import json
from collections import defaultdict

from django.db.models import Sum
from django.db.models.functions import ExtractMonth
from django.shortcuts import render
from django.contrib.auth.decorators import login_required
from django.utils import timezone

from app.expenses.models import Expense
from app.monthly.models import Income, MonthlyFixedExpense

from .models import PlannedExpense

MONTH_LABELS = [
	"Jan",
	"Feb",
	"Mar",
	"Apr",
	"May",
	"Jun",
	"Jul",
	"Aug",
	"Sep",
	"Oct",
	"Nov",
	"Dec",
]
MONTH_LABELS_FULL = [
	"January",
	"February",
	"March",
	"April",
	"May",
	"June",
	"July",
	"August",
	"September",
	"October",
	"November",
	"December",
]


@login_required
def year_view(request):
	today = timezone.localdate()
	year = int(request.GET.get("year", today.year))
	is_current_year = year == today.year

	# Income by month (single query)
	income_rows = (
		Income.objects.filter(date__year=year)
		.annotate(m=ExtractMonth("date"))
		.values("m")
		.annotate(total=Sum("amount"))
	)
	income_map = {r["m"]: float(r["total"]) for r in income_rows}
	income_by_month = [income_map.get(m, 0) for m in range(1, 13)]

	# Fixed expenses by month (single query)
	fe_rows = (
		MonthlyFixedExpense.objects.filter(year=year)
		.values("month")
		.annotate(total=Sum("amount"))
	)
	fe_map = {r["month"]: float(r["total"]) for r in fe_rows}
	fe_by_month = [fe_map.get(m, 0) for m in range(1, 13)]

	# Variable expenses by month (single query)
	var_rows = (
		Expense.objects.filter(created_at__year=year)
		.annotate(m=ExtractMonth("created_at"))
		.values("m")
		.annotate(total=Sum("amount"))
	)
	var_map = {r["m"]: float(r["total"]) for r in var_rows}

	# Planned expenses by month (single query)
	planned_rows = (
		PlannedExpense.objects.filter(year=year)
		.values("month")
		.annotate(total=Sum("amount"))
	)
	planned_map = {r["month"]: float(r["total"]) for r in planned_rows}

	var_expenses_by_month = [
		var_map.get(m, 0) + planned_map.get(m, 0) for m in range(1, 13)
	]

	# Category breakdown (2 queries instead of N*12)
	cat_annual = (
		Expense.objects.filter(created_at__year=year)
		.values("category__id", "category__name")
		.annotate(total=Sum("amount"))
		.filter(total__gt=0)
	)
	cat_monthly_rows = (
		Expense.objects.filter(created_at__year=year)
		.annotate(m=ExtractMonth("created_at"))
		.values("category__id", "category__name", "m")
		.annotate(total=Sum("amount"))
	)
	cat_monthly_map = defaultdict(lambda: [0.0] * 12)
	for r in cat_monthly_rows:
		cat_monthly_map[r["category__id"]][r["m"] - 1] = float(r["total"])

	category_totals = []
	category_monthly = []
	for r in cat_annual:
		cat_id = r["category__id"]
		cat_name = r["category__name"]
		category_totals.append({"name": cat_name, "total": float(r["total"])})
		category_monthly.append({"name": cat_name, "data": cat_monthly_map[cat_id]})

	total_expenses = sum(c["total"] for c in category_totals)
	total_income = sum(income_by_month)
	total_fe = sum(fe_by_month)
	planned_total = sum(planned_map.values())

	# Planned expenses for tables
	planned_months_data = []
	planned_items = PlannedExpense.objects.filter(year=year)
	items_by_month = defaultdict(list)
	for item in planned_items:
		items_by_month[item.month].append(item)
	for m in range(1, 13):
		month_items = items_by_month.get(m, [])
		planned_months_data.append(
			{
				"month": m,
				"label": MONTH_LABELS_FULL[m - 1],
				"items": month_items,
				"total": sum(i.amount for i in month_items),
			}
		)

	# Clone years for planned expenses
	clone_pe_years = list(
		PlannedExpense.objects.exclude(year=year)
		.values_list("year", flat=True)
		.distinct()
		.order_by("-year")
	)

	# Available years for navigation
	expense_years = set(
		Expense.objects.values_list("created_at__year", flat=True).distinct()
	)
	income_years = set(Income.objects.values_list("date__year", flat=True).distinct())
	planned_years = set(
		PlannedExpense.objects.values_list("year", flat=True).distinct()
	)
	all_years = expense_years | income_years | planned_years | {today.year}
	has_prev_year = (year - 1) in all_years

	context = {
		"year": year,
		"prev_year": year - 1,
		"next_year": year + 1,
		"is_current_year": is_current_year,
		"has_prev_year": has_prev_year,
		"month_labels_json": json.dumps(MONTH_LABELS),
		"income_by_month_json": json.dumps(income_by_month),
		"var_expenses_by_month_json": json.dumps(var_expenses_by_month),
		"fe_by_month_json": json.dumps(fe_by_month),
		"category_totals": category_totals,
		"category_totals_json": json.dumps(category_totals),
		"category_monthly_json": json.dumps(category_monthly),
		"total_expenses": total_expenses + planned_total,
		"total_income": total_income,
		"total_fe": total_fe,
		"months_data": planned_months_data,
		"grand_total": planned_total,
		"clone_years": clone_pe_years,
	}
	return render(request, "pages/yearly/year.html", context)