from mailu import app, db, dkim, login_manager

from sqlalchemy.ext import declarative
from passlib import context, hash
from datetime import datetime, date
from email.mime import text

import sqlalchemy
import re
import time
import os
import glob
import smtplib
import idna
import dns


class IdnaDomain(db.TypeDecorator):
    """ Stores a Unicode string in it's IDNA representation (ASCII only)
    """

    impl = db.String(80)

    def process_bind_param(self, value, dialect):
        return idna.encode(value).decode("ascii")

    def process_result_value(self, value, dialect):
        return idna.decode(value)


class IdnaEmail(db.TypeDecorator):
    """ Stores a Unicode string in it's IDNA representation (ASCII only)
    """

    impl = db.String(255, collation="NOCASE")

    def process_bind_param(self, value, dialect):
        localpart, domain_name = value.split('@')
        return "{0}@{1}".format(
            localpart,
            idna.encode(domain_name).decode('ascii'),
        )

    def process_result_value(self, value, dialect):
        localpart, domain_name = value.split('@')
        return "{0}@{1}".format(
            localpart,
            idna.decode(domain_name),
        )


class CommaSeparatedList(db.TypeDecorator):
    """ Stores a list as a comma-separated string, compatible with Postfix.
    """

    impl = db.String

    def process_bind_param(self, value, dialect):
        if type(value) is not list:
            raise TypeError("Shoud be a list")
        for item in value:
            if "," in item:
                raise ValueError("No item should contain a comma")
        return ",".join(value)

    def process_result_value(self, value, dialect):
        return filter(bool, value.split(","))


# Many-to-many association table for domain managers
managers = db.Table('manager',
    db.Column('domain_name', IdnaDomain, db.ForeignKey('domain.name')),
    db.Column('user_email', IdnaEmail, db.ForeignKey('user.email'))
)


class Base(db.Model):
    """ Base class for all models
    """

    __abstract__ = True

    created_at = db.Column(db.Date, nullable=False, default=datetime.now)
    updated_at = db.Column(db.Date, nullable=True, onupdate=datetime.now)
    comment = db.Column(db.String(255), nullable=True)


class Domain(Base):
    """ A DNS domain that has mail addresses associated to it.
    """
    __tablename__ = "domain"

    name = db.Column(IdnaDomain, primary_key=True, nullable=False)
    managers = db.relationship('User', secondary=managers,
        backref=db.backref('manager_of'), lazy='dynamic')
    max_users = db.Column(db.Integer, nullable=False, default=0)
    max_aliases = db.Column(db.Integer, nullable=False, default=0)
    max_quota_bytes = db.Column(db.Integer(), nullable=False, default=0)
    signup_enabled = db.Column(db.Boolean(), nullable=False, default=False)

    @property
    def dkim_key(self):
        file_path = app.config["DKIM_PATH"].format(
            domain=self.name, selector=app.config["DKIM_SELECTOR"])
        if os.path.exists(file_path):
            with open(file_path, "rb") as handle:
                return handle.read()

    @dkim_key.setter
    def dkim_key(self, value):
        file_path = app.config["DKIM_PATH"].format(
            domain=self.name, selector=app.config["DKIM_SELECTOR"])
        with open(file_path, "wb") as handle:
            handle.write(value)

    @property
    def dkim_publickey(self):
        dkim_key = self.dkim_key
        if dkim_key:
            return dkim.strip_key(self.dkim_key).decode("utf8")

    def generate_dkim_key(self):
        self.dkim_key = dkim.gen_key()

    def has_email(self, localpart):
        for email in self.users + self.aliases:
            if email.localpart == localpart:
                return True
        else:
            return False

    def check_mx(self):
        try:
            hostnames = app.config['HOSTNAMES'].split(',')
            return any(
                str(rset).split()[-1][:-1] in hostnames
                for rset in dns.resolver.query(self.name, 'MX')
            )
        except Exception as e:
            return False

    def __str__(self):
        return self.name

    def __eq__(self, other):
        try:
            return self.name == other.name
        except AttributeError:
            return False


class Alternative(Base):
    """ Alternative name for a served domain.
    The name "domain alias" was avoided to prevent some confusion.
    """

    __tablename__ = "alternative"

    name = db.Column(IdnaDomain, primary_key=True, nullable=False)
    domain_name = db.Column(IdnaDomain, db.ForeignKey(Domain.name))
    domain = db.relationship(Domain,
        backref=db.backref('alternatives', cascade='all, delete-orphan'))

    def __str__(self):
        return self.name


class Relay(Base):
    """ Relayed mail domain.
    The domain is either relayed publicly or through a specified SMTP host.
    """

    __tablename__ = "relay"

    name = db.Column(db.String(80), primary_key=True, nullable=False)
    smtp = db.Column(db.String(80), nullable=True)

    def __str__(self):
        return self.name


class Email(object):
    """ Abstraction for an email address (localpart and domain).
    """

    localpart = db.Column(db.String(80), nullable=False)

    @declarative.declared_attr
    def domain_name(cls):
        return db.Column(IdnaDomain, db.ForeignKey(Domain.name),
            nullable=False, default=IdnaDomain)

    # This field is redundant with both localpart and domain name.
    # It is however very useful for quick lookups without joining tables,
    # especially when the mail server is reading the database.
    @declarative.declared_attr
    def email(cls):
        updater = lambda context: "{0}@{1}".format(
            context.current_parameters["localpart"],
            context.current_parameters["domain_name"],
        )
        return db.Column(IdnaEmail,
            primary_key=True, nullable=False,
            default=updater)

    def sendmail(self, subject, body):
        """ Send an email to the address.
        """
        from_address = "{0}@{1}".format(
            app.config['POSTMASTER'],
            idna.encode(app.config['DOMAIN']).decode('ascii'),
        )
        with smtplib.SMTP(app.config['HOST_AUTHSMTP'], port=10025) as smtp:
            to_address = "{0}@{1}".format(
                self.localpart,
                idna.encode(self.domain_name).decode('ascii'),
            )
            msg = text.MIMEText(body)
            msg['Subject'] = subject
            msg['From'] = from_address
            msg['To'] = to_address
            smtp.sendmail(from_address, [to_address], msg.as_string())


    def __str__(self):
        return self.email


class User(Base, Email):
    """ A user is an email address that has a password to access a mailbox.
    """
    __tablename__ = "user"

    domain = db.relationship(Domain,
        backref=db.backref('users', cascade='all, delete-orphan'))
    password = db.Column(db.String(255), nullable=False)
    quota_bytes = db.Column(db.Integer(), nullable=False, default=10**9)
    quota_bytes_used = db.Column(db.Integer(), nullable=False, default=0)
    global_admin = db.Column(db.Boolean(), nullable=False, default=False)
    enabled = db.Column(db.Boolean(), nullable=False, default=True)

    # Features
    enable_imap = db.Column(db.Boolean(), nullable=False, default=True)
    enable_pop = db.Column(db.Boolean(), nullable=False, default=True)

    # Filters
    forward_enabled = db.Column(db.Boolean(), nullable=False, default=False)
    forward_destination = db.Column(db.String(255), nullable=True, default=None)
    forward_keep = db.Column(db.Boolean(), nullable=False, default=True)
    reply_enabled = db.Column(db.Boolean(), nullable=False, default=False)
    reply_subject = db.Column(db.String(255), nullable=True, default=None)
    reply_body = db.Column(db.Text(), nullable=True, default=None)
    reply_startdate = db.Column(db.Date, nullable=False,
        default=date(1900, 1, 1))
    reply_enddate = db.Column(db.Date, nullable=False,
        default=date(2999, 12, 31))

    # Settings
    displayed_name = db.Column(db.String(160), nullable=False, default="")
    spam_enabled = db.Column(db.Boolean(), nullable=False, default=True)
    spam_threshold = db.Column(db.Integer(), nullable=False, default=80.0)

    # Flask-login attributes
    is_authenticated = True
    is_active = True
    is_anonymous = False

    def get_id(self):
        return self.email

    @property
    def destination(self):
        if self.forward_enabled:
            result = self.self.forward_destination
            if self.forward_keep:
                result += ',' + self.email
            return result
        else:
            return self.email

    @property
    def reply_active(self):
        now = datetime.datetime.now()
        return (
            self.reply_enabled and
            self.reply_startdate < now and
            self.reply_enddate > now
        )

    scheme_dict = {'SHA512-CRYPT': "sha512_crypt",
                   'SHA256-CRYPT': "sha256_crypt",
                   'MD5-CRYPT': "md5_crypt",
                   'CRYPT': "des_crypt"}
    pw_context = context.CryptContext(
        schemes = scheme_dict.values(),
        default=scheme_dict[app.config['PASSWORD_SCHEME']],
    )

    def check_password(self, password):
        reference = re.match('({[^}]+})?(.*)', self.password).group(2)
        return User.pw_context.verify(password, reference)

    def set_password(self, password, hash_scheme=app.config['PASSWORD_SCHEME'], raw=False):
        """Set password for user with specified encryption scheme
           @password: plain text password to encrypt (if raw == True the hash itself)
        """
        # for the list of hash schemes see https://wiki2.dovecot.org/Authentication/PasswordSchemes
        if raw:
            self.password = '{'+hash_scheme+'}' + password
        else:
            self.password = '{'+hash_scheme+'}' + User.pw_context.encrypt(password, self.scheme_dict[hash_scheme])

    def get_managed_domains(self):
        if self.global_admin:
            return Domain.query.all()
        else:
            return self.manager_of

    def get_managed_emails(self, include_aliases=True):
        emails = []
        for domain in self.get_managed_domains():
            emails.extend(domain.users)
            if include_aliases:
                emails.extend(domain.aliases)
        return emails

    def send_welcome(self):
        if app.config["WELCOME"].lower() == "true":
            self.sendmail(app.config["WELCOME_SUBJECT"],
                app.config["WELCOME_BODY"])

    @classmethod
    def login(cls, email, password):
        user = cls.query.get(email)
        return user if (user and user.enabled and user.check_password(password)) else None

login_manager.user_loader(User.query.get)


class Alias(Base, Email):
    """ An alias is an email address that redirects to some destination.
    """
    __tablename__ = "alias"

    domain = db.relationship(Domain,
        backref=db.backref('aliases', cascade='all, delete-orphan'))
    wildcard = db.Column(db.Boolean(), nullable=False, default=False)
    destination = db.Column(CommaSeparatedList, nullable=False, default=[])

    @classmethod
    def resolve(cls, localpart, domain_name):
        return cls.query.filter(
            sqlalchemy.and_(cls.domain_name == domain_name,
                sqlalchemy.or_(
                    sqlalchemy.and_(
                        cls.wildcard == False,
                        cls.localpart == localpart
                    ), sqlalchemy.and_(
                        cls.wildcard == True,
                        sqlalchemy.bindparam("l", localpart).like(cls.localpart)
                    )
                )
            )
        ).first()


class Token(Base):
    """ A token is an application password for a given user.
    """
    __tablename__ = "token"

    id = db.Column(db.Integer(), primary_key=True)
    user_email = db.Column(db.String(255), db.ForeignKey(User.email),
        nullable=False)
    user = db.relationship(User,
        backref=db.backref('tokens', cascade='all, delete-orphan'))
    password = db.Column(db.String(255), nullable=False)
    ip = db.Column(db.String(255))

    def check_password(self, password):
        return hash.sha256_crypt.verify(password, self.password)

    def set_password(self, password):
        self.password = hash.sha256_crypt.using(rounds=1000).hash(password)

    def __str__(self):
        return self.comment


class Fetch(Base):
    """ A fetched account is a repote POP/IMAP account fetched into a local
    account.
    """
    __tablename__ = "fetch"

    id = db.Column(db.Integer(), primary_key=True)
    user_email = db.Column(db.String(255), db.ForeignKey(User.email),
        nullable=False)
    user = db.relationship(User,
        backref=db.backref('fetches', cascade='all, delete-orphan'))
    protocol = db.Column(db.Enum('imap', 'pop3'), nullable=False)
    host = db.Column(db.String(255), nullable=False)
    port = db.Column(db.Integer(), nullable=False)
    tls = db.Column(db.Boolean(), nullable=False)
    username = db.Column(db.String(255), nullable=False)
    password = db.Column(db.String(255), nullable=False)
    keep = db.Column(db.Boolean(), nullable=False)
    last_check = db.Column(db.DateTime, nullable=True)
    error = db.Column(db.String(1023), nullable=True)