from calendar import monthrange
from collections import defaultdict
from datetime import date, timedelta

from django.contrib.auth.decorators import login_required
from django.contrib.auth.mixins import LoginRequiredMixin
from django.db.models import Avg, Max, Min, Sum
from django.utils import timezone
from django.views.generic import CreateView, ListView, TemplateView

from .forms import FuelPurchaseForm
from .models import FuelPurchase, MonthlyTrip


class FuelPurchaseMonthlyListView(ListView):
    model = FuelPurchase
    template_name = "fuelpurchase_list.html"
    context_object_name = "purchases"

    def get_queryset(self):
        year = int(self.kwargs.get("year", timezone.now().year))
        month = int(self.kwargs.get("month", timezone.now().month))
        self.current_year = year
        self.current_month = month

        # Haetaan MonthlyTrip heti
        self.monthly_trip = MonthlyTrip.objects.filter(year=year, month=month).first()

        if not self.monthly_trip:
            # Jos ei ole olemassa, ei ole ostoksiakaan
            return FuelPurchase.objects.none()

        return (
            FuelPurchase.objects
            .filter(monthly_trip=self.monthly_trip)
            .select_related("monthly_trip")
            .order_by("-purchase_date")
        )

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        qs = self.object_list

        summary = qs.aggregate(
            total_cost_sum=Sum("total_cost"),
            total_litres_sum=Sum("amount_litres"),
            avg_price=Avg("price_per_litre"),
            min_price=Min("price_per_litre"),
            max_price=Max("price_per_litre"),
        )

        context["summary"] = summary
        context["current_year"] = self.current_year
        context["current_month"] = self.current_month
        context["month_kilometers"] = self.monthly_trip.kilometers if self.monthly_trip else 0

        # Kuukausinavigointi
        current_date = date(self.current_year, self.current_month, 1)
        prev_month = current_date - timedelta(days=1)
        next_month = (current_date.replace(day=28) + timedelta(days=4)).replace(day=1)

        context["prev_year"] = prev_month.year
        context["prev_month"] = prev_month.month
        context["next_year"] = next_month.year
        context["next_month"] = next_month.month

        # Kaikki kuukaudet alasvetovalikkoon
        context["available_months"] = FuelPurchase.objects.dates(
            "purchase_date", "month", order="DESC"
        )

        return context


class FuelPurchaseCreateView(LoginRequiredMixin, CreateView):
    model = FuelPurchase
    form_class = FuelPurchaseForm
    template_name = "fuelpurchase_add.html"
    success_url = "/"


class MonthlyTripView(TemplateView):
    template_name = 'main/monthly_trips.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)

        all_distances = MonthlyTrip.objects.all().order_by('year', 'month')
        years = sorted(set(d.year for d in all_distances))

        table_data = defaultdict(dict)
        year_totals = defaultdict(int)

        for entry in all_distances:
            table_data[entry.month][entry.year] = entry.kilometers
            year_totals[entry.year] += entry.kilometers

        month_names = dict(MonthlyTrip.MONTH_CHOICES)

        context.update({
            'years': years,
            'table_data': table_data,
            'month_names': month_names,
            'year_totals': year_totals,
        })
        return context