import random
from typing import Iterable, Optional


def section_exercise_count(section: str, fitness_level: int, rng=random) -> int:
    """Return section exercise count range by fitness level."""
    level = fitness_level or 2
    if section == 'warmup':
        if level <= 1:
            return rng.randint(5, 7)
        if level >= 3:
            return rng.randint(3, 5)
        return rng.randint(4, 6)
    if section == 'cooldown':
        if level <= 1:
            return rng.randint(4, 5)
        if level >= 3:
            return rng.randint(2, 3)
        return rng.randint(3, 4)
    raise ValueError(f'Unknown section: {section}')


def rounded_duration(
    raw_duration: int,
    *,
    min_duration: int,
    duration_multiple: int,
) -> int:
    """Round duration to configured multiple and clamp to minimum."""
    return max(min_duration, round(raw_duration / duration_multiple) * duration_multiple)


def build_duration_entries(
    exercises: Iterable,
    *,
    duration_min: int,
    duration_max: int,
    min_duration: int,
    duration_multiple: int,
    rng=random,
) -> list[dict]:
    """Build ordered duration entries from exercises."""
    entries = []
    for idx, ex in enumerate(exercises, start=1):
        duration = rng.randint(duration_min, duration_max)
        entries.append({
            'exercise': ex,
            'duration': rounded_duration(
                duration,
                min_duration=min_duration,
                duration_multiple=duration_multiple,
            ),
            'order': idx,
        })
    return entries


def build_section_superset(name: str, entries: list[dict]) -> Optional[dict]:
    """Build a single-round warmup/cooldown superset payload."""
    if not entries:
        return None
    return {
        'name': name,
        'rounds': 1,
        'rest_between_rounds': 0,
        'exercises': entries,
    }