from django.db import models
from students.models import Student
from teachers.models import Subject

class Grade(models.Model):
    TERM_CHOICES = [('1', 'Term 1'), ('2', 'Term 2'), ('3', 'Term 3'), ('final', 'Final')]

    student = models.ForeignKey(Student, on_delete=models.CASCADE, related_name='grades')
    subject = models.ForeignKey(Subject, on_delete=models.CASCADE, related_name='grades')
    term = models.CharField(max_length=10, choices=TERM_CHOICES, default='1')
    score = models.DecimalField(max_digits=5, decimal_places=2)
    max_score = models.DecimalField(max_digits=5, decimal_places=2, default=100)
    academic_year = models.CharField(max_length=20, default='2024-2025')
    remarks = models.TextField(blank=True)
    created_at = models.DateTimeField(auto_now_add=True)

    @property
    def percentage(self):
        if self.max_score > 0:
            return round((self.score / self.max_score) * 100, 1)
        return 0

    @property
    def letter_grade(self):
        p = self.percentage
        if p >= 90: return 'A+'
        if p >= 80: return 'A'
        if p >= 70: return 'B'
        if p >= 60: return 'C'
        if p >= 50: return 'D'
        return 'F'

    def __str__(self):
        return f"{self.student} - {self.subject} - {self.term}"

    class Meta:
        ordering = ['-created_at']