import base64
import mimetypes
from base64 import b64encode
from collections import Mapping, MutableMapping
from datetime import datetime
from email.mime.base import MIMEBase
from email.utils import formatdate, getaddresses, unquote
from time import mktime

import six
from django.conf import settings
from django.core.mail.message import sanitize_address, DEFAULT_ATTACHMENT_MIME_TYPE
from django.utils.encoding import force_text
from django.utils.functional import Promise
from django.utils.timezone import utc, get_fixed_timezone
from six.moves.urllib.parse import urlsplit, urlunsplit

from .exceptions import AnymailConfigurationError, AnymailInvalidAddress


BASIC_NUMERIC_TYPES = six.integer_types + (float,)  # int, float, and (on Python 2) long


UNSET = object()  # Used as non-None default value


def combine(*args):
    """
    Combines all non-UNSET args, by shallow merging mappings and concatenating sequences

    >>> combine({'a': 1, 'b': 2}, UNSET, {'b': 3, 'c': 4}, UNSET)
    {'a': 1, 'b': 3, 'c': 4}
    >>> combine([1, 2], UNSET, [3, 4], UNSET)
    [1, 2, 3, 4]
    >>> combine({'a': 1}, None, {'b': 2})  # None suppresses earlier args
    {'b': 2}
    >>> combine()
    UNSET

    """
    result = UNSET
    for value in args:
        if value is None:
            # None is a request to suppress any earlier values
            result = UNSET
        elif value is not UNSET:
            if result is UNSET:
                try:
                    result = value.copy()  # will shallow merge if dict-like
                except AttributeError:
                    result = value  # will concatenate if sequence-like
            else:
                try:
                    result.update(value)  # shallow merge if dict-like
                except AttributeError:
                    result = result + value  # concatenate if sequence-like
    return result


def last(*args):
    """Returns the last of its args which is not UNSET.

    (Essentially `combine` without the merge behavior)

    >>> last(1, 2, UNSET, 3, UNSET, UNSET)
    3
    >>> last(1, 2, None, UNSET)  # None suppresses earlier args
    UNSET
    >>> last()
    UNSET

    """
    for value in reversed(args):
        if value is None:
            # None is a request to suppress any earlier values
            return UNSET
        elif value is not UNSET:
            return value
    return UNSET


def getfirst(dct, keys, default=UNSET):
    """Returns the value of the first of keys found in dict dct.

    >>> getfirst({'a': 1, 'b': 2}, ['c', 'a'])
    1
    >>> getfirst({'a': 1, 'b': 2}, ['b', 'a'])
    2
    >>> getfirst({'a': 1, 'b': 2}, ['c'])
    KeyError
    >>> getfirst({'a': 1, 'b': 2}, ['c'], None)
    None
    """
    for key in keys:
        try:
            return dct[key]
        except KeyError:
            pass
    if default is UNSET:
        raise KeyError("None of %s found in dict" % ', '.join(keys))
    else:
        return default


def update_deep(dct, other):
    """Merge (recursively) keys and values from dict other into dict dct

    Works with dict-like objects: dct (and descendants) can be any MutableMapping,
    and other can be any Mapping
    """
    for key, value in other.items():
        if key in dct and isinstance(dct[key], MutableMapping) and isinstance(value, Mapping):
            update_deep(dct[key], value)
        else:
            dct[key] = value
    # (like dict.update(), no return value)


def parse_address_list(address_list, field=None):
    """Returns a list of EmailAddress objects from strings in address_list.

    Essentially wraps :func:`email.utils.getaddresses` with better error
    messaging and more-useful output objects

    Note that the returned list might be longer than the address_list param,
    if any individual string contains multiple comma-separated addresses.

    :param list[str]|str|None|list[None] address_list:
        the address or addresses to parse
    :param str|None field:
        optional description of the source of these addresses, for error message
    :return list[:class:`EmailAddress`]:
    :raises :exc:`AnymailInvalidAddress`:
    """
    if isinstance(address_list, six.string_types) or is_lazy(address_list):
        address_list = [address_list]

    if address_list is None or address_list == [None]:
        return []

    # For consistency with Django's SMTP backend behavior, extract all addresses
    # from the list -- which may split comma-seperated strings into multiple addresses.
    # (See django.core.mail.message: EmailMessage.message to/cc/bcc/reply_to handling;
    # also logic for ADDRESS_HEADERS in forbid_multi_line_headers.)
    address_list_strings = [force_text(address) for address in address_list]  # resolve lazy strings
    name_email_pairs = getaddresses(address_list_strings)
    if name_email_pairs == [] and address_list_strings == [""]:
        name_email_pairs = [('', '')]  # getaddresses ignores a single empty string
    parsed = [EmailAddress(display_name=name, addr_spec=email)
              for (name, email) in name_email_pairs]

    # Sanity-check, and raise useful errors
    for address in parsed:
        if address.username == '' or address.domain == '':
            # Django SMTP allows username-only emails, but they're not meaningful with an ESP
            errmsg = "Invalid email address '{problem}' parsed from '{source}'{where}.".format(
                problem=address.addr_spec,
                source=", ".join(address_list_strings),
                where=" in `%s`" % field if field else "",
            )
            if len(parsed) > len(address_list):
                errmsg += " (Maybe missing quotes around a display-name?)"
            raise AnymailInvalidAddress(errmsg)

    return parsed


def parse_single_address(address, field=None):
    """Parses a single EmailAddress from str address, or raises AnymailInvalidAddress

    :param str address: the fully-formatted email str to parse
    :param str|None field: optional description of the source of this address, for error message
    :return :class:`EmailAddress`: if address contains a single email
    :raises :exc:`AnymailInvalidAddress`: if address contains no or multiple emails
    """
    parsed = parse_address_list([address], field=field)
    count = len(parsed)
    if count > 1:
        raise AnymailInvalidAddress(
            "Only one email address is allowed; found {count} in '{address}'{where}.".format(
                count=count, address=address, where=" in `%s`" % field if field else ""))
    else:
        return parsed[0]


class EmailAddress(object):
    """A sanitized, complete email address with easy access
    to display-name, addr-spec (email), etc.

    Similar to Python 3.6+ email.headerregistry.Address

    Instance properties, all read-only:
    :ivar str display_name:
        the address's display-name portion (unqouted, unescaped),
        e.g., 'Display Name, Inc.'
    :ivar str addr_spec:
        the address's addr-spec portion (unquoted, unescaped),
        e.g., 'user@example.com'
    :ivar str username:
        the local part (before the '@') of the addr-spec,
        e.g., 'user'
    :ivar str domain:
        the domain part (after the '@') of the addr-spec,
        e.g., 'example.com'

    :ivar str address:
        the fully-formatted address, with any necessary quoting and escaping,
        e.g., '"Display Name, Inc." <user@example.com>'
        (also available as `str(EmailAddress)`)
    """

    def __init__(self, display_name='', addr_spec=None):
        self._address = None  # lazy formatted address
        if addr_spec is None:
            try:
                display_name, addr_spec = display_name  # unpack (name,addr) tuple
            except ValueError:
                pass
        self.display_name = display_name
        self.addr_spec = addr_spec
        try:
            self.username, self.domain = addr_spec.split("@", 1)
            # do we need to unquote username?
        except ValueError:
            self.username = addr_spec
            self.domain = ''

    @property
    def address(self):
        if self._address is None:
            # (you might be tempted to use `encoding=settings.DEFAULT_CHARSET` here,
            # but that always forces the display-name to quoted-printable/base64,
            # even when simple ascii would work fine--and be more readable)
            self._address = self.formataddr()
        return self._address

    def formataddr(self, encoding=None):
        """Return a fully-formatted email address, using encoding.

        This is essentially the same as :func:`email.utils.formataddr`
        on the EmailAddress's name and email properties, but uses
        Django's :func:`~django.core.mail.message.sanitize_address`
        for improved PY2/3 compatibility, consistent handling of
        encoding (a.k.a. charset), and proper handling of IDN
        domain portions.

        :param str|None encoding:
            the charset to use for the display-name portion;
            default None uses ascii if possible, else 'utf-8'
            (quoted-printable utf-8/base64)
        """
        return sanitize_address((self.display_name, self.addr_spec), encoding)

    def __str__(self):
        return self.address


class Attachment(object):
    """A normalized EmailMessage.attachments item with additional functionality

    Normalized to have these properties:
    name: attachment filename; may be None
    content: bytestream
    mimetype: the content type; guessed if not explicit
    inline: bool, True if attachment has a Content-ID header
    content_id: for inline, the Content-ID (*with* <>); may be None
    cid: for inline, the Content-ID *without* <>; may be empty string
    """

    def __init__(self, attachment, encoding):
        # Note that an attachment can be either a tuple of (filename, content, mimetype)
        # or a MIMEBase object. (Also, both filename and mimetype may be missing.)
        self._attachment = attachment
        self.encoding = encoding  # should we be checking attachment["Content-Encoding"] ???
        self.inline = False
        self.content_id = None
        self.cid = ""

        if isinstance(attachment, MIMEBase):
            self.name = attachment.get_filename()
            self.content = attachment.get_payload(decode=True)
            if self.content is None:
                if hasattr(attachment, 'as_bytes'):
                    self.content = attachment.as_bytes()
                else:
                    # Python 2.7 fallback
                    self.content = attachment.as_string().encode(self.encoding)
            self.mimetype = attachment.get_content_type()

            if get_content_disposition(attachment) == 'inline':
                self.inline = True
                self.content_id = attachment["Content-ID"]  # probably including the <...>
                if self.content_id is not None:
                    self.cid = unquote(self.content_id)  # without the <, >
        else:
            (self.name, self.content, self.mimetype) = attachment

        self.name = force_non_lazy(self.name)
        self.content = force_non_lazy(self.content)

        # Guess missing mimetype from filename, borrowed from
        # django.core.mail.EmailMessage._create_attachment()
        if self.mimetype is None and self.name is not None:
            self.mimetype, _ = mimetypes.guess_type(self.name)
        if self.mimetype is None:
            self.mimetype = DEFAULT_ATTACHMENT_MIME_TYPE

    @property
    def b64content(self):
        """Content encoded as a base64 ascii string"""
        content = self.content
        if isinstance(content, six.text_type):
            content = content.encode(self.encoding)
        return b64encode(content).decode("ascii")


def get_content_disposition(mimeobj):
    """Return the message's content-disposition if it exists, or None.

    Backport of py3.5 :func:`~email.message.Message.get_content_disposition`
    """
    value = mimeobj.get('content-disposition')
    if value is None:
        return None
    # _splitparam(value)[0].lower() :
    return str(value).partition(';')[0].strip().lower()


def get_anymail_setting(name, default=UNSET, esp_name=None, kwargs=None, allow_bare=False):
    """Returns an Anymail option from kwargs or Django settings.

    Returns first of:
    - kwargs[name] -- e.g., kwargs['api_key'] -- and name key will be popped from kwargs
    - settings.ANYMAIL['<ESP_NAME>_<NAME>'] -- e.g., settings.ANYMAIL['MAILGUN_API_KEY']
    - settings.ANYMAIL_<ESP_NAME>_<NAME> -- e.g., settings.ANYMAIL_MAILGUN_API_KEY
    - settings.<ESP_NAME>_<NAME> (only if allow_bare) -- e.g., settings.MAILGUN_API_KEY
    - default if provided; else raises AnymailConfigurationError

    If allow_bare, allows settings.<ESP_NAME>_<NAME> without the ANYMAIL_ prefix:
    ANYMAIL = { "MAILGUN_API_KEY": "xyz", ... }
    ANYMAIL_MAILGUN_API_KEY = "xyz"
    MAILGUN_API_KEY = "xyz"
    """

    try:
        value = kwargs.pop(name)
        if name in ['username', 'password']:
            # Work around a problem in django.core.mail.send_mail, which calls
            # get_connection(... username=None, password=None) by default.
            # We need to ignore those None defaults (else settings like
            # 'SENDGRID_USERNAME' get unintentionally overridden from kwargs).
            if value is not None:
                return value
        else:
            return value
    except (AttributeError, KeyError):
        pass

    if esp_name is not None:
        setting = "{}_{}".format(esp_name.upper().replace(" ", "_"), name.upper())
    else:
        setting = name.upper()
    anymail_setting = "ANYMAIL_%s" % setting

    try:
        return settings.ANYMAIL[setting]
    except (AttributeError, KeyError):
        try:
            return getattr(settings, anymail_setting)
        except AttributeError:
            if allow_bare:
                try:
                    return getattr(settings, setting)
                except AttributeError:
                    pass
            if default is UNSET:
                message = "You must set %s or ANYMAIL = {'%s': ...}" % (anymail_setting, setting)
                if allow_bare:
                    message += " or %s" % setting
                message += " in your Django settings"
                raise AnymailConfigurationError(message)
            else:
                return default


def collect_all_methods(cls, method_name):
    """Return list of all `method_name` methods for cls and its superclass chain.

    List is in MRO order, with no duplicates. Methods are unbound.

    (This is used to simplify mixins and subclasses that contribute to a method set,
    without requiring superclass chaining, and without requiring cooperating
    superclasses.)
    """
    methods = []
    for ancestor in cls.__mro__:
        try:
            validator = getattr(ancestor, method_name)
        except AttributeError:
            pass
        else:
            if validator not in methods:
                methods.append(validator)
    return methods


def querydict_getfirst(qdict, field, default=UNSET):
    """Like :func:`django.http.QueryDict.get`, but returns *first* value of multi-valued field.

    >>> from django.http import QueryDict
    >>> q = QueryDict('a=1&a=2&a=3')
    >>> querydict_getfirst(q, 'a')
    '1'
    >>> q.get('a')
    '3'
    >>> q['a']
    '3'

    You can bind this to a QueryDict instance using the "descriptor protocol":
    >>> q.getfirst = querydict_getfirst.__get__(q)
    >>> q.getfirst('a')
    '1'
    """
    # (Why not instead define a QueryDict subclass with this method? Because there's no simple way
    # to efficiently initialize a QueryDict subclass with the contents of an existing instance.)
    values = qdict.getlist(field)
    if len(values) > 0:
        return values[0]
    elif default is not UNSET:
        return default
    else:
        return qdict[field]  # raise appropriate KeyError


EPOCH = datetime(1970, 1, 1, tzinfo=utc)


def timestamp(dt):
    """Return the unix timestamp (seconds past the epoch) for datetime dt"""
    # This is the equivalent of Python 3.3's datetime.timestamp
    try:
        return dt.timestamp()
    except AttributeError:
        if dt.tzinfo is None:
            return mktime(dt.timetuple())
        else:
            return (dt - EPOCH).total_seconds()


def rfc2822date(dt):
    """Turn a datetime into a date string as specified in RFC 2822."""
    # This is almost the equivalent of Python 3.3's email.utils.format_datetime,
    # but treats naive datetimes as local rather than "UTC with no information ..."
    timeval = timestamp(dt)
    return formatdate(timeval, usegmt=True)


def angle_wrap(s):
    """Return s surrounded by angle brackets, added only if necessary"""
    # This is the inverse behavior of email.utils.unquote
    # (which you might think email.utils.quote would do, but it doesn't)
    if len(s) > 0:
        if s[0] != '<':
            s = '<' + s
        if s[-1] != '>':
            s = s + '>'
    return s


def is_lazy(obj):
    """Return True if obj is a Django lazy object."""
    # See django.utils.functional.lazy. (This appears to be preferred
    # to checking for `not isinstance(obj, six.text_type)`.)
    return isinstance(obj, Promise)


def force_non_lazy(obj):
    """If obj is a Django lazy object, return it coerced to text; otherwise return it unchanged.

    (Similar to django.utils.encoding.force_text, but doesn't alter non-text objects.)
    """
    if is_lazy(obj):
        return six.text_type(obj)

    return obj


def force_non_lazy_list(obj):
    """Return a (shallow) copy of sequence obj, with all values forced non-lazy."""
    try:
        return [force_non_lazy(item) for item in obj]
    except (AttributeError, TypeError):
        return force_non_lazy(obj)


def force_non_lazy_dict(obj):
    """Return a (deep) copy of dict obj, with all values forced non-lazy."""
    try:
        return {key: force_non_lazy_dict(value) for key, value in obj.items()}
    except (AttributeError, TypeError):
        return force_non_lazy(obj)


def get_request_basic_auth(request):
    """Returns HTTP basic auth string sent with request, or None.

    If request includes basic auth, result is string 'username:password'.
    """
    try:
        authtype, authdata = request.META['HTTP_AUTHORIZATION'].split()
        if authtype.lower() == "basic":
            return base64.b64decode(authdata).decode('utf-8')
    except (IndexError, KeyError, TypeError, ValueError):
        pass
    return None


def get_request_uri(request):
    """Returns the "exact" url used to call request.

    Like :func:`django.http.request.HTTPRequest.build_absolute_uri`,
    but also inlines HTTP basic auth, if present.
    """
    url = request.build_absolute_uri()
    basic_auth = get_request_basic_auth(request)
    if basic_auth is not None:
        # must reassemble url with auth
        parts = urlsplit(url)
        url = urlunsplit((parts.scheme, basic_auth + '@' + parts.netloc,
                          parts.path, parts.query, parts.fragment))
    return url


try:
    from email.utils import parsedate_to_datetime  # Python 3.3+
except ImportError:
    from email.utils import parsedate_tz

    # Backport Python 3.3+ email.utils.parsedate_to_datetime
    def parsedate_to_datetime(s):
        # *dtuple, tz = _parsedate_tz(data)
        dtuple = parsedate_tz(s)
        tz = dtuple[-1]
        # if tz is None:  # parsedate_tz returns 0 for "-0000"
        if tz is None or (tz == 0 and "-0000" in s):
            # "... indicates that the date-time contains no information
            # about the local time zone" (RFC 2822 #3.3)
            return datetime(*dtuple[:6])
        else:
            # tzinfo = datetime.timezone(datetime.timedelta(seconds=tz))  # Python 3.2+ only
            tzinfo = get_fixed_timezone(tz // 60)  # don't use timedelta (avoid Django bug #28739)
            return datetime(*dtuple[:6], tzinfo=tzinfo)


def parse_rfc2822date(s):
    """Parses an RFC-2822 formatted date string into a datetime.datetime

    Returns None if string isn't parseable. Returned datetime will be naive
    if string doesn't include known timezone offset; aware if it does.

    (Same as Python 3 email.utils.parsedate_to_datetime, with improved
    handling for unparseable date strings.)
    """
    try:
        return parsedate_to_datetime(s)
    except (IndexError, TypeError, ValueError):
        # despite the docs, parsedate_to_datetime often dies on unparseable input
        return None