{#- The per-category spec fields. Every category's fieldset is rendered and all but the
    selected one is hidden, so switching category needs no fetch and no round-trip — and
    the form still works with JS off (every fieldset is present, just collapsed).
    🔴 Field names are PREFIXED `spec.` so a spec can never collide with a column name:
    `name` the item and `name` a hypothetical spec would otherwise be the same key. -#}
{% macro spec_fields(categories, current='', values={}) %}
{% for c in categories %}
<div class="specset" data-cat="{{ c.slug }}" {% if c.slug != current %}hidden{% endif %}>
  {% for f in c.fields %}
  <label class="spec">{{ f.label }}{% if f.unit %} <small>({{ f.unit }})</small>{% endif %}
    {%- if f.type == 'choice' %}
    <select name="spec.{{ f.key }}" {% if c.slug != current %}disabled{% endif %}>
      <option value="">—</option>
      {% for ch in f.choices %}<option value="{{ ch }}" {{ 'selected' if values.get(f.key) == ch }}>{{ ch|replace('_',' ') }}</option>{% endfor %}
    </select>
    {%- elif f.type == 'bool' %}
    <input type="checkbox" name="spec.{{ f.key }}" value="1" {{ 'checked' if values.get(f.key) }} {% if c.slug != current %}disabled{% endif %}>
    {%- elif f.type in ('length_in', 'length_mm') %}
    {#- Stored as millimetres always; entered in whichever unit the thing is actually sold
        in. specs.py converts at the door — see the note there on why there are two. -#}
    <input type="number" step="{{ '0.05' if f.type == 'length_in' else '1' }}" min="0"
           name="spec.{{ f.key }}"
           value="{{ ('%g'|format(values[f.key] / 25.4)) if (f.type == 'length_in' and values.get(f.key)) else (values.get(f.key) or '') }}"
           {% if c.slug != current %}disabled{% endif %}>
    {%- elif f.type in ('int', 'decimal') %}
    <input type="number" step="{{ '1' if f.type == 'int' else 'any' }}" name="spec.{{ f.key }}"
           value="{{ values.get(f.key) or '' }}" {% if c.slug != current %}disabled{% endif %}>
    {%- else %}
    <input name="spec.{{ f.key }}" value="{{ values.get(f.key) or '' }}" {% if c.slug != current %}disabled{% endif %}>
    {%- endif %}
    {% if f.help %}<small class="hint">{{ f.help }}</small>{% endif %}
  </label>
  {% endfor %}
</div>
{% endfor %}
{% endmacro %}