Add inline SVG consumption graphs

jon/db/add_views.sql

@@ -58,3 +58,29 @@ FROM garfield.inventory_items
   ) m USING (item_id)
 ORDER BY inventory_items.name;
 
+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

@@ -1,6 +1,7 @@
 SELECT
   *
 FROM all_inventory_item_overview
+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

@@ -1,9 +1,33 @@
+{% 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 %}
 <table>
   <tr>
     <th>ID</th>
+    <th>Graph</th>
     <th>Barcode</th>
     <th>Name</th>
     <th>Preis (Netto)</th>
@@ -18,6 +42,7 @@
 {% for item in items %}
   <tr>
     <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>