Connected.Framework/Connected.Data/Schema/Sql/Columns.cs

using Connected.Entities.Annotations;
using Connected.Entities.Storage;
using System.Data;
using System.Text;

namespace Connected.Data.Schema.Sql;

internal class Columns : SynchronizationQuery<List<ISchemaColumn>>
{
    public Columns(ExistingSchema existing)
    {
        Existing = existing;
    }

    private ExistingSchema Existing { get; }

    protected override async Task<List<ISchemaColumn>> OnExecute()
    {
        var result = new List<ISchemaColumn>();
        var rdr = await Context.OpenReader(new StorageOperation { CommandText = CommandText });

        while (rdr.Read())
        {
            var column = new ExistingColumn(Existing)
            {
                IsNullable = !string.Equals(rdr.GetValue("IS_NULLABLE", string.Empty), "NO", StringComparison.OrdinalIgnoreCase),
                DataType = SchemaExtensions.ToDbType(rdr.GetValue("DATA_TYPE", string.Empty)),
                MaxLength = rdr.GetValue("CHARACTER_MAXIMUM_LENGTH", 0),
                Name = rdr.GetValue("COLUMN_NAME", string.Empty),
            };

            if (column.DataType == DbType.Decimal || column.DataType == DbType.VarNumeric)
            {
                column.Precision = rdr.GetValue("NUMERIC_PRECISION", 0);
                column.Scale = rdr.GetValue("NUMERIC_SCALE", 0);
            }

            if (column.DataType == DbType.DateTime2
                || column.DataType == DbType.Time
                || column.DataType == DbType.DateTimeOffset)
                column.DatePrecision = rdr.GetValue("DATETIME_PRECISION", 0);

            if (column.DataType == DbType.Date)
                column.DateKind = DateKind.Date;
            else if (column.DataType == DbType.DateTime)
            {
                if (string.Compare(rdr.GetValue("DATA_TYPE", string.Empty), "smalldatetime", true) == 0)
                    column.DateKind = DateKind.SmallDateTime;
            }
            else if (column.DataType == DbType.DateTime2)
                column.DateKind = DateKind.DateTime2;
            else if (column.DataType == DbType.Time)
                column.DateKind = DateKind.Time;
            else if (column.DataType == DbType.Binary)
            {
                if (string.Compare(rdr.GetValue("DATA_TYPE", string.Empty), "varbinary", true) == 0)
                    column.BinaryKind = BinaryKind.VarBinary;
                else if (string.Compare(rdr.GetValue("DATA_TYPE", string.Empty), "binary", true) == 0)
                    column.BinaryKind = BinaryKind.Binary;
            }

            column.IsVersion = string.Equals(rdr.GetValue("DATA_TYPE", string.Empty), "timestamp", StringComparison.OrdinalIgnoreCase);

            result.Add(column);
        }

        rdr.Close();

        return result;
    }

    private string CommandText
    {
        get
        {
            var text = new StringBuilder();

            text.AppendLine($"SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = '{Context.Schema.SchemaName()}' AND TABLE_NAME = '{Context.Schema.Name}'");

            return text.ToString();
        }
    }
}