from app import db
from datetime import datetime


class StudentEnrollment(db.Model):
    """Association table: student (User) ↔ Commission enrollment managed by Bedelía."""
    __tablename__ = 'student_enrollments'

    id = db.Column(db.Integer, primary_key=True)
    student_id = db.Column(
        db.Integer,
        db.ForeignKey('users.id', ondelete='CASCADE'),
        nullable=False,
        index=True
    )
    commission_id = db.Column(
        db.Integer,
        db.ForeignKey('commissions.id', ondelete='CASCADE'),
        nullable=False,
        index=True
    )
    status = db.Column(db.String(20), nullable=False, default='activo')  # activo | retirado | condicional
    enrolled_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    notes = db.Column(db.Text, nullable=True)

    # Unique constraint: a student can only be enrolled once per commission
    __table_args__ = (
        db.UniqueConstraint('student_id', 'commission_id', name='uq_student_commission'),
    )

    # Relationships
    student = db.relationship('User', backref=db.backref('enrollments', lazy='dynamic', cascade='all, delete-orphan'))
    commission = db.relationship('Commission', backref=db.backref('enrollments', lazy='dynamic', cascade='all, delete-orphan'))

    def to_dict(self):
        return {
            'id': self.id,
            'student_id': self.student_id,
            'student_name': self.student.name if self.student else None,
            'student_email': self.student.email if self.student else None,
            'commission_id': self.commission_id,
            'status': self.status,
            'enrolled_at': self.enrolled_at.isoformat() if self.enrolled_at else None,
            'notes': self.notes,
        }

    def __repr__(self):
        return f'<StudentEnrollment student={self.student_id} commission={self.commission_id} status={self.status}>'