fix: refactor script to be more modular and add price to config

these changes should lower the spam score for systems that use e.g.
spamassassin and increase the likelihood of the email being delivered.

config.json

@@ -1,7 +1,8 @@
 {
-"server":"your.email.server",
-"port":587,
-"user":"you@yourmail.com",
-"pass":"yourPassword",
-"sender":"santa@yourmail.com"
+    "server":"your.email.server",
+    "port":587,
+    "user":"you@yourmail.com",
+    "pass":"yourPassword",
+    "sender":"santa@yourmail.com",
+    "price": "75€"
 }

participants.json

@@ -1,3 +1,5 @@
 [
-{"name":"Alice","mail":"alice@mail.com","gender":"e"},{"name":"Bob","mail":"bob@mail.com","gender":"er"},{"name":"Chris","mail":"chris@mail.com","gender":"er"}
+    {"name":"Alice","mail":"alice@stefansterz.com","gender":"e"},
+    {"name":"Bob","mail":"bob@stefansterz.com","gender":"er"},
+    {"name":"Chris","mail":"chris@stefansterz.com","gender":"er"}
 ]

wichteln.py

@@ -1,3 +1,6 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
 '''
 This script creates randoms pairs from a list of participants in a secret santa
 game and sends them an email to notify them who the person is that they should
@@ -8,80 +11,120 @@ buy presents for.
 from argparse import ArgumentParser
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
-from email.utils import formatdate
+from email.utils import formatdate, make_msgid
 import json
 import random
 import smtplib
+from typing import Literal
+import types
 
-parser = ArgumentParser()
-parser.add_argument('-p', '--participants',
-                    dest='pFileLocation',
-                    default='participants.json',
-                    help='read a list of participants from PARTICIPANTFILE',
-                    metavar='PARTICIPANTFILE')
-parser.add_argument('-c', '--config',
-                    dest='cFileLocation',
-                    default='config.json',
-                    help='read the configuration from CONFIGFILE',
-                    metavar='CONFIGFILE')
-args = parser.parse_args()
 
-# load and prepare a list containing all participants
-with open(args.pFileLocation, 'r') as pFile:
-  participants = json.load(pFile)
+def secret_santa_matching(participants: list) -> list:
+    # create a copy of the list to make choosing a partner easier
+    copy = list(enumerate(participants[:]))
 
-# create a copy of the list to make choosing a partner easier
-copy = list(enumerate(participants[:]))
+    # choose a partner for each participant
+    for i in range(len(participants)):
 
-# choose a partner for each participant
-for i in range(len(participants)):
+        # if the last participant has only themselves left to choose, make them
+        # switch partners with another random participant
+        if len(copy) == 1 and participants[i] == copy[0][1]:
 
-  # if the last participant has only themselves left to choose, make them
-  # switch partners with another random participant
-  if len(copy) == 1 and participants[i] == copy[0][1]:
+            current = participants[i]
+            participants.remove(current)
+            partner = random.choice(participants)
 
-    current = participants[i]
-    participants.remove(current)
-    partner = random.choice(participants)
+            current['partner'] = partner['partner']
+            partner['partner'] = current['name'] + ' (' + current['mail']+')'
+            participants.append(current)
+            break
 
-    current['partner'] = partner['partner']
-    partner['partner'] = current['name'] + ' (' + current['mail']+')'
-    participants.append(current)
-    break
+        # otherwise choose a random partner for each participant
+        else:
+            partner = random.choice(copy)
+            while partner[0] == i:
+                partner = random.choice(copy)
 
-  # otherwise choose a random partner for each participant
-  else:
-    partner = random.choice(copy)
-    while partner[0] == i:
-      partner = random.choice(copy)
+            participants[i]['partner'] = partner[1]['name'] + \
+                ' ('+partner[1]['mail']+')'
+            copy.remove(partner)
 
-    participants[i]['partner'] = partner[1]['name']+' ('+partner[1]['mail']+')'
-    copy.remove(partner)
+    return participants
 
-# load mail server configuration and open smtp server connection
-with open(args.cFileLocation, 'r') as cFile:
-  config = json.load(cFile)
-  
-server = smtplib.SMTP(config['server'], config['port'])
-server.ehlo()
-server.starttls()
-server.ehlo()
-server.login(config['user'], config['pass'])
 
-# create emails for all participants and send them
-# change the text for the mail here if you want to
-for r in participants:
-  
-  msg = MIMEMultipart('alternative')
-  msg['From'] = config['sender']
-  msg['To'] = r['mail']
-  msg['Subject'] = 'Wichteln 🎄'
-  msg['Date'] = formatdate(localtime=True)
-  
-  body = 'Lieb'+r['gender']+' '+r['name']+'!\n\n'
-  body += 'Du bist heuer Wichtel für '+r['partner']+'.\n'
-  body += 'Das Geschenk sollte nicht mehr als 50€ kosten.\n\n'
-  body += 'Frohe Weihnachten!\n— Dein Christkind 👼'
-  
-  msg.attach(MIMEText(body, 'plain', 'utf-8'))
-  server.sendmail(config['sender'], r['mail'], msg.as_string())
+def send_secret_santa_mails(participants: list, config: dict):
+    open smtp connection
+    server = smtplib.SMTP(config['server'], config['port'])
+    server.ehlo()
+    server.starttls()
+    server.ehlo()
+    server.login(config['user'], config['pass'])
+
+    # create emails for all participants and send them
+    # change the text for the mail here if you want to
+    for r in participants:
+        msg = MIMEMultipart('alternative')
+        msg['From'] = config['sender']
+        msg['To'] = r['mail']
+        msg['Subject'] = 'Wichteln 🎄'
+        msg['Message-ID'] = make_msgid(domain=config['sender']
+                                       .split('@')[1]
+                                       .strip('>'))
+        msg['Date'] = formatdate(localtime=True)
+
+        plain = f'''Lieb{r['gender']} {r['name']}!
+
+Du bist heuer Wichtel für {r['partner']}.
+Das Geschenk sollte nicht mehr als {config['price']} kosten.
+
+Frohe Weihnachten!
+— Dein Christkind 👼'''
+
+        html = f'''
+<html>
+  <head></head>
+  <body>
+    <p>Lieb{r['gender']} {r['name']}!<br><br>
+       Du bist heuer Wichtel für {r['partner']}.<br>
+       Das Geschenk sollte nicht mehr als {config['price']} kosten.<br><br>
+       Frohe Weihnachten!<br>
+       — Dein Christkind 👼
+    </p>
+  </body>
+</html>
+'''
+
+        msg.attach(MIMEText(plain, 'plain', 'utf-8'))
+        msg.attach(MIMEText(html, 'html', 'utf-8'))
+        print('Sending email to', r['name'], '...')
+        server.sendmail(config['sender'], r['mail'], msg.as_string())
+
+
+def main():
+    parser = ArgumentParser()
+    parser.add_argument('-p', '--participants',
+                        dest='pFileLocation',
+                        default='participants.json',
+                        help='read list of participants from PARTICIPANTFILE',
+                        metavar='PARTICIPANTFILE')
+    parser.add_argument('-c', '--config',
+                        dest='cFileLocation',
+                        default='config.json',
+                        help='read the configuration from CONFIGFILE',
+                        metavar='CONFIGFILE')
+    args = parser.parse_args()
+
+    matches = []
+
+    # load and prepare a list containing all participants
+    with open(args.pFileLocation, 'r') as pFile:
+        matches = secret_santa_matching(json.load(pFile))
+
+    # load mail server configuration
+    with open(args.cFileLocation, 'r') as cFile:
+        config = json.load(cFile)
+        send_secret_santa_mails(matches, config)
+
+
+if __name__ == '__main__':
+    main()