RaspberryIO/Unosquare.Swan/Networking/SmtpServerReply.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;

namespace Unosquare.Swan.Networking {
  /// <summary>
  /// Represents an SMTP server response object.
  /// </summary>
  public class SmtpServerReply {
    #region Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="SmtpServerReply"/> class.
    /// </summary>
    /// <param name="responseCode">The response code.</param>
    /// <param name="statusCode">The status code.</param>
    /// <param name="content">The content.</param>
    public SmtpServerReply(Int32 responseCode, String statusCode, params String[] content) {
      this.Content = new List<String>();
      this.ReplyCode = responseCode;
      this.EnhancedStatusCode = statusCode;
      this.Content.AddRange(content);
      this.IsValid = responseCode >= 200 && responseCode < 600;
      this.ReplyCodeSeverity = SmtpReplyCodeSeverities.Unknown;
      this.ReplyCodeCategory = SmtpReplyCodeCategories.Unknown;

      if(!this.IsValid) {
        return;
      }

      if(responseCode >= 200) {
        this.ReplyCodeSeverity = SmtpReplyCodeSeverities.PositiveCompletion;
      }

      if(responseCode >= 300) {
        this.ReplyCodeSeverity = SmtpReplyCodeSeverities.PositiveIntermediate;
      }

      if(responseCode >= 400) {
        this.ReplyCodeSeverity = SmtpReplyCodeSeverities.TransientNegative;
      }

      if(responseCode >= 500) {
        this.ReplyCodeSeverity = SmtpReplyCodeSeverities.PermanentNegative;
      }

      if(responseCode >= 600) {
        this.ReplyCodeSeverity = SmtpReplyCodeSeverities.Unknown;
      }

      if(Int32.TryParse(responseCode.ToString(CultureInfo.InvariantCulture).Substring(1, 1), out Int32 middleDigit)) {
        if(middleDigit >= 0 && middleDigit <= 5) {
          this.ReplyCodeCategory = (SmtpReplyCodeCategories)middleDigit;
        }
      }
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="SmtpServerReply"/> class.
    /// </summary>
    public SmtpServerReply()
        : this(0, String.Empty, String.Empty) {
      // placeholder
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="SmtpServerReply"/> class.
    /// </summary>
    /// <param name="responseCode">The response code.</param>
    /// <param name="statusCode">The status code.</param>
    /// <param name="content">The content.</param>
    public SmtpServerReply(Int32 responseCode, String statusCode, String content)
        : this(responseCode, statusCode, new[] { content }) {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="SmtpServerReply"/> class.
    /// </summary>
    /// <param name="responseCode">The response code.</param>
    /// <param name="content">The content.</param>
    public SmtpServerReply(Int32 responseCode, String content)
        : this(responseCode, String.Empty, content) {
    }

    #endregion

    #region Pre-built responses (https://tools.ietf.org/html/rfc5321#section-4.2.2)

    /// <summary>
    /// Gets the command unrecognized reply.
    /// </summary>
    public static SmtpServerReply CommandUnrecognized =>
        new SmtpServerReply(500, "Syntax error, command unrecognized");

    /// <summary>
    /// Gets the syntax error arguments reply.
    /// </summary>
    public static SmtpServerReply SyntaxErrorArguments =>
        new SmtpServerReply(501, "Syntax error in parameters or arguments");

    /// <summary>
    /// Gets the command not implemented reply.
    /// </summary>
    public static SmtpServerReply CommandNotImplemented => new SmtpServerReply(502, "Command not implemented");

    /// <summary>
    /// Gets the bad sequence of commands reply.
    /// </summary>
    public static SmtpServerReply BadSequenceOfCommands => new SmtpServerReply(503, "Bad sequence of commands");

    /// <summary>
    /// Gets the protocol violation reply.
    /// </summary>=
    public static SmtpServerReply ProtocolViolation =>
        new SmtpServerReply(451, "Requested action aborted: error in processing");

    /// <summary>
    /// Gets the system status bye reply.
    /// </summary>
    public static SmtpServerReply SystemStatusBye =>
        new SmtpServerReply(221, "Service closing transmission channel");

    /// <summary>
    /// Gets the system status help reply.
    /// </summary>=
    public static SmtpServerReply SystemStatusHelp => new SmtpServerReply(221, "Refer to RFC 5321");

    /// <summary>
    /// Gets the bad syntax command empty reply.
    /// </summary>
    public static SmtpServerReply BadSyntaxCommandEmpty => new SmtpServerReply(400, "Error: bad syntax");

    /// <summary>
    /// Gets the OK reply.
    /// </summary>
    public static SmtpServerReply Ok => new SmtpServerReply(250, "OK");

    /// <summary>
    /// Gets the authorization required reply.
    /// </summary>
    public static SmtpServerReply AuthorizationRequired => new SmtpServerReply(530, "Authorization Required");

    #endregion

    #region Properties

    /// <summary>
    /// Gets the response severity.
    /// </summary>
    public SmtpReplyCodeSeverities ReplyCodeSeverity {
      get;
    }

    /// <summary>
    /// Gets the response category.
    /// </summary>
    public SmtpReplyCodeCategories ReplyCodeCategory {
      get;
    }

    /// <summary>
    /// Gets the numeric response code.
    /// </summary>
    public Int32 ReplyCode {
      get;
    }

    /// <summary>
    /// Gets the enhanced status code.
    /// </summary>
    public String EnhancedStatusCode {
      get;
    }

    /// <summary>
    /// Gets the content.
    /// </summary>
    public List<String> Content {
      get;
    }

    /// <summary>
    /// Returns true if the response code is between 200 and 599.
    /// </summary>
    public Boolean IsValid {
      get;
    }

    /// <summary>
    /// Gets a value indicating whether this instance is positive.
    /// </summary>
    public Boolean IsPositive => this.ReplyCode >= 200 && this.ReplyCode <= 399;

    #endregion

    #region Methods

    /// <summary>
    /// Parses the specified text into a Server Reply for thorough analysis.
    /// </summary>
    /// <param name="text">The text.</param>
    /// <returns>A new instance of SMTP server response object.</returns>
    public static SmtpServerReply Parse(String text) {
      String[] lines = text.Split(new[] { "\r\n" }, StringSplitOptions.RemoveEmptyEntries);
      if(lines.Length == 0) {
        return new SmtpServerReply();
      }

      String[] lastLineParts = lines.Last().Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries);
      String enhancedStatusCode = String.Empty;
      _ = Int32.TryParse(lastLineParts[0], out Int32 responseCode);
      if(lastLineParts.Length > 1) {
        if(lastLineParts[1].Split('.').Length == 3) {
          enhancedStatusCode = lastLineParts[1];
        }
      }

      List<String> content = new List<String>();

      for(Int32 i = 0; i < lines.Length; i++) {
        String splitChar = i == lines.Length - 1 ? " " : "-";

        String[] lineParts = lines[i].Split(new[] { splitChar }, 2, StringSplitOptions.None);
        String lineContent = lineParts.Last();
        if(String.IsNullOrWhiteSpace(enhancedStatusCode) == false) {
          lineContent = lineContent.Replace(enhancedStatusCode, String.Empty).Trim();
        }

        content.Add(lineContent);
      }

      return new SmtpServerReply(responseCode, enhancedStatusCode, content.ToArray());
    }

    /// <summary>
    /// Returns a <see cref="System.String" /> that represents this instance.
    /// </summary>
    /// <returns>
    /// A <see cref="System.String" /> that represents this instance.
    /// </returns>
    public override String ToString() {
      String responseCodeText = this.ReplyCode.ToString(CultureInfo.InvariantCulture);
      String statusCodeText = String.IsNullOrWhiteSpace(this.EnhancedStatusCode)
          ? String.Empty
          : $" {this.EnhancedStatusCode.Trim()}";
      if(this.Content.Count == 0) {
        return $"{responseCodeText}{statusCodeText}";
      }

      StringBuilder builder = new StringBuilder();

      for(Int32 i = 0; i < this.Content.Count; i++) {
        Boolean isLastLine = i == this.Content.Count - 1;

        _ = builder.Append(isLastLine
            ? $"{responseCodeText}{statusCodeText} {this.Content[i]}"
            : $"{responseCodeText}-{this.Content[i]}\r\n");
      }

      return builder.ToString();
    }

    #endregion
  }
}