#! /usr/bin/env python3

# (C) Olivier Berger 2001-2002
# (C) François Poulain 2019
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.
#

# This program is used to mail a message to several recipients, thus
# providing customization for each recipient.

import sys, getopt, re
import smtplib, time, mimetypes
from email.header import Header
from email.message import EmailMessage

#
# displays usage of the program, then quit
#
def usage(returncode):
    print(
        """SYNTAX:
    """,
        sys.argv[0],
        """ -t tofile -b bodyfile [-p attachedfile]
    
    tofile   : sort of CSV file containing addresses of recipients
    bodyfile : template of the mail to be sent
    attachedfile : optionnal attachment
    """,
    )
    sys.exit(returncode)


TOFILE = None
BODYFILE = None
JOINFILE = None


# read the recipients file where values are separated by | characters
def read_recipients():
    recipientfile = open(TOFILE)
    lines = recipientfile.readlines()
    return [line[:-1].split("|") for line in lines]


def read_body():
    bodyfile = open(BODYFILE)
    body = ""
    for line in bodyfile.readlines():
        body = body + line
    return body


def read_join():
    try:
        with open(JOINFILE, "rb") as fp:
            ctype, encoding = mimetypes.guess_type(JOINFILE)
            if ctype is None or encoding is not None:
                ctype = "application/octet-stream"
            maintype, subtype = ctype.split("/", 1)
            metadata = {
                "filename": JOINFILE,
                "maintype": maintype,
                "subtype": subtype,
            }
            return (fp.read(), metadata)
    except Exception as e:
        print("read error: %s" % e)
        exit(1)


def replace_values(bodytemplate, values):
    body = bodytemplate

    for i in range(len(values)):
        i = i + 1
        pattern = "${{%02d}}" % i

        body = body.replace(pattern, values[i - 1])

    return body


# patterns for header of the mail
FROMPATTERN = re.compile(r"^From: *(.*)")
SUBJECTPATTERN = re.compile(r"^Subject: *(.*)")
CCPATTERN = re.compile(r"^Cc: *(.*)")
BCCPATTERN = re.compile(r"^Bcc: *(.*)")
REPLYTOPATTERN = re.compile(r"^Reply-To: *(.*)")


def qencode_subject(message):
    subjectmatches = re.search(r"^Subject: *(.*)$", message, re.MULTILINE)
    if subjectmatches == None:
        return message
    subjectstr = subjectmatches.group(1)
    h = Header(subjectstr, "utf-8")
    qsubjectstr = h.encode()
    return message.replace(subjectstr, qsubjectstr, 1)


def send_message(message, to, attachment):

    lines = message.split("\n")

    # identify headers in the template
    fromvalue = None
    subjectvalue = None
    ccvalue = None
    bccvalue = None
    replytovalue = None

    for index, line in enumerate(lines):
        if not line:
            body = "\n".join(lines[index + 1 :])
            break

        frommatches = FROMPATTERN.match(line)
        subjectmatches = SUBJECTPATTERN.match(line)
        ccmatches = CCPATTERN.match(line)
        bccmatches = BCCPATTERN.match(line)
        replytomatches = REPLYTOPATTERN.match(line)

        if frommatches:
            fromvalue = frommatches.group(1)
        if subjectmatches:
            subjectvalue = subjectmatches.group(1)
        if ccmatches:
            ccvalue = ccmatches.group(1)
        if bccmatches:
            bccvalue = bccmatches.group(1)
        if replytomatches:
            replytovalue = replytomatches.group(1)

    # lists all addresses to which the mail will be sent
    dests = [to]

    if ccvalue:
        dests.append(ccvalue)
    if bccvalue:
        dests.append(bccvalue)

    msg = EmailMessage()
    msg["Subject"] = subjectvalue
    msg["From"] = fromvalue
    msg["To"] = to
    if replytovalue:
        msg["Reply-To"] = replytovalue
    if ccvalue:
        msg["Cc"] = ccvalue
    msg.set_content(body)
    if attachment:
        msg.add_attachment(attachment[0], **attachment[1])

    print(
        "Sending : %s, from %s to %s, dests : %s"
        % (subjectvalue, fromvalue, dests[0], repr(dests))
    )

    # sending the mail to its recipients using the local mailer via SMTP
    server = smtplib.SMTP("localhost", "25")
    server.set_debuglevel(1)
    server.send_message(msg)
    server.quit()


if __name__ == "__main__":

    # handle options of the program
    try:
        opts, args = getopt.getopt(sys.argv[1:], "t:b:p:")
    except getopt.error as msg:
        print("getopt error: %s" % msg)
        usage(1)

    for name, value in opts:
        if name == "-t":
            TOFILE = value
        elif name == "-b":
            BODYFILE = value
        elif name == "-p":
            JOINFILE = value
        else:
            print("argument: ", name, " invalid")
            usage(1)

    if not TOFILE or not BODYFILE:
        usage(1)

    # read the recipients file
    sets = read_recipients()

    # read the template of the mail
    bodytemplate = read_body()

    # optionnaly read the attachment of the mail
    attachment = None
    if JOINFILE:
        attachment = read_join()

    # counter to be able to pause each 10 mails send
    counter = 0

    # send mail to each recipient
    for set in sets:

        values = set

        # the recipient is always in first column
        recipient = values[0]

        # replace substitution variables in the template for each recipient
        body = replace_values(bodytemplate, values)

        # send message
        send_message(body, recipient, attachment)

        # pause every 10 mails for 5 secs so that the MTA doesn't explode
        counter = counter + 1
        if counter >= 10:
            counter = 0
            print("suspending execution for 5 secs")
            time.sleep(5)