from datetime import datetime
from app.extensions import db


class Assignment(db.Model):
    """Records the assignment of an asset to a user.

    Every assignment (including past ones) is kept permanently so that
    asset history is preserved even after a user record is masked.
    """
    __tablename__ = 'assignments'

    id = db.Column(db.Integer, primary_key=True)

    asset_id = db.Column(db.Integer, db.ForeignKey('assets.id'), nullable=False)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)

    assigned_date = db.Column(db.Date, nullable=False, default=datetime.utcnow)
    returned_date = db.Column(db.Date, nullable=True)

    assigned_by_id = db.Column(db.Integer, db.ForeignKey('admin_users.id'), nullable=True)
    returned_by_id = db.Column(db.Integer, db.ForeignKey('admin_users.id'), nullable=True)

    notes = db.Column(db.Text, nullable=True)
    is_active = db.Column(db.Boolean, default=True, nullable=False)

    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

    assigned_by = db.relationship('AdminUser', foreign_keys=[assigned_by_id])
    returned_by = db.relationship('AdminUser', foreign_keys=[returned_by_id])

    # Paperwork linked to this assignment
    paperwork_docs = db.relationship('Paperwork', backref='assignment', lazy='dynamic')

    def __repr__(self):
        return f'<Assignment asset={self.asset_id} user={self.user_id} active={self.is_active}>'