using System.Reflection;
using System.Text;

namespace NathanMcRae;

public class Tsv<T> where T : SaneTsv.TsvRecord
{
  public virtual List<T> Records { get; set; }
}

public class CommentedTsv<T> : Tsv<T> where T : SaneTsv.TsvRecord
{
  public override List<T> Records { get; set; }
  public string FileComment { get; set; } = null;
}

/// <summary>
/// Sane Tab-Separated Values
/// </summary>
public class SaneTsv
{
  // Like an enum, but more extensible
  public class ColumnType { }
  public class StringType : ColumnType { }
  public class BooleanType : ColumnType { }
  public class Float32Type : ColumnType { }
  public class Float32LEType : ColumnType { }
  public class Float64Type : ColumnType { }
  public class Float64LEType : ColumnType { }
  public class UInt32Type : ColumnType { }
  public class UInt64Type : ColumnType { }
  public class Int32Type : ColumnType { }
  public class Int64Type : ColumnType { }
  public class BinaryType : ColumnType { }

  protected enum FormatType
  {
    SIMPLE_TSV = 0,
    TYPED_TSV = 1,
    COMMENTED_TSV = 2,
  }

  public static readonly byte[] TrueEncoded = Encoding.UTF8.GetBytes("TRUE");
  public static readonly byte[] FalseEncoded = Encoding.UTF8.GetBytes("FALSE");

  // TODO: We need to be able to update all these in tandem somehow
  public string[] ColumnNames { get; protected set; }
  public Type[] ColumnTypes { get; protected set; }
  protected static bool? _littleEndian = null;
  public static bool LittleEndian
  {
    get
    {
      if (_littleEndian == null)
      {
        _littleEndian = BitConverter.GetBytes(double.NegativeInfinity)[7] == 255;
      }
      return _littleEndian.Value;
    }
  }

  public static Tsv<T> ParseSimpleTsv<T>(byte[] inputBuffer) where T : TsvRecord, new()
  {
    return Parse<T>(inputBuffer, FormatType.SIMPLE_TSV);
  }

  public static Tsv<T> ParseTypedTsv<T>(byte[] inputBuffer) where T : TsvRecord, new()
  {
    return Parse<T>(inputBuffer, FormatType.TYPED_TSV);
  }

  public static CommentedTsv<T> ParseCommentedTsv<T>(byte[] inputBuffer) where T : CommentedTsvRecord, new()
  {
    // TODO: add the file comment?
    return (CommentedTsv<T>)Parse<T>(inputBuffer, FormatType.COMMENTED_TSV);
  }

  // TODO: Have parsing errors include line / column #
  protected static Tsv<T> Parse<T>(byte[] inputBuffer, FormatType format) where T : TsvRecord, new()
  {
    Tsv<T> parsed;
    if (format == FormatType.COMMENTED_TSV)
    {
      parsed = new CommentedTsv<T>();
    }
    else
    {
      parsed = new Tsv<T>();
    }
    parsed.Records = new List<T>();

    var headerTypes = new List<Type>();
    var headerNames = new List<string>();
    var headerPropertyInfos = new List<PropertyInfo>();
    int columnCount = 0;

    foreach (PropertyInfo property in typeof(T).GetProperties())
    {
      TypedTsvColumnAttribute attribute = (TypedTsvColumnAttribute)Attribute.GetCustomAttribute(property, typeof(TypedTsvColumnAttribute));
      if (attribute == null)
      {
        continue;
      }

      headerNames.Add(attribute.ColumnName ?? property.Name);
      headerTypes.Add(attribute.ColumnType ?? GetColumnFromType(property.PropertyType));
      headerPropertyInfos.Add(property);
      // TODO: Check that the property type and given column type are compatible
      columnCount++;
    }

    var fieldBytes = new List<byte>();
    var fields = new List<byte[]>();
    var currentComment = new StringBuilder();

    int numFields = -1;
    int line = 1;
    int currentLineStart = 0;
    for (int i = 0; i < inputBuffer.Count(); i++)
    {
      if (inputBuffer[i] == '\\')
      {
        if (i + 1 == inputBuffer.Count())
        {
          throw new Exception($"Found '\\' at end of input");
        }
        if (inputBuffer[i + 1] == 'n')
        {
          fieldBytes.Add((byte)'\n');
          i++;
        }
        else if (inputBuffer[i + 1] == '\\')
        {
          fieldBytes.Add((byte)'\\');
          i++;
        }
        else if (inputBuffer[i + 1] == 't')
        {
          fieldBytes.Add((byte)'\t');
          i++;
        }
        else if (inputBuffer[i + 1] == '#')
        {
          fieldBytes.Add((byte)'#');
          i++;
        }
        else
        {
          throw new Exception($"Expected 'n', 't', '#', or '\\' after '\\' at line {line} column {i - currentLineStart}");
        }
      }
      else if (inputBuffer[i] == '\t')
      {
        // end of field
        fields.Add(fieldBytes.ToArray());
        fieldBytes.Clear();
      }
      else if (inputBuffer[i] == '\n')
      {
        fields.Add(fieldBytes.ToArray());
        fieldBytes.Clear();

        if (numFields < 0)
        {
          // This is the header

          numFields = fields.Count;

          int numTypesBlank = 0;

          for (int j = 0; j < fields.Count; j++)
          {
            string columnString;
            try
            {
              columnString = Encoding.UTF8.GetString(fields[j]);
            }
            catch (Exception e)
            {
              throw new Exception($"Header {fields.Count} is not valid UTF-8", e);
            }

            string columnTypeString;
            string columnName;
            if (columnString.Contains(':'))
            {
              if (format == FormatType.SIMPLE_TSV)
              {
                throw new Exception($"Header {fields.Count} contain ':', which is not allowed for column names");
              }
              columnTypeString = columnString.Split(":").Last();
              columnName = columnString.Substring(0, columnString.Length - columnTypeString.Length - 1);
            }
            else
            {
              if (format > FormatType.SIMPLE_TSV)
              {
                throw new Exception($"Header {fields.Count} has no type");
              }
              columnTypeString = "";
              columnName = columnString;
            }

            Type type;

            switch (columnTypeString)
            {
              case "":
                numTypesBlank++;
                type = typeof(StringType);
                break;
              case "string":
                type = typeof(StringType);
                break;
              case "boolean":
                type = typeof(BooleanType);
                break;
              case "float32":
                type = typeof(Float32Type);
                break;
              case "float32-le":
                type = typeof(Float32LEType);
                break;
              case "float64":
                type = typeof(Float64Type);
                break;
              case "float64-le":
                type = typeof(Float64LEType);
                break;
              case "uint32":
                type = typeof(UInt32Type);
                break;
              case "uint64":
                type = typeof(UInt64Type);
                break;
              case "int32":
                type = typeof(Int32Type);
                break;
              case "int64":
                type = typeof(Int64Type);
                break;
              case "binary":
                type = typeof(BinaryType);
                break;
              default:
                throw new Exception($"Invalid type '{columnTypeString}' for column {j}");
            }

            // TODO: Check column name uniqueness
            // TODO: Allow lax parsing (only worry about parsing columns that are given in the specifying type

            if (headerNames[j] != columnName)
            {
              throw new Exception($"Column {j} has name {columnName}, but expected {headerNames[j]}");
            }

            if (headerTypes[j] != type)
            {
              throw new Exception($"Column {j} has type {type}, but expected {headerTypes[j]}");
            }
          }

          if (currentComment.Length > 0)
          {
            if (parsed is CommentedTsv<T> commentedParsed)
            {
              commentedParsed.FileComment = currentComment.ToString();
              currentComment.Clear();
            }
            else
            {
              throw new Exception("Found a file comment, but parser wasn't expecting a comment");
            }
          }


          fields.Clear();
        }
        else if (numFields != fields.Count)
        {
          throw new Exception($"Expected {numFields} fields on line {line}, but found {fields.Count}");
        }
        else
        {
          string comment = null;
          if (currentComment.Length > 0)
          {
            comment = currentComment.ToString();
            currentComment.Clear();
          }
          parsed.Records.Add(ParseCurrentRecord<T>(headerTypes.ToArray(), headerPropertyInfos.ToArray(), fields, comment, line));
          fields.Clear();
        }

        line++;
        currentLineStart = i + 1;
      }
      else if (inputBuffer[i] == '#')
      {
        if (i == currentLineStart && format >= FormatType.COMMENTED_TSV)
        {
          int j = i;
          for (; j < inputBuffer.Length && inputBuffer[j] != '\n'; j++) { }
          if (j < inputBuffer.Length)
          {
            var commentBytes = new byte[j - i - 1];
            Array.Copy(inputBuffer, i + 1, commentBytes, 0, j - i - 1);
            if (currentComment.Length > 0)
            {
              currentComment.Append('\n');
            }
            currentComment.Append(Encoding.UTF8.GetString(commentBytes));
            i = j;
            currentLineStart = i + 1;
            line++;
          }
          else
          {
            throw new Exception("Comments at end of file are not allowed");
          }
        }
        else
        {
          throw new Exception($"Found unescaped '#' at line {line}, column {i - currentLineStart}");
        }
      }
      else
      {
        fieldBytes.Add(inputBuffer[i]);
      }
    }

    fields.Add(fieldBytes.ToArray());

    if (numFields == 0)
    {
      throw new Exception("Found 0 fields on last line. Possibly because of extra \\n after last record");
    }
    if (numFields != fields.Count)
    {
      throw new Exception($"Expected {numFields} fields on line {parsed.Records.Count + 2}, but found {fields.Count}");
    }
    else
    {
      string comment = null;
      if (currentComment.Length > 0)
      {
        comment = currentComment.ToString();
        currentComment.Clear();
      }
      parsed.Records.Add(ParseCurrentRecord<T>(headerTypes.ToArray(), headerPropertyInfos.ToArray(), fields, comment, line));
      fields.Clear();
    }

    return parsed;
  }

  protected static T ParseCurrentCommentedRecord<T>(Type[] columnTypes, PropertyInfo[] properties, List<byte[]> fields, string comment, int line) where T : CommentedTsvRecord, new()
  {
    return (T)ParseCurrentRecord<T>(columnTypes, properties, fields, comment, line);
  }

  protected static T ParseCurrentRecord<T>(Type[] columnTypes, PropertyInfo[] properties, List<byte[]> fields, string comment, int line) where T : TsvRecord, new()
  {
    T record = new T();

    if (record is CommentedTsvRecord commentedRecord)
    {
      commentedRecord.Comment = comment;
    }
    else if (comment != null)
    {
      throw new Exception($"Found comment for line {line}, but format does not support comments");
    }

    record.Line = line;

    for (int j = 0; j < fields.Count; j++)
    {
      // All other types require the content to be UTF-8. Binary fields can ignore that.
      if (columnTypes[j] == typeof(BinaryType))
      {
        // TODO: Use faster method for property setting
        // e.g. https://blog.marcgravell.com/2012/01/playing-with-your-member.html
        // or https://stackoverflow.com/questions/1027980/improving-performance-reflection-what-alternatives-should-i-consider
        // or https://stackoverflow.com/questions/12767091/why-are-propertyinfo-setvalue-and-getvalue-so-slow
        properties[j].SetValue(record, fields[j]);
        continue;
      }
      else if (columnTypes[j] == typeof(Float32LEType))
      {
        byte[] floatBytes;
        if (!LittleEndian)
        {
          floatBytes = new byte[sizeof(float)];
          for (int k = 0; k < sizeof(float); k++)
          {
            floatBytes[k] = fields[j][sizeof(float) - 1 - k];
          }
        }
        else
        {
          floatBytes = fields[j];
        }
        properties[j].SetValue(record, BitConverter.ToSingle(floatBytes, 0));

        continue;
      }
      else if (columnTypes[j] == typeof(Float64LEType))
      {
        byte[] floatBytes;
        if (!LittleEndian)
        {
          floatBytes = new byte[sizeof(double)];
          for (int k = 0; k < sizeof(double); k++)
          {
            floatBytes[k] = fields[j][sizeof(double) - 1 - k];
          }
        }
        else
        {
          floatBytes = fields[j];
        }
        properties[j].SetValue(record, BitConverter.ToDouble(floatBytes, 0));

        continue;
      }

      string fieldString;
      try
      {
        fieldString = Encoding.UTF8.GetString(fields[j]);
      }
      catch (Exception e)
      {
        throw new Exception($"Field {j} on line {line} is not valid UTF-8", e);
      }

      // TODO: Add checking for numeric types format

      if (columnTypes[j] == typeof(StringType))
      {
        properties[j].SetValue(record, fieldString);
      }
      else if (columnTypes[j] == typeof(BooleanType))
      {
        bool parsedBool;
        if (fieldString == "TRUE")
        {
          parsedBool = true;
        }
        else if (fieldString == "FALSE")
        {
          parsedBool = false;
        }
        else
        {
          throw new Exception($"Field {j} on line {line} is not valid boolean. Must be 'TRUE' or 'FALSE' exactly");
        }

        properties[j].SetValue(record, parsedBool);
      }
      else if (columnTypes[j] == typeof(Float32Type))
      {
        float parsedFloat;
        if (!float.TryParse(fieldString, out parsedFloat))
        {
          if (fieldString == "-inf")
          {
            parsedFloat = float.NegativeInfinity;
          }
          else if (fieldString == "+inf")
          {
            parsedFloat = float.PositiveInfinity;
          }
          else
          {
            throw new Exception($"Field {j} on line {line} is not valid single-precision float");
          }
        }

        properties[j].SetValue(record, parsedFloat);
      }
      else if (columnTypes[j] == typeof(Float64Type))
      {
        double parsedDouble;
        if (!double.TryParse(fieldString, out parsedDouble))
        {
          if (fieldString == "-inf")
          {
            parsedDouble = float.NegativeInfinity;
          }
          else if (fieldString == "+inf")
          {
            parsedDouble = float.PositiveInfinity;
          }
          else
          {
            throw new Exception($"Field {j} on line {line} is not valid double-precision float");
          }
        }

        properties[j].SetValue(record, parsedDouble);
      }
      else if (columnTypes[j] == typeof(UInt32Type))
      {
        if (!UInt32.TryParse(fieldString, out UInt32 parsedUInt32))
        {
          throw new Exception($"Field {j} on line {line} is not valid UInt32");
        }

        properties[j].SetValue(record, parsedUInt32);
      }
      else if (columnTypes[j] == typeof(UInt64Type))
      {
        if (!UInt64.TryParse(fieldString, out UInt64 parsedUInt64))
        {
          throw new Exception($"Field {j} on line {line} is not valid UInt64");
        }

        properties[j].SetValue(record, parsedUInt64);
      }
      else if (columnTypes[j] == typeof(Int32Type))
      {
        if (!Int32.TryParse(fieldString, out Int32 parsedInt32))
        {
          throw new Exception($"Field {j} on line {line} is not valid Int32");
        }

        properties[j].SetValue(record, parsedInt32);
      }
      else if (columnTypes[j] == typeof(Int64Type))
      {
        if (!Int64.TryParse(fieldString, out Int64 parsedInt64))
        {
          throw new Exception($"Field {j} on line {line} is not valid Int64");
        }

        properties[j].SetValue(record, parsedInt64);
      }
      else
      {
        throw new Exception($"Unexpected type {columnTypes[j]}");
      }
    }

    return record;
  }

  public static byte[] SerializeSimpleTsv(IList<string> header, IList<IList<string>> data)
  {
    var escapedString = new StringBuilder();

    // Serialize header
    for (int i = 0; i < header.Count; i++)
    {
      if (header[i].Contains(':'))
      {
        throw new Exception($"Column {i} contains the character ':'");
      }

      for (int j = i + 1; j < header.Count; j++)
      {
        if (header[i] == header[j])
        {
          throw new Exception("Column names in header must be unique");
        }
      }

      for (int j = 0; j < header[i].Count(); j++)
      {
        if (header[i][j] == '\n')
        {
          escapedString.Append("\\n");
        }
        else if (header[i][j] == '\t')
        {
          escapedString.Append("\\t");
        }
        else if (header[i][j] == '\\')
        {
          escapedString.Append("\\\\");
        }
        else if (header[i][j] == '#')
        {
          escapedString.Append("\\#");
        }
        else
        {
          escapedString.Append(header[i][j]);
        }
      }

      if (i == header.Count - 1)
      {
        escapedString.Append('\n');
      }
      else
      {
        escapedString.Append('\t');
      }
    }

    // Serialize data
    for (int i = 0; i < data.Count; i++)
    {
      for (int j = 0; j < data[i].Count; j++)
      {
        for (int k = 0; k < data[i][j].Length; k++)
        {
          if (data[i][j][k] == '\n')
          {
            escapedString.Append("\\n");
          }
          else if (data[i][j][k] == '\t')
          {
            escapedString.Append("\\t");
          }
          else if (data[i][j][k] == '\\')
          {
            escapedString.Append("\\\\");
          }
          else if (data[i][j][k] == '#')
          {
            escapedString.Append("\\#");
          }
          else
          {
            escapedString.Append(data[i][j][k]);
          }
        }

        if (j < data[i].Count - 1)
        {
          escapedString.Append('\t');
        }
        else if (i < data.Count - 1)
        {
          escapedString.Append('\n');
        }
      }
    }

    return Encoding.UTF8.GetBytes(escapedString.ToString());
  }

  public static byte[] SerializeSimpleTsvParallel(IList<string> header, IList<IList<string>> data)
  {
    var serialized = new List<byte>();
    var escapedString = new StringBuilder();

    // Serialize header
    for (int i = 0; i < header.Count; i++)
    {
      if (header[i].Contains(':'))
      {
        throw new Exception($"Column {i} contains the character ':'");
      }

      for (int j = i + 1; j < header.Count; j++)
      {
        if (header[i] == header[j])
        {
          throw new Exception("Column names in header must be unique");
        }
      }

      for (int j = 0; j < header[i].Count(); j++)
      {
        if (header[i][j] == '\n')
        {
          escapedString.Append("\\n");
        }
        else if (header[i][j] == '\t')
        {
          escapedString.Append("\\t");
        }
        else if (header[i][j] == '\\')
        {
          escapedString.Append("\\\\");
        }
        else if (header[i][j] == '#')
        {
          escapedString.Append("\\#");
        }
        else
        {
          escapedString.Append(header[i][j]);
        }
      }

      if (i == header.Count - 1)
      {
        escapedString.Append('\n');
      }
      else
      {
        escapedString.Append('\t');
      }
    }

    serialized.AddRange(Encoding.UTF8.GetBytes(escapedString.ToString()));

    // TODO: need to figure out where the crossover it
    // Complication: it probably depends on processor count
    if (data.Count < 100)
    {
      serialized.AddRange(Encoding.UTF8.GetBytes(SerializeSimpleTsvParallel(data, 0, data.Count)));
    }
    else
    {
      int tasks = Environment.ProcessorCount - 1;
      int splitCount = data.Count / tasks;
      byte[][] bytes = new byte[tasks][];
      Parallel.For(0, tasks, i =>
      {
        int endIndex;
        if (i == tasks - 1)
        {
          endIndex = data.Count;
        }
        else
        {
          endIndex = (i + 1) * splitCount;
        }
        string escapedString = SerializeSimpleTsvParallel(data, i * splitCount, endIndex);
        bytes[i] = Encoding.UTF8.GetBytes(escapedString);
      });

      for (int i = 0; i < tasks; i++)
      {
        serialized.AddRange(bytes[i]);
      }
    }

    return serialized.ToArray();
  }

  public static string SerializeSimpleTsvParallel(IList<IList<string>> data, int startIndex, int endIndex)
  {
    var escapedString = new StringBuilder();

    // Serialize data
    for (int i = startIndex; i < endIndex; i++)
    {
      for (int j = 0; j < data[i].Count; j++)
      {
        for (int k = 0; k < data[i][j].Length; k++)
        {
          if (data[i][j][k] == '\n')
          {
            escapedString.Append("\\n");
          }
          else if (data[i][j][k] == '\t')
          {
            escapedString.Append("\\t");
          }
          else if (data[i][j][k] == '\\')
          {
            escapedString.Append("\\\\");
          }
          else if (data[i][j][k] == '#')
          {
            escapedString.Append("\\#");
          }
          else
          {
            escapedString.Append(data[i][j][k]);
          }
        }

        if (j < data[i].Count - 1)
        {
          escapedString.Append('\t');
        }
        else if (i < data.Count - 1)
        {
          escapedString.Append('\n');
        }
      }
    }

    return escapedString.ToString();
  }


  public static (string[] columns, string[][] data) ParseSimpleTsv(byte[] inputBuffer)
  {
    string[] columnNames = null;

    var fieldBytes = new List<byte>();
    var fields = new List<byte[]>();
    var records = new List<string[]>();

    int numFields = -1;
    int line = 1;
    int currentLineStart = 0;
    for (int i = 0; i < inputBuffer.Count(); i++)
    {
      if (inputBuffer[i] == '\\')
      {
        if (i + 1 == inputBuffer.Count())
        {
          throw new Exception($"Found '\\' at end of input");
        }
        if (inputBuffer[i + 1] == 'n')
        {
          fieldBytes.Add((byte)'\n');
          i++;
        }
        else if (inputBuffer[i + 1] == '\\')
        {
          fieldBytes.Add((byte)'\\');
          i++;
        }
        else if (inputBuffer[i + 1] == 't')
        {
          fieldBytes.Add((byte)'\t');
          i++;
        }
        else if (inputBuffer[i + 1] == '#')
        {
          fieldBytes.Add((byte)'#');
          i++;
        }
        else
        {
          throw new Exception($"Expected 'n', 't', '#', or '\\' after '\\' at line {line} column {i - currentLineStart}");
        }
      }
      else if (inputBuffer[i] == '\t')
      {
        // end of field
        fields.Add(fieldBytes.ToArray());
        fieldBytes.Clear();
      }
      else if (inputBuffer[i] == '\n')
      {
        fields.Add(fieldBytes.ToArray());
        fieldBytes.Clear();

        if (numFields < 0)
        {
          // This is the header

          numFields = fields.Count;

          columnNames = new string[numFields];

          for (int j = 0; j < fields.Count; j++)
          {
            string columnString;
            try
            {
              columnString = Encoding.UTF8.GetString(fields[j]);
            }
            catch (Exception e)
            {
              throw new Exception($"Column name {fields.Count} is not valid UTF-8", e);
            }

            if (columnString.Contains(':'))
            {
              throw new Exception($"Header {fields.Count} contain ':', which is not allowed for column names");
            }

            columnNames[j] = columnString;
          }

          fields.Clear();
        }
        else if (numFields != fields.Count)
        {
          throw new Exception($"Expected {numFields} fields on line {line}, but found {fields.Count}");
        }
        else
        {
          var fieldStrings = new string[fields.Count];
          for (int j = 0; j < fields.Count; j++)
          {
            try
            {
              fieldStrings[j] = Encoding.UTF8.GetString(fields[j]);
            }
            catch (Exception e)
            {
              throw new Exception($"Line {line}, column {j} is not valid UTF-8", e);
            }
          }
          records.Add(fieldStrings);
          fields.Clear();
        }

        line++;
        currentLineStart = i + 1;
      }
      else if (inputBuffer[i] == '#')
      {
        throw new Exception($"Found unescaped '#' at line {line}, column {i - currentLineStart}");
      }
      else
      {
        fieldBytes.Add(inputBuffer[i]);
      }
    }

    fields.Add(fieldBytes.ToArray());

    if (numFields == 0)
    {
      throw new Exception("Found 0 fields on last line. Possibly because of extra \\n after last record");
    }
    if (numFields != fields.Count)
    {
      throw new Exception($"Expected {numFields} fields on line {line}, but found {fields.Count}");
    }
    else
    {
      var fieldStrings = new string[fields.Count];
      for (int j = 0; j < fields.Count; j++)
      {
        try
        {
          fieldStrings[j] = Encoding.UTF8.GetString(fields[j]);
        }
        catch (Exception e)
        {
          throw new Exception($"Line {line}, column {j} is not valid UTF-8", e);
        }
      }
      records.Add(fieldStrings);
      fields.Clear();
    }

    return (columnNames, records.ToArray());
  }

  public static (string[] columns, string[][] data) ParseSimpleTsvParallel(byte[] inputBuffer)
  {
    string[] columnNames = null;
    var headers = new List<byte[]>();
    var fieldBytes = new List<byte>();
    int startOfData = -1;
    for (int i = 0; i < inputBuffer.Count(); i++)
    {
      if (inputBuffer[i] == '\\')
      {
        if (i + 1 == inputBuffer.Count())
        {
          throw new Exception($"Found '\\' at end of input");
        }
        if (inputBuffer[i + 1] == 'n')
        {
          fieldBytes.Add((byte)'\n');
          i++;
        }
        else if (inputBuffer[i + 1] == '\\')
        {
          fieldBytes.Add((byte)'\\');
          i++;
        }
        else if (inputBuffer[i + 1] == 't')
        {
          fieldBytes.Add((byte)'\t');
          i++;
        }
        else if (inputBuffer[i + 1] == '#')
        {
          fieldBytes.Add((byte)'#');
          i++;
        }
        else
        {
          throw new Exception($"Expected 'n', 't', '#', or '\\' after '\\' at line {1} column {i}");
        }
      }
      else if (inputBuffer[i] == '\t')
      {
        // end of field
        headers.Add(fieldBytes.ToArray());
        fieldBytes.Clear();
      }
      else if (inputBuffer[i] == '\n')
      {
        // This is the end of the header
        headers.Add(fieldBytes.ToArray());
        startOfData = i + 1;

        columnNames = new string[headers.Count];
        fieldBytes.Clear();

        for (int j = 0; j < headers.Count; j++)
        {
          string columnString;
          try
          {
            columnString = Encoding.UTF8.GetString(headers[j]);
          }
          catch (Exception e)
          {
            throw new Exception($"Column {headers.Count} name is not valid UTF-8", e);
          }

          if (columnString.Contains(':'))
          {
            throw new Exception($"Header {headers.Count} contain ':', which is not allowed for column names");
          }

          columnNames[j] = columnString;
        }

        // Done parsing header
        break;
      }
      else if (inputBuffer[i] == '#')
      {
        throw new Exception($"Found unescaped '#' at line 1, column {i}");
      }
      else
      {
        fieldBytes.Add(inputBuffer[i]);
      }
    }

    return (columnNames, ParseSimpleTsvParallel(inputBuffer, columnNames.Length, startOfData, inputBuffer.Length));
  }

  public static string[][] ParseSimpleTsvParallel(byte[] inputBuffer, int numFields, int startIndex, int endIndex)
  {
    var fieldBytes = new List<byte>();
    var fields = new List<byte[]>();
    var records = new List<string[]>();

    int line = 1;
    int currentLineStart = 0;

    // Go back to the start of the current line
    int i = startIndex;
    while (inputBuffer[i] != '\n')
    {
      i--;
    }

    // We want to start at the first byte of the current line
    i++;

    for (; i < endIndex; i++)
    {
      if (inputBuffer[i] == '\\')
      {
        if (i + 1 == inputBuffer.Count())
        {
          throw new Exception($"Found '\\' at end of input");
        }
        if (inputBuffer[i + 1] == 'n')
        {
          fieldBytes.Add((byte)'\n');
          i++;
        }
        else if (inputBuffer[i + 1] == '\\')
        {
          fieldBytes.Add((byte)'\\');
          i++;
        }
        else if (inputBuffer[i + 1] == 't')
        {
          fieldBytes.Add((byte)'\t');
          i++;
        }
        else if (inputBuffer[i + 1] == '#')
        {
          fieldBytes.Add((byte)'#');
          i++;
        }
        else
        {
          throw new Exception($"Expected 'n', 't', '#', or '\\' after '\\' at line {line} column {i - currentLineStart}");
        }
      }
      else if (inputBuffer[i] == '\t')
      {
        // end of field
        fields.Add(fieldBytes.ToArray());
        fieldBytes.Clear();
      }
      else if (inputBuffer[i] == '\n')
      {
        fields.Add(fieldBytes.ToArray());
        fieldBytes.Clear();

        if (numFields != fields.Count)
        {
          throw new Exception($"Expected {numFields} fields on line {line}, but found {fields.Count}");
        }
        else
        {
          var fieldStrings = new string[fields.Count];
          for (int j = 0; j < fields.Count; j++)
          {
            try
            {
              fieldStrings[j] = Encoding.UTF8.GetString(fields[j]);
            }
            catch (Exception e)
            {
              throw new Exception($"Line {line}, column {j} is not valid UTF-8", e);
            }
          }
          records.Add(fieldStrings);
          fields.Clear();
        }

        line++;
        currentLineStart = i + 1;
      }
      else if (inputBuffer[i] == '#')
      {
        throw new Exception($"Found unescaped '#' at line {line}, column {i - currentLineStart}");
      }
      else
      {
        fieldBytes.Add(inputBuffer[i]);
      }
    }

    fields.Add(fieldBytes.ToArray());

    if (fields.Count == 0)
    {
      throw new Exception("Found 0 fields on last line. Possibly because of extra \\n after last record");
    }
    if (numFields != fields.Count)
    {
      throw new Exception($"Expected {numFields} fields on line {line}, but found {fields.Count}");
    }
    else
    {
      var fieldStrings = new string[fields.Count];
      for (int j = 0; j < fields.Count; j++)
      {
        try
        {
          fieldStrings[j] = Encoding.UTF8.GetString(fields[j]);
        }
        catch (Exception e)
        {
          throw new Exception($"Line {line}, column {j} is not valid UTF-8", e);
        }
      }
      records.Add(fieldStrings);
      fields.Clear();
    }
    
    return records.ToArray();
  }

  public static Type GetColumnFromType(Type type)
  {
    if (type == typeof(string))
    {
      return typeof(StringType);
    }
    else if (type == typeof(bool))
    {
      return typeof(BooleanType);
    }
    else if (type == typeof(float))
    {
      return typeof(Float32Type);
    }
    else if (type == typeof(double))
    {
      return typeof(Float64Type);
    }
    else if (type == typeof(UInt32))
    {
      return typeof(UInt32Type);
    }
    else if (type == typeof(UInt64))
    {
      return typeof(UInt64Type);
    }
    else if (type == typeof(Int32))
    {
      return typeof(Int32Type);
    }
    else if (type == typeof(Int64))
    {
      return typeof(Int64Type);
    }
    else if (type == typeof(byte[]))
    {
      return typeof(BinaryType);
    }
    else
    {
      throw new Exception($"Invalid type: {type}");
    }
  }

  public static string GetNameFromColumn(Type type)
  {
    if (type == typeof(StringType))
    {
      return "string";
    }
    else if (type == typeof(BooleanType))
    {
      return "boolean";
    }
    else if (type == typeof(Float32Type))
    {
      return "float32";
    }
    else if (type == typeof(Float32LEType))
    {
      return "float32-le";
    }
    else if (type == typeof(Float64Type))
    {
      return "float64";
    }
    else if (type == typeof(Float64LEType))
    {
      return "float64-le";
    }
    else if (type == typeof(UInt32Type))
    {
      return "uint32";
    }
    else if (type == typeof(UInt64Type))
    {
      return "uint64";
    }
    else if (type == typeof(Int32Type))
    {
      return "int32";
    }
    else if (type == typeof(Int64Type))
    {
      return "int64";
    }
    else if (type == typeof(BinaryType))
    {
      return "binary";
    }
    else
    {
      throw new Exception($"Invalid type: {type}");
    }
  }

  public static byte[] SerializeSimpleTsv<T>(IList<T> data) where T : TsvRecord
  {
    return SerializeTsv<T>(data, FormatType.SIMPLE_TSV);
  }

  public static byte[] SerializeTypedTsv<T>(IList<T> data) where T : TsvRecord
  {
    return SerializeTsv<T>(data, FormatType.TYPED_TSV);
  }

  public static byte[] SerializeCommentedTsv<T>(IList<T> data, string fileComment) where T : CommentedTsvRecord
  {
    return SerializeTsv<T>(data, FormatType.COMMENTED_TSV);
  }

  protected static byte[] SerializeTsv<T>(IList<T> data, FormatType tsvFormat) where T : TsvRecord
  {
    var bytes = new List<byte>();

    var headerTypes = new List<Type>();
    var headerNames = new List<string>();
    var headerPropertyInfos = new List<PropertyInfo>();
    int columnCount = 0;

    foreach (PropertyInfo property in typeof(T).GetProperties())
    {
      TsvColumnAttribute attribute = (TsvColumnAttribute)Attribute.GetCustomAttribute(property, typeof(TsvColumnAttribute));
      if (attribute == null)
      {
        continue;
      }

      string headerName = attribute.ColumnName ?? property.Name;
      headerNames.Add(headerName);
      Type headerType = attribute.ColumnType ?? GetColumnFromType(property.PropertyType);
      if (tsvFormat == FormatType.SIMPLE_TSV && headerType != typeof(StringType))
      {
        throw new Exception($"Serializing Simple TSV requires all columns be of type string, but column '{headerName}' has type '{headerType}'");
      }
      headerTypes.Add(headerType);
      headerPropertyInfos.Add(property);
      // TODO: Check that the property type and given column type are compatible
      columnCount++;
    }

    // Serialize header
    for (int i = 0; i < headerNames.Count; i++)
    {
      for (int j = i + 1; j < headerNames.Count; j++)
      {
        if (headerNames[i] == headerNames[j])
        {
          throw new Exception("Column names in header must be unique");
        }
      }

      byte[] nameEncoded = Encoding.UTF8.GetBytes(headerNames[i]);

      for (int j = 0; j < nameEncoded.Length; j++)
      {
        if (nameEncoded[j] == '\n')
        {
          bytes.Add((byte)'\\');
          bytes.Add((byte)'n');
        }
        else if (nameEncoded[j] == '\t')
        {
          bytes.Add((byte)'\\');
          bytes.Add((byte)'t');
        }
        else if (nameEncoded[j] == '\\')
        {
          bytes.Add((byte)'\\');
          bytes.Add((byte)'\\');
        }
        else if (nameEncoded[j] == '#')
        {
          bytes.Add((byte)'\\');
          bytes.Add((byte)'#');
        }
        else
        {
          bytes.Add(nameEncoded[j]);
        }
      }

      if (tsvFormat != FormatType.SIMPLE_TSV)
      {
        bytes.Add((byte)':');
        try
        {
          bytes.AddRange(Encoding.UTF8.GetBytes(GetNameFromColumn(headerTypes[i])));
        }
        catch (Exception e)
        {
          throw new Exception($"Invalid header type for column {i}", e);
        }
      }

      if (i == headerNames.Count - 1)
      {
        bytes.Add((byte)'\n');
      }
      else
      {
        bytes.Add((byte)'\t');
      }
    }

    // Serialize data
    for (int i = 0; i < data.Count; i++)
    {
      for (int j = 0; j < columnCount; j++)
      {
        object datum = headerPropertyInfos[j].GetValue(data[i]);

        try
        {
          byte[] fieldEncoded = null;
          // Some fields definitely don't need escaping, so we add them directly to bytes
          bool skipEscaping = false;

          if (headerTypes[j] == typeof(StringType))
          {
            fieldEncoded = Encoding.UTF8.GetBytes((string)datum);
          }
          else if (headerTypes[j] == typeof(BooleanType))
          {
            bytes.AddRange((bool)datum ? TrueEncoded : FalseEncoded);
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(Float32Type))
          {
            if (datum is float f)
            {
              if (float.IsNegativeInfinity(f))
              {
                bytes.AddRange(Encoding.UTF8.GetBytes("-inf"));
              }
              else if (float.IsPositiveInfinity(f))
              {
                bytes.AddRange(Encoding.UTF8.GetBytes("+inf"));
              }
              else
              {
                // See https://learn.microsoft.com/en-us/dotnet/standard/base-types/standard-numeric-format-strings#round-trip-format-specifier-r
                bytes.AddRange(Encoding.UTF8.GetBytes(((float)datum).ToString("G9")));
              }
            }
            else
            {
              throw new InvalidCastException();
            }
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(Float32LEType))
          {
            if (LittleEndian)
            {
              fieldEncoded = BitConverter.GetBytes((float)datum);
            }
            else
            {
              byte[] floatBytes = BitConverter.GetBytes((float)datum);
              fieldEncoded = new byte[sizeof(float)];
              for (int k = 0; k < sizeof(float); k++)
              {
                fieldEncoded[k] = floatBytes[sizeof(float) - 1 - k];
              }
            }
          }
          else if (headerTypes[j] == typeof(Float64Type))
          {
            if (datum is double d)
            {
              if (double.IsNegativeInfinity(d))
              {
                bytes.AddRange(Encoding.UTF8.GetBytes("-inf"));
              }
              else if (double.IsPositiveInfinity(d))
              {
                bytes.AddRange(Encoding.UTF8.GetBytes("+inf"));
              }
              else
              {
                // See https://learn.microsoft.com/en-us/dotnet/standard/base-types/standard-numeric-format-strings#round-trip-format-specifier-r
                bytes.AddRange(Encoding.UTF8.GetBytes((d).ToString("G17")));
              }
            }
            else
            {
              throw new InvalidCastException();
            }
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(Float64LEType))
          {
            if (LittleEndian)
            {
              fieldEncoded = BitConverter.GetBytes((double)datum);
            }
            else
            {
              byte[] doubleBytes = BitConverter.GetBytes((double)datum);
              fieldEncoded = new byte[sizeof(double)];
              for (int k = 0; k < sizeof(double); k++)
              {
                fieldEncoded[k] = doubleBytes[sizeof(double) - 1 - k];
              }
            }
          }
          else if (headerTypes[j] == typeof(UInt32Type))
          {
            bytes.AddRange(Encoding.UTF8.GetBytes(((UInt32)datum).ToString()));
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(UInt64Type))
          {
            bytes.AddRange(Encoding.UTF8.GetBytes(((UInt64)datum).ToString()));
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(Int32Type))
          {
            bytes.AddRange(Encoding.UTF8.GetBytes(((Int32)datum).ToString()));
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(Int64Type))
          {
            bytes.AddRange(Encoding.UTF8.GetBytes(((Int64)datum).ToString()));
            skipEscaping = true;
          }
          else if (headerTypes[j] == typeof(BinaryType))
          {
            fieldEncoded = (byte[])datum;
          }
          else
          {
            throw new Exception($"Unexpected column type {headerTypes[j]} for column {j}");
          }

          if (!skipEscaping)
          {
            for (int k = 0; k < fieldEncoded.Length; k++)
            {
              if (fieldEncoded[k] == '\n')
              {
                bytes.Add((byte)'\\');
                bytes.Add((byte)'n');
              }
              else if (fieldEncoded[k] == '\t')
              {
                bytes.Add((byte)'\\');
                bytes.Add((byte)'t');
              }
              else if (fieldEncoded[k] == '\\')
              {
                bytes.Add((byte)'\\');
                bytes.Add((byte)'\\');
              }
              else if (fieldEncoded[k] == '#')
              {
                bytes.Add((byte)'\\');
                bytes.Add((byte)'#');
              }
              else
              {
                bytes.Add(fieldEncoded[k]);
              }
            }
          }

          if (j < columnCount - 1)
          {
            bytes.Add((byte)'\t');
          }
          else if (i < data.Count - 1)
          {
            bytes.Add((byte)'\n');
          }
        }
        catch (InvalidCastException e)
        {
          throw new Exception($"Record {i}, field {j} expected type compatible with {GetNameFromColumn(headerTypes[j])}", e);
        }
      }
    }

    return bytes.ToArray();
  }

  public class SimpleTsvRecord
  {
    public string[] ColumnNames { get; }
    public string Comment { get; }
    public string[] Fields { get; }
    public int? Line { get; }

    public string this[string columnName] => Fields[Array.IndexOf(ColumnNames, columnName)];
    public string this[int columnIndex] => Fields[columnIndex];

    public SimpleTsvRecord(string[] columnNames, string[] fields, string comment, int line)
    {
      ColumnNames = columnNames;
      Fields = fields;
      Comment = comment;
      Line = line;
    }
  }

  public class TsvRecord
  {
    public int? Line { get; set; }
    public TsvRecord(int? line)
    {
      Line = line;
    }

    public TsvRecord() { }
  }

  public class CommentedTsvRecord : TsvRecord
  {
    public string Comment { get; set; }

    public CommentedTsvRecord(string comment, int? line)
    {
      Comment = comment;
      Line = line;
    }

    public CommentedTsvRecord() { }
  }

  public class TestRecord : CommentedTsvRecord
  {
    [TypedTsvColumn("my-column")]
    public string MyColumn { get; set; }
  }

  // TODO: Add column ordering
  public class TsvColumnAttribute : Attribute
  {
    public string ColumnName { get; }
    public virtual Type ColumnType { get; }

    public TsvColumnAttribute()
    {
      ColumnType = typeof(StringType);
    }
    public TsvColumnAttribute(string columnName)
    {
      ColumnType = typeof(StringType);
      ColumnName = columnName;
    }
  }

  // TODO: Add column ordering
  public class TypedTsvColumnAttribute : TsvColumnAttribute
  {
    public override Type ColumnType { get; }

    public TypedTsvColumnAttribute() { }

    public TypedTsvColumnAttribute(string columnName) : base(columnName) { }

    public TypedTsvColumnAttribute(string columnName, Type columnType) : base(columnName)
    {
      if (columnType.BaseType != typeof(ColumnType))
      {
        throw new Exception("Column type must inherit from SaneTsv.ColumnType");
      }
      ColumnType = columnType;
    }

    public TypedTsvColumnAttribute(Type columnType)
    {
      if (columnType.BaseType != typeof(ColumnType))
      {
        throw new Exception("Column type must inherit from SaneTsv.ColumnType");
      }
      ColumnType = columnType;
    }
  }
}