homepage: sensor history json download

app.py

@@ -3,6 +3,7 @@ import json
 from flask import Flask, Response
 from flask import render_template, render_template_string, escape
 from flask import request, send_file
+from flask import jsonify
 from flask_socketio import SocketIO, join_room
 
 from random import randint
@@ -81,6 +82,10 @@ def dist(filename):
     print('Missing', filename)
     return ''
 
+@app.route('/sensors.json')
+def get_sensors():
+    return jsonify(sensors.get_history())
+
 @app.route('/recipe')
 def recipe():
     return render_template('recipe.html', recipe=phasectrl.recipe)

sensors.py

@@ -212,7 +212,7 @@ class Sensors():
 
     def get_history(self, n=None):
         l = len(self.history)
-        return tuple(islice(self.history, max(0, l - n), l))
+        return tuple(islice(self.history, max(0, l - (n or l)), l))
 
 sensors = Sensors()
 

templates/index.html

@@ -47,6 +47,9 @@
                 Update #of points
               </a>
             </div>
+            <a class="button is-link" href="/sensors.json">
+              Download
+            </a>
           </div>
           <div id="data-plot"></div>
           <br/>