"""
Models for the enrollments app.
"""
from django.db import models
from django.conf import settings
from apps.courses.models import Course
from utils.choices import ENROLLMENT_STATUS_CHOICES, ENROLLMENT_PENDING


PAYMENT_METHOD_NONE = ''
PAYMENT_METHOD_MANUAL = 'manual'
PAYMENT_METHOD_STRIPE = 'stripe'
PAYMENT_METHOD_FREE = 'free'

PAYMENT_METHOD_CHOICES = [
    (PAYMENT_METHOD_NONE, 'Not selected'),
    (PAYMENT_METHOD_MANUAL, 'Manual payment'),
    (PAYMENT_METHOD_STRIPE, 'Stripe'),
    (PAYMENT_METHOD_FREE, 'Free course'),
]


class Enrollment(models.Model):
    """
    Represents a student's enrollment request for a course.
    Enrollment starts as Pending until payment is confirmed
    (manual approval or Stripe checkout success).
    """
    student = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='enrollments',
        limit_choices_to={'role': 'student'}
    )
    course = models.ForeignKey(
        Course,
        on_delete=models.CASCADE,
        related_name='enrollments'
    )
    status = models.CharField(
        max_length=20,
        choices=ENROLLMENT_STATUS_CHOICES,
        default=ENROLLMENT_PENDING
    )
    payment_method = models.CharField(
        max_length=20,
        choices=PAYMENT_METHOD_CHOICES,
        blank=True,
        default=PAYMENT_METHOD_NONE,
    )
    payment_proof = models.ImageField(
        upload_to='payment_proofs/',
        blank=True,
        null=True
    )
    payment_note = models.TextField(blank=True, null=True, help_text="Optional note about payment")
    stripe_session_id = models.CharField(max_length=255, blank=True)
    stripe_payment_intent = models.CharField(max_length=255, blank=True)
    requested_at = models.DateTimeField(auto_now_add=True)
    approved_at = models.DateTimeField(blank=True, null=True)
    approved_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='approved_enrollments'
    )
    rejection_reason = models.TextField(blank=True, null=True)
    promo_code = models.ForeignKey(
        'promotions.PromoCode',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='enrollments',
    )
    original_amount = models.DecimalField(max_digits=8, decimal_places=2, null=True, blank=True)
    discount_amount = models.DecimalField(max_digits=8, decimal_places=2, default=0)
    payable_amount = models.DecimalField(
        max_digits=8,
        decimal_places=2,
        null=True,
        blank=True,
        help_text='Amount due after promo. Null = use full course price.',
    )

    class Meta:
        ordering = ['-requested_at']
        verbose_name = 'Enrollment'
        verbose_name_plural = 'Enrollments'
        # Prevent duplicate active enrollments
        unique_together = ('student', 'course')

    def __str__(self):
        return f"{self.student.username} → {self.course.title} [{self.status}]"

    @property
    def is_approved(self):
        return self.status == 'approved'

    @property
    def is_pending(self):
        return self.status == 'pending'

    @property
    def is_rejected(self):
        return self.status == 'rejected'