from decimal import Decimal, InvalidOperation

from django.db.models import Sum
from django.template.loader import render_to_string
from liveview import liveview_handler, send

from app.expenses.models import FixedExpenseConcept
from app.expenses.templatetags.money import format_money
from app.monthly.models import MonthlyFixedExpense
from app.monthly.services import update_budget


def _ensure_entries_exist(year, month):
	"""Create missing MonthlyFixedExpense entries in bulk."""
	concepts = FixedExpenseConcept.objects.all()
	existing_ids = set(
		MonthlyFixedExpense.objects.filter(year=year, month=month).values_list(
			"concept_id", flat=True
		)
	)
	to_create = [
		MonthlyFixedExpense(year=year, month=month, concept=c)
		for c in concepts
		if c.id not in existing_ids
	]
	if to_create:
		MonthlyFixedExpense.objects.bulk_create(to_create)


def _render_fixed_expenses_table(year, month):
	_ensure_entries_exist(year, month)
	entries = MonthlyFixedExpense.objects.filter(year=year, month=month).select_related(
		"concept"
	)
	total = entries.aggregate(total=Sum("amount"))["total"] or Decimal("0")
	return render_to_string(
		"pages/monthly/partials/fixed_expenses_table.html",
		{"entries": entries, "total": total, "year": year, "month": month},
	)


@liveview_handler("save_monthly_fixed_expense")
def save_monthly_fixed_expense(consumer, content):
	form = content.get("form", {})
	entry_id = form.get("entry_id", "")
	year = int(form.get("year", 0))
	month = int(form.get("month", 0))
	amount_raw = form.get("fe_amount", "").replace(",", ".")

	if not entry_id or not year or not month:
		return

	try:
		amount = Decimal(amount_raw) if amount_raw else Decimal("0")
		entry = MonthlyFixedExpense.objects.get(id=entry_id)
		entry.amount = amount
		entry.save()
	except (InvalidOperation, ValueError, MonthlyFixedExpense.DoesNotExist):
		return

	total = MonthlyFixedExpense.objects.filter(year=year, month=month).aggregate(
		total=Sum("amount")
	)["total"] or Decimal("0")
	send(consumer, {"target": "#fe-total", "html": f"{format_money(total)} €"})
	update_budget(consumer, year, month)


@liveview_handler("clone_fixed_expenses")
def clone_fixed_expenses(consumer, content):
	form = content.get("form", {})
	source = form.get("clone_fe_source", "")
	year = int(form.get("year", 0))
	month = int(form.get("month", 0))

	if not source or not year or not month:
		return

	try:
		src_year, src_month = source.split("-")
		src_year, src_month = int(src_year), int(src_month)
	except ValueError:
		return

	source_entries = MonthlyFixedExpense.objects.filter(
		year=src_year, month=src_month
	).select_related("concept")

	_ensure_entries_exist(year, month)
	for src in source_entries:
		MonthlyFixedExpense.objects.filter(
			year=year, month=month, concept=src.concept
		).update(amount=src.amount)

	html = _render_fixed_expenses_table(year, month)
	send(consumer, {"target": "#fixed-expenses-table", "html": html})
	update_budget(consumer, year, month)