Switch to server side rendered SVG based graph library

app.py

@@ -3,12 +3,13 @@ import json
 from urllib import response
 from dateutil.relativedelta import relativedelta
 import os
-from flask import Flask, render_template, redirect, request, url_for, jsonify, Response
+from flask import Flask, render_template
 import jinja_partials
 from flask_htmx import HTMX
 import minify_html
 from urllib.parse import urlparse
 from flask_socketio import SocketIO
+import pygal
 
 from db import DataBase
 
@@ -54,13 +55,12 @@ def overview():
     cadences = db.get_all_cadences()
     last_cadence = cadences[-1]['rpm']
 
-    plot = {
-        "x": [c['logged_at'] for c in cadences],
-        "y": [c['rpm'] for c in cadences],
-        "type": 'scatter'
-    }
+    graph = pygal.Line(show_y_guides=False, show_legend=False)
+    graph.x_labels = [c['logged_at'] for c in cadences]
+    graph.add('RPM',  [c['rpm'] for c in cadences])
+    graph_data = graph.render_data_uri()
 
-    return render_template('overview.html', last_cadence=last_cadence, plot=plot, cadences=cadences)
+    return render_template('overview.html', last_cadence=last_cadence, cadences=cadences, graph_data=graph_data)
 
 
 if __name__ == '__main__':