from flask import current_app
from flask_login import UserMixin, AnonymousUserMixin
from itsdangerous import BadSignature, TimedJSONWebSignatureSerializer
from werkzeug.security import generate_password_hash, check_password_hash
from . import db
from . import login_manager
from datetime import datetime
import os
import shutil
import logging


class Permission:
    """
    Defines User permissions as integers by the power of 2. User permission
    can be evaluated using the bitwise operator &. 3 equals to CREATE_JOB and
    DELETE_JOB and so on.
    """
    CREATE_JOB = 1
    DELETE_JOB = 2
    # WRITE = 4
    # MODERATE = 8
    ADMIN = 16


class Role(db.Model):
    """
    Model for the different roles Users can have. Is a one-to-many
    relationship. A Role can be associated with many User rows.
    """
    __tablename__ = 'roles'
    # Primary key
    id = db.Column(db.Integer, primary_key=True)
    default = db.Column(db.Boolean, default=False, index=True)
    name = db.Column(db.String(64), unique=True)
    permissions = db.Column(db.Integer)
    # Relationships
    users = db.relationship('User', backref='role', lazy='dynamic')

    def __init__(self, **kwargs):
        super(Role, self).__init__(**kwargs)
        if self.permissions is None:
            self.permissions = 0

    def __repr__(self):
        """
        String representation of the Role. For human readability.
        """
        return '<Role %r>' % self.name

    def add_permission(self, perm):
        """
        Add new permission to Role. Input is a Permission.
        """
        if not self.has_permission(perm):
            self.permissions += perm

    def remove_permission(self, perm):
        """
        Removes permission from a Role. Input a Permission.
        """
        if self.has_permission(perm):
            self.permissions -= perm

    def reset_permissions(self):
        """
        Resets permissions to zero. Zero equals no permissions at all.
        """
        self.permissions = 0

    def has_permission(self, perm):
        """
        Checks if a Role has a specific Permission. Does this with the bitwise
        operator.
        """
        return self.permissions & perm == perm

    @staticmethod
    def insert_roles():
        """
        Inserts roles into the databes. This has to be executed befor Users are
        added to the database. Otherwiese Users will not have a Role assigned
        to them. Order of the roles dictionary determines the ID of each role.
        User hast the ID 1 and Administrator has the ID 2.
        """
        roles = {
                    'User': [Permission.CREATE_JOB],
                    'Administrator': [Permission.ADMIN,
                                      Permission.CREATE_JOB,
                                      Permission.DELETE_JOB]
        }
        default_role = 'User'
        for r in roles:
            role = Role.query.filter_by(name=r).first()
            if role is None:
                role = Role(name=r)
            role.reset_permissions()
            for perm in roles[r]:
                role.add_permission(perm)
            role.default = (role.name == default_role)
            db.session.add(role)
        db.session.commit()


class User(UserMixin, db.Model):
    """
    Model for Users that are registered to Opaque.
    """
    __tablename__ = 'users'
    # Primary key
    id = db.Column(db.Integer, primary_key=True)
    confirmed = db.Column(db.Boolean, default=False)
    email = db.Column(db.String(254), unique=True, index=True)
    password_hash = db.Column(db.String(128))
    registration_date = db.Column(db.DateTime(), default=datetime.utcnow)
    role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
    username = db.Column(db.String(64), unique=True, index=True)
    # Relationships
    corpora = db.relationship('Corpus', backref='creator', lazy='dynamic',
                              cascade='save-update, merge, delete')
    jobs = db.relationship('Job', backref='creator', lazy='dynamic',
                           cascade='save-update, merge, delete')

    def __repr__(self):
        """
        String representation of the User. For human readability.
        """
        return '<User %r>' % self.username

    def __init__(self, **kwargs):
        super(User, self).__init__(**kwargs)
        if self.role is None:
            if self.email == current_app.config['OPAQUE_ADMIN']:
                self.role = Role.query.filter_by(name='Administrator').first()
            if self.role is None:
                self.role = Role.query.filter_by(default=True).first()

    def generate_confirmation_token(self, expiration=3600):
        """
        Generates a confirmation token for user confirmation via email.
        """
        s = TimedJSONWebSignatureSerializer(current_app.config['SECRET_KEY'],
                                            expiration)
        return s.dumps({'confirm': self.id}).decode('utf-8')

    def generate_reset_token(self, expiration=3600):
        """
        Generates a reset token for password reset via email.
        """
        s = TimedJSONWebSignatureSerializer(current_app.config['SECRET_KEY'],
                                            expiration)
        return s.dumps({'reset': self.id}).decode('utf-8')

    def confirm(self, token):
        """
        Confirms User if the given token is valid and not expired.
        """
        s = TimedJSONWebSignatureSerializer(current_app.config['SECRET_KEY'])
        try:
            data = s.loads(token.encode('utf-8'))
        except BadSignature:
            return False
        if data.get('confirm') != self.id:
            return False
        self.confirmed = True
        db.session.add(self)
        return True

    @staticmethod
    def reset_password(token, new_password):
        """
        Resets password for User if the given token is valid and not expired.
        """
        s = TimedJSONWebSignatureSerializer(current_app.config['SECRET_KEY'])
        try:
            data = s.loads(token.encode('utf-8'))
        except BadSignature:
            return False
        user = User.query.get(data.get('reset'))
        if user is None:
            return False
        user.password = new_password
        db.session.add(user)
        return True

    @property
    def password(self):
        raise AttributeError('password is not a readable attribute')

    @password.setter
    def password(self, password):
        self.password_hash = generate_password_hash(password)

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

    def can(self, perm):
        """
        Checks if a User with its current role can doe something. Checks if the
        associated role actually has the needed Permission.
        """
        return self.role is not None and self.role.has_permission(perm)

    def is_administrator(self):
        """
        Checks if User has Admin permissions.
        """
        return self.can(Permission.ADMIN)

    def corpora_as_dict(self):
        corpora = {}
        for corpus in self.corpora:
            corpora[str(corpus.id)] = corpus.to_dict()
        return corpora

    def jobs_as_dict(self):
        jobs = {}
        for job in self.jobs:
            jobs[str(job.id)] = job.to_dict()
        return jobs

    def delete_user(self):
        """
        Delete user from database. Also delete all associated jobs and corpora
        files.
        """
        logger = logging.getLogger(__name__)
        delete_path = os.path.join('/mnt/opaque/', str(self.id))
        logger.warning('Delete path for user is: {}'.format(delete_path))
        while os.path.exists(delete_path):
            try:
                shutil.rmtree(delete_path, ignore_errors=True)
                logger.warning('Path does still exist.')
            except OSError:
                pass
        db.session.delete(self)
        db.session.commit()


class AnonymousUser(AnonymousUserMixin):
    """
    Model replaces the default AnonymousUser.
    """

    def can(self, permissions):
        return False

    def is_administrator(self):
        return False


class Job(db.Model):
    """
    Class to define Jobs.
    """
    __tablename__ = 'jobs'
    # Primary key
    id = db.Column(db.Integer, primary_key=True)
    creation_date = db.Column(db.DateTime(), default=datetime.utcnow)
    description = db.Column(db.String(255))
    end_date = db.Column(db.DateTime())
    mem_mb = db.Column(db.Integer)
    n_cores = db.Column(db.Integer)
    service = db.Column(db.String(64))
    '''
    ' Service specific arguments as string list.
    ' Example: ["-l eng", "--keep-intermediates", "--skip-binarization"]
    '''
    service_args = db.Column(db.String(255))
    service_version = db.Column(db.String(16))
    status = db.Column(db.String(16))
    title = db.Column(db.String(32))
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'))

    def __init__(self, **kwargs):
        super(Job, self).__init__(**kwargs)

    def __repr__(self):
        """
        String representation of the Job. For human readability.
        """
        return '<Job %r>' % self.title

    def to_dict(self):
        return {'id': self.id,
                'creation_date': self.creation_date.timestamp(),
                'description': self.description,
                'end_date': (self.end_date.timestamp() if self.end_date else
                             None),
                'mem_mb': self.mem_mb,
                'n_cores': self.n_cores,
                'service': self.service,
                'service_args': self.service_args,
                'service_version': self.service_version,
                'status': self.status,
                'title': self.title,
                'user_id': self.user_id}

    def flag_for_stop(self):
        """
        Flag running or failed job (anything that is not completed) with
        stopping. Opaque daemon will end services flaged with 'stopping'.
        """
        self.status = 'stopping'
        db.session.commit()

    def delete_job(self):
        """
        Delete job with given job id from database. Also delete associated job
        files. Contianers are still running for a few seconds after
        the associated service has been removed. This is the reason for the
        while loop. The loop checks if the file path to all the job files still
        exists and removes it again and again till the container did shutdown
        for good.
        See: https://docs.docker.com/engine/swarm/swarm-tutorial/delete-service/
        """
        logger = logging.getLogger(__name__)
        delete_path = os.path.join('/mnt/opaque/', str(self.user_id), 'jobs',
                                   str(self.id))
        logger.warning('Delete path is: {}'.format(delete_path))
        while os.path.exists(delete_path):
            try:
                shutil.rmtree(delete_path, ignore_errors=True)
                logger.warning('Path does still exist.')
            except OSError:
                pass
        db.session.delete(self)
        db.session.commit()


class Corpus(db.Model):
    """
    Class to define a corpus.
    """
    __tablename__ = 'corpora'
    # Primary key
    id = db.Column(db.Integer, primary_key=True)
    creation_date = db.Column(db.DateTime(), default=datetime.utcnow)
    description = db.Column(db.String(255))
    title = db.Column(db.String(32))
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'))

    def __init__(self, **kwargs):
        super(Corpus, self).__init__(**kwargs)

    def __repr__(self):
        """
        String representation of the corpus. For human readability.
        """
        return '<Corpus %r>' % self.title

    def to_dict(self):
        return {'id': self.id,
                'creation_date': self.creation_date.timestamp(),
                'description': self.description,
                'title': self.title,
                'user_id': self.user_id}

    def delete_corpus(self):
        logger = logging.getLogger(__name__)
        delete_path = os.path.join('/mnt/opaque/', str(self.user_id), 'corpora',
                                   str(self.id))
        logger.warning('Delete path is: {}'.format(delete_path))
        while os.path.exists(delete_path):
            try:
                shutil.rmtree(delete_path, ignore_errors=True)
                logger.warning('Path does still exist.')
            except OSError:
                pass
        db.session.delete(self)
        db.session.commit()


'''
' Flask-Login is told to use the application’s custom anonymous user by setting
' its class in the login_manager.anonymous_user attribute.
'''
login_manager.anonymous_user = AnonymousUser


@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))