Lab3Challenge2Delphi

program Lab3Challenge2;

{$APPTYPE CONSOLE}

{$R *.res}

Uses
    System.SysUtils;

Const
    DEFAULT_INPUT_FILE = './input.txt';
    DEFAULT_OUTPUT_FILE = './output.txt';

    PRINT_TYPE_MIN = 0;
    PRINT_TYPE_MAX = 2;

    SCAN_TYPE_MIN = 0;
    SCAN_TYPE_MAX = 1;

Function Calculate(Const Value: String): String;
Var
    I: Integer;
    Res: String;
    Symbols: Set Of AnsiChar;
Begin
    Symbols := ['+', '-', '*', '/', '.', ',', '=', '^', '%', '0', '2', '4', '6', '8'];
    For I := 1 To Length(Value) Do
    Begin
        If (CharinSet(Value[I], Symbols)) Then
            Res := Res + Value[I];
    End;

    Calculate := Res;
End;

Function IsTextFile(Const FilePath: String): Boolean;
Var
    IsTxt: Boolean;
    Len: Integer;
Begin
    Len := Length(FilePath);
    IsTxt := ((Len > 2) And (FilePath[Len - 3] = '.') And (FilePath[Len - 2] = 't') And (FilePath[Len - 1] = 'x') And
        (FilePath[Len] = 't'));

    IsTextFile := IsTxt;
End;

Function CheckFileAvailability(Const FilePath: String; Read: Boolean): Boolean;
Var
    IsAvailable: Boolean;
    Checkable: TextFile;
Begin
    IsAvailable := True;
    AssignFile(Checkable, FilePath);
    Try
        If (Read) Then
            Reset(Checkable)
        Else
        Begin
            If (FileExists(FilePath)) Then
                Append(Checkable)
            Else
                Rewrite(Checkable);
        End;
        Close(Checkable);
    Except
        IsAvailable := False;
    End;

    If (IsAvailable And Not IsTextFile(FilePath)) Then
        IsAvailable := False;

    CheckFileAvailability := IsAvailable;
End;

Function TakeIntValueFromConsole(Const Description: String): Integer;
Var
    Value: Integer;
    IsCorrect: Boolean;
Begin
    IsCorrect := False;
    Value := 0;
    Repeat
        Write(Description);
        Try
            Readln(Value);
            IsCorrect := True;
        Except
            Writeln('Enter number, not string or anything else!');
        End;
    Until IsCorrect;

    TakeIntValueFromConsole := Value;
End;

Function TakeIntValueInRangeFromConsole(Const Description: String; Min: Integer; Max: Integer): Integer;
Var
    Value: Integer;
    IsCorrect: Boolean;
Begin
    Repeat
        Value := TakeIntValueFromConsole(Description);
        IsCorrect := True;
        If ((Value < Min) Or (Value > Max)) Then
        Begin
            Writeln('Value must be in range from ', Min, ' to ', Max, '!');
            IsCorrect := False;
        End;
    Until IsCorrect;

    TakeIntValueInRangeFromConsole := Value;
End;

Procedure TakeCorrectFile(Var FileToAssign: TextFile; Input: Boolean);
Var
    FilePath: String;
    IsCorrect: Boolean;
Begin
    Repeat
        Var
        DefaultFilePath := DEFAULT_OUTPUT_FILE;
        If (Input) Then
        Begin
            Write('Enter path to input file (when empty - ', DEFAULT_INPUT_FILE, '): ');
            DefaultFilePath := DEFAULT_INPUT_FILE;
        End
        Else
            Write('Enter path to output file (when empty - ', DEFAULT_OUTPUT_FILE, '): ');

        ReadLn(FilePath);
        If (FilePath = '') Then
            FilePath := DefaultFilePath;
        IsCorrect := True;

        If (Not CheckFileAvailability(FilePath, Input)) Then
        Begin
            IsCorrect := False;
            WriteLn('This path contains wrong file or file, which cannot be accessed! Enter another path!');
        End;
    Until IsCorrect;

    AssignFile(FileToAssign, FilePath);
    If (Input) Then
        Reset(FileToAssign)
    Else
        Rewrite(FileToAssign);
End;

Function ReadStringFromFile(): String;
Var
    Val: String;
    FileToRead: TextFile;
    IsCorrect: Boolean;
Begin
    Repeat
        TakeCorrectFile(FileToRead, True);
        ReadLn(FileToRead, Val);
        IsCorrect := True;
        If (Length(Val) = 0) Then
        Begin
            IsCorrect := False;
            WriteLn('String cannot be empty!');
        End;
    Until IsCorrect;

    ReadStringFromFile := Val;
End;

Function ReadStringFromConsole(): String;
Var
    Val: String;
    IsCorrect: Boolean;
Begin
    Repeat
        Write('Enter string to calculate: ');
        ReadLn(Val);
        IsCorrect := True;
        If (Length(Val) = 0) Then
        Begin
            IsCorrect := False;
            WriteLn('String cannot be empty!');
        End;
    Until IsCorrect;

    ReadStringFromConsole := Val;
End;

Function ReadString(): String;
Var
    ReadType: Integer;
    Val: String;
Begin
    WriteLn;
    WriteLn('How to read values for calculations?');
    WriteLn('0 - From keyboard (console)');
    WriteLn('1 - From file');
    ReadType := TakeIntValueInRangeFromConsole('Enter read type: ', SCAN_TYPE_MIN, SCAN_TYPE_MAX);
    If (ReadType = 1) Then
        Val := ReadStringFromFile()
    Else
        Val := ReadStringFromConsole();

    ReadString := Val;
End;

Function SaveResultIntoFile(Const Val: String): Boolean;
Var
    Saved: Boolean;
    FileToSave: TextFile;
    I: Integer;
Begin
    Saved := True;
    TakeCorrectFile(FileToSave, False);
    Write(FileToSave, Val);
    Close(FileToSave);

    SaveResultIntoFile := Saved;
End;
Procedure PrintResult(Const Val: String);
Var
    WriteType: Integer;
    Saved: Boolean;

Begin
    Saved := False;
    WriteLn;
    WriteLn('Where post result?');
    WriteLn('0 - Only into console');
    WriteLn('1 - Only into file');
    WriteLn('2 - Into console and into file');
    WriteType := TakeIntValueInRangeFromConsole('Enter write type: ', PRINT_TYPE_MIN, PRINT_TYPE_MAX);
    Case WriteType Of
        0:
        Begin
            WriteLn;
            WriteLn('Set of arithmetic signs and even numbers: ', Val);
        End;
        1:
        Begin
            Saved := SaveResultIntoFile(Val);
        End;
        2:
        Begin
            Saved := SaveResultIntoFile(Val);
            WriteLn;
            WriteLn('Set of arithmetic signs and even numbers: ', Val);
        End;
    End;

    If (Saved) Then
        WriteLn('Result saved into file!');
End;

Begin
    Var Input, Res: String;
    WriteLn('2. Given a non-empty sequence of symbols, it is required to construct and print a set whose elements are the signs of arithmetic operations and even numbers found in the sequence.');
    Input := ReadString();
    Res := Calculate(Input);
    PrintResult(Res);
    WriteLn('Press [ENTER] to close program...');
    ReadLn;
End.