using System;
using System.IO;

namespace Ant.Service.Utilities
{
    internal sealed class TopCommand : Pop3Command<RetrResponse>
    {
        private int _messageNumber;
        private int _lineCount;

        /// <summary>
        /// Initializes a new instance of the <see cref="TopCommand"/> class.
        /// </summary>
        /// <param name="stream">The stream.</param>
        /// <param name="messageNumber">The message number.</param>
        /// <param name="lineCount">The line count.</param>
        internal TopCommand(Stream stream, int messageNumber, int lineCount)
            : base(stream, true, Pop3State.Transaction)
        {
            if (messageNumber < 1)
            {
                throw new ArgumentOutOfRangeException("messageNumber");
            }

            if (lineCount < 0)
            {
                throw new ArgumentOutOfRangeException("lineCount");
            }

            _messageNumber = messageNumber;
            _lineCount = lineCount;
        }

        /// <summary>
        /// Abstract method intended for inheritors to
        /// build out the byte[] request message for
        /// the specific command.
        /// </summary>
        /// <returns>
        /// The byte[] containing the request message.
        /// </returns>
        protected override byte[] CreateRequestMessage()
        {
            return GetRequestMessage(Pop3Commands.Top, _messageNumber.ToString(), " ", _lineCount.ToString(), Pop3Commands.Crlf);
        }

        /// <summary>
        /// Creates the response.
        /// </summary>
        /// <param name="buffer">The buffer.</param>
        /// <returns>
        /// The <c>Pop3Response</c> containing the results of the
        /// Pop3 command execution.
        /// </returns>
        protected override RetrResponse CreateResponse(byte[] buffer)
        {
            Pop3Response response = Pop3Response.CreateResponse(buffer);

            if (response == null)
            {
                return null;
            }

            string[] messageLines = GetResponseLines(StripPop3HostMessage(buffer, response.HostMessage));

            return new RetrResponse(response, messageLines);
        }
    }
}