Discussion of .srf file linq parser 2

2ndParser.cs

public void Parse(IEnumerable<string> data)
{
	DateTime start = DateTime.Now;


	var stream = data.Where(x => !string.IsNullOrEmpty(x));
	if (stream.First().StartsWith("surf", false, null))
	{
		throw new FileFormatException("SURF Header");
	}

	var splitedByZ = stream.Skip(1).GroupBy(x => x.First() == 'Z');
	var normalLines = splitedByZ.Single(x => !x.Key);

	var zBuf = splitedByZ.SingleOrDefault(x => x.Key);
	IDictionary<int, int> alphaData;
	IEnumerable<int> zData;
	IEnumerable<int> lightData;
	if (zBuf == null)
	{
		alphaData = new Dictionary<int, int>();
		zData = new int[0];
		lightData = new int[0];
	}
	else
	{
		var zLines = zBuf.GroupBy(x => x.Skip(1).First()).Select(x => new KeyValuePair<char, IEnumerable<int>>(x.Key, x.SelectMany(y => y.Split(' ').Skip(1)).Select(y => int.Parse(y))));

		//Alpha
		var alphaLines = zLines.SingleOrDefault(x => x.Key == 'A').Value;
		if (alphaLines == null)
		{
			alphaData = new Dictionary<int, int>();
		}
		else
		{
			var alphaGroup = alphaLines.Select((x, i) => new { Index = i, Value = x }).GroupBy(x => x.Index % 2 == 0);
			alphaData = alphaGroup.Single(x => x.Key).Zip(alphaGroup.Single(x => !x.Key), (key, value) => new { Key = key.Value, Value = value.Value })
				.ToDictionary(x => x.Key, x => x.Value);
		}

		//Z
		zData = zLines.SingleOrDefault(x => x.Key == 'Z').Value ?? new int[0];

		//Light
		lightData = zLines.SingleOrDefault(x => x.Key == 'L').Value ?? new int[0];
	}

	//Vertex
	var vertexLines = normalLines.TakeWhile(x => x.First() == 'V');
	Vertices = vertexLines.Select(x => Vertex.Create(x));

	//Face
	var faceLines = normalLines.SkipWhile(x => x.First() == 'V');
	Faces = Face.CreateFaces(faceLines, alphaData, zData, lightData);
	
	
	RequiredTime = DateTime.Now - start;
}

Face.cs

struct Face
{
	public IEnumerable<int> VertexIndices { get; set; }
	public Color4 Color { get; set; }
	public bool IsEmit { get; set; }
	public Vector3 Normal { get; set; }
	public Vector3 Centroid { get; set; }
	public bool IsCpuRenderIgnore { get; set; }
	public bool IsLight { get; set; }

	static public IEnumerable<Face> CreateFaces(IEnumerable<string> data, IDictionary<int, int> alpha, IEnumerable<int> z, IEnumerable<int> light)
	{
		var e = data.GetEnumerator();
		bool isFace = false;
		Face f = new Face();
		for (var i = 0; e.MoveNext(); i++)
		{
			switch (e.Current.First())
			{
				case 'F':
					isFace = true;
					break;
				case 'B':
					if (!isFace)
					{
						throw new FileFormatException("F行とE行の外にB行があります。");
					}
					f.IsEmit = true;
					break;
				case 'C':
					if (!isFace)
					{
						throw new FileFormatException("F行とE行の外にC行があります。");
					}
					var color = e.Current.Split(' ');
					if (color.Length == 4)
					{
						f.Color = new Color4()
						{
							R = float.Parse(color[1]) / 255f,
							G = float.Parse(color[2]) / 255f,
							B = float.Parse(color[3]) / 255f,
							A = alpha.ContainsKey(i) ? alpha[i] : 0f
						};
					}
					else if (color.Length == 2)
					{
						f.Color = new Color4()
						{
							R = (float)Math.Floor(((int.Parse(color[1]) & 992) >> 5) * 255.0f / 31.0f),
							G = (float)Math.Floor(((int.Parse(color[1]) & 31744) >> 10) * 255.0f / 31.0f),
							B = (float)Math.Floor(((int.Parse(color[1]) & 31)) * 255.0f / 31.0f),
							A = alpha.ContainsKey(i) ? alpha[i] : 0f
						};
					}
					else
					{
						throw new FileFormatException("色のフォーマットが異常です。" + string.Concat(color));
					}
					break;
				case 'N':
					if (!isFace)
					{
						throw new FileFormatException("F行とE行の外にN行があります。");
					}
					var normal = e.Current.Split(' ');
					f.Normal = new Vector3()
					{
						X = -float.Parse(normal[1]),
						Y = float.Parse(normal[2]),
						Z = float.Parse(normal[3])
					};
					f.Centroid = new Vector3()
					{
						X = -float.Parse(normal[4]),
						Y = float.Parse(normal[5]),
						Z = float.Parse(normal[6])
					};
					break;
				case 'V':
					if (!isFace)
					{
						throw new FileFormatException("F行とE行の外に面定義と思われるV行があります。");
					}
					f.VertexIndices = e.Current.Split(' ').Skip(1).Select(x => int.Parse(x));
					break;
				case 'E':
					if (isFace)
					{
						f.IsCpuRenderIgnore = z.Contains(i);
						f.IsLight = light.Contains(i);
						yield return f;
					}
					else
					{
						yield break;
					}
					isFace = false;
					break;
				default:
					break;
			}
		}
	}
}

Vertex.cs

struct Vertex
{
	public Vector3 Position { get; set; }
	public bool IsRound { get; set; }
	public Vector3 Normal { get; set; }

	static public Vertex Create(string data)
	{
		var e = data.Split(' ');

		return new Vertex()
		{
			Position = new Vector3()
			{
				X = -float.Parse(e[1]),
				Y = float.Parse(e[2]),
				Z = float.Parse(e[3])
			},
			IsRound = (e.Length > 5 && "R".Equals(e[4]))
		};

	}
}