3_2 *3

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

resourcestring
   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';
   IncorrectInputFilePathMessage = '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';
   ShouldCreateMessage = 'Do you want to create output file? [Y]es or [N]o';
   ShouldCreateErrorMessage = 'Incorrect answer, choose [Y]es or [N]o';
   EmptySequenceMessage = 'Your sequence doesn''t contain any of assumed symbols';
   OutputMessage = 'Composed set based on your sequence';
   Mask = '-+*/02468';

function GetInputFilePath: string;
var
   Path: string;
begin
   Writeln('Enter input file path');
   Readln(Path);
   while not FileExists(Path) do
   begin
      Writeln(IncorrectInputFilePathMessage);
      Readln(Path);
   end;
   GetInputFilePath := Path;
end;

function ShouldCreateOutputFile: Boolean;
var
   Answer: string;
begin
   Writeln(ShouldCreateMessage);
   Readln(Answer);
   Answer := LowerCase(Answer);
   while (Answer <> 'y') and (Answer <> 'n') do
   begin
      Writeln(ShouldCreateErrorMessage);
      Readln(Answer);
   end;
   ShouldCreateOutputFile := Answer = 'y';
end;

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

function ChooseInputMode(var OutputFilePath: string): 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 ShouldCreateOutputFile() then
      OutputFilePath := GetOutputFilePath()
   else
      OutputFilePath := '';

   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 PrintSetToConsole(Sequence: TSet);
var
   i: Integer;
begin
   if Sequence = [] then
      Writeln(EmptySequenceMessage)
   else
   begin
      Writeln(OutputMessage);
      for i := 0 to 255 do
         if Chr(i) in Sequence then
            Write(Chr(i), ' ');
   end;
end;

procedure PrintSetToFile(Sequence: TSet; OutputFilePath: string);
var
   i: Integer;
   OutputFile: TextFile;
begin
   AssignFile(OutputFile, OutputFilePath);
   Rewrite(OutputFile);
   if Sequence = [] then
      Writeln(OutputFile, EmptySequenceMessage)
   else
   begin
      Writeln(OutputFile, OutputMessage);
      for i := 0 to 255 do
         if Chr(i) in Sequence then
            Write(OutputFile, Chr(i), ' ');
   end;
   CloseFile(OutputFile);
end;

procedure Main;
var
   InputFilePath, OutputFilePath, InputString: string;
   Sequence: TSet;
begin
   Writeln(InstructionMessage);
   case ChooseInputMode(OutputFilePath) of
      WithFile:
      begin
         InputFilePath := GetInputFilePath();
         InputString := ReadFromFile(InputFilePath);
      end;
      Console:
         InputString := ReadFromConsole();
   end;
   Sequence := GetSetFromString(InputString);
   if OutputFilePath <> '' then
      PrintSetToFile(Sequence, OutputFilePath);
   PrintSetToConsole(Sequence);
   Readln;
end;

begin
   Main();
end.