laatzen/LaaProductionWeb/FluentSQL/FluentSQL.cs

namespace LaaProductionWeb.Data
{
    using LaaProductionWeb.Data.Interfaces;

    using System;
    using System.Collections.Generic;
    using System.Data;
    using System.Data.SqlClient;
    using System.Linq;

    public class FluentSQL : IFluentSQL
    {
        private readonly string connectionString;

        public FluentSQL(string connectionString)
        {
            connectionString.ThrowIfNullOrWhiteSpace(nameof(connectionString));

            var connectionStringBuilder = new SqlConnectionStringBuilder(connectionString);

            this.connectionString = connectionStringBuilder.ToString();
        }

        public FluentSQLCommand CreateCommand(string commandText) 
            => new FluentSQLCommand(this, commandText);

        internal int ExecuteNonQuery(FluentSQLCommand command)
        {
            command.ThrowIfNull(nameof(command));

            var rowsAffected = 0;

            using (var sqlConnection = new SqlConnection(this.connectionString))
            {
                sqlConnection.OpenWithErrorHandling();

                using (var sqlCommand = sqlConnection.CreateCommand())
                {
                    sqlCommand.CommandText = command.CommandText;

                    sqlCommand.Parameters.AddRange(command.Parameters);

                    rowsAffected = sqlCommand.ExecuteNonQuery();

                    sqlCommand.Parameters.Clear();
                }
            }

            return rowsAffected;
        }

        internal IEnumerable<T> ExecuteReader<T>(FluentSQLCommand command, Func<IFluentSQLReader, T> expression)
        {
            command.ThrowIfNull(nameof(command));
            expression.ThrowIfNull(nameof(expression));

            using (var sqlConnection = new SqlConnection(this.connectionString))
            {
                sqlConnection.OpenWithErrorHandling();

                using (var sqlCommand = sqlConnection.CreateCommand())
                {
                    sqlCommand.CommandText = command.CommandText;

                    sqlCommand.Parameters.AddRange(command.Parameters);

                    using (FluentSQLReader sqlReader = sqlCommand.ExecuteReader(CommandBehavior.SequentialAccess))
                    {
                        sqlCommand.Parameters.Clear();

                        while (sqlReader.Read())
                        {
                            yield return expression(sqlReader);
                        }
                    }
                }
            }
        }

        internal T ExecuteScalar<T>(FluentSQLCommand command, Func<IFluentSQLReader, T> expression)
        {
            command.ThrowIfNull(nameof(command));
            expression.ThrowIfNull(nameof(expression));

            var scalarResult = default(T);

            using (var sqlConnection = new SqlConnection(this.connectionString))
            {
                sqlConnection.OpenWithErrorHandling();

                using (var sqlCommand = sqlConnection.CreateCommand())
                {
                    sqlCommand.CommandText = command.CommandText;

                    sqlCommand.Parameters.AddRange(command.Parameters);

                    var scalarObject = sqlCommand.ExecuteScalar();

                    sqlCommand.Parameters.Clear();

                    if (scalarObject is T scalarValue)
                    {
                        scalarResult = scalarValue;
                    }
                }
            }

            return scalarResult;
        }

        internal T FirstOrDefault<T>(FluentSQLCommand command, Func<IFluentSQLReader, T> expression) 
            => this
                .ExecuteReader(command, expression)
                .FirstOrDefault();
    }
}