsBuilder Add(IFormattable value, bool escape = true)
		=> Add(value, DefaultFormatProvider, escape);

	/// <summary>
	/// Adds the specified values to the list of arguments.
	/// </summary>
	public ArgumentsBuilder Add(IEnumerable<IFormattable> values, IFormatProvider formatProvider, bool escape = true)
	{
		foreach (var value in values)
		{
			Add(value, formatProvider, escape);
		}

		return this;
	}

	/// <summary>
	/// Adds the specified values to the list of arguments.
	/// The values are converted to string using invariant culture.
	/// </summary>
	public ArgumentsBuilder Add(IEnumerable<IFormattable> values, bool escape = true)
		=> Add(values, DefaultFormatProvider, escape);

	/// <summary>
	/// Builds the resulting arguments string.
	/// </summary>
	public string Build() => _buffer.ToString();
}

public partial class ArgumentsBuilder
{
	private static string Escape(string argument)
	{
		// Short circuit if the argument is clean and doesn't need escaping
		if (argument.Length > 0 && argument.All(c => !char.IsWhiteSpace(c) && c is not '"'))
			return argument;

		var buffer = new StringBuilder();

		buffer.Append('"');

		for (var i = 0; i < argument.Length;)
		{
			var c = argument[i++];

			switch (c)
			{
				case '\\':
					{
						var backslashCount = 1;
						while (i < argument.Length && argument[i] == '\\')
						{
							backslashCount++;
							i++;
						}

						if (i == argument.Length)
						{
							buffer.Append('\\', backslashCount * 2);
						}
						else if (argument[i] == '"')
						{
							buffer.Append('\\', backslashCount * 2 + 1).Append('"');

							i++;
						}
						else
						{
							buffer.Append('\\', backslashCount);
						}

						break;
					}
				case '"':
					buffer.Append('\\').Append('"');
					break;
				default:
					buffer.Append(c);
					break;
			}
		}

		buffer.Append('"');

		return buffer.ToString();
	}
}