from datetime import datetime
from app import db


class MilestoneGrade(db.Model):
    """
    Calificación y seguimiento pedagógico individual de un alumno en un hito evaluativo (Fase 3 MVP).
    Vincula un AcademicMilestone con un estudiante matriculado (StudentEnrollment / User).
    """
    __tablename__ = 'milestone_grades'

    id = db.Column(db.Integer, primary_key=True)
    milestone_id = db.Column(
        db.Integer,
        db.ForeignKey('academic_milestones.id', ondelete='CASCADE'),
        nullable=False,
        index=True
    )
    enrollment_id = db.Column(
        db.Integer,
        db.ForeignKey('student_enrollments.id', ondelete='CASCADE'),
        nullable=False,
        index=True
    )
    student_id = db.Column(
        db.Integer,
        db.ForeignKey('users.id', ondelete='CASCADE'),
        nullable=False,
        index=True
    )
    score = db.Column(db.Float, nullable=True)          # Calificación numérica de 1.0 a 10.0
    is_absent = db.Column(db.Boolean, default=False)    # Flag de Ausente
    feedback = db.Column(db.Text, nullable=True)        # Devolución formativa/pedagógica
    graded_by_user_id = db.Column(
        db.Integer,
        db.ForeignKey('users.id', ondelete='SET NULL'),
        nullable=True
    )
    graded_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

    # Restricción de unicidad: un estudiante tiene una única nota por hito
    __table_args__ = (
        db.UniqueConstraint('milestone_id', 'student_id', name='uq_milestone_student'),
    )

    # Relaciones
    milestone = db.relationship('AcademicMilestone', backref=db.backref('grades', lazy='dynamic', cascade='all, delete-orphan'))
    enrollment = db.relationship('StudentEnrollment', backref=db.backref('milestone_grades', lazy='dynamic', cascade='all, delete-orphan'))
    student = db.relationship('User', foreign_keys=[student_id], backref=db.backref('received_grades', lazy='dynamic'))
    graded_by = db.relationship('User', foreign_keys=[graded_by_user_id])

    @property
    def is_passed(self) -> bool:
        """Determina si la nota está aprobada (>= 4.00 y no ausente)."""
        if self.is_absent or self.score is None:
            return False
        return self.score >= 4.0

    @property
    def display_score(self) -> str:
        """Representación textual estándar: 'Ausente', '7.5' o '-'."""
        if self.is_absent:
            return 'Ausente'
        if self.score is not None:
            return f'{self.score:.1f}' if self.score % 1 != 0 else f'{int(self.score)}'
        return '-'

    def to_dict(self):
        return {
            'id': self.id,
            'milestone_id': self.milestone_id,
            'milestone_title': self.milestone.title if self.milestone else None,
            'milestone_type': self.milestone.tipo if self.milestone else None,
            'milestone_color': self.milestone.color if self.milestone else None,
            'enrollment_id': self.enrollment_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,
            'score': self.score,
            'display_score': self.display_score,
            'is_absent': bool(self.is_absent),
            'is_passed': self.is_passed,
            'feedback': self.feedback or '',
            'graded_by_user_id': self.graded_by_user_id,
            'graded_by_name': self.graded_by.name if self.graded_by else None,
            'graded_at': self.graded_at.isoformat() if self.graded_at else None,
            'updated_at': self.updated_at.isoformat() if self.updated_at else None,
        }

    def __repr__(self):
        return f'<MilestoneGrade milestone={self.milestone_id} student={self.student_id} score={self.display_score}>'