<?pas
// Interfaces and Polymorphism Demo

type
  ILogger = interface
    procedure Log(msg: String);
  end;

type
  ISerializer = interface
    function Serialize(data: Variant): String;
  end;

// Console logger implementation
type
  TConsoleLogger = class(TObject, ILogger)
    procedure Log(msg: String);
    begin
      PrintLn('[CONSOLE] ' + msg);
    end;
  end;

// File logger implementation  
type
  TFileLogger = class(TObject, ILogger)
    FPrefix: String;

    constructor Create(prefix: String);
    begin
      FPrefix := prefix;
    end;

    procedure Log(msg: String);
    begin
      PrintLn('[FILE:' + FPrefix + '] ' + msg);
    end;
  end;

// Function accepting interface (polymorphism)
procedure ProcessWithLogging(logger: ILogger; data: String);
begin
  logger.Log('Processing: ' + data);
  logger.Log('Complete');
end;

// Using different implementations interchangeably
var console: ILogger := new TConsoleLogger;
var fileLog: ILogger := new TFileLogger('app.log');

ProcessWithLogging(console, 'Task A');
ProcessWithLogging(fileLog, 'Task B');

// Runtime check with 'implements' operator
if TConsoleLogger implements ILogger then
  PrintLn('TConsoleLogger supports ILogger');
?>