A 28-year-old primigravida at 39 weeks gestation presents to the labor ward with regular uterine contractions every 3–4 minutes for the past 6 hours. On examination, cervical dilation is 4 cm, cervical effacement is 80%, and the fetal head is at −2 station. Fetal heart rate is reassuring. The patient is in mild discomfort and able to walk around the ward. Which stage and phase of labor is she currently in?