{#- chirp-ui: Calendar component
    Month grid. Server must pass weeks (list of 7-day rows; 0 = empty cell).

    Usage:
        from "chirpui/calendar.html" import calendar

        calendar(weeks=[[0,0,1,2,3,4,5],[6,7,8,...],...],
                 month_label="January 2025",
                 prev_url="/calendar/2024/12", next_url="/calendar/2025/2")

    weeks: from calendar.monthcalendar(year, month) — 0 = empty cell.
-#}

{% def calendar(weeks, month_label, prev_url=none, next_url=none, cls="") %}
<div class="chirpui-calendar{{ " " ~ cls if cls else "" }}">
    <header class="chirpui-calendar__header">
        <h3 class="chirpui-calendar__title">{{ month_label }}</h3>
        <nav class="chirpui-calendar__nav">
            {% if prev_url %}
            <a href="{{ prev_url }}" class="chirpui-calendar__nav-link" aria-label="Previous month">←</a>
            {% end %}
            {% if next_url %}
            <a href="{{ next_url }}" class="chirpui-calendar__nav-link" aria-label="Next month">→</a>
            {% end %}
        </nav>
    </header>
    <div class="chirpui-calendar__weekdays">
        <span>Sun</span><span>Mon</span><span>Tue</span><span>Wed</span><span>Thu</span><span>Fri</span><span>Sat</span>
    </div>
    <div class="chirpui-calendar__grid">
        {% for week in weeks %}
        {% for day in week %}
        <div class="chirpui-calendar__day{{ " chirpui-calendar__day--empty" if day == 0 else "" }}">
            {% if day != 0 %}
            <span class="chirpui-calendar__day-num">{{ day }}</span>
            {% end %}
        </div>
        {% end %}
        {% end %}
    </div>
</div>
{% end %}