import pandas as pd
import numpy as np


def optimize_slotting(df: pd.DataFrame):
    """
    Assign aisle/rack based on velocity.
    Fast → aisles 1–5
    Medium → 6–12
    Slow → 13–20
    """

    df = df.copy()

    def assign_location(row):
        if row["Velocity"].lower() == "fast":
            aisle = np.random.randint(1, 6)
        elif row["Velocity"].lower() == "medium":
            aisle = np.random.randint(6, 12)
        else:
            aisle = np.random.randint(13, 20)
        rack = np.random.randint(1, 30)
        return aisle, rack

    df["Suggested Aisle"], df["Suggested Rack"] = zip(*df.apply(assign_location, axis=1))
    return df