Explain the role of the pineal gland and melatonin in the regulation of circadian rhythms and sleep-wake cycles?

Can you explain the role of the pineal gland and melatonin in the regulation of circadian rhythms and sleep-wake cycles? How does the pineal gland produce and release melatonin in response to changes in environmental light-dark cycles, influencing the timing and quality of sleep? Additionally, how do disruptions in circadian rhythms, such as shift work, jet lag, and exposure to artificial light at night, impact melatonin secretion and sleep patterns, leading to sleep disorders and associated health consequences?