using System;
using System.Runtime.InteropServices;
using static flecs_hub.flecs;
using static flecs_hub.flecs.Runtime;

namespace gaemstone.Utility;

public unsafe static class CStringExtensions
{
	public static CString Empty { get; } = (CString)"";
	public static CString ETX { get; } = (CString)"\x3"; // TODO: Temporary, until flecs supports Empty.

	public static unsafe byte[]? FlecsToBytes(this CString str)
	{
		if (str.IsNull) return null;
		var pointer = (byte*)(nint)str;
		// Find length of the string by locating the NUL character.
		var length = 0; while (true) if (pointer[length++] == 0) break;
		// Create span over the region, NUL included, copy it into an array.
		return new Span<byte>(pointer, length).ToArray();
	}

	public static byte[]? FlecsToBytesAndFree(this CString str)
		{ var result = str.FlecsToBytes(); str.FlecsFree(); return result; }

	public static string? FlecsToString(this CString str)
		=> Marshal.PtrToStringUTF8(str);

	public static string? FlecsToStringAndFree(this CString str)
		{ var result = str.FlecsToString(); str.FlecsFree(); return result; }

	public static void FlecsFree(this CString str)
		{ if (!str.IsNull) ecs_os_get_api().free_.Data.Pointer((void*)(nint)str); }
}