from flask_login import UserMixin
from sqlalchemy import MetaData
from sqlalchemy.ext.automap import automap_base
from sqlalchemy.orm import Session, backref, relationship
from werkzeug.security import generate_password_hash, check_password_hash


class ConfigModels():
    """ConfigModels class

    Provide SQLAlchemy ORM models for ConfigDB queries.
    """

    def __init__(self, db_engine, conn_str=None, extra_tables=[]):
        """Constructor

        :param DatabaseEngine db_engine: Database engine with DB connections
        """
        if conn_str:
            self.engine = db_engine.db_engine(conn_str)
        else:
            self.engine = db_engine.config_db()

        # init models
        self.base = None
        self.custom_models = {}
        self.init_models(extra_tables)

    def session(self):
        """Create a new session."""
        return Session(self.engine)

    def model(self, name):
        """Get SQLAlchemy model.

        :param str name: Table name of model
        """
        # get automap model or custom model
        if name == 'users':
            return self.user_model
        else:
            return self.base.classes.get(name) or self.custom_models.get(name)

    def init_models(self, extra_tables):
        """Setup SQLAlchemy ORM models."""

        # Generate required models from ConfigDB using automap
        TABLES = [
            'users', 'user_infos', 'groups', 'roles',
            'groups_users', 'users_roles', 'groups_roles',
            'resources', 'resource_types', 'permissions',
            'registrable_groups', 'registration_requests',
            'last_update'
        ] + extra_tables

        def table_selector(table_name, meta_data):
            return (table_name in TABLES)

        metadata = MetaData()
        metadata.reflect(self.engine, schema='qwc_config', only=table_selector)
        Base = automap_base(metadata=metadata)

        # setup user model for flask_login
        class User(UserMixin, Base):
            __tablename__ = 'users'
            __table_args__ = ({"schema": "qwc_config"})

            def set_password(self, password):
                self.password_hash = generate_password_hash(password)

            def check_password(self, password):
                return check_password_hash(self.password_hash, password)

        Base.prepare()

        self.base = Base
        self.user_model = User

        UserInfo = Base.classes.user_infos
        Group = Base.classes.groups
        Role = Base.classes.roles

        # single user info per user
        User.user_info = relationship(
            UserInfo,
            uselist=False,
            back_populates="user"
        )

        # sorted user groups
        User.sorted_groups = relationship(
            Group,
            secondary='qwc_config.groups_users',
            order_by=Group.name,
            # avoid duplicate group DELETE on User delete
            viewonly=True
        )
        # sorted user roles
        User.sorted_roles = relationship(
            Role,
            secondary='qwc_config.users_roles',
            order_by=Role.name,
            # avoid duplicate role DELETE on User delete
            viewonly=True
        )

        Group.users_collection = relationship(
            User,
            secondary='qwc_config.groups_users'
        )

        # sorted group users
        Group.sorted_users = relationship(
            User,
            secondary='qwc_config.groups_users',
            order_by=User.name,
            # avoid duplicate user DELETE on Group delete
            viewonly=True
        )
        # sorted group roles
        Group.sorted_roles = relationship(
            Role,
            secondary='qwc_config.groups_roles',
            order_by=Role.name,
            # avoid duplicate role DELETE on Group delete
            viewonly=True
        )

        Role.users_collection = relationship(
            User,
            secondary='qwc_config.users_roles'
        )

        # sorted role users
        Role.sorted_users = relationship(
            User,
            secondary='qwc_config.users_roles',
            order_by=User.name,
            # avoid duplicate user DELETE on Role delete
            viewonly=True
        )
        # sorted roles groups
        Role.sorted_groups = relationship(
            Group,
            secondary='qwc_config.groups_roles',
            order_by=Group.name,
            # avoid duplicate group DELETE on Role delete
            viewonly=True
        )

        # sorted resource children and parent
        Resource = Base.classes.resources
        Resource.children = relationship(
            Resource,
            foreign_keys=[Resource.parent_id],
            order_by=Resource.name,
            backref=backref('parent', remote_side=[Resource.id])
        )

        # resource type
        ResourceType = Base.classes.resource_types
        Resource.resource_type = relationship(
            ResourceType
        )

        # permission role and resource with singular attribute names
        Permission = Base.classes.permissions
        Permission.role = relationship(
            Role
        )
        Permission.resource = relationship(
            Resource
        )

        # group for registrable group with singular attribute name
        RegistrableGroup = Base.classes.registrable_groups
        RegistrableGroup.group = relationship(
            Group
        )

        # user and registrable group for registration request with
        # singular attribute names
        RegistrationRequest = Base.classes.registration_requests
        RegistrationRequest.user = relationship(
            User
        )
        RegistrationRequest.registrable_group = relationship(
            RegistrableGroup
        )

        # user registration requests
        User.registration_requests = relationship(
            RegistrationRequest,
            # destroy registration requests on user delete
            cascade="save-update, merge, delete"
        )
