# This Python file uses the following encoding: utf-8

# The software in this package is distributed under the GNU General
# Public License version 2 (with a special exception described below).
#
# A copy of GNU General Public License (GPL) is included in this distribution,
# in the file COPYING.GPL.
#
# As a special exception, if other files instantiate templates or use macros
# or inline functions from this file, or you compile this file and link it
# with other works to produce a work based on this file, this file
# does not by itself cause the resulting work to be covered
# by the GNU General Public License.
#
# However the source code for this file must still be made available
# in accordance with section (3) of the GNU General Public License.
#
# This exception does not invalidate any other reasons why a work based
# on this file might be covered by the GNU General Public License.
#
# Copyright (c) 2016-2018 Intra2net AG <info@intra2net.com>

"""
Class :py:class:`MailValidator`, a fully-featured email sender and checker.

Copyright: Intra2net AG
"""

import time
import os
import difflib
import socket
from inspect import currentframe
import re
import subprocess
import logging

import smtplib
from email.mime.audio import MIMEAudio
from email.mime.base import MIMEBase
from email.mime.image import MIMEImage
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.encoders import encode_base64
from email.utils import formatdate
from email.parser import Parser
import mimetypes

from . import arnied_wrapper

log = logging.getLogger('pyi2ncommon.mail_utils')


class EmailException(Exception):
    """Base class for custom exceptions raised from `MailValidator`."""

    pass


class EmailNotFound(EmailException):        # pylint: disable=missing-docstring
    pass


class InvalidEmailHeader(EmailException):   # pylint: disable=missing-docstring
    pass


class InvalidEmailContent(EmailException):  # pylint: disable=missing-docstring
    pass


class EmailIDError(EmailException):         # pylint: disable=missing-docstring
    pass


class MismatchedEmailID(EmailIDError):      # pylint: disable=missing-docstring
    pass


class MissingEmailID(EmailIDError):         # pylint: disable=missing-docstring
    pass


class EmailMismatch(EmailException):        # pylint: disable=missing-docstring
    pass


class MailValidator:
    """Class for validation of emails."""

    def target_path(self, new_value=None):
        """Getter/Setter for property `target_path`."""
        if new_value is not None:
            self._target_path = new_value
        else:
            return self._target_path
    target_path = property(target_path, target_path)

    def source_path(self, new_value=None):
        """Getter/Setter for property `source_path`."""
        if new_value is not None:
            self._source_path = new_value
        else:
            return self._source_path
    source_path = property(source_path, source_path)

    def smtp_sender(self, new_value=None):
        """Getter/Setter for property `smtp_sender`."""
        if new_value is not None:
            self._smtp_sender = new_value
        else:
            return self._smtp_sender
    smtp_sender = property(smtp_sender, smtp_sender)

    def compare_emails_method(self, method="basic"):
        """
        Set email comparison method for validation.

        :param str method: one of "basic", "headers"
        :raises: :py:class:`ValueError` if chosen method is invalid
        """
        if method == "basic":
            self._compare_emails_method = self._default_compare_emails
        elif method == "headers":
            self._compare_emails_method = self._compare_emails_by_basic_headers
        elif method == "existence":
            self._compare_emails_method = self._compare_emails_by_existence
        else:
            raise ValueError("Invalid email comparison method %s" % method)
    compare_emails_method = property(fset=compare_emails_method)

    def __init__(self, source_path, target_path):
        """
        Construct a validator instance.

        :param str source_path: path to find source emails (not sent)
        :param str target_path: path to find target emails (received)

        .. note:: The comparison method can be redefined using the variety of
            private method implementations.
        """
        self._target_path = target_path
        self._source_path = source_path
        self._smtp_sender = "no_source@inject.smtp"
        self._compare_emails_method = self._default_compare_emails

    def inject_emails(self, username, original_user):
        """
        Inject emails from `source_path` to `target_path`.

        This uses the script *restore_mail_inject.pl* which injects the mails
        using IMAP (as opposed to :py:meth:`inject_smtp`).

        :param str username: username for the mail injection script
        :param str original_user: original username for the mail injection
                                  script

        In order to restore acl rights as well put a mailbox.dump file in the
        source path.
        """
        log.info("Injecting emails for user %s", username)

        # inject emails from test data
        cmd = "/usr/intranator/bin/restore_mail_inject.pl -u " + username + \
              " -s " + self.source_path
        if original_user != "":
            cmd += " -m " + os.path.join(self.source_path, "mailboxes.dump") + \
                   " -o " + original_user

        result = subprocess.check_output(cmd, shell=True)
        log.debug(result)

    def _prepare_recipients(self, recipients):
        """
        Prepare recipient list: ensure list of proper addresses.

        If given a simple string, make a list of strings out of it.
        If any recipient is just a username, append "@" + localhost to it.
        Also check that recipients are just email addresses.
        """
        hostname = socket.gethostname()
        if isinstance(recipients, str):
            recipients = [recipients, ]
        result = []
        for recipient in recipients:
            if '@' in recipient:
                result.append(recipient)
            else:
                result.append(recipient + '@' + hostname)
            for bad_char in '<>"\'':
                if bad_char in recipient:
                    raise ValueError('Recipient must be a "raw" email address,'
                                     ' not {!r}'.format(recipient))
        return result

    def inject_smtp(self, usernames, emails):
        """
        Inject emails from `source_path` using python's SMTP library.

        As opposed to :py:meth:`inject_emails`, this actually sends the mail
        to the local mail server (meaning filtering, archiving, ... will
        happen).

        :param usernames: username(s) of the localhost receiver(s) for each
                          email or proper email address(es)
        :type usernames: str or [str]
        :param emails: paths to files including full emails (header + body)
                       to be sent to each user
        :type emails: [str]
        """
        recipients = self._prepare_recipients(usernames)
        log.info("Sending emails to %s", ','.join(recipients))
        with smtplib.SMTP('localhost') as server:
            for email in emails:
                log.info("Sending email %s", email)
                with open(os.path.join(self.source_path, email), 'rb') \
                        as file_handle:
                    email_content = file_handle.read()
                server.sendmail(self.smtp_sender, recipients, email_content)

        # Wait till SMTP queue is processed
        arnied_wrapper.wait_for_email_transfer()

    def verify_email_id(self, email, emails_list, timeout, in_target=True):
        """
        Verify that the id of an email is present in a list.

        Returns that email's match in this list.

        :param str email: email filename
        :param emails_list: email among which the first email has to be found
        :type emails_list: [str]
        :param int timeout: timeout for extracting the source and target emails
        :param bool in_target: whether the verified email is on the target side

        If `in_target` is set to True we are getting the target id from the
        target list of a source email. Otherwise, we assume a target email from
        a source list.
        """
        if in_target:
            email = self._extract_email_paths(self.source_path, [email],
                                              timeout)[0]
            emails_list = self._extract_email_paths(self.target_path,
                                                    emails_list, timeout)
        else:
            email = self._extract_email_paths(self.target_path, [email],
                                              timeout)[0]
            emails_list = self._extract_email_paths(self.source_path,
                                                    emails_list, timeout)

        email_id = self._extract_message_id(email)
        match = self._find_message_with_id(email_id, emails_list)
        return os.path.basename(match)

    def verify_emails(self, source_emails, target_emails, timeout):
        """
        Check injected e-mails for a user.

        :param source_emails: emails at the source location
        :type source_emails: [str]
        :param target_emails: emails at the target (server) location
        :type target_emails: [str]
        :param int timeout: timeout for extracting the source and target emails
        :raises: :py:class:`EmailNotFound` if target email is not found on
                 server
        """
        source_paths = self._extract_email_paths(self.source_path,
                                                 source_emails, timeout)
        target_paths = self._extract_email_paths(self.target_path,
                                                 target_emails, timeout)

        log.info("Verifying emails at %s with %s", self.target_path,
                 self.source_path)
        for target in target_paths:
            log.info("Verifying email %s", target)
            target_id = self._extract_message_id(target)
            source = self._find_message_with_id(target_id, source_paths)
            source_paths.remove(source)
            self._compare_emails_method(target, source, 1)

        if len(source_paths) > 0:
            raise EmailNotFound("%s target mails could not be found on server."
                                "\n%s"
                                % (len(source_paths), "\n".join(source_paths)))
        else:
            log.info("All e-mails at %s verified!", self.target_path)

    def assert_header(self, emails, header, present_values=None,
                      absent_values=None, timeout=30):
        """
        Check headers for present and missing strings in a list of messages.

        :param emails: emails whose headers will be checked
        :type emails: [str]
        :param str header: header that will be validated for each email
        :param present_values: strings that have to be present in the header
        :type present_values: [str] or None
        :param absent_values: strings that have to be absent in the header
        :type absent_values: [str] or None
        :param int timeout: timeout for extracting the source and target emails
        :raises: :py:class:`InvalidEmailHeader` if email header is not valid

        Every list of present and respectively absent values contains
        alternative values. At least one of present and one of absent should be
        satisfied.
        """
        target_paths = self._extract_email_paths(self.target_path, emails,
                                                 timeout)
        for email_path in target_paths:
            with open(email_path, "r") as email_file:
                verified_email = Parser().parse(email_file, headersonly=True)
                log.debug("Extracted email headers:\n%s", verified_email)

            log.info("Checking header '%s' in %s", header, email_path)
            if not present_values:
                present_values = []
            else:
                log.info("for present '%s'", "', '".join(present_values))
            if not absent_values:
                absent_values = []
            else:
                log.info("for absent '%s'", "', '".join(absent_values))
            present_valid = False
            for present in present_values:
                if present in verified_email[header]:
                    present_valid = True
            absent_valid = False
            for absent in absent_values:
                if absent not in verified_email[header]:
                    absent_valid = True

            if not present_valid and len(present_values) > 0:
                raise InvalidEmailHeader("Message header '%s' in %s is not "
                                         "valid:\n%s"
                                         % (header, email_path,
                                            verified_email[header]))
            if not absent_valid and len(absent_values) > 0:
                raise InvalidEmailHeader("Message header '%s' in %s is not "
                                         "valid:\n%s"
                                         % (header, email_path,
                                            verified_email[header]))
            log.info("Message header '%s' in %s is valid!", header, email_path)

    def assert_content(self, emails, content_type, present_values=None,
                       absent_values=None, timeout=30):
        """
        Check headers for present/missing strings in a list of messages.

        :param emails: emails whose content will be checked
        :type emails: [str]
        :param str content_type: type of the content that will be checked for
                                 values
        :param present_values: strings that have to be present in the content
        :type present_values: [str] or None
        :param absent_values: strings that have to be absent in the content
        :type absent_values: [str] or None
        :param int timeout: timeout for extracting the source and target emails
        :raises: :py:class:`InvalidEmailContent` if email content is not valid

        Every list of present and respectively absent values contains
        alternative values. At least one of present and one of absent should be
        satisfied.
        """
        target_paths = self._extract_email_paths(self.target_path, emails,
                                                 timeout)
        for email_path in target_paths:
            with open(email_path, "r") as email_file:
                verified_email = Parser().parse(email_file)
            log.debug("Extracted email content:\n%s", verified_email)
            content = ""
            for part in verified_email.walk():
                log.debug("Extracted %s part while looking for %s",
                          part.get_content_type(), content_type)
                if part.get_content_type() == content_type:
                    content = part.get_payload(decode=True)
                    if isinstance(content, bytes):
                        content = content.decode()
                    # NOTE: only one such element is expected
                    break

            log.info("Checking content '%s' in %s", content_type, email_path)
            if not present_values:
                present_values = []
            else:
                log.info("for present '%s'", "', '".join(present_values))
            if not absent_values:
                absent_values = []
            else:
                log.info("for absent '%s'", "', '".join(absent_values))
            present_valid = False
            for present in present_values:
                if present in content:
                    present_valid = True
            absent_valid = False
            for absent in absent_values:
                if absent not in content:
                    absent_valid = True

            if not present_valid and len(present_values) > 0:
                raise InvalidEmailContent("Message content '%s' in %s is not "
                                          "valid:\n%s"
                                          % (content_type, email_path, content))
            if not absent_valid and len(absent_values) > 0:
                raise InvalidEmailContent("Message content '%s' in %s is not "
                                          "valid:\n%s"
                                          % (content_type, email_path, content))
            log.info("Message content '%s' in %s is valid!",
                     content_type, email_path)

    def send_email_with_files(self, usernames, file_list,
                              wait_for_transfer=True,
                              autotest_signature=None,
                              subject="my subject"):
        """
        Send a generated email with optional attachments.

        :param usernames: username(s) of the localhost receiver(s) or proper
                          email address(es)
        :type usernames: str or [str]
        :param file_list: files attached to an email; can be empty
        :type file_list: [str]
        :param wait_for_transfer: specify whether to wait until arnied_wrapper
                                  confirms email transfer; you can also specify
                                  a fixed timeout (seconds)
        :type wait_for_transfer: bool or int
        :param autotest_signature: text to insert as value for header
                                   X-Autotest-Signature for simpler recognition
                                   of mail (if None do not add header)
        :type autotest_signature: str or None
        :param str subject: Subject of created mails
        """
        text = 'This is an autogenerated email.\n'

        recipients = self._prepare_recipients(usernames)

        if file_list:   # empty or None or so
            msg = MIMEMultipart()     # pylint: disable=redefined-variable-type
            msg.attach(MIMEText(text, _charset='utf-8'))
        else:
            msg = MIMEText(text, _charset='utf-8')  # pylint: disable=redefined-variable-type
        msg['From'] = self.smtp_sender
        msg['To'] = ', '.join(recipients)
        msg['Subject'] = subject
        msg['Date'] = formatdate(localtime=True)
        msg.preamble = 'This is a multi-part message in MIME format.\n'
        msg.add_header('X-Autotest-Creator',
                       self.__class__.__module__ + '.' +
                       self.__class__.__name__ + '.' +
                       currentframe().f_code.co_name)
        # (with help from http://stackoverflow.com/questions/5067604/determine-
        #      function-name-from-within-that-function-without-using-traceback)
        if autotest_signature:
            msg.add_header('X-Autotest-Signature', autotest_signature)

        # attach files
        for filename in file_list:
            fullpath = os.path.join(self.source_path, filename)

            # Guess the content type based on the file's extension.  Encoding
            # will be ignored, although we should check for simple things like
            # gzip'd or compressed files.
            ctype, encoding = mimetypes.guess_type(fullpath)
            if ctype is None or encoding is not None:
                # No guess could be made, or the file is encoded (compressed),
                # so use a generic bag-of-bits type.
                ctype = 'application/octet-stream'

            maintype, subtype = ctype.split('/', 1)
            log.debug("Creating message containing file {} of mime type {}"
                      .format(filename, ctype))
            part = None
            if maintype == 'text':
                with open(fullpath, 'rt') as file_handle:
                    # Note: we should handle calculating the charset
                    part = MIMEText(file_handle.read(), _subtype=subtype)   # pylint:disable=redefined-variable-type
            elif maintype == 'image':
                with open(fullpath, 'rb') as file_handle:
                    part = MIMEImage(file_handle.read(), _subtype=subtype)  # pylint:disable=redefined-variable-type
            elif maintype == 'audio':
                with open(fullpath, 'rb') as file_handle:
                    part = MIMEAudio(file_handle.read(), _subtype=subtype)  # pylint:disable=redefined-variable-type
            else:
                part = MIMEBase(maintype, subtype)                          # pylint:disable=redefined-variable-type
                with open(fullpath, 'rb') as file_handle:
                    part.set_payload(file_handle.read())
                # Encode the payload using Base64
                encode_base64(part)
            # Set the filename parameter
            part.add_header('Content-Disposition', 'attachment',
                            filename=filename)
            msg.attach(part)

        log.debug("Message successfully created")
        # send via SMTP

        log.debug("Sending message from %s to %s"
                  % (self.smtp_sender, ', '.join(recipients)))
        with smtplib.SMTP('localhost') as server:
            server.sendmail(self.smtp_sender, recipients, msg.as_string())

        # wait for transfer; complicated by isinstance(False, int) == True
        if wait_for_transfer is False:
            pass
        elif wait_for_transfer is True:
            arnied_wrapper.wait_for_email_transfer()
        else:
            arnied_wrapper.wait_for_email_transfer(timeout=wait_for_transfer)

    def _extract_email_paths(self, path, emails, timeout):
        """Check and return the absolute paths of a list of emails."""
        log.debug("Extracting messages %s", emails)
        if len(emails) == 0:
            emails = os.listdir(path)
        email_paths = []
        for expected_email in emails:
            # TODO: this can be improved by matching the emails themselves
            if expected_email in ["cyrus.cache", "cyrus.header", "cyrus.index",
                                  "Entw&APw-rfe", "Gesendete Elemente",
                                  "Gel&APY-schte Elemente", "mailboxes.dump",
                                  "tmp"]:
                continue
            email_path = os.path.join(path, expected_email)
            for i in range(timeout):
                if os.path.isfile(email_path):
                    email_paths.append(email_path)
                    break
                elif i == timeout - 1:
                    raise EmailNotFound("Target message %s could not be found "
                                        "on server at %s within %ss"
                                        % (expected_email, path, timeout))
                time.sleep(1)
        log.debug("%s mails extracted at %s.", len(email_paths), path)
        return email_paths

    def _find_message_with_id(self, message_id, message_paths):
        """Find message with id among a list of message paths."""
        log.debug("Looking for a match for the message with id %s", message_id)
        for message_path in message_paths:
            extracted_id = self._extract_message_id(message_path)
            log.debug("Extracted id %s from candidate %s", extracted_id,
                      message_path)
            if message_id == extracted_id:
                log.debug("Found match at %s", message_path)
                return message_path
        raise MismatchedEmailID("The message with id %s could not be matched "
                                "or wasn't expected among %s"
                                % (message_id, ", ".join(message_paths)))

    def _extract_message_id(self, message_path):
        """
        Given a message file path extract the Message-ID.

        :raises: :py:class:`MissingEmailID` if no Message-ID was found.
        """
        message_id = ""
        with open(message_path, errors='ignore') as file_handle:
            content = file_handle.read()
        for line in content.split("\n"):
            match_id = re.match("Autotest-Message-ID: (.+)", line)
            if match_id is not None:
                message_id = match_id.group(1).rstrip('\r\n')
        if message_id == "":
            raise MissingEmailID(f"No id was found in target message {message_path}, "
                                 f"so it cannot be properly matched")
        return message_id

    def _default_compare_emails(self, source_email_path, target_email_path,
                                tolerance=1):
        """
        Compare target emails with source ones.

        Uses python provided diff functionality to compare complete mail files.
        """
        with open(source_email_path, "r") as source_email_file:
            source_email = source_email_file.read()
        with open(target_email_path, "r") as target_email_file:
            target_email = target_email_file.read()
        matcher = difflib.SequenceMatcher(None, source_email, target_email)
        diffratio = matcher.ratio()
        log.debug("Target message comparison ratio is %s.", diffratio)
        # log.info("%s $$$ %s", source_email, target_email)
        if diffratio < tolerance:
            raise EmailMismatch("Target message is too different from the "
                                "source (difference %s < tolerance %s).",
                                diffratio, tolerance)

    def _compare_emails_by_basic_headers(self, source_email_path,
                                         target_email_path, tolerance=1):
        """
        Compare target emails with source ones.

        Uses python provided diff functionality to compare headers and mail
        "body".

        Argument `tolerance` not used!
        """
        with open(source_email_path, errors="ignore") as file_handle:
            source_email = Parser().parse(file_handle)
            source_body = ""
            for part in source_email.walk():
                if part.get_content_type() in ["text/plain", "text/html"]:
                    source_body = part.get_payload()
                    break

        with open(target_email_path, errors="ignore") as file_handle:
            target_email = Parser().parse(file_handle)
            target_body = ""
            for part in target_email.walk():
                if part.get_content_type() in ["text/plain", "text/html"]:
                    target_body = part.get_payload()
                    break

        if source_email['From'] != target_email['From']:
            raise EmailMismatch("Target message sender %s is too different "
                                "from the source one %s" %
                                (target_email['From'], source_email['From']))
        if source_email['To'] != target_email['To']:
            raise EmailMismatch("Target message recipient %s is too different "
                                "from the source one %s" %
                                (target_email['To'], source_email['To']))
        if source_email['Subject'] != target_email['Subject']:
            raise EmailMismatch("Target message subject '%s' is too different "
                                "from the source one '%s'" %
                                (target_email['Subject'],
                                 source_email['Subject']))
        if source_email['Date'] != target_email['Date']:
            raise EmailMismatch("Target message date %s is too different from "
                                "the source one %s" %
                                (target_email['Date'], source_email['Date']))
        if source_body != target_body:
            raise EmailMismatch("Target message body '%s' is too different "
                                "from the source one '%s'" %
                                (target_body, source_body))

    def _compare_emails_by_existence(self, source_email_path,
                                     target_email_path, tolerance=1):
        """
        Weak email validation based only on presence of file.

        DOES NOT CHECK ANYTHING!
        """
        return True