3_2 *2

program Laba_3_2;
{$APPTYPE CONSOLE}
uses
   SysUtils;
type
   TInputMode = (WithFile, Console);
   TSet = set of Char;

const
   InstructionMessage
      = 'This program composes a set consisting of arithmetic operands and even digits';
   WayOfInputMessage = 'Where do you want to input data from? [F]ile or [C]onsole';
   IncorrectInputFilePath = 'Incorrect input file path, check if file exists and try again';
   IncorrectWayOfInputMessage = 'Incorrect way of input, choose [F]ile or [C]onsole';
   OutputFileExistsErrorMessage = 'Incorrect output file, such file already exists, try again';
   Mask = '-+*/02468';

function GetInputFilePath(): string;//ïðîâåðêà íà ïóñòîòó
var
   Path: string;
begin
   Writeln('Enter input file path');
   Readln(Path);
   while not FileExists(Path) do
   begin
      Writeln(IncorrectInputFilePath);
      Readln(Path);
   end;
   GetInputFilePath := Path;
end;

function CreateOutputFile(): Boolean;
var
   Answer: string;
begin
   Writeln('Do you want to create output file? [Y]es or [N]o');
   Readln(Answer);
   Answer := LowerCase(Answer);
   while (Answer <> 'y') and (Answer <> 'n') do
   begin
      Writeln('Incorrect way of input, choose [Y]es or [N]o');
      Readln(Answer);
   end;

   if Answer = 'y' then
      CreateOutputFile := True
   else
      CreateOutputFile := False;
end;

function GetOutputFilePath(): string;
var
   Path: string;
begin
   if CreateOutputFile then
   begin
      Writeln('Enter output file path');
      Readln(Path);
      while FileExists(Path) do
      begin
         Writeln(OutputFileExistsErrorMessage);
         Readln(Path);
      end;
   end
   else
      Path := '';
   GetOutputFilePath := Path;
end;

function ChooseInputMode(): TInputMode;
var
   Mode: string;
begin
   Writeln(WayOfInputMessage);
   Readln(Mode);
   Mode := LowerCase(Mode);
   while (Mode <> 'c') and (Mode <> 'f') do
   begin
      Writeln(IncorrectWayOfInputMessage);
      Readln(Mode);
   end;
   if Mode = 'f' then
      ChooseInputMode := WithFile
   else
      ChooseInputMode := Console;
end;

function ReadFromFile(InputFilePath: string): string;
var
   InputFile: TextFile;
   InputString: string;
begin
   AssignFile(InputFile, InputFilePath);
   Reset(InputFile);
   Readln(InputFile, InputString);
   CloseFile(InputFile);
   ReadFromFile := InputString;
end;

function ReadFromConsole(): string;
var
   InputString: string;
begin
   Writeln('Input sequence of symbols');
   Readln(InputString);
   ReadFromConsole := InputString;
end;

function GetSetFromString(InputString: string): TSet;
var
   StringLength, i: Integer;
   Sequence: TSet;
begin
   Sequence := [];
   StringLength := Length(InputString);
   for i := 1 to StringLength do
      if (Pos(InputString[i], Mask) <> 0) and not(InputString[i] in Sequence) then
         Include(Sequence, InputString[i]);
   GetSetFromString := Sequence;
end;

procedure PrintSet(Sequence: TSet; OutputFilePath: string);
var
   i: Integer;
   OutputFile: TextFile;
   ShouldWriteToFile: Boolean;
begin
   if OutputFilePath = '' then
      ShouldWriteToFile := False
   else
      ShouldWriteToFile := True;
   AssignFile(OutputFile, OutputFilePath);
   Rewrite(OutputFile);
   if Sequence = [] then
   begin
      if ShouldWriteToFile then
         Writeln(OutputFile, 'Your sequence doesn''t contain any of assumed symbols');
      Writeln('Your sequence doesn''t contain any of assumed symbols')
   end
   else
   begin
      if ShouldWriteToFile then
         Writeln(OutputFile, 'Composed set based on your sequence');
      Writeln('Composed set based on your sequence')
      for i := 0 to 255 do
         if Chr(i) in Sequence then
         begin
            if ShouldWriteToFile then
               Write(OutputFile, Chr(i), ' ');
            Write(Chr(i), ' ');
         end;
   end;
   CloseFile(OutputFile);
end;

procedure Main();
var
   InputFilePath, OutputFilePath, InputString: string;
   SequenceString: TSet;
begin
   Writeln(InstructionMessage);
   case ChooseInputMode() of
      WithFile:
      begin
         InputFilePath := GetInputFilePath();
         InputString := ReadFromFile(InputFilePath);
         OutputFilePath := GetOutputFilePath();
      end;
      Console:
         InputString := ReadFromConsole();
   end;
   SequenceString := GetSetFromString(InputString);
   PrintSet(SequenceString, OutputFilePath);
   Readln;
end;

begin
   Main();
end.