A 52-year-old man presents with a 3-month history of a painless swelling in the right groin that increases in size by evening and reduces when he lies down. On examination, a bulge is palpable above and medial to the pubic tubercle. The swelling is soft, compressible, and reduces on lying flat. Cough impulse is positive. There is no tenderness or induration. What is the most likely diagnosis?