Add inline SVG consumption graphs

jon/templates/inventory/index.html

@@ -1,3 +1,26 @@
+{% macro consumption_graph_svg(values) -%}
+{% set stroke_width = 8 %}
+{% set width = 300 %}
+{% set height = 100 %}
+{% set padding = 4 %}
+{% set dx = (width - 2 * padding) / ((values | length) + 1) %}
+{% set dy = (height - 2 * padding) / ((values + [1]) | max) %}
+<svg viewBox="0 0 {{ width }} {{ height }}" role="img" class="consumption-graph">
+  <polyline
+    points="
+    {% for value in values %}
+      {{ padding + loop.index * dx }}, {{ height - padding - value * dy }}
+    {% endfor %}
+    "
+    stroke="green"
+    stroke-width="{{ stroke_width }}"
+    stroke-linecap="round"
+    stroke-linejoin="round"
+    fill="none"
+  >
+</svg>
+{% endmacro -%}
+
 {% extends "base.html" %}
 
 {% block content %}
@@ -5,6 +28,7 @@
   <tr>
     <th>Stat</th>
     <th>ID</th>
+    <th>Graph</th>
     <th>Barcode</th>
     <th>Name</th>
     <th>Preis (Netto)</th>
@@ -23,6 +47,7 @@
       {% if item.other_lines_count != 0 %}<span title="{% if item.other_lines_count == 1 %}Neuerer Eintrag mit demselben Barcode ist aktiv{% else %}{{ item.other_lines_count }} Einträge mit demselben Barcode sind aktiv{% endif %}">🔄</span>{% endif %}
     </td>
     <td><a href="/inventory/item/{{ item.item_id }}">{{ item.item_id }}</a></td>
+    <td>{{ consumption_graph_svg(item.last_n_days_sales) }}</td>
     <td><code>{{ item.item_barcode }}</code></td>
     <td>{{ item.name }}</td>
     <td class="--align-right">{{ format_currency(item.unit_price) }}</td>