"""Greeting construction: pure functions with no I/O, easy to test."""

import datetime

DEFAULT_NAME = "friend"


def time_of_day_greeting(now=None):
    """Return a salutation that matches the local time of day."""
    hour = (now or datetime.datetime.now()).hour
    if 5 <= hour < 12:
        return "Good morning"
    if 12 <= hour < 18:
        return "Good afternoon"
    return "Good evening"


def greet(name=DEFAULT_NAME, shout=False, salutation=None):
    """Build a greeting such as "Hello, Ada!"."""
    if salutation is None:
        salutation = "Hello"
    message = f"{salutation}, {name}!"
    return message.upper() if shout else message