import math
import random


def pick_reps_for_exercise(exercise, wt_params: dict, tier_ranges: dict, rng=random) -> int:
    """Pick reps from tier-specific range, then fallback to generic wt params."""
    tier = (getattr(exercise, 'exercise_tier', None) or 'accessory').lower()
    selected_range = tier_ranges.get(tier) or (wt_params['rep_min'], wt_params['rep_max'])
    low, high = int(selected_range[0]), int(selected_range[1])
    if low > high:
        low, high = high, low
    return rng.randint(low, high)


def apply_rep_volume_floor(entries: list[dict], rounds: int, min_volume: int) -> None:
    """Mutate entries in-place so reps*rounds meets the minimum volume floor."""
    if rounds <= 0:
        return
    for entry in entries:
        reps = entry.get('reps')
        if reps and reps * rounds < min_volume:
            entry['reps'] = max(reps, math.ceil(min_volume / rounds))


def working_rest_seconds(rest_override, default_rest: int, minimum_rest: int = 15) -> int:
    """Return guarded positive working rest in seconds."""
    rest = rest_override or default_rest or 45
    return max(minimum_rest, int(rest))


def sort_entries_by_hr(entries: list[dict], is_early_block: bool) -> None:
    """Sort entries by HR elevation and re-number order."""
    entries.sort(
        key=lambda e: getattr(e.get('exercise'), 'hr_elevation_rating', 5) or 5,
        reverse=is_early_block,
    )
    for idx, entry in enumerate(entries, start=1):
        entry['order'] = idx