from registrasion import forms
from registrasion import models as rego
from registrasion.controllers.cart import CartController
from registrasion.controllers.invoice import InvoiceController
from registrasion.controllers.product import ProductController

from django.contrib.auth.decorators import login_required
from django.core.exceptions import ObjectDoesNotExist
from django.core.exceptions import ValidationError
from django.db import transaction
from django.shortcuts import redirect
from django.shortcuts import render


@login_required
def product_category(request, category_id):
    ''' Registration selections form for a specific category of items '''

    PRODUCTS_FORM_PREFIX = "products"
    VOUCHERS_FORM_PREFIX = "vouchers"

    category_id = int(category_id)  # Routing is [0-9]+
    category = rego.Category.objects.get(pk=category_id)
    current_cart = CartController.for_user(request.user)

    CategoryForm = forms.CategoryForm(category)

    products = rego.Product.objects.filter(category=category)
    products = products.order_by("order")

    if request.method == "POST":
        cat_form = CategoryForm(request.POST, request.FILES, prefix=PRODUCTS_FORM_PREFIX)
        voucher_form = forms.VoucherForm(request.POST, prefix=VOUCHERS_FORM_PREFIX)

        if voucher_form.is_valid():
            # Apply voucher
            # leave
            voucher = voucher_form.cleaned_data["voucher"]
            try:
                current_cart.apply_voucher(voucher)
            except Exception as e:
                voucher_form.add_error("voucher", e)
        elif cat_form.is_valid():
            try:
                with transaction.atomic():
                    for product_id, quantity, field_name \
                            in cat_form.product_quantities():
                        product = rego.Product.objects.get(pk=product_id)
                        try:
                            current_cart.set_quantity(
                                product, quantity, batched=True)
                        except ValidationError as ve:
                            cat_form.add_error(field_name, ve)
                    if cat_form.errors:
                        raise ValidationError("Cannot add that stuff")
                    current_cart.end_batch()
            except ValidationError as ve:
                pass

    else:
        # Create initial data for each of products in category
        items = rego.ProductItem.objects.filter(
            product__category=category,
            cart=current_cart.cart,
        )
        quantities = []
        for product in products:
            # Only add items that are enabled.
            prod = ProductController(product)
            try:
                quantity = items.get(product=product).quantity
            except ObjectDoesNotExist:
                quantity = 0
            quantities.append((product, quantity))

        initial = CategoryForm.initial_data(quantities)
        cat_form = CategoryForm(prefix=PRODUCTS_FORM_PREFIX, initial=initial)

        voucher_form = forms.VoucherForm(prefix=VOUCHERS_FORM_PREFIX)

    for product in products:
        # Remove fields that do not have an enabling condition.
        prod = ProductController(product)
        if not prod.can_add_with_enabling_conditions(request.user, 0):
            cat_form.disable_product(product)


    data = {
        "category": category,
        "form": cat_form,
        "voucher_form": voucher_form,
    }

    return render(request, "product_category.html", data)


@login_required
def checkout(request):
    ''' Runs checkout for the current cart of items, ideally generating an
    invoice. '''

    current_cart = CartController.for_user(request.user)
    current_invoice = InvoiceController.for_cart(current_cart.cart)

    return redirect("invoice", current_invoice.invoice.id)


@login_required
def invoice(request, invoice_id):
    ''' Displays an invoice for a given invoice id. '''

    invoice_id = int(invoice_id)
    inv = rego.Invoice.objects.get(pk=invoice_id)
    current_invoice = InvoiceController(inv)

    data = {
        "invoice": current_invoice.invoice,
    }

    return render(request, "invoice.html", data)

@login_required
def pay_invoice(request, invoice_id):
    ''' Marks the invoice with the given invoice id as paid.
    WORK IN PROGRESS FUNCTION. Must be replaced with real payment workflow.

    '''

    invoice_id = int(invoice_id)
    inv = rego.Invoice.objects.get(pk=invoice_id)
    current_invoice = InvoiceController(inv)
    if not inv.paid and not current_invoice.is_valid():
        current_invoice.pay("Demo invoice payment", inv.value)

    return redirect("invoice", current_invoice.invoice.id)