from dateutil.relativedelta import relativedelta

from django.contrib import messages
from django.contrib.auth.decorators import login_required
from django.db.models import Count
from django.db.models.functions import ExtractYear, ExtractMonth
from django.http import HttpResponse
from django.shortcuts import render
from django.urls import reverse
from django.utils import timezone
from django.views.decorators.http import require_http_methods
from django.utils.translation import gettext_lazy as _

from cachalot.api import invalidate

from apps.common.decorators.htmx import only_htmx
from apps.transactions.models import Transaction


@only_htmx
@login_required
@require_http_methods(["GET"])
def toasts(request):
    return render(request, "common/fragments/toasts.html")


@only_htmx
@login_required
@require_http_methods(["GET"])
def month_year_picker(request):
    field = request.GET.get("field", "reference_date")
    for_ = request.GET.get("for", None)
    url = None

    if for_ == "calendar":
        url = "calendar"
    elif for_ == "monthly_overview":
        url = "monthly_overview"

    # Get current month and year from request or use current date
    current_date = timezone.localdate(timezone.now())
    current_month = int(request.GET.get("month", current_date.month))
    current_year = int(request.GET.get("year", current_date.year))

    # Set start and end dates
    start_date = timezone.datetime(current_year - 1, 1, 1).date()
    end_date = timezone.datetime(current_year + 1, 12, 31).date()

    # Get years from transactions
    transaction_years = Transaction.objects.dates(field, "year", order="ASC")

    # Extend start_date and end_date if necessary
    if transaction_years:
        start_date = min(start_date, transaction_years.first().replace(month=1, day=1))
        end_date = max(end_date, transaction_years.last().replace(month=12, day=31))

    # Generate all months between start_date and end_date
    all_months = []
    current_month_date = start_date
    while current_month_date <= end_date:
        all_months.append(current_month_date)
        current_month_date += relativedelta(months=1)

    # Get transaction counts for each month
    transaction_counts = (
        Transaction.objects.annotate(year=ExtractYear(field), month=ExtractMonth(field))
        .values("year", "month")
        .annotate(transaction_count=Count("id"))
        .order_by("year", "month")
    )

    # Create a dictionary for quick lookup
    count_dict = {
        (item["year"], item["month"]): item["transaction_count"]
        for item in transaction_counts
    }

    # Create the final result
    result = [
        {
            "year": date.year,
            "month": date.month,
            "transaction_count": count_dict.get((date.year, date.month), 0),
            "url": (
                reverse(url, kwargs={"month": date.month, "year": date.year})
                if url
                else ""
            ),
        }
        for date in all_months
    ]

    return render(
        request,
        "common/fragments/month_year_picker.html",
        {
            "month_year_data": result,
            "current_month": current_month,
            "current_year": current_year,
        },
    )


@only_htmx
@login_required
@require_http_methods(["GET"])
def invalidate_cache(request):
    invalidate()

    messages.success(request, _("Cache cleared successfully"))

    return HttpResponse(
        status=204,
        headers={
            "HX-Trigger": "updated",
        },
    )