import csv
from datetime import timedelta

from django.http import HttpResponse
from django.shortcuts import render, redirect
from django.contrib.auth.decorators import login_required
from django.utils import timezone

from .models import Category, Expense, FixedExpenseConcept
from .forms import ExpenseForm


@login_required
def dashboard(request):
	form = ExpenseForm()
	context = {"form": form}
	return render(request, "pages/expenses/dashboard.html", context)


@login_required
def add_expense(request):
	if request.method == "POST":
		form = ExpenseForm(request.POST)
		if form.is_valid():
			form.save()
			return redirect("expenses:expense_success")

		context = {"form": form}
		return render(request, "pages/expenses/dashboard.html", context)

	return redirect("expenses:dashboard")


@login_required
def expense_success(request):
	return render(request, "pages/expenses/expense_success.html")


@login_required
def week_view(request):
	from collections import OrderedDict
	from decimal import Decimal

	today = timezone.localdate()
	offset = int(request.GET.get("offset", 0))
	monday = today - timedelta(days=today.weekday()) + timedelta(weeks=offset)
	sunday = monday + timedelta(days=6)
	expenses = Expense.objects.filter(
		created_at__date__gte=monday,
		created_at__date__lte=sunday,
	).select_related("category", "subcategory")

	categories_data = OrderedDict()
	total = Decimal("0")
	for expense in expenses:
		cat = expense.category
		if cat.id not in categories_data:
			categories_data[cat.id] = {
				"category": cat,
				"expenses": [],
				"subcategory_totals": OrderedDict(),
				"total": Decimal("0"),
			}
		entry = categories_data[cat.id]
		entry["expenses"].append(expense)
		entry["total"] += expense.amount
		total += expense.amount

		sub = expense.subcategory
		if sub.id not in entry["subcategory_totals"]:
			entry["subcategory_totals"][sub.id] = {
				"subcategory": sub,
				"total": Decimal("0"),
			}
		entry["subcategory_totals"][sub.id]["total"] += expense.amount

	is_current_week = offset == 0
	context = {
		"categories_data": categories_data.values(),
		"total": total,
		"monday": monday,
		"sunday": sunday,
		"offset": offset,
		"prev_offset": offset - 1,
		"next_offset": offset + 1,
		"is_current_week": is_current_week,
	}
	return render(request, "pages/expenses/week.html", context)


@login_required
def settings_view(request):
	categories = Category.objects.all().prefetch_related("subcategories")
	fixed_expenses = FixedExpenseConcept.objects.all()
	context = {"categories": categories, "fixed_expenses": fixed_expenses}
	return render(request, "pages/expenses/settings.html", context)


@login_required
def export_csv(request):
	response = HttpResponse(content_type="text/csv")
	response["Content-Disposition"] = 'attachment; filename="kakebo_expenses.csv"'
	response.write("\ufeff")  # BOM for Excel UTF-8

	writer = csv.writer(response, delimiter=";")
	writer.writerow(["Date", "Concept", "Amount", "Category", "Subcategory"])

	expenses = Expense.objects.all().select_related("category", "subcategory")
	for expense in expenses:
		writer.writerow(
			[
				expense.created_at.strftime("%Y-%m-%d"),
				expense.concept,
				str(expense.amount),
				expense.category.name,
				expense.subcategory.name,
			]
		)

	return response