send.py

"""
Example: sending example 05's digest email via SMTP.

Run `python3 run_all.py` first (or at least
`python3 examples/05-plain-text/run.py`) so dist/05-plain-text/digest.html
and digest.txt exist.

Uses Python's built-in smtplib and email modules -- nothing extra to
install for this example. For ESP-specific sending, consider:
  - SendGrid: pip install sendgrid
  - Amazon SES: pip install boto3
  - Postmark: pip install postmarker
  - Mailgun: pip install requests (use its REST API)
"""

import os
import secrets
import sys

# import smtplib
# from email.mime.multipart import MIMEMultipart
# from email.mime.text import MIMEText

ROOT = os.path.dirname(os.path.abspath(__file__))
html_path = os.path.join(ROOT, "dist", "05-plain-text", "digest.html")
text_path = os.path.join(ROOT, "dist", "05-plain-text", "digest.txt")

if not os.path.isfile(html_path) or not os.path.isfile(text_path):
    print("Missing dist/05-plain-text/digest.{html,txt} -- run `python3 run_all.py` first.", file=sys.stderr)
    sys.exit(1)

with open(html_path, encoding="utf-8") as f:
    html = f.read()
with open(text_path, encoding="utf-8") as f:
    text = f.read()

# msg = MIMEMultipart("alternative")
# msg["Subject"] = "This week at Northwind Coffee"
# msg["From"] = "Northwind Coffee <digest@northwindcoffee.example>"
# msg["To"] = "subscriber@example.com"
# msg.attach(MIMEText(text, "plain"))  # least capable part first
# msg.attach(MIMEText(html, "html"))   # most capable part second
#
# with smtplib.SMTP("smtp.example.com", 587) as server:
#     server.starttls()
#     server.login("your-username", "your-password")
#     server.send_message(msg)
#     print("sent")

# What MIMEMultipart builds under the hood, spelled out by hand: a
# multipart/alternative message with the plain-text part first (least
# capable first) and the HTML part second, joined by a MIME boundary.
boundary = "nwc-" + secrets.token_hex(16)
message = (
    "From: Northwind Coffee <digest@northwindcoffee.example>\r\n"
    "To: subscriber@example.com\r\n"
    "Subject: This week at Northwind Coffee\r\n"
    "MIME-Version: 1.0\r\n"
    f'Content-Type: multipart/alternative; boundary="{boundary}"\r\n'
    "\r\n"
    f"--{boundary}\r\n"
    "Content-Type: text/plain; charset=utf-8\r\n"
    "\r\n"
    f"{text}\r\n"
    f"--{boundary}\r\n"
    "Content-Type: text/html; charset=utf-8\r\n"
    "\r\n"
    f"{html}\r\n"
    f"--{boundary}--\r\n"
)

print("SMTP config not set -- edit send.py with your credentials.")
print(f"HTML part:      {len(html.encode('utf-8'))} bytes")
print(f"Text part:       {len(text.encode('utf-8'))} bytes")
print(f"Multipart total: {len(message.encode('utf-8'))} bytes")