#! /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)