import sys
try:
    from hashlib import sha1
except ImportError:
    sys.exit('ImportError: no module named hashlib\nIf you are on python2.4 this library is not part of python. Please install it. Example: easy_install hashlib')
import os
from datetime import datetime

from sqlalchemy import Table, ForeignKey, Column
from sqlalchemy.types import String, Unicode, UnicodeText, Integer, DateTime, \
                             Boolean, Float
from sqlalchemy.orm import relation, backref, synonym

from sipbmp3web.model import DeclarativeBase, metadata, DBSession


# This is the association table for the many-to-many relationship between
# groups and permissions.
group_permission_table = Table('tg_group_permission', metadata,
    Column('group_id', Integer, ForeignKey('tg_group.group_id',
        onupdate="CASCADE", ondelete="CASCADE")),
    Column('permission_id', Integer, ForeignKey('tg_permission.permission_id',
        onupdate="CASCADE", ondelete="CASCADE"))
)

# This is the association table for the many-to-many relationship between
# groups and members - this is, the memberships.
user_group_table = Table('tg_user_group', metadata,
    Column('user_id', Integer, ForeignKey('tg_user.user_id',
        onupdate="CASCADE", ondelete="CASCADE")),
    Column('group_id', Integer, ForeignKey('tg_group.group_id',
        onupdate="CASCADE", ondelete="CASCADE"))
)

# auth model

class Group(DeclarativeBase):
    """An ultra-simple group definition.
    """
    __tablename__ = 'tg_group'

    group_id = Column(Integer, autoincrement=True, primary_key=True)
    group_name = Column(Unicode(16), unique=True, nullable=False)
    display_name = Column(Unicode(255))
    created = Column(DateTime, default=datetime.now)
    users = relation('User', secondary=user_group_table, backref='groups')

    def __repr__(self):
        return '<Group: name=%s>' % self.group_name

    def __unicode__(self):
        return self.group_name

#
# The 'info' argument we're passing to the email_address and password columns
# contain metadata that Rum (http://python-rum.org/) can use generate an
# admin interface for your models.
#
class User(DeclarativeBase):
    """Reasonably basic User definition. Probably would want additional
    attributes.
    """
    __tablename__ = 'tg_user'

    user_id = Column(Integer, autoincrement=True, primary_key=True)
    user_name = Column(Unicode(16), unique=True, nullable=False)
    email_address = Column(Unicode(255), unique=True, nullable=False,
                           info={'rum': {'field':'Email'}})
    display_name = Column(Unicode(255))
    _password = Column('password', Unicode(80),
                       info={'rum': {'field':'Password'}})
    created = Column(DateTime, default=datetime.now)

    def __repr__(self):
        return '<User: email="%s", display name="%s">' % (
                self.email_address, self.display_name)

    def __unicode__(self):
        return self.display_name or self.user_name

    @property
    def permissions(self):
        perms = set()
        for g in self.groups:
            perms = perms | set(g.permissions)
        return perms

    @classmethod
    def by_email_address(cls, email):
        """A class method that can be used to search users
        based on their email addresses since it is unique.
        """
        return DBSession.query(cls).filter(cls.email_address==email).first()

    @classmethod
    def by_user_name(cls, username):
        """A class method that permits to search users
        based on their user_name attribute.
        """
        return DBSession.query(cls).filter(cls.user_name==username).first()


    def _set_password(self, password):
        """Hash password on the fly."""
        hashed_password = password

        if isinstance(password, unicode):
            password_8bit = password.encode('UTF-8')
        else:
            password_8bit = password
        
        salt = sha1()
        salt.update(os.urandom(60))
        hash = sha1()
        hash.update(password_8bit + salt.hexdigest())
        hashed_password = salt.hexdigest() + hash.hexdigest()

        # make sure the hased password is an UTF-8 object at the end of the
        # process because SQLAlchemy _wants_ a unicode object for Unicode columns
        if not isinstance(hashed_password, unicode):
            hashed_password = hashed_password.decode('UTF-8')

        self._password = hashed_password

    def _get_password(self):
        """returns password
        """
        return self._password

    password = synonym('_password', descriptor=property(_get_password,
                                                        _set_password))

    def validate_password(self, password):
        """Check the password against existing credentials.

        :param password: the password that was provided by the user to
            try and authenticate. This is the clear text version that we will
            need to match against the hashed one in the database.
        :type password: unicode object.
        :return: Whether the password is valid.
        :rtype: bool
        
        """
        hashed_pass = sha1()
        hashed_pass.update(password + self.password[:40])
        return self.password[40:] == hashed_pass.hexdigest()


class Permission(DeclarativeBase):
    """A relationship that determines what each Group can do
    """
    __tablename__ = 'tg_permission'

    permission_id = Column(Integer, autoincrement=True, primary_key=True)
    permission_name = Column(Unicode(16), unique=True, nullable=False)
    description = Column(Unicode(255))
    groups = relation(Group, secondary=group_permission_table,
                      backref='permissions')

    def __unicode__(self):
        return self.permission_name