laba3.1 (Delphi)

program laba3_1;
uses
  System.SysUtils;

function InputPath(): String; Forward;
function InputLineFromConsole(): String; Forward;
function InputLineFromFile(Path: String): String; Forward;
function CheckLine(Line: String): Boolean; Forward;
procedure OutputToFile(Path: String; RomanNumber: String; SourceNumber: String); Forward;
procedure OutputToConsole(RomanNumber: String; SourceNumber: String); Forward;

function ChooseSourceOfInput(): Integer;
var
    Choice: Integer;
    IsCorrect: Boolean;
begin
    Writeln('Choose where to enter data. Enter 1 or 2:');
    Writeln('1.File');
    Writeln('2.Console');
    repeat
        IsCorrect := True;
        try
            Readln(Choice);
        except
            Writeln('Enter an integer!');
            IsCorrect := False;
        end;

        if (IsCorrect) and (Choice <> 1) and (Choice <> 2) then
        begin
            Writeln('Enter 1 or 2!');
            IsCorrect := False;
        end;
    until IsCorrect;
    ChooseSourceOfInput := Choice;
end;

function InputLine(Source: Integer): String;
var
    Line, PathInput: String;
begin
    Case Source of
        1:
        begin
            Writeln('Enter the absolute link to the input file');
            PathInput := InputPath();
            Line := InputLineFromFile(PathInput);
        end;
        2:
        begin
            Line := InputLineFromConsole();
        end;
    end;
    InputLine := Line;
end;

function InputPath(): String;
var
    Path: String;
    IsCorrect: Boolean;
begin
    repeat
        IsCorrect := True;
        Readln(Path);

        if not FileExists(Path) then
        begin
            IsCorrect := False;
            Writeln('File not found! Enter the absolute link to the file');
        end;
    until IsCorrect;
    InputPath := Path;
end;

function InputLineFromFile(Path: String): String;
var
    Line: String;
    InputFile: TextFile;
    IsCorrect: Boolean;
begin
    AssignFile(InputFile, Path);
    Reset(InputFile);
    if not eof(InputFile) then
        Readln(InputFile, Line)
    else
    begin
        Writeln('The line is missing from your file! Enter it from console');
        Line := InputLineFromConsole();
    end;

    IsCorrect := CheckLine(Line);
    if not IsCorrect then
    begin
        Line := InputLineFromConsole();
    end;

    CloseFile(InputFile);
    InputLineFromFile := Line;
end;

function InputLineFromConsole(): String;
var
    Line: String;
    IsCorrect: Boolean;
begin
    Writeln('Enter the line');
    repeat
        IsCorrect := True;
        Readln(Line);
        IsCorrect := CheckLine(Line);
    until IsCorrect;
    InputLineFromConsole := Line;
end;

function CheckLine(Line: String): Boolean;
var
    Flag: Boolean;
    Number: Integer;
begin
    Flag := True;

    if Length(Line) = 0 then
    begin
        Writeln('You entered an empty line! Repeat enter');
        Flag := False;
    end;

    if Flag then
    begin
        try
            Number := StrToInt(Line);
        except
            Writeln('This line cannot be represented as an integer! Enter line from console');
            Flag := False
        end;
    end;

    if ((Number < 1) or (Number > 2000)) and (Flag) then
    begin
        Writeln('The number must be in the range from 1 to 2000 Enter line from console');
        Flag := False;
    end;

    CheckLine := Flag;
end;

function ConvertToRoman(SourceNumber: String): String;
Const
    UnitsOfRoman: Array [0..9] of String = ('','I','II','III','IV','V','VI','VII','VIII','IX');
    TensOfRoman: Array [0..9] of String = ('','X','XX','XXX','XL','L','LX','LXX','LXXX','XC');
    HundredsOfRoman: Array [0..9] of String = ('','C','CC','CCC','CD','D','DC','DCC','DCCC','CM');
    ThousandsOfRoman: Array [0..2] of String = ('','M','MM');
var
    Digits: Array [0..3] of Integer;
    I, J: Integer;
    RomanNumber: String;
begin
    for I := 0 to 3 do
        Digits[I] := 0;

    J := 1;
    for I := 4 - Length(SourceNumber) to 3 do
    begin
        Digits[I] := StrToInt(SourceNumber[J]);
        Inc(J);
    end;
    RomanNumber := ThousandsOfRoman[Digits[0]] + HundredsOfRoman[Digits[1]] + TensOfRoman[Digits[2]] + UnitsOfRoman[Digits[3]];
    ConvertToRoman := RomanNumber;
end;

procedure OutputResult(Source: Integer; RomanNumber: String; SourceNumber: String);
var
    PathOutput: String;
begin
    if Source = 1 then
    begin
        Writeln;
        Writeln('Enter the absolute link to the output file');
        PathOutput := InputPath();
        OutputToFile(PathOutput, RomanNumber, SourceNumber);
    end
    else
    begin
        OutputToConsole(RomanNumber, SourceNumber);
    end;
end;

procedure OutputToFile(Path: String; RomanNumber: String; SourceNumber: String);
var
    OutputFile: TextFile;
begin
    AssignFile(OutputFile, Path);
    Reset(OutputFile);
    Rewrite(OutputFile);
    Writeln(OutputFile, SourceNumber, ' = ',RomanNumber);
    CloseFile(OutputFile);
    Writeln('The data is successfully recorded in the file');
end;

procedure OutputToConsole(RomanNumber: String; SourceNumber: String);
begin
    Writeln(SourceNumber, ' = ',RomanNumber);
end;

procedure Main();
var
    Source: Integer;
    SourceNumber, RomanNumber: String;
begin
    Writeln('The program converts the number to the Roman numeral system');
    Source := ChooseSourceOfInput();
    SourceNumber := InputLine(Source);
    RomanNumber := ConvertToRoman(SourceNumber);
    OutputResult(Source, RomanNumber, SourceNumber);
    Readln;
end;

begin
    Main;
end.