#!/usr/bin/python

# TODO
#
# More complete error handling for SMTP exceptions

import re
import sys
import netrc
import getpass
import mailbox
import smtplib
import optparse
import email.Parser

fromaddr = 'tmz@pobox.com'
smtphost = 'sasl.smtp.pobox.com'
smtpport = '587'

confirm_re = re.compile('^confirm [a-z0-9]{40}$')
subject_re = re.compile('.*requires\n?[\s]+approval$', re.DOTALL)

usage = '%prog [options] mailbox'
parser = optparse.OptionParser(usage=usage)
parser.add_option('-a', '--approve', dest='approve',
                  action='store_true', default=False,
                  help='Approve, rather than discard, message(s) [%default]')
parser.add_option('-f', '--from', dest='fromaddr', default=fromaddr,
                  metavar='address',
                  help='From address to use as a last resort [%default]')
parser.add_option('-H', '--smtp-host', dest='smtphost', default=smtphost,
                  help='SMTP hostname [%default]', metavar='hostname')
parser.add_option('-P', '--smtp-port', dest='smtpport', default=smtpport,
                  help='SMTP port number [%default]', metavar='port')
parser.add_option('-v', '--verbose', dest='verbose',
                  action='store_true', default=False,
                  help='Enable more verbose output')
opts, args = parser.parse_args()

fromaddr = opts.fromaddr
smtphost = opts.smtphost
smtpport = opts.smtpport

class LoginInfoError(StandardError):
    pass

def get_login_info(host):
    try:
        net_rc = netrc.netrc()
        if host not in net_rc.hosts:
            raise LoginInfoError('No machine entry for %s in ~/.netrc' % host)
        return net_rc.authenticators(host)
    except Exception, error:
        raise LoginInfoError(error)

# This comes from http://code.activestate.com/recipes/576553/
def mbox_generator(input, sep=''):
    """Yield each message found in 'input'."""
    assert type(input) is file
    parsestr = email.Parser.Parser().parsestr
    data = []
    while True:
        line = input.readline()
        if sep and line.rstrip() == sep:
            line = 'From nobody'
        if line[:5] == 'From ' or line == '':
            if data:
                yield parsestr(''.join(data))
                data = []
            elif line == '':
                raise StopIteration
        else:
            data.append(line)

try:
    if args:
        if len(args) > 1:
            parser.error('Only one mailbox argument is supported')
        # python < 2.5 doesn't have mailbox.mbox
        try:
            mbox = mailbox.mbox(args[0])
        except AttributeError:
            mbox = mbox_generator(open(args[0]))
    else:
        mbox = mbox_generator(sys.stdin, sep='~###~')
except Exception, e:
    raise SystemExit(e)

# FIXME this won't work with mbox_generator
#if not mbox:
#    print 'No messages found'

seen = []
confirmations = []

# FIXME this won't work with mbox_generator
#print 'Processing %s messages...' % len(mbox)
if opts.verbose:
    print 'Processing messages...'

for msg in mbox:
    # No point looking any further if the msg subject isn't correct
    if 'subject' not in msg or not subject_re.match(msg['subject']):
        if opts.verbose:
            print 'No matching subject, skipping...'
        continue
    found = False
    for part in msg.walk():
        if 'subject' not in part or 'from' not in part:
            if opts.verbose:
                print 'Message part lacks subject or from, skipping...'
            continue
        frm = listaddr = part['from']
        subject = part['subject']
        if confirm_re.match(subject):
            found = True
            if subject in seen:
                if opts.verbose:
                    print 'Skipping duplicate message (%s)' % subject
                break
            reply = email.Message.Message()
            reply['To'] = frm
            #reply['To'] = 'tmz@pobox.com'
            if 'delivered-to' in msg and msg['delivered-to']:
                reply['From'] = msg['delivered-to']
            else:
                reply['From'] = fromaddr
            reply['Subject'] = subject
            if opts.approve:
                list = msg['subject'].split()[0]
                try:
                    password = get_login_info(listaddr)[2]
                except LoginInfoError, error:
                    print 'Unable to find %s password: %s' % (list, error)
                    try:
                        password = getpass.getpass('%s password: ' % list)
                    except Exception, error:
                        raise SystemExit('Unable to get password: %s' % error)
                if not password:
                    raise SystemExit('Failed to get %s password' % list)
                reply['Approve'] = password
            seen.append(subject)
            confirmations.append(reply)
            break
    if not found:
        print 'No confirmation part found in message (%s)' % msg['subject']

if confirmations:
    mode = opts.approve and 'approval' or 'discard'
    print 'Sending %s %s confirmation(s)... ' % (len(confirmations), mode)
    try:
        login, account, password = get_login_info(smtphost)
    except LoginInfoError, error:
        raise SystemExit(error)
    # FIXME Do proper smtp error handling
    try:
        smtp = smtplib.SMTP(smtphost, smtpport)
        smtp.starttls()
        smtp.ehlo('localhost.localdomain')
        smtp.login(login, password)
        failed = []
        for msg in confirmations:
            errors = smtp.sendmail(msg['from'], [msg['to']], msg.as_string())
            if not errors:
                print 'Sent %s' % msg['subject']
            else:
                failed.append(errors)
        # quit() could throw an sslerror or another error we don't care about
        try: smtp.quit()
        except: pass
    except Exception, error:
        print 'Sending confirmations failed: %s' % error

    for errors in failed:
        for addr in errors:
            errno, errmsg = errors[addr]
            print 'Delivery to %s failed: %s (%s)' % (addr, errmsg, errno)