{ lTelnet CopyRight (C) 2004-2008 Ales Katona

  This library is Free software; you can rediStribute it and/or modify it
  under the terms of the GNU Library General Public License as published by
  the Free Software Foundation; either version 2 of the License, or (at your
  option) any later version.

  This program is diStributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; withOut even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License
  for more details.

  You should have received a Copy of the GNU Library General Public License
  along with This library; if not, Write to the Free Software Foundation,
  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

  This license has been modified. See File LICENSE for more inFormation.
  Should you find these sources withOut a LICENSE File, please contact
  me at ales@chello.sk
}

unit lTelnet;

{$mode objfpc}{$H+}
//{$define debug}

interface

uses
  Classes, SysUtils, lNet, lControlStack;
  
const
  // Telnet printer signals
  TS_NUL         = #0;
  TS_ECHO        = #1;
  TS_SGA         = #3; // Surpass go-ahead
  TS_BEL         = #7;
  TS_BS          = #8;
  TS_HT          = #9;
  TS_LF          = #10;
  TS_VT          = #11;
  TS_FF          = #12;
  TS_CR          = #13;
  // Telnet control signals
  TS_NAWS        = #31;
  TS_DATA_MARK   = #128;
  TS_BREAK       = #129;
  TS_HYI         = #133; // Hide Your Input
  // Data types codes
  TS_STDTELNET   = #160;
  TS_TRANSPARENT = #161;
  TS_EBCDIC      = #162;
  // Control bytes
  TS_SE          = #240;
  TS_NOP         = #241;
  TS_GA          = #249; // go ahead currently ignored(full duplex)
  TS_SB          = #250;
  TS_WILL        = #251;
  TS_WONT        = #252;
  TS_DO          = #253;
  TS_DONT        = #254;
  // Mother of all power
  TS_IAC         = #255;
  
type
  TLTelnetClient = class;

  TLTelnetControlChars = set of Char;

  TLHowEnum = (TE_WILL = 251, TE_WONT, TE_DO, TE_DONW);

  TLSubcommandCallback= function(command: char; const parameters, defaultResponse: string): string;
  TLSubcommandEntry= record
                       callback: TLSubcommandCallback;
                       defaultResponse: string;
                       requiredParams: integer
                     end;
  TLSubcommandArray= array[#$00..#$ff] of TLSubcommandEntry;
  EInsufficientSubcommandParameters= class(Exception);

  { TLTelnet }

  TLTelnet = class(TLComponent, ILDirect)
   protected
    FStack: TLControlStack;
    FConnection: TLTcp;
    FPossible: TLTelnetControlChars;
    FActiveOpts: TLTelnetControlChars;
    FOutput: TMemoryStream;
    FOperation: Char;
    FCommandCharIndex: Byte;
    FOnReceive: TLSocketEvent;
    FOnConnect: TLSocketEvent;
    FOnDisconnect: TLSocketEvent;
    FOnError: TLSocketErrorEvent;
    FCommandArgs: string[3];
    FOrders: TLTelnetControlChars;
    FBuffer: array of Char;
    FBufferIndex: Integer;
    FBufferEnd: Integer;
    FSubcommandCallbacks: TLSubcommandArray;
    procedure InflateBuffer;
    function AddToBuffer(const aStr: string): Boolean; inline;
    
    function Question(const Command: Char; const Value: Boolean): Char;
    
    function GetConnected: Boolean;
    
    function GetTimeout: Integer;
    procedure SetTimeout(const Value: Integer);

    function GetSocketClass: TLSocketClass;
    procedure SetSocketClass(Value: TLSocketClass);

    function GetSession: TLSession;
    procedure SetSesssion(const AValue: TLSession);
    procedure SetCreator(AValue: TLComponent); override;

    procedure StackFull;
    procedure DoubleIAC(var s: string);
    function TelnetParse(const msg: string): Integer;
    function React(const Operation, Command: Char): boolean; virtual; abstract;
    procedure SendCommand(const Command: Char; const Value: Boolean); virtual; abstract;

    procedure OnCs(aSocket: TLSocket);
   public
    constructor Create(aOwner: TComponent); override;
    destructor Destroy; override;
    
    function Get(out aData; const aSize: Integer; aSocket: TLSocket = nil): Integer; virtual; abstract;
    function GetMessage(out msg: string; aSocket: TLSocket = nil): Integer; virtual; abstract;
    
    function Send(const aData; const aSize: Integer; aSocket: TLSocket = nil): Integer; virtual; abstract;
    function SendMessage(const msg: string; aSocket: TLSocket = nil): Integer; virtual; abstract;
    
    function OptionIsSet(const Option: Char): Boolean;
    function RegisterOption(const aOption: Char; const aCommand: Boolean): Boolean;
    procedure SetOption(const Option: Char);
    procedure UnSetOption(const Option: Char);

    function RegisterSubcommand(aOption: char; callback: TLSubcommandCallback;
                const defaultResponse: string= ''; requiredParams: integer= 0): boolean;

    procedure Disconnect(const Forced: Boolean = True); override;
    
    procedure SendCommand(const aCommand: Char; const How: TLHowEnum); virtual;
   public
    property Output: TMemoryStream read FOutput;
    property Connected: Boolean read GetConnected;
    property Timeout: Integer read GetTimeout write SetTimeout;
    property OnReceive: TLSocketEvent read FOnReceive write FOnReceive;
    property OnDisconnect: TLSocketEvent read FOnDisconnect write FOnDisconnect;
    property OnConnect: TLSocketEvent read FOnConnect write FOnConnect;
    property OnError: TLSocketErrorEvent read FOnError write FOnError;
    property Connection: TLTCP read FConnection;
    property SocketClass: TLSocketClass read GetSocketClass write SetSocketClass;
    property Session: TLSession read GetSession write SetSesssion;
  end;

  { TLTelnetClient }

  TLTelnetClient = class(TLTelnet, ILClient)
   protected
    FLocalEcho: Boolean;
    procedure OnEr(const msg: string; aSocket: TLSocket);
    procedure OnDs(aSocket: TLSocket);
    procedure OnRe(aSocket: TLSocket);
    procedure OnCo(aSocket: TLSocket);

    function React(const Operation, Command: Char): boolean; override;
    
    procedure SendCommand(const Command: Char; const Value: Boolean); override;
   public
    constructor Create(aOwner: TComponent); override;
    
    function Connect(const anAddress: string; const aPort: Word): Boolean;
    function Connect: Boolean;
    
    function Get(out aData; const aSize: Integer; aSocket: TLSocket = nil): Integer; override;
    function GetMessage(out msg: string; aSocket: TLSocket = nil): Integer; override;
    
    function Send(const aData; const aSize: Integer; aSocket: TLSocket = nil): Integer; override;
    function SendMessage(const msg: string; aSocket: TLSocket = nil): Integer; override;
    
    procedure CallAction; override;
   public
    property LocalEcho: Boolean read FLocalEcho write FLocalEcho;
  end;


function LTelnetSubcommandCallback(command: char; const parameters, defaultResponse: string): string;

implementation

uses
  Math;

const   subcommandEndLength= 2;

var
  zz: Char;
  TNames: array[Char] of string;

//*******************************TLTelnetClient********************************

constructor TLTelnet.Create(aOwner: TComponent);
begin
  inherited Create(aOwner);
  
  FConnection := TLTCP.Create(nil);
  FConnection.Creator := Self;
  FConnection.OnCanSend := @OnCs;
  
  FOutput := TMemoryStream.Create;
  FCommandCharIndex := 0;
  FStack := TLControlStack.Create;
  FStack.OnFull := @StackFull;
end;

destructor TLTelnet.Destroy;
begin
  Disconnect(True);
  FOutput.Free;
  FConnection.Free;
  FStack.Free;
  inherited Destroy;
end;

function TLTelnet.GetConnected: Boolean;
begin
  Result := FConnection.Connected;
end;

function TLTelnet.GetSession: TLSession;
begin
  Result := FConnection.Session;
end;

procedure TLTelnet.SetSesssion(const AValue: TLSession);
begin
  FConnection.Session := aValue;
end;

procedure TLTelnet.SetCreator(AValue: TLComponent);
begin
  inherited SetCreator(AValue);
  FConnection.Creator := aValue;
end;

procedure TLTelnet.InflateBuffer;
var
  n: Integer;
begin
  n := Max(Length(FBuffer), 25);
  SetLength(FBuffer, n * 10);
end;

function TLTelnet.AddToBuffer(const aStr: string): Boolean; inline;
begin
  Result := False;
  
  while Length(aStr) + FBufferEnd > Length(FBuffer) do
    InflateBuffer;
    
  Move(aStr[1], FBuffer[FBufferEnd], Length(aStr));
  Inc(FBufferEnd, Length(aStr));
end;

function TLTelnet.Question(const Command: Char; const Value: Boolean): Char;
begin
  Result := TS_NOP;
  if Value then begin
    if Command in FOrders then
      Result := TS_DO
    else
      Result := TS_WILL;
  end else begin
    if Command in FOrders then
      Result := TS_DONT
    else
      Result := TS_WONT;
  end;
end;

function TLTelnet.GetSocketClass: TLSocketClass;
begin
  Result := FConnection.SocketClass;
end;

function TLTelnet.GetTimeout: Integer;
begin
  Result := FConnection.Timeout;
end;

procedure TLTelnet.SetSocketClass(Value: TLSocketClass);
begin
  FConnection.SocketClass := Value;
end;

procedure TLTelnet.SetTimeout(const Value: Integer);
begin
  FConnection.Timeout := Value;
end;

procedure TLTelnet.StackFull;
begin
  {$ifdef debug}
  Writeln('**STACKFULL**');
  {$endif}
  if FStack[1] = TS_IAC then
    begin
      FOutput.WriteByte(Byte(FStack[1]));
      FOutput.WriteByte(Byte(FStack[2]));
      FStack.Clear
    end else
      if React(FStack[1], FStack[2]) then
        FStack.Clear
end;

procedure TLTelnet.DoubleIAC(var s: string);
var
  i: Longint;
begin
  i := 0;
  if Length(s) > 0 then
    while i < Length(s) do begin
      Inc(i);
      if s[i] = TS_IAC then begin
        Insert(TS_IAC, s, i);
        Inc(i, 2);
      end;
    end;
end;

function TLTelnet.TelnetParse(const msg: string): Integer;
var
  i: Longint;
begin
  Result := 0;
  for i := 1 to Length(msg) do
    if (FStack.ItemIndex > 0) or (msg[i] = TS_IAC) then begin
      if msg[i] = TS_GA then
        FStack.Clear
      else
        FStack.Push(msg[i])
    end else begin
      FOutput.WriteByte(Byte(msg[i]));
      Inc(Result);
    end;
end;

procedure TLTelnet.OnCs(aSocket: TLSocket);
var
  n: Integer;
begin
  n := 1;

  while (n > 0) and (FBufferIndex < FBufferEnd) do begin
    n := FConnection.Send(FBuffer[FBufferIndex], FBufferEnd - FBufferIndex);

    if n > 0 then
      Inc(FBufferIndex, n);
  end;
  
  if FBufferEnd - FBufferIndex < FBufferIndex then begin // if we can move the "right" side of the buffer back to the left
    Move(FBuffer[FBufferIndex], FBuffer[0], FBufferEnd - FBufferIndex);
    FBufferEnd := FBufferEnd - FBufferIndex;
    FBufferIndex := 0;
  end;
end;

function TLTelnet.OptionIsSet(const Option: Char): Boolean;
begin
  Result := False;
  Result := Option in FActiveOpts;
end;

function TLTelnet.RegisterOption(const aOption: Char;
                                     const aCommand: Boolean): Boolean;
begin
  Result := False;
  if not (aOption in FPossible) then begin
    FPossible := FPossible + [aOption];
    if aCommand then
      FOrders := FOrders + [aOption];
    Result := True;
  end;
end;

procedure TLTelnet.SetOption(const Option: Char);
begin
  if Option in FPossible then
    SendCommand(Option, True);
end;

procedure TLTelnet.UnSetOption(const Option: Char);
begin
  if Option in FPossible then
    SendCommand(Option, False);
end;

(* If already set, the callback can be reverted to nil but it can't be changed  *)
(* in a single step. The default response, if specified, is used by the         *)
(* LTelnetSubcommandCallback() function and is available to others; the         *)
(* callback will not be invoked until there is at least the indicated number of *)
(* parameter bytes available.                                                   *)
//
function TLTelnet.RegisterSubcommand(aOption: char; callback: TLSubcommandCallback;
            const defaultResponse: string= ''; requiredParams: integer= 0): boolean;

begin
  result := (not Assigned(FSubcommandCallbacks[aOption].callback)) or (@callback = nil);
  if result then begin
    FSubcommandCallbacks[aOption].callback := callback;
    FSubcommandCallbacks[aOption].defaultResponse := defaultResponse;
    Inc(requiredParams, subcommandEndLength);
    if requiredParams < 0 then          (* Assume -subcommandEndLength is a     *)
      requiredParams := 0;              (* valid parameter.                     *)
    FSubcommandCallbacks[aOption].requiredParams := requiredParams;
  end
end { TLTelnet.RegisterSubcommand } ;

procedure TLTelnet.Disconnect(const Forced: Boolean = True);
begin
  FConnection.Disconnect(Forced);
end;

procedure TLTelnet.SendCommand(const aCommand: Char; const How: TLHowEnum);
begin
  {$ifdef debug}
  Writeln('**SENT** ', TNames[Char(How)], ' ', TNames[aCommand]);
  {$endif}
  AddToBuffer(TS_IAC + Char(How) + aCommand);
  OnCs(nil);
end;

//****************************TLTelnetClient*****************************

constructor TLTelnetClient.Create(aOwner: TComponent);
begin
  inherited Create(aOwner);
  FConnection.OnError := @OnEr;
  FConnection.OnDisconnect := @OnDs;
  FConnection.OnReceive := @OnRe;
  FConnection.OnConnect := @OnCo;

  FPossible := [TS_ECHO, TS_HYI, TS_SGA];
  FActiveOpts := [];
  FOrders := [];
end;

procedure TLTelnetClient.OnEr(const msg: string; aSocket: TLSocket);
begin
  if Assigned(FOnError) then
    FOnError(msg, aSocket)
  else
    FOutput.Write(Pointer(msg)^, Length(msg));
end;

procedure TLTelnetClient.OnDs(aSocket: TLSocket);
begin
  if Assigned(FOnDisconnect) then
    FOnDisconnect(aSocket);
end;

procedure TLTelnetClient.OnRe(aSocket: TLSocket);
var
  s: string;
begin
  if aSocket.GetMessage(s) > 0 then
    if (TelnetParse(s) > 0) and Assigned(FOnReceive) then
      FOnReceive(aSocket);
end;

procedure TLTelnetClient.OnCo(aSocket: TLSocket);
begin
  if Assigned(FOnConnect) then
    FOnConnect(aSocket);
end;

function TLTelnetClient.React(const Operation, Command: Char): boolean;

  procedure Accept(const Operation, Command: Char);
  begin
    FActiveOpts := FActiveOpts + [Command];
    {$ifdef debug}
    Writeln('**SENT** ', TNames[Operation], ' ', TNames[Command]);
    {$endif}
    AddToBuffer(TS_IAC + Operation + Command);
    OnCs(nil);
  end;
  
  procedure Refuse(const Operation, Command: Char);
  begin
    FActiveOpts := FActiveOpts - [Command];
    {$ifdef debug}
    Writeln('**SENT** ', TNames[Operation], ' ', TNames[Command]);
    {$endif}
    AddToBuffer(TS_IAC + Operation + Command);
    OnCs(nil);
  end;

(* Retrieve the parameters from the current instance, and pass them explicitly  *)
(* to the callback. Return false if there are insufficient parameters on the    *)
(* stack.                                                                       *)
//
  function subcommand(command: char): boolean;

  var   parameters, response: string;
        i: integer;

  begin
    FStack.AllowInflation := true;      (* We might need more than the standard *)
    if FStack.ItemIndex > 65536 then    (* command, but protect against parse   *)
      {%H- 6018 } exit(true);           (* failure which could be a DoS attack. *)
    i := FStack.ItemIndex - TL_CSLENGTH; (* Number of parameter bytes available.*)
    if i < FSubcommandCallbacks[command].requiredParams then
      exit(false);                      (* Early insufficient-parameters decision *)
    result := true;
    if FStack.ItemIndex > TL_CSLENGTH then begin
      SetLength(parameters, FStack.ItemIndex - TL_CSLENGTH );
      Move(FStack[3], parameters[1], FStack.ItemIndex - TL_CSLENGTH );
      if (Length(parameters) >= 2) and (parameters[Length(parameters)] = TS_IAC) and
                                (parameters[Length(parameters) - 1] <> TS_IAC) then
        exit(false);                    (* Special case: need at least one more *)
      i := 1;
      while i <= Length(parameters) - 1 do      (* Undouble IACs                *)
        if (parameters[i] = TS_IAC) and (parameters[i + 1] = TS_IAC) then
          Delete(parameters, i, 1)
        else
          Inc(i)
    end else
      parameters := '';
    if Length(parameters) < FSubcommandCallbacks[command].requiredParams then
      exit(false);                      (* Insufficient params after IAC undouble *)
    if (FSubcommandCallbacks[command].requiredParams >= subcommandEndLength) and
                                (Length(parameters) >= subcommandEndLength) then
      SetLength(parameters, Length(parameters) - subcommandEndLength);
    try
      response := FSubcommandCallbacks[command].callback(command, parameters,
                                FSubcommandCallbacks[command].defaultResponse)
    except
      on e: EInsufficientSubcommandParameters do
        Exit(false)                     (* Late insufficient-parameters decision *)
      else
        Raise                           (* Application-specific error           *)
    end;
    DoubleIAC(response);
    AddToBuffer(TS_IAC + TS_SB + command + response + TS_IAC + TS_SE);
    OnCs(nil)
  end { subcommand } ;

begin
  result := true;                       (* Stack will normally be cleared       *)
  {$ifdef debug}
  Writeln('**GOT** ', TNames[Operation], ' ', TNames[Command]);
  {$endif}
  case Operation of
    TS_DO   : if Command in FPossible then Accept(TS_WILL, Command)
              else Refuse(TS_WONT, Command);
              
    TS_DONT : if Command in FPossible then Refuse(TS_WONT, Command);
    
    TS_WILL : if Command in FPossible then FActiveOpts := FActiveOpts + [Command]
              else Refuse(TS_DONT, Command);
                 
    TS_WONT : if Command in FPossible then FActiveOpts := FActiveOpts - [Command];
    TS_SB   : if not Assigned(FSubcommandCallbacks[command].callback) then
                refuse(TS_WONT, command)
              else
                result := subcommand(command)

(* In the final case above, the stack will not be cleared if sufficient         *)
(* parameters to keep the subcommand happy have not yet been parsed out of the  *)
(* message.                                                                     *)

  end;
end;

procedure TLTelnetClient.SendCommand(const Command: Char; const Value: Boolean);
begin
  if Connected then begin
    {$ifdef debug}
    Writeln('**SENT** ', TNames[Question(Command, Value)], ' ', TNames[Command]);
    {$endif}
    case Question(Command, Value) of
      TS_WILL : FActiveOpts := FActiveOpts + [Command];
    end;
    AddToBuffer(TS_IAC + Question(Command, Value) + Command);
    OnCs(nil);
  end;
end;

function TLTelnetClient.Connect(const anAddress: string; const aPort: Word): Boolean;
begin
  Result := FConnection.Connect(anAddress, aPort);
end;

function TLTelnetClient.Connect: Boolean;
begin
  Result  :=  FConnection.Connect(FHost, FPort);
end;

function TLTelnetClient.Get(out aData; const aSize: Integer; aSocket: TLSocket): Integer;
begin
  Result := FOutput.Read(aData {%H- 5058 } , aSize);
  if FOutput.Position = FOutput.Size then
    FOutput.Clear;
end;

function TLTelnetClient.GetMessage(out msg: string; aSocket: TLSocket): Integer;
begin
  Result := 0;
  msg := '';
  if FOutput.Size > 0 then begin
    FOutput.Position := 0;
    SetLength(msg, FOutput.Size);
    Result := FOutput.Read(PChar(msg)^, Length(msg));
    FOutput.Clear;
  end;
end;

function TLTelnetClient.Send(const aData; const aSize: Integer;
  aSocket: TLSocket): Integer;
var
  Tmp: string;
begin
  {$ifdef debug}
  Writeln('**SEND START** ');
  {$endif}
  Result := 0;
  if aSize > 0 then begin
    SetLength(Tmp, aSize);
    Move(aData, PChar(Tmp)^, aSize);
    DoubleIAC(Tmp);
    if LocalEcho and (not OptionIsSet(TS_ECHO)) and (not OptionIsSet(TS_HYI)) then
      FOutput.Write(PChar(Tmp)^, Length(Tmp));
      
    AddToBuffer(Tmp);
    OnCs(nil);
    
    Result := aSize;
  end;
  {$ifdef debug}
  Writeln('**SEND END** ');
  {$endif}
end;

function TLTelnetClient.SendMessage(const msg: string; aSocket: TLSocket
  ): Integer;
begin
  Result := Send(PChar(msg)^, Length(msg));
end;

procedure TLTelnetClient.CallAction;
begin
  FConnection.CallAction;
end;

(* This is a default callback for use with the RegisterSubcommand() method. It  *)
(* may be used where the result is unchanging, for example in order to return   *)
(* the terminal type.                                                           *)
//
function LTelnetSubcommandCallback(command: char; const parameters, defaultResponse: string): string;

begin
  result := defaultResponse
end { LTelnetSubcommandCallback } ;


initialization
  for zz := #0 to #255 do
    TNames[zz] := IntToStr(Ord(zz));
  TNames[#1] := 'TS_ECHO';
  TNames[#133] := 'TS_HYI';
  TNames[#251] := 'TS_WILL';
  TNames[#252] := 'TS_WONT';
  TNames[#253] := 'TS_DO';
  TNames[#254] := 'TS_DONT';

end.