using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace FontPreview;

internal static class FontNameParser
{
	private struct NameRec
	{
		public int PlatformID;

		public int EncodingID;

		public int LanguageID;

		public int NameID;

		public byte[] Data;
	}

	private const int TTF_DIRREC_LEN = 16;

	internal static string GetDisplayName(string fontPath, string fallback)
	{
		try
		{
			string text = Parse(fontPath);
			return string.IsNullOrEmpty(text) ? fallback : text;
		}
		catch
		{
			return fallback;
		}
	}

	private static string Parse(string path)
	{
		using FileStream fileStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
		byte[] array = new byte[12];
		if (!ReadFully(fileStream, array, 0, 12))
		{
			return null;
		}
		long num;
		if (array[0] == 116 && array[1] == 116 && array[2] == 99 && array[3] == 102)
		{
			byte[] array2 = new byte[4];
			if (!ReadFully(fileStream, array2, 0, 4))
			{
				return null;
			}
			num = Be32(array2, 0);
		}
		else
		{
			num = 0L;
		}
		fileStream.Seek(num + 4, SeekOrigin.Begin);
		byte[] array3 = new byte[2];
		if (!ReadFully(fileStream, array3, 0, 2))
		{
			return null;
		}
		int num2 = (array3[0] << 8) | array3[1];
		fileStream.Seek(num + 12, SeekOrigin.Begin);
		long num3 = 0L;
		long num4 = 0L;
		byte[] array4 = new byte[16];
		for (int i = 0; i < num2; i++)
		{
			if (!ReadFully(fileStream, array4, 0, 16))
			{
				return null;
			}
			if (array4[0] == 110 && array4[1] == 97 && array4[2] == 109 && array4[3] == 101)
			{
				num3 = Be32(array4, 8);
				num4 = Be32(array4, 12);
				break;
			}
		}
		if (num3 == 0 || num4 <= 0 || num4 > 4194304)
		{
			return null;
		}
		byte[] array5 = new byte[num4];
		fileStream.Seek(num3, SeekOrigin.Begin);
		if (!ReadFully(fileStream, array5, 0, (int)num4))
		{
			return null;
		}
		List<NameRec> list = new List<NameRec>();
		int num5 = (array5[2] << 8) | array5[3];
		int num6 = (array5[4] << 8) | array5[5];
		int num7 = 6;
		for (int i = 0; i < num5; i++)
		{
			if (num7 + 12 > num4)
			{
				break;
			}
			int platformID = (array5[num7] << 8) | array5[num7 + 1];
			int encodingID = (array5[num7 + 2] << 8) | array5[num7 + 3];
			int languageID = (array5[num7 + 4] << 8) | array5[num7 + 5];
			int nameID = (array5[num7 + 6] << 8) | array5[num7 + 7];
			int num8 = (array5[num7 + 8] << 8) | array5[num7 + 9];
			int num9 = (array5[num7 + 10] << 8) | array5[num7 + 11];
			if (num9 >= 0 && num8 > 0 && num6 + num9 + num8 <= num4)
			{
				NameRec item = default(NameRec);
				item.PlatformID = platformID;
				item.EncodingID = encodingID;
				item.LanguageID = languageID;
				item.NameID = nameID;
				item.Data = new byte[num8];
				Array.Copy(array5, num6 + num9, item.Data, 0, num8);
				list.Add(item);
			}
			num7 += 12;
		}
		int[] array6 = new int[4] { 1, 4, 6, 16 };
		int[] array7 = array6;
		foreach (int nameID2 in array7)
		{
			string text = PickBest(list, nameID2);
			if (!string.IsNullOrEmpty(text))
			{
				return text;
			}
		}
		return null;
	}

	private static string PickBest(List<NameRec> recs, int nameID)
	{
		List<NameRec> list = new List<NameRec>();
		foreach (NameRec rec in recs)
		{
			if (rec.NameID == nameID)
			{
				list.Add(rec);
			}
		}
		if (list.Count == 0)
		{
			return null;
		}
		foreach (NameRec item in list)
		{
			if (item.PlatformID == 3 && item.LanguageID == 2052)
			{
				string text = Decode(item);
				if (!string.IsNullOrEmpty(text))
				{
					return text;
				}
			}
		}
		foreach (NameRec item2 in list)
		{
			if (item2.PlatformID == 3 && item2.LanguageID == 1033)
			{
				string text = Decode(item2);
				if (!string.IsNullOrEmpty(text))
				{
					return text;
				}
			}
		}
		foreach (NameRec item3 in list)
		{
			if (item3.PlatformID == 3 && item3.LanguageID == 0)
			{
				string text = Decode(item3);
				if (!string.IsNullOrEmpty(text))
				{
					return text;
				}
			}
		}
		foreach (NameRec item4 in list)
		{
			if (item4.PlatformID == 3)
			{
				string text = Decode(item4);
				if (!string.IsNullOrEmpty(text))
				{
					return text;
				}
			}
		}
		foreach (NameRec item5 in list)
		{
			if (item5.PlatformID == 0)
			{
				string text = Decode(item5);
				if (!string.IsNullOrEmpty(text))
				{
					return text;
				}
			}
		}
		foreach (NameRec item6 in list)
		{
			if (item6.PlatformID == 1)
			{
				string text = Decode(item6);
				if (!string.IsNullOrEmpty(text))
				{
					return text;
				}
			}
		}
		return null;
	}

	private static string Decode(NameRec r)
	{
		string text;
		try
		{
			text = ((r.PlatformID != 3 && r.PlatformID != 0) ? Encoding.GetEncoding(28591).GetString(r.Data) : Encoding.BigEndianUnicode.GetString(r.Data));
		}
		catch
		{
			return null;
		}
		text = text.Trim('\0', ' ', '\t', '\r', '\n');
		return string.IsNullOrEmpty(text) ? null : text;
	}

	private static bool ReadFully(Stream s, byte[] buf, int off, int len)
	{
		int num;
		for (int i = 0; i < len; i += num)
		{
			num = s.Read(buf, off + i, len - i);
			if (num <= 0)
			{
				return false;
			}
		}
		return true;
	}

	private static uint Be32(byte[] b, int off)
	{
		return (uint)((b[off] << 24) | (b[off + 1] << 16) | (b[off + 2] << 8) | b[off + 3]);
	}
}