using System.Text;
using System.Text.RegularExpressions;

namespace DysonNetwork.Drive.Extensions;

public static class StringExtensions
{
    private static readonly Regex _matchFirstCap = new(@"(.)([A-Z][a-z])");
    private static readonly Regex _matchAllCap = new(@"([a-z0-9])([A-Z])");
    
    public static string ToSnakeCase(this string input)
    {
        if (string.IsNullOrEmpty(input))
            return input;

        // Handle the first character
        var result = new StringBuilder();
        result.Append(char.ToLowerInvariant(input[0]));

        // Process the rest of the string
        for (int i = 1; i < input.Length; i++)
        {
            if (char.IsUpper(input[i]))
            {
                result.Append('_');
                result.Append(char.ToLowerInvariant(input[i]));
            }
            else
            {
                result.Append(input[i]);
            }
        }

        // Replace any remaining uppercase letters with lowercase
        var output = result.ToString().ToLowerInvariant();
        
        // Handle special cases (acronyms)
        output = _matchFirstCap.Replace(output, "$1_$2");
        output = _matchAllCap.Replace(output, "$1_$2");
        
        return output.ToLowerInvariant();
    }
}