adding simplistic webserver

sem-6000-web.md

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+# Simple Webfrontend
+_"Simplistic python/flask wrapper for the _sem-6000.exp_ command"_
+
+This little webserver lets you control your known (`.known_sem6`) devices through a browser.
+
+## Getting started
+Install flask and yattag python modules.
+```
+sudo pip3 install flask yattag
+```
+
+## Check functionality
+Start the service once.
+```
+$ python3 ./sem-6000-web.py
+```
+Access via _http://IP:5000_
+
+## Register as Service
+Register as SystemD service at bootup.
+```
+sudo systemctl enable --now "$(pwd)/sem-6000-web.service"
+```
+
+Check the status and logs.
+```
+systemctl status sem-6000-web
+journalctl -f -u sem-6000-web
+```

sem-6000-web.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+import os, subprocess
+from flask import Flask, request, Response, abort
+from yattag import Doc
+
+
+# learn known devices
+devices = []
+with open(os.path.expanduser("~/.known_sem6"), 'r') as f:
+    for line in f.readlines():
+        devices.append(line.strip().split(' ')[-1])
+
+actions = [ 'on', 'off', 'toggle', 'status' ]
+
+
+def run_command(command):
+    """ execute the given command, return it's std-out and -err"""
+    result = subprocess.run(command.split(' '), stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    out = result.stdout.decode('utf-8'); err = result.stderr.decode('utf-8')
+    out = F"{command}{os.linesep}{out}"
+    if err != '':
+        out = F"{out}{os.linesep}{err}"
+    return out
+
+
+# flask application starts here
+app = Flask(__name__)
+
+@app.route('/sem/<path:device>/', methods=["GET", "POST"])
+def handle_sem(device):
+    """ run this when '/sem/<device>/?action=<action>' was accessed """
+    # verfiy parameters
+    if device not in devices:
+        return abort(404, F"device '{device}' unknown")
+
+    action = request.args.get('action')  # parse GET or POST arguments to identify 'action' parameter
+    if request.environ['REQUEST_METHOD'] == 'POST':
+        action = request.form['action']
+
+    if action is None:
+        action = 'status'
+
+    if action not in actions:
+        return abort(404, F"action '{action}' unknown")
+
+    # start assembly of page
+    doc, tag, text = Doc().tagtext()
+    with tag('title'):
+        text(device)
+
+    # if request was anything than 'status' redirect back to status
+    if action != 'status':
+        doc.asis(F"<meta http-equiv=\"refresh\" content=\"1;{request.environ['PATH_INFO']}\">")
+
+    # add buttons at the top of page
+    with tag('form', method='get', action=request.environ['PATH_INFO']):
+        with tag('table', border='0', style="text-align:center;"):
+            for a in actions:
+                with tag('td'):
+                    with tag('input', type='submit', name='action', value=a):
+                        pass
+
+    # add section with output of command
+    with tag('hr'):
+        with tag('pre'):
+            # assemble and run command
+            text(run_command(F"./sem-6000.exp {device} --{action} --print"))
+    with tag('hr'):
+        pass
+
+    # render and return page
+    return Response(doc.getvalue(), mimetype='text/html;charset=UTF-8')
+
+
+@app.route('/', methods=["GET"])
+def handle_root():
+    """ run this when '/' was accessed """
+    # start assembly of page
+    doc, tag, text = Doc().tagtext()
+    with tag('h1'):
+        text('known SEM-6000 devices')
+
+    for device in devices:
+        with tag('h2'):
+            with tag('a', href=F"/sem/{device}/"): text(F"Device {device}")
+
+    # render and return page
+    return Response(doc.getvalue(), mimetype='text/html;charset=UTF-8')
+
+
+if __name__ == "__main__":
+    app.run(debug=False, host='0.0.0.0', port=5000)
+

sem-6000-web.service

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+[Unit]
+Description=voltcraft sem-6000 web control
+After=bluetooth.target
+
+[Service]
+User=pi
+WorkingDirectory=/home/pi/voltcraft-sem-6000
+ExecStart=/usr/bin/python3 sem-6000-web.py
+
+[Install]
+WantedBy=multi-user.target