namespace LaaProduction.SQL
{
    using LaaProduction.SQL.Interfaces;

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

    public class SQLCommand : ISQLCommand
    {
        private readonly SQLConnection sqlConnection;
        private readonly IDictionary<string, SqlParameter> parameters;

        public SQLCommand(SQLConnection sqlConnection, string commandText)
        {
            this.sqlConnection = sqlConnection.EnsureNotNull(nameof(sqlConnection));
            this.CommandText = commandText.EnsureNotNullOrWhiteSpace(nameof(commandText));
            this.parameters = new Dictionary<string, SqlParameter>();
        }

        internal string CommandText { get; }

        internal SqlParameter[] Parameters 
            => this.parameters.Values.ToArray();

        public int ExecuteNonQuery()
            => this.sqlConnection.ExecuteNonQuery(this);

        public IEnumerable<T> ExecuteReader<T>(Func<ISQLReader, T> expression)
        {
            foreach (var result in this.sqlConnection.ExecuteReader(this, expression))
            {
                yield return result;
            }
        }

        public T ExecuteScalar<T>(Func<ISQLReader, T> expression)
            => this.sqlConnection.ExecuteScalar(this, expression);

        public T FirstOrDefault<T>(Func<ISQLReader, T> expression)
            => this.sqlConnection.FirstOrDefault(this, expression);

        public ISQLCommand SetParameter(string name, object value)
        {
            name.ThrowIfNullOrWhiteSpace(nameof(name));

            if (value is null)
            {
                value = DBNull.Value;
            }

            var parameter = new SqlParameter(name, value);

            this.parameters[name] = parameter;

            return this;
        }

        public ISQLCommand SetParameters(IEnumerable<KeyValuePair<string, object>> parameters)
        {
            foreach (var kvp in parameters)
            {
                this.SetParameter(kvp.Key, kvp.Value);
            }

            return this;
        }
    }
}