graders/clamp.py

"""
Shared epsilon-clamping utility.
Validator requires scores strictly between 0 and 1: (0.001 … 0.999)
"""
EPSILON = 0.001
SCORE_MIN = EPSILON        # 0.001
SCORE_MAX = 1.0 - EPSILON  # 0.999

def clamp(score: float) -> float:
    """Clamp any score to (0.001, 0.999) — never exactly 0 or 1."""
    try:
        v = float(score)
    except (TypeError, ValueError):
        return 0.5  # safe default for bad inputs
    if v != v:  # NaN guard
        return 0.5
    return max(SCORE_MIN, min(SCORE_MAX, v))