A 44 years old male smoker presents with a 9-year history of current headaches occurred twice-monthly, always in the early hours of the morning. The headaches have increased to an average of 2 episodes per day. The acute episodes can occur at any time, and last between 2 and 4 hours. He always has a nocturnal event. Attacks are triggered immediately after drinking alcohol or with strong smells. The pain is excruciating and focused around his right eye. He becomes severely agitated during attacks, often pacing the room or rocking back and forth. On examination, his right eye is reddened with lacrimation and drooping of the eyelid, and right-sided rhinorrhea. What is the most likely diagnosis?