from django.db import models
from django.conf import settings
from credit_scoring.models import CreditApplication
from documents.models import Document
from datetime import date
from decimal import Decimal
import uuid

class Invoice(models.Model):
    STATUS_CHOICES = [
        ('DRAFT', 'Draft'),
        ('SUBMITTED', 'Submitted'),
        ('UNDER_REVIEW', 'Under Review'),
        ('APPROVED', 'Approved for Funding'),
        ('FUNDED', 'Funded'),
        ('REPAID', 'Repaid'),
        ('DECLINED', 'Declined'),
        ('OVERDUE', 'Overdue'),
    ]
    
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    credit_application = models.ForeignKey(CreditApplication, on_delete=models.CASCADE, related_name='invoices')
    invoice_number = models.CharField(max_length=100, unique=True)
    client_company = models.CharField(max_length=200)
    invoice_date = models.DateField()
    due_date = models.DateField()
    invoice_amount = models.DecimalField(max_digits=15, decimal_places=2)
    discounting_amount = models.DecimalField(max_digits=15, decimal_places=2, blank=True, null=True)
    interest_rate = models.DecimalField(max_digits=5, decimal_places=2, blank=True, null=True)
    interest_amount = models.DecimalField(max_digits=15, decimal_places=2, blank=True, null=True)
    status = models.CharField(max_length=20, choices=STATUS_CHOICES, default='DRAFT')
    supporting_document = models.ForeignKey(Document, on_delete=models.SET_NULL, null=True, blank=True)
    notes = models.TextField(blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        db_table = 'invoices'
        ordering = ['-invoice_date']
    
    def __str__(self):
        return f"Invoice {self.invoice_number} - {self.client_company} - {self.status}"
    
    def calculate_discount(self):
        """Calculate discounting amount based on scoring"""
        from datetime import date
        
        # Ensure we're working with date objects
        if isinstance(self.due_date, str):
            from datetime import datetime
            self.due_date = datetime.strptime(self.due_date, '%Y-%m-%d').date()
        
        days_to_due = (self.due_date - date.today()).days
        
        if days_to_due <= 14:
            self.interest_rate = Decimal('3.00')
        elif days_to_due <= 30:
            self.interest_rate = Decimal('5.68')
        elif days_to_due <= 45:
            self.interest_rate = Decimal('6.00')
        elif days_to_due <= 60:
            self.interest_rate = Decimal('7.37')
        else:
            self.interest_rate = Decimal('9.00')
        
        self.interest_amount = (self.invoice_amount * self.interest_rate) / Decimal('100')
        self.discounting_amount = self.invoice_amount - self.interest_amount
        self.save()
        return self.discounting_amount

class InvoicePayment(models.Model):
    PAYMENT_STATUS = [
        ('PENDING', 'Pending'),
        ('PROCESSING', 'Processing'),
        ('COMPLETED', 'Completed'),
        ('FAILED', 'Failed'),
    ]
    
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    invoice = models.ForeignKey(Invoice, on_delete=models.CASCADE, related_name='payments')
    amount_paid = models.DecimalField(max_digits=15, decimal_places=2)
    payment_date = models.DateField()
    transaction_reference = models.CharField(max_length=100, unique=True)
    status = models.CharField(max_length=20, choices=PAYMENT_STATUS, default='PENDING')
    paid_by_client = models.CharField(max_length=200)
    created_at = models.DateTimeField(auto_now_add=True)
    
    @classmethod
    def get_or_create_with_update(cls, invoice_number, defaults=None):
        """Get or create invoice, updating defaults if exists"""
        try:
            invoice = cls.objects.get(invoice_number=invoice_number)
            if defaults:
                for key, value in defaults.items():
                    setattr(invoice, key, value)
                invoice.save()
            return invoice, False
        except cls.DoesNotExist:
            if defaults:
                return cls.objects.create(invoice_number=invoice_number, **defaults), True
            return cls.objects.create(invoice_number=invoice_number), True

class Meta:
    db_table = 'invoice_payments'
    
    def __str__(self):
        return f"Payment for {self.invoice.invoice_number} - {self.amount_paid}"