from datetime import datetime, timedelta
from typing import Tuple

def calculate_sm2(q: int, repetitions: int, ease_factor: float, previous_interval: int) -> Tuple[int, float]:
    """
    Implements the standard SuperMemo-2 (SM-2) algorithm.
    q: quality of the response (0-5)
       5: perfect response
       4: correct response after a hesitation
       3: correct response caught with serious difficulty
       2: incorrect response; where the correct one seemed easy to recall
       1: incorrect response; the correct one remembered
       0: complete blackout
    """
    if q < 3:
        # If the answer was incorrect, reset repetitions and schedule for immediate review (1 day)
        return 1, ease_factor

    # Calculate new Easiness Factor
    new_ef = ease_factor + (0.1 - (5 - q) * (0.08 + (5 - q) * 0.02))
    if new_ef < 1.3:
        new_ef = 1.3

    # Calculate next interval (in days)
    if repetitions == 0:
        new_interval = 1
    elif repetitions == 1:
        new_interval = 3  # Calibrated for intense JEE/NEET daily sprint cycles
    elif repetitions == 2:
        new_interval = 7
    else:
        new_interval = round(previous_interval * new_ef)

    return new_interval, new_ef