unit uRnaTranscription;

interface
uses Generics.Collections;

type
  complement = class
  private
    class var
      fDnaToRna: TDictionary<char, char>;
  public
    class function OfDna(nucleotide: string): string; static;
  end;

implementation
uses SysUtils;

class function complement.OfDna(nucleotide: string): string;
var i: integer;
    lRNA: string;
    elements: TArray<char>;
    RNAelement: char;
begin
  result := '';
  lRNA := '';
  if not trim(nucleotide).IsEmpty then
  begin
    fDnaToRna := TDictionary<char, char>.Create;
    with fDnatoRna do
    begin
      add('G','C');
      add('C','G');
      add('T','A');
      add('A','U');
    end;
    elements := nucleotide.ToUpper.ToCharArray;
    i := 0;
    while i <= high(elements) do
    begin
      if fDnaToRna.TryGetValue(elements[i],RNAelement) then
      begin
        lRNA := lRNA + RNAelement;
        inc(i);
      end
      else
      begin
        lRNA := '';
        break;
      end;
    end;
  end;
  result := lRNA;
end;

end.