Add inline SVG consumption graphs

jon/db/add_views.sql

@@ -59,7 +59,6 @@ FROM garfield.inventory_items
 ORDER BY inventory_items.name;
 
 -- How many *other* active inventory lines exist with the same barcode in the same location that are newer?
-
 CREATE TEMPORARY VIEW more_recent_inventory_lines_with_same_barcode AS
 SELECT
   a.item_id,
@@ -74,3 +73,31 @@ LEFT JOIN garfield.inventory_items AS b
       AND b.available
       AND b.bought > a.bought
 GROUP BY a.item_id;
+
+-- Get an array of how often items were sold over the last 14 days
+CREATE TEMPORARY VIEW inventory_last_n_days_sales AS
+WITH
+last_n_days AS (
+  SELECT generate_series(now() - interval '14 days', now(), interval '1 day')::date AS sale_date
+),
+last_n_days_sales AS (
+  SELECT
+    item_id,
+    sale_date,
+    count(snack_sales_log_timestamp) AS sale_date_sales
+  FROM garfield.inventory_items
+  LEFT JOIN garfield.inventory_map ON item_id = inventory_id
+  -- Is there a better way of writing this?
+  -- TODO: Try to speed this query up
+  CROSS JOIN last_n_days
+  LEFT JOIN garfield.snack_sales_log
+         ON inventory_map.snack_id = snack_sales_log.snack_id
+        AND DATE_TRUNC('day', snack_sales_log_timestamp) = sale_date
+  GROUP BY item_id, sale_date
+  ORDER BY item_id, sale_date
+)
+SELECT
+  item_id,
+  array_agg(sale_date_sales) AS last_n_days_sales
+FROM last_n_days_sales
+GROUP BY item_id

jon/db/get_inventory_overview.sql

@@ -2,6 +2,7 @@ SELECT
   *
 FROM all_inventory_item_overview
 LEFT JOIN more_recent_inventory_lines_with_same_barcode USING (item_id)
+LEFT JOIN inventory_last_n_days_sales USING (item_id)
 WHERE (%(location_id)s IS NULL OR location = %(location_id)s)
   AND available
 ORDER BY

jon/static/jon.css

@@ -74,3 +74,7 @@ th {
 details {
   font-size: 0.8em;
 }
+.consumption-graph {
+  display: block;
+  height: 1em;
+}

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>