PluralKit/Myriad/Serialization/JsonSnakeCaseNamingPolicy.cs

using System;
using System.Text;
using System.Text.Json;

namespace Myriad.Serialization
{
    // From https://github.com/J0rgeSerran0/JsonNamingPolicy/blob/master/JsonSnakeCaseNamingPolicy.cs, no NuGet :/
    public class JsonSnakeCaseNamingPolicy: JsonNamingPolicy
    {
        private readonly string _separator = "_";

        public override string ConvertName(string name)
        {
            if (string.IsNullOrEmpty(name) || string.IsNullOrWhiteSpace(name)) return string.Empty;

            ReadOnlySpan<char> spanName = name.Trim();

            var stringBuilder = new StringBuilder();
            var addCharacter = true;

            var isPreviousSpace = false;
            var isPreviousSeparator = false;
            var isCurrentSpace = false;
            var isNextLower = false;
            var isNextUpper = false;
            var isNextSpace = false;

            for (var position = 0; position < spanName.Length; position++)
            {
                if (position != 0)
                {
                    isCurrentSpace = spanName[position] == 32;
                    isPreviousSpace = spanName[position - 1] == 32;
                    isPreviousSeparator = spanName[position - 1] == 95;

                    if (position + 1 != spanName.Length)
                    {
                        isNextLower = spanName[position + 1] > 96 && spanName[position + 1] < 123;
                        isNextUpper = spanName[position + 1] > 64 && spanName[position + 1] < 91;
                        isNextSpace = spanName[position + 1] == 32;
                    }

                    if (isCurrentSpace &&
                        (isPreviousSpace ||
                         isPreviousSeparator ||
                         isNextUpper ||
                         isNextSpace))
                    {
                        addCharacter = false;
                    }
                    else
                    {
                        var isCurrentUpper = spanName[position] > 64 && spanName[position] < 91;
                        var isPreviousLower = spanName[position - 1] > 96 && spanName[position - 1] < 123;
                        var isPreviousNumber = spanName[position - 1] > 47 && spanName[position - 1] < 58;

                        if (isCurrentUpper &&
                            (isPreviousLower ||
                             isPreviousNumber ||
                             isNextLower ||
                             isNextSpace ||
                             isNextLower && !isPreviousSpace))
                        {
                            stringBuilder.Append(_separator);
                        }
                        else
                        {
                            if (isCurrentSpace &&
                                !isPreviousSpace &&
                                !isNextSpace)
                            {
                                stringBuilder.Append(_separator);
                                addCharacter = false;
                            }
                        }
                    }
                }

                if (addCharacter)
                    stringBuilder.Append(spanName[position]);
                else
                    addCharacter = true;
            }

            return stringBuilder.ToString().ToLower();
        }
    }
}