# Copyright (c) 2013, Frappe Technologies Pvt. Ltd. and contributors
# For license information, please see license.txt
import datetime
from typing import List

import frappe
from frappe import _, scrub
from frappe.utils import get_first_day as get_first_day_of_month
from frappe.utils import get_first_day_of_week, get_quarter_start, getdate

from erpnext.accounts.utils import get_fiscal_year
from erpnext.stock.report.stock_balance.stock_balance import (
	get_item_details,
	get_items,
	get_stock_ledger_entries,
)
from erpnext.stock.utils import is_reposting_item_valuation_in_progress


def execute(filters=None):
	is_reposting_item_valuation_in_progress()
	filters = frappe._dict(filters or {})
	columns = get_columns(filters)
	data = get_data(filters)
	chart = get_chart_data(columns)

	return columns, data, None, chart


def get_columns(filters):
	columns = [
		{"label": _("Item"), "options": "Item", "fieldname": "name", "fieldtype": "Link", "width": 140},
		{
			"label": _("Item Name"),
			"options": "Item",
			"fieldname": "item_name",
			"fieldtype": "Link",
			"width": 140,
		},
		{
			"label": _("Item Group"),
			"options": "Item Group",
			"fieldname": "item_group",
			"fieldtype": "Link",
			"width": 140,
		},
		{"label": _("Brand"), "fieldname": "brand", "fieldtype": "Data", "width": 120},
		{"label": _("UOM"), "fieldname": "uom", "fieldtype": "Data", "width": 120},
	]

	ranges = get_period_date_ranges(filters)

	for dummy, end_date in ranges:
		period = get_period(end_date, filters)

		columns.append(
			{"label": _(period), "fieldname": scrub(period), "fieldtype": "Float", "width": 120}
		)

	return columns


def get_period_date_ranges(filters):
	from dateutil.relativedelta import relativedelta

	from_date = round_down_to_nearest_frequency(filters.from_date, filters.range)
	to_date = getdate(filters.to_date)

	increment = {"Monthly": 1, "Quarterly": 3, "Half-Yearly": 6, "Yearly": 12}.get(filters.range, 1)

	periodic_daterange = []
	for dummy in range(1, 53, increment):
		if filters.range == "Weekly":
			period_end_date = from_date + relativedelta(days=6)
		else:
			period_end_date = from_date + relativedelta(months=increment, days=-1)

		if period_end_date > to_date:
			period_end_date = to_date
		periodic_daterange.append([from_date, period_end_date])

		from_date = period_end_date + relativedelta(days=1)
		if period_end_date == to_date:
			break

	return periodic_daterange


def round_down_to_nearest_frequency(date: str, frequency: str) -> datetime.datetime:
	"""Rounds down the date to nearest frequency unit.
	example:

	>>> round_down_to_nearest_frequency("2021-02-21", "Monthly")
	datetime.datetime(2021, 2, 1)

	>>> round_down_to_nearest_frequency("2021-08-21", "Yearly")
	datetime.datetime(2021, 1, 1)
	"""

	def _get_first_day_of_fiscal_year(date):
		fiscal_year = get_fiscal_year(date)
		return fiscal_year and fiscal_year[1] or date

	round_down_function = {
		"Monthly": get_first_day_of_month,
		"Quarterly": get_quarter_start,
		"Weekly": get_first_day_of_week,
		"Yearly": _get_first_day_of_fiscal_year,
	}.get(frequency, getdate)
	return round_down_function(date)


def get_period(posting_date, filters):
	months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]

	if filters.range == "Weekly":
		period = "Week " + str(posting_date.isocalendar()[1]) + " " + str(posting_date.year)
	elif filters.range == "Monthly":
		period = str(months[posting_date.month - 1]) + " " + str(posting_date.year)
	elif filters.range == "Quarterly":
		period = "Quarter " + str(((posting_date.month - 1) // 3) + 1) + " " + str(posting_date.year)
	else:
		year = get_fiscal_year(posting_date, company=filters.company)
		period = str(year[2])

	return period


def get_periodic_data(entry, filters):
	"""Structured as:
	Item 1
	        - Balance (updated and carried forward):
	                        - Warehouse A : bal_qty/value
	                        - Warehouse B : bal_qty/value
	        - Jun 2021 (sum of warehouse quantities used in report)
	                        - Warehouse A : bal_qty/value
	                        - Warehouse B : bal_qty/value
	        - Jul 2021 (sum of warehouse quantities used in report)
	                        - Warehouse A : bal_qty/value
	                        - Warehouse B : bal_qty/value
	Item 2
	        - Balance (updated and carried forward):
	                        - Warehouse A : bal_qty/value
	                        - Warehouse B : bal_qty/value
	        - Jun 2021 (sum of warehouse quantities used in report)
	                        - Warehouse A : bal_qty/value
	                        - Warehouse B : bal_qty/value
	        - Jul 2021 (sum of warehouse quantities used in report)
	                        - Warehouse A : bal_qty/value
	                        - Warehouse B : bal_qty/value
	"""

	expected_ranges = get_period_date_ranges(filters)
	expected_periods = []
	for _start_date, end_date in expected_ranges:
		expected_periods.append(get_period(end_date, filters))

	periodic_data = {}
	for d in entry:
		period = get_period(d.posting_date, filters)
		bal_qty = 0

		fill_intermediate_periods(periodic_data, d.item_code, period, expected_periods)

		# if period against item does not exist yet, instantiate it
		# insert existing balance dict against period, and add/subtract to it
		if periodic_data.get(d.item_code) and not periodic_data.get(d.item_code).get(period):
			previous_balance = periodic_data[d.item_code]["balance"].copy()
			periodic_data[d.item_code][period] = previous_balance

		if d.voucher_type == "Stock Reconciliation" and not d.batch_no:
			if periodic_data.get(d.item_code) and periodic_data.get(d.item_code).get("balance").get(
				d.warehouse
			):
				bal_qty = periodic_data[d.item_code]["balance"][d.warehouse]

			qty_diff = d.qty_after_transaction - bal_qty
		else:
			qty_diff = d.actual_qty

		if filters["value_quantity"] == "Quantity":
			value = qty_diff
		else:
			value = d.stock_value_difference

		# period-warehouse wise balance
		periodic_data.setdefault(d.item_code, {}).setdefault("balance", {}).setdefault(d.warehouse, 0.0)
		periodic_data.setdefault(d.item_code, {}).setdefault(period, {}).setdefault(d.warehouse, 0.0)

		periodic_data[d.item_code]["balance"][d.warehouse] += value
		periodic_data[d.item_code][period][d.warehouse] = periodic_data[d.item_code]["balance"][
			d.warehouse
		]

	return periodic_data


def fill_intermediate_periods(
	periodic_data, item_code: str, current_period: str, all_periods: List[str]
) -> None:
	"""There might be intermediate periods where no stock ledger entry exists, copy previous previous data.

	Previous data is ONLY copied if period falls in report range and before period being processed currently.

	args:
	        current_period: process till this period (exclusive)
	        all_periods: all periods expected in report via filters
	        periodic_data: report's periodic data
	        item_code: item_code being processed
	"""

	previous_period_data = None
	for period in all_periods:
		if period == current_period:
			return

		if (
			periodic_data.get(item_code)
			and not periodic_data.get(item_code).get(period)
			and previous_period_data
		):
			# This period should exist since it's in report range, assign previous period data
			periodic_data[item_code][period] = previous_period_data.copy()

		previous_period_data = periodic_data.get(item_code, {}).get(period)


def get_data(filters):
	data = []
	items = get_items(filters)
	sle = get_stock_ledger_entries(filters, items)
	item_details = get_item_details(items, sle, filters)
	periodic_data = get_periodic_data(sle, filters)
	ranges = get_period_date_ranges(filters)

	today = getdate()

	for dummy, item_data in item_details.items():
		row = {
			"name": item_data.name,
			"item_name": item_data.item_name,
			"item_group": item_data.item_group,
			"uom": item_data.stock_uom,
			"brand": item_data.brand,
		}
		previous_period_value = 0.0
		for start_date, end_date in ranges:
			period = get_period(end_date, filters)
			period_data = periodic_data.get(item_data.name, {}).get(period)
			if period_data:
				row[scrub(period)] = previous_period_value = sum(period_data.values())
			else:
				row[scrub(period)] = previous_period_value if today >= start_date else None

		data.append(row)

	return data


def get_chart_data(columns):
	labels = [d.get("label") for d in columns[5:]]
	chart = {"data": {"labels": labels, "datasets": []}}
	chart["type"] = "line"

	return chart