from django import forms
from django.core.exceptions import ValidationError
from django.forms import formset_factory
from myapp.models import Invoice, InvoiceItem
 
class InvoiceItemForm(forms.ModelForm):
    class Meta:
        model = InvoiceItem
        fields = ['description', 'quantity', 'unit_price']
    
    def clean_quantity(self):
        quantity = self.cleaned_data['quantity']
        if quantity <= 0:
            raise ValidationError('Quantity must be positive')
        return quantity
    
    def clean(self):
        super().clean()
        if self.cleaned_data.get('quantity') and self.cleaned_data.get('unit_price'):
            total = self.cleaned_data['quantity'] * self.cleaned_data['unit_price']
            if total > 100000:
                raise ValidationError('Line total exceeds maximum allowed value')
        return self.cleaned_data
 
class InvoiceForm(forms.ModelForm):
    class Meta:
        model = Invoice
        fields = ['client_name', 'invoice_date', 'notes']
 
    
    def clean_client_name(self):
        name = self.cleaned_data['client_name']
        if len(name) < 3:
            raise ValidationError('Client name too short')
        return name.upper()
 
def validate_invoice_formset(formset):
    if formset.total() == 0:
        raise ValidationError('At least one invoice item required')
    if formset.total() > 50:
        raise ValidationError('Maximum 50 items per invoice allowed')
    
    totals = []
    for form in formset.forms:
        if form.is_valid():
            qty = form.cleaned_data.get('quantity', 0)
            price = form.cleaned_data.get('unit_price', 0)
            totals.append(qty * price)
    
    if totals and sum(totals) > 500000:
        raise ValidationError('Invoice total exceeds credit limit')
 
InvoiceItemFormSet = formset_factory(InvoiceItemForm, extra=1, can_delete=True)
InvoiceFormSet = formset_factory(InvoiceForm)