from datetime import datetime

from app import db

from twitter import Twitter, OAuth
import secrets
from lib import decompose_interval
from datetime import timedelta

class TimestampMixin(object):
    created_at = db.Column(db.DateTime, server_default=db.func.now(), nullable=False)
    updated_at = db.Column(db.DateTime, server_default=db.func.now(), onupdate=db.func.now(), nullable=False)

    def touch(self):
        self.updated_at=db.func.now()

class RemoteIDMixin(object):
    @property
    def service(self):
        if not self.id:
            return None
        return self.id.split(":")[0]

    @property
    def twitter_id(self):
        if not self.id:
            return None
        if self.service != "twitter":
            raise Exception("tried to get twitter id for a {} {}".format(self.service, type(self)))
        return self.id.split(":")[1]

    @twitter_id.setter
    def twitter_id(self, id):
        self.id = "twitter:{}".format(id)


@decompose_interval('policy_delete_every')
@decompose_interval('policy_keep_younger')
class Account(TimestampMixin, RemoteIDMixin):
    __tablename__ = 'accounts'
    id = db.Column(db.String, primary_key=True)

    policy_enabled = db.Column(db.Boolean, server_default='FALSE', nullable=False)
    policy_keep_latest = db.Column(db.Integer, server_default='100', nullable=False)
    policy_keep_favourites = db.Column(db.Boolean, server_default='TRUE', nullable=False)
    policy_delete_every = db.Column(db.Interval, server_default='30 minutes', nullable=False)
    policy_keep_younger = db.Column(db.Interval, server_default='365 days', nullable=False)

    display_name = db.Column(db.String)
    screen_name = db.Column(db.String)
    avatar_url = db.Column(db.String)
    reported_post_count = db.Column(db.Integer)

    last_fetch = db.Column(db.DateTime, server_default='epoch')
    last_delete = db.Column(db.DateTime, server_default='epoch')

    def touch_fetch(self):
        self.last_fetch = db.func.now()

    def touch_delete(self):
        self.last_delete = db.func.now()

    @db.validates('policy_keep_younger', 'policy_delete_every')
    def validate_intervals(self, key, value):
        if not (value == timedelta(0) or value >= timedelta(minutes=1)):
            value = timedelta(minutes=1)
        return value

    @db.validates('policy_keep_latest')
    def validate_empty_string_is_zero(self, key, value):
        if type(value) == str and value.strip() == '':
            return 0
        return value


    # backref: tokens
    # backref: twitter_archives
    # backref: posts
    # backref: sessions

    def __repr__(self):
        return f"<Account({self.id}, {self.screen_name}, {self.display_name})>"

    def post_count(self):
        return Post.query.with_parent(self).count()

    def estimate_eligible_for_delete(self):
        """
        this is an estimation because we do not know if favourite status has changed since last time a post was refreshed
        and it is unfeasible to refresh every single post every time we need to know how many posts are eligible to delete
        """
        latest_n_posts = db.session.query(Post.id).with_parent(self).order_by(db.desc(Post.created_at)).limit(self.policy_keep_latest)
        query = Post.query.with_parent(self).\
            filter(Post.created_at + self.policy_keep_younger <= db.func.now()).\
            filter(~Post.id.in_(latest_n_posts))
        if(self.policy_keep_favourites):
            query = query.filter_by(favourite = False)
        return query.count()


    def force_log_out(self):
        Session.query.with_parent(self).delete()
        db.session.commit()


class Account(Account, db.Model):
    pass


class OAuthToken(db.Model, TimestampMixin):
    __tablename__ = 'oauth_tokens'

    token = db.Column(db.String, primary_key=True)
    token_secret = db.Column(db.String, nullable=False)

    account_id = db.Column(db.String, db.ForeignKey('accounts.id', ondelete='CASCADE', onupdate='CASCADE'), nullable=True)
    account = db.relationship(Account, backref=db.backref('tokens', order_by=lambda: db.desc(OAuthToken.created_at)))

    # note: account_id is nullable here because we don't know what account a token is for
    # until we call /account/verify_credentials with it
class Session(db.Model, TimestampMixin):
    __tablename__ = 'sessions'

    id = db.Column(db.String, primary_key=True, default=lambda: secrets.token_urlsafe())

    account_id = db.Column(db.String, db.ForeignKey('accounts.id', ondelete='CASCADE', onupdate='CASCADE'), nullable=False)
    account = db.relationship(Account, lazy='joined', backref='sessions')

class Post(db.Model, TimestampMixin, RemoteIDMixin):
    __tablename__ = 'posts'

    id = db.Column(db.String, primary_key=True)
    body = db.Column(db.String)

    author_id = db.Column(db.String, db.ForeignKey('accounts.id', ondelete='CASCADE', onupdate='CASCADE'), nullable=False)
    author = db.relationship(Account,
            backref=db.backref('posts', order_by=lambda: db.desc(Post.created_at)))

    favourite = db.Column(db.Boolean, server_default='FALSE', nullable=False)

    def __repr__(self):
        snippet = self.body
        if len(snippet) > 20:
            snippet = snippet[:19] + "✂"
        return '<Post ({}, "{}", Author: {})>'.format(self.id, snippet, self.author_id)

class TwitterArchive(db.Model, TimestampMixin):
    __tablename__ = 'twitter_archives'

    id = db.Column(db.Integer, primary_key=True)
    account_id = db.Column(db.String, db.ForeignKey('accounts.id', onupdate='CASCADE', ondelete='CASCADE'), nullable=False)
    account = db.relationship(Account, backref=db.backref('twitter_archives', order_by=lambda: db.desc(TwitterArchive.id)))
    body = db.deferred(db.Column(db.LargeBinary, nullable=False))
    chunks = db.Column(db.Integer)
    chunks_successful = db.Column(db.Integer, server_default='0', nullable=False)
    chunks_failed = db.Column(db.Integer, server_default='0', nullable=False)

    def status(self):
        if self.chunks is None or self.chunks_failed > 0:
            return 'failed'
        if self.chunks_successful == self.chunks:
            return 'successful'
        return 'pending'