"""
This module is essentially a wrapper for Python's premailer and whatever the 
default mail transfer is (usually Postfix). Note that the premailer package 
(https://pypi.org/project/premailer/) is required for style embedding.

This module provides the following methods:
    - `mailprep`:   embed CSS styles into inline HTML tags
    - `sendmail`:   send HTML or plaintext email using default mail handler
"""

import logging
logger = logging.getLogger(__name__)

from os.path import isfile
import premailer
from email.mime.text import MIMEText
import subprocess


def mailprep(htmlin, stylesheet):
    """
    Embed CSS styles from a file into inline HTML tags. Requires the premailer
    package (https://pypi.org/project/premailer/).
    """

    logger.debug("Converting stylesheet " + stylesheet + " to inline tags")
    if not isfile(stylesheet):
        logger.warning("Cannot read stylesheet {}: file does not exist".format(stylesheet))
        raise FileNotFoundError 
    pm = premailer.Premailer(htmlin, external_styles=stylesheet)
    htmlout = pm.transform()
    logger.info("Converted stylesheet to inline tags")
    return htmlout


def sendmail(mailbin, body, recipient, subject, html=True, sender=""):
    """
    Prepare and send an email in either HTML or plain text format. The default
    MTA path is usually correct, but can be modified in the config option
    "mailbin" in the [mail] section.
    """

    logger.debug("Sending email")
    msg = MIMEText(body, 'html' if html else 'plain')
    if sender:
        msg["From"] = sender
    msg["To"] = recipient
    msg["Content-type"] = "text/html: te: text/html" if html else "text/plain: te: text/plain"
    msg["Subject"] = subject
    mailproc = subprocess.Popen([mailbin, "--debug-level=" + str(10 if logging.root.level == logging.DEBUG else 0), "-t"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
    logger.debug("Compiled message and opened process")
    try:
        stdout = mailproc.communicate(msg.as_bytes(), timeout=15)
        logger.debug("sendmail output: {}".format(stdout))
        logger.info("Sent email to {0}".format(recipient))
        return 0
    except Exception as e:
        mailproc.kill()
        logger.warning("Failed to send message: {0}".format(str(e)))