import sys, os
import subprocess
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.message import MIMEMessage
from traceback import format_exception, format_exception_only

from .config import config

def sendmail(msg):
    sendmail_executable = None
    for pth in ( '/usr/sbin', '/usr/bin', '/usr/local/sbin', '/usr/local/bin', '/sbin', '/bin'):
        if os.access(os.path.join(pth, 'sendmail'), os.X_OK):
            sendmail_executable = os.path.join(pth, 'sendmail')
            break
    if sendmail_executable is None:
        raise FileNotFoundError('Could not find sendmail executable')

    pipe = subprocess.Popen([ sendmail_executable, '-t' ], stdin=subprocess.PIPE)
    stdout, stderr = pipe.communicate(msg.as_bytes())
    return pipe.wait()

def install_exception_handler(incoming_msg):
    bounce_address = config.get('bounce_address')
    if bounce_address is None:
        return

    def exception_handler(exctype, value, traceback):
        exc_text = ''.join(format_exception(exctype, value, traceback))
        msg = MIMEMultipart()
        txt_msg = MIMEText('''There was a problem processing an incoming DMARC report:

{}'''.format(exc_text))
        txt_msg['Content-Disposition'] = 'inline'
        msg.attach(txt_msg)
        att = MIMEMessage(incoming_msg)
        att['Content-Disposition'] = 'attachment'
        att['Content-Description'] = 'Original DMARC report message'
        msg.attach(att)
        msg['To'] = bounce_address
        msg['From'] = bounce_address
        msg['Subject'] = 'Exception: ' + format_exception_only(exctype, value)[-1][:70]
        sendmail(msg)

    sys.excepthook = exception_handler