using BaseOUDAL.EFExtensions;
using Dapper;
using MySqlConnector;
using System.Data;
using System.Reflection;
using System.Text;

namespace YLErp.BLL
{
    public static class MySqlBulkExtensions
    {
        public static void BulkInsert<T>(this DbContext context, IEnumerable<T> entities)
        {
            if (entities != null && entities.Any())
            {
                var conn = context.Database.GetDbConnection() as MySqlConnection;
                BulkInsert(conn, entities);
            }
        }

        /// <summary>
        /// Inserts entities into table <typeparamref name="T"/>s (by default).
        /// </summary>
        /// <typeparam name="T">The type being inserted.</typeparam>
        /// <param name="connection">Open SqlConnection</param>
        /// <param name="data">Entities to insert</param>
        /// <param name="transaction">The transaction to run under, null (the default) if none</param>
        /// <param name="batchSize">Number of bulk items inserted together, 0 (the default) if all</param>
        /// <param name="bulkCopyTimeout">Number of seconds before bulk command execution timeout, 30 (the default)</param>
        private static void BulkInsert<T>(MySqlConnection connection, IEnumerable<T> data, IDbTransaction transaction = null)
        {
            BulkInsert(connection, typeof(T), data.Cast<object>(), transaction);
        }

        /// <summary>
        /// Inserts entities into table.
        /// by default, the table is named after the data type specified.
        /// </summary>
        /// <param name="connection">Open SqlConnection</param>
        /// <param name="type">The type being inserted.</param>
        /// <param name="data">Entities to insert</param>
        /// <param name="transaction">The transaction to run under, null (the default) if none</param>
        /// <param name="batchSize">Number of bulk items inserted together, 0 (the default) if all</param>
        /// <param name="bulkCopyTimeout">Number of seconds before bulk command execution timeout, 30 (the default)</param>
        private static void BulkInsert(MySqlConnection connection, Type type, IEnumerable<object> data, IDbTransaction transaction = null)
        {
            var tableName = TableMapper.GetTableName(type);
            var allProperties = PropertiesCache.TypePropertiesCache(type);
            var computedProperties = PropertiesCache.ComputedPropertiesCache(type);
            var columns = PropertiesCache.GetColumnNamesCache(type);

            var selProperties = allProperties.Except(computedProperties).ToList();
            if (!selProperties.Any())
            {
                return;
            }

            var selcols = string.Join(", ", selProperties.Select(property => $"`{columns[property.Name]}`"));
            var sCommand = new StringBuilder();

            sCommand.Append("INSERT INTO `").Append(tableName)
                    .Append("` (").Append(selcols).Append(") VALUES ");

            DumpInertValues(sCommand, data, selProperties).AppendLine(";");

            var sql = sCommand.ToString();

            System.Diagnostics.Debug.WriteLine("$$$$$$$$$$");
            System.Diagnostics.Debug.WriteLine(sql);
            connection.Execute(sql, null, transaction);
        }

        private static StringBuilder DumpInertValues<T>(StringBuilder sb, IEnumerable<T> data, IList<PropertyInfo> properties)
        {
            System.Diagnostics.Debug.Assert(properties.Count > 0);

            var typeCasts = new Type[properties.Count];

            for (var i = 0; i < properties.Count; i++)
            {
                if (properties[i].PropertyType.IsEnum)
                {
                    typeCasts[i] = Enum.GetUnderlyingType(properties[i].PropertyType);
                }
                else
                {
                    typeCasts[i] = null;
                }
            }

            foreach (var item in data)
            {
                sb.AppendLine().Append("(");

                for (var i = 0; i < properties.Count; i++)
                {
                    var value = properties[i].GetValue(item, null);

                    if (value == null)
                    {
                        sb.Append("NULL");
                    }
                    else if (value is string str)
                    {
                        sb.Append('\'').Append(MySqlHelper.EscapeString(str)).Append('\'');
                    }
                    else if (value is DateTime dt)
                    {
                        sb.Append('\'').Append(dt.ToString("yyyy-MM-dd HH:mm:ss")).Append('\'');
                    }
                    else if (value is double dd)
                    {
                        sb.Append(double.IsNaN(dd) ? 0 : dd);
                    }
                    else if (typeCasts[i] != null)
                    {
                        sb.Append(Convert.ChangeType(value, typeCasts[i]));
                    }
                    else
                    {
                        sb.Append(value);
                    }
                    sb.Append(',');
                }

                sb.Remove(sb.Length - 1, 1).Append("),");
            }

            return sb.Remove(sb.Length - 1, 1);
        }
    }
}