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)
        {
            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();
            ReadObject(ref reader, (ref Utf8JsonReader reader, string propertyName) =>
            {
                if (propertyName == "Columns")
                {
                    ReadObject(ref reader, (ref Utf8JsonReader reader, string name) =>
                    {
                        var type = reader.GetString();
                        result.Columns.Add(new CoreColumn { ColumnName = name, DataType = CoreUtils.GetEntity(type ?? "") });
                    });
                }
                else if (propertyName == "Rows")
                {
                    ReadArray(ref reader, (ref Utf8JsonReader reader) =>
                    {
                        var iCol = 0;
                        var newRow = result.NewRow();
                        ReadArray(ref reader, (ref Utf8JsonReader reader) =>
                        {
                            var col = result.Columns[iCol];
                            newRow[col.ColumnName] = CoreUtils.ChangeType(ReadJson(ref reader), col.DataType);
                            iCol++;
                        });
                        result.Rows.Add(newRow);
                    });
                }
                else
                {
                    reader.Skip();
                }
            });

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