mailfetch.py

#
# mailfetch.py
# 
# The purpose of this module is extract *.stl and *.obj model
# attachments and the sender's email address, from print requests
# sent to a default email account. In a normal case, a PrintJob object
# is created and passed to the pipeline module for further processing.
# Catastrophic errors are noted via the logger module.
#

import imaplib    # Facilitates connection to mailserver
import email      # Facilitates message parsing/extraction
import os         # Used to construct attachment save path
import config     # Module for importing configuration variable values
import pipeline   # Module to facilitate the entire model to print process
import getpass    # Module to ask for email account password
import logger     # Module to log useful messages
import socket     # Used to enforce timeout error condition

# General Program Flow:
#    - Read values of configuration variables in mailfetch.conf
#    - Prompt user for the account password
#    - Make a connection to the server
#    - Pass login credentials to the server
#    - Construct a list of unread messages
#    - "Walk" through parts of each message to find attachments
#    - Extract and save found attachments
#    - Logout and close connection

# this means you only need to log in once.
# run once at the top of the pipeline
mail_password = None
mlogger = logger.Logger('mailfetch')
def initialize():
    global mail_password
    if mail_password == None:
        mail_password = get_password()
    
# reads email, gets attachments, returns all attachments as list
def poll(verbose = True):
    global mail_password
    if mail_password == None:
        mail_password = get_password()

    # Read program config file for common variable values
    try:
        mailfetch_config = config.read_config()
        servername = mailfetch_config["Mailfetch"]["server"]
        portnumber = mailfetch_config["Mailfetch"]["port"]
        username = mailfetch_config["Mailfetch"]["username"]
        mailbox = mailfetch_config["Mailfetch"]["mailbox"]
        savedir = mailfetch_config["Mailfetch"]["savedir"]
        allowedtypes = mailfetch_config["Mailfetch"]["extensions"]
    except:
        mlogger.log("Mailfetch configuration error")
        print("Exiting.")
        return -1

    # Try to open a connection to the email server.
    # Using a method from the socket library, I am temporarily
    # imposing a timeout restriction to keep the program from
    # hanging on an invalid mailserver name.
    # After the connection, timeout must be reset to NONE to
    # place the socket back in blocking mode.
    socket.setdefaulttimeout(10)
    try:
        connection = open_connection(servername,portnumber)
    except:
        mlogger.log("Mailfetch failed to open connection to",servername,":",portnumber)
        print("Exiting.")
        return -2
    socket.setdefaulttimeout(None)

    # If a socket is opened successfully, try to login to the server
    try:
        login(connection,username,mail_password,mailbox)
    except:
        mlogger.log("Mailfetch failed to login to",servername,":",portnumber)
        print("Exiting.")
        return -3

    # Populate a list with parsed email info
    infolist = []
    messagelist = get_message_list(connection)
    for message in messagelist:
        email = get_message_contents(connection,message)

        # If the email is not multipart, don't process further.
        # Only multipart messages have attachments.
        if email.get_content_maintype() != 'multipart':
            continue

        # Iterate over the parts of an individual message
        for part in email.walk():
            # An attachment itself is NOT multipart
            if part.get_content_maintype() == 'multipart':
                continue

            # A condition where no attachment is to be found
            if part.get('Content-Disposition') is None:
                continue

            # Only proceed if the attachment extension matches those allowed
            filename = part.get_filename()
            extension = filename[-4:-1]
            if extension not in allowedtypes:
                continue

            # If we make it this far, extract and save the attachment
            path = extract_attachment(part,savedir)
            
            # put all the information here
            sendaddr = get_sender_addr(connection,message)
            jobinfo = pipeline.PrintJob(path,sendaddr)
            infolist.append(jobinfo)

    # Close connections and return list of job request info
    connection.close()
    connection.logout()
    return infolist

# Prompt user to enter password for the default email account
# ~AW: This will have to be automated eventually
def get_password():
    prompt = "Enter the account password:"
    pwd = getpass.getpass(prompt)
    return pwd

# Open a connection to server:port
def open_connection(server,port):
    socket = imaplib.IMAP4_SSL(server,port)
    mlogger.log("Connecting to server",server,"...")
    return socket

# Login to mailserver
#     socket - Connection opened from open_connection()
#     id - the email account username
#     pwd - the password for the account
#     mbox - name of the mailbox to check
def login(socket,id,pwd,mbox):
    socket.login(id,pwd)
    mlogger.log("Logged in as",id,"...")

    socket.select(mbox)
    mlogger.log("Selected Mailbox:",mbox)

    return 0

def get_message_list(socket):
    # Look for messages not yet marked as read, get a list of id's, and use the id's
    # to get to the message body
    typ, data = socket.search(None,"UNSEEN")
    list = data[0].split()
    mlogger.log("Returning Message List...")
    return list

def get_message_contents(socket,msg):
    typ, data = socket.fetch(msg, "(RFC822)")
    body = data[0][1]
    contents = email.message_from_bytes(body) # parsing the mail content to get a mail object
    return contents

def get_sender_addr(socket,msg):
    # There is some redundancy here, as this function initially does everytning
    # in the first 3 lines of get_message_contents(). Improve Later !!!
    typ, data = socket.fetch(msg, "(RFC822)")
    body = data[0][1]
    contents = email.message_from_bytes(body)
    sender = email.utils.parseaddr(contents['From'])
    mlogger.log(sender[1])
    return sender[1] # The sender addr
    
def extract_attachment(attachment,path):
    filename = attachment.get_filename()
    counter = 0

    # If there is no filename... create one (Think about this !!!)
    # Also, join the filename and directory path to construct final save location
    if not filename:
        filename = 'attachment-%03d%s' % (counter, '.sav')
        counter += 1
    save_path = os.path.join(path,filename)

    # Don't overwrite a preexisting file with the same name
    if not os.path.isfile(save_path):
        save_attachment(save_path,attachment)
    else:
        # should this throw an exception?
        mlogger.log(save_path,"already exists ...")
    return save_path

def save_attachment(location,attachment):
    fileptr = open(location,'wb')
    fileptr.write(attachment.get_payload(decode=True))
    mlogger.log("Saved attachment",location)
    fileptr.close()
    
    return 0

if __name__ == '__main__':
    initialize()
    poll()