inabox/InABox.Core/CoreTable/CoreTableJsonConverter.cs

using System;
using System.Reflection;
using System.Text.Json;

namespace InABox.Core
{

    public class CoreTableJsonConverter : CustomJsonConverter<CoreTable>
    {
        public override void Write(Utf8JsonWriter writer, CoreTable value, JsonSerializerOptions options)
        {
            if (value == null)
            {
                writer.WriteNullValue();
                return;
            }
            
            writer.WriteStartObject();

            // Columns
            writer.WritePropertyName("Columns");
            writer.WriteStartObject();
            foreach (var column in value.Columns)
                writer.WriteString(column.ColumnName, column.DataType.EntityName());
            writer.WriteEndObject();
            
            // Rows
            writer.WritePropertyName("Rows");
            writer.WriteStartArray();
            foreach (var row in value.Rows)
            {
                writer.WriteStartArray();
                foreach (var column in value.Columns)
                {
                    WriteJson(writer, row[column.ColumnName]);
                }
                writer.WriteEndArray();
            }
            writer.WriteEndArray();

            writer.WriteEndObject();
        }
        
        public override CoreTable? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType == JsonTokenType.Null)
                return null;

            var result = new CoreTable();
            try
            {
                reader.Read();
                while(reader.TokenType != JsonTokenType.EndObject)
                {
                    if (reader.TokenType == JsonTokenType.PropertyName)
                    {
                        var propertyName = reader.GetString();
                        reader.Read(); // Move to property value
                        if (propertyName == "Columns")
                        {
                            if(reader.TokenType != JsonTokenType.StartObject)
                            {
                                throw new SerialisationException($"Unexpected token type after \"Columns\": {reader.TokenType}");
                            }
                            reader.Read(); // Skip over StartObject
                            while (reader.TokenType != JsonTokenType.EndObject)
                            {
                                string name = reader.GetString()!;
                                reader.Read(); // Advance to the property value
                                var type = reader.GetString();
                                result.Columns.Add(new CoreColumn { ColumnName = name, DataType = CoreUtils.GetEntity(type ?? "") });
                                reader.Read(); // Move to next token
                            }
                            reader.Read(); // Skip EndObject
                        }
                        else if (propertyName == "Rows")
                        {
                            if(reader.TokenType != JsonTokenType.StartArray)
                            {
                                throw new SerialisationException($"Unexpected token type after \"Rows\": {reader.TokenType}");
                            }
                            reader.Read(); // Skip StartArray
                            while (reader.TokenType != JsonTokenType.EndArray)
                            {
                                if(reader.TokenType != JsonTokenType.StartArray)
                                {
                                    throw new SerialisationException($"Unexpected token type: {reader.TokenType}");
                                }
                                reader.Read(); // Skip StartArray
                                var iCol = 0;
                                var newrow = result.NewRow();
                                while (reader.TokenType != JsonTokenType.EndArray)
                                {
                                    var col = result.Columns[iCol];
                                    newrow[col.ColumnName] = CoreUtils.ChangeType(ReadJson(reader), col.DataType);
                                    reader.Read();
                                    iCol++;
                                }
                                result.Rows.Add(newrow);
                                reader.Read(); // Skip EndArray
                            }
                            reader.Read(); // Skip EndArray
                        }
                    }
                }
            }
            catch(SerialisationException e)
            {
                Logger.Send(LogType.Error, "", $"SerialisationException: {e.Message}");
                return null;
            }
            catch (Exception e)
            {
                Logger.Send(LogType.Error, "", string.Format("*** Unknown Error: {0}\n{1}", e.Message, e.StackTrace));
            }

            return result;
        }
        
        public override bool CanConvert(Type objectType)
        {
            return typeof(CoreTable).IsAssignableFrom(objectType);
        }
    }
}