using System.Text;

namespace NathanMcRae;

/// <summary>
/// Sane Tab-Separated Values
/// </summary>
public class Stsv
{
  // TODO: We need to be able to update all these in tandem somehow
  public string[] ColumnNames { get; protected set; }
  public Dictionary<string, List<string>> Columns { get; protected set; }
  public List<StsvRecord> Records { get; protected set; }

  public static Stsv Parse(byte[] inputBuffer)
  {
    var parsed = new Stsv();
    parsed.Columns = new Dictionary<string, List<string>>();
    parsed.ColumnNames = new string[] { };
    parsed.Records = new List<StsvRecord>();

    var fieldBytes = new List<byte>();
    var fields = new List<string>();
    int numFields = -1;
    for (int i = 0; i < inputBuffer.Count(); i++)
    {
      if (inputBuffer[i] == '\\')
      {
        if (i + 1 == inputBuffer.Count())
        {
          throw new Exception($"Found '\\' at end of input");
        }
        if (inputBuffer[i + 1] == 'n')
        {
          fieldBytes.Add((byte)'\n');
          i++;
        }
        else if (inputBuffer[i + 1] == '\\')
        {
          fieldBytes.Add((byte)'\\');
          i++;
        }
        else if (inputBuffer[i + 1] == 't')
        {
          fieldBytes.Add((byte)'\t');
          i++;
        }
        else
        {
          throw new Exception($"Expected 'n', 't', or '\\' after '\\' at {i}");
        }
      }
      else if (inputBuffer[i] == '\t')
      {
        // end of field
        try
        {
          fields.Add(Encoding.UTF8.GetString(fieldBytes.ToArray()));
        }
        catch (Exception e)
        {
          throw new Exception($"Field {fields.Count} on line {parsed.Records.Count + 1} is not valid UTF-8", e);
        }
        fieldBytes.Clear();
      }
      else if (inputBuffer[i] == '\n')
      {
        try
        {
          fields.Add(Encoding.UTF8.GetString(fieldBytes.ToArray()));
        }
        catch (Exception e)
        {
          throw new Exception($"Field {fields.Count} on line {parsed.Records.Count + 1} is not valid UTF-8", e);
        }
        fieldBytes.Clear();

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

          numFields = fields.Count;

          parsed.ColumnNames = new string[numFields];

          for (int j = 0; j < fields.Count; j++)
          {
            string columnName = fields[j];

            try
            {
              parsed.Columns.Add(columnName, new List<string>());
            }
            catch (Exception e)
            {
              throw new Exception($"Column name {columnName} is not unique", e);
            }

            parsed.ColumnNames[j] = columnName;
          }

          fields.Clear();
        }
        else if (numFields != fields.Count)
        {
          throw new Exception($"Expected {numFields} fields on line {parsed.Records.Count + 2}, but found {fields.Count}");
        }
        else
        {
          for (int j = 0; j < fields.Count; j++)
          {
              parsed.Columns[parsed.ColumnNames[j]].Add(fields[j]);
          }

          parsed.Records.Add(new StsvRecord(parsed, fields.ToArray()));
          fields.Clear();
        }
      }
      else
      {
        fieldBytes.Add(inputBuffer[i]);
      }
    }

    try
    {
      fields.Add(Encoding.UTF8.GetString(fieldBytes.ToArray()));
    }
    catch (Exception e)
    {
      throw new Exception($"Field {fields.Count} on line {parsed.Records.Count + 1} is not valid UTF-8", e);
    }

    if (numFields != fields.Count)
    {
      throw new Exception($"Expected {numFields} fields on line {parsed.Records.Count + 2}, but found {fields.Count}");
    }
    else
    {
      for (int j = 0; j < fields.Count; j++)
      {
        try
        {
          parsed.Columns[parsed.ColumnNames[j]].Add(fields[j]);
        }
        catch (Exception e)
        {
          throw new Exception($"Field {j} on line {parsed.Records.Count + 1} is not valid UTF-8", e);
        }
      }

      parsed.Records.Add(new StsvRecord(parsed, fields.ToArray()));
      fields.Clear();
    }

    return parsed;
  }

  public StsvRecord this[int i] => Records[i];

  public class StsvRecord
  {
    public Stsv Parent { get; }
    public string[] Fields { get; }

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

    public StsvRecord(Stsv parent, string[] fields)
    {
      Parent = parent;
      Fields = fields;
    }
  }
}