"""Per-user playlist edit permission for viewer-role accounts."""
from datetime import datetime
from app.extensions import db


class PlaylistPermission(db.Model):
    """
    Grants a viewer-role user edit access to a specific playlist.

    admin / editor users have implicit access to all playlists;
    this table is only consulted for the 'viewer' role.
    """
    __tablename__ = 'playlist_permissions'

    id          = db.Column(db.Integer, primary_key=True)
    user_id     = db.Column(db.Integer, db.ForeignKey('user.id',     ondelete='CASCADE'), nullable=False)
    playlist_id = db.Column(db.Integer, db.ForeignKey('playlist.id', ondelete='CASCADE'), nullable=False)
    granted_at  = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)

    user     = db.relationship('User',     backref=db.backref('playlist_permissions', lazy='dynamic', cascade='all, delete-orphan'))
    playlist = db.relationship('Playlist', backref=db.backref('permitted_users',      lazy='dynamic', cascade='all, delete-orphan'))

    __table_args__ = (
        db.UniqueConstraint('user_id', 'playlist_id', name='uq_user_playlist_perm'),
    )

    def __repr__(self):
        return f'<PlaylistPermission user={self.user_id} playlist={self.playlist_id}>'