# Copyright (c) 2021, Frappe Technologies Pvt. Ltd. and Contributors
# License: GNU General Public License v3. See license.txt

import frappe
from frappe import _
from frappe.utils import add_days, add_months, comma_sep, getdate, today

from erpnext.setup.doctype.employee.employee import get_all_employee_emails, get_employee_email

from hrms.hr.utils import get_holidays_for_employee


# -----------------
# HOLIDAY REMINDERS
# -----------------
def send_reminders_in_advance_weekly():
	to_send_in_advance = int(frappe.db.get_single_value("HR Settings", "send_holiday_reminders"))
	frequency = frappe.db.get_single_value("HR Settings", "frequency")
	if not (to_send_in_advance and frequency == "Weekly"):
		return

	send_advance_holiday_reminders("Weekly")


def send_reminders_in_advance_monthly():
	to_send_in_advance = int(frappe.db.get_single_value("HR Settings", "send_holiday_reminders"))
	frequency = frappe.db.get_single_value("HR Settings", "frequency")
	if not (to_send_in_advance and frequency == "Monthly"):
		return

	send_advance_holiday_reminders("Monthly")


def send_advance_holiday_reminders(frequency):
	"""Send Holiday Reminders in Advance to Employees
	`frequency` (str): 'Weekly' or 'Monthly'
	"""
	if frequency == "Weekly":
		start_date = getdate()
		end_date = add_days(getdate(), 7)
	elif frequency == "Monthly":
		# Sent on 1st of every month
		start_date = getdate()
		end_date = add_months(getdate(), 1)
	else:
		return

	employees = frappe.db.get_all("Employee", filters={"status": "Active"}, pluck="name")
	for employee in employees:
		holidays = get_holidays_for_employee(
			employee, start_date, end_date, only_non_weekly=True, raise_exception=False
		)

		send_holidays_reminder_in_advance(employee, holidays)


def send_holidays_reminder_in_advance(employee, holidays):
	if not holidays:
		return

	employee_doc = frappe.get_doc("Employee", employee)
	employee_email = get_employee_email(employee_doc)
	frequency = frappe.db.get_single_value("HR Settings", "frequency")
	sender_email = get_sender_email()
	email_header = _("Holidays this Month.") if frequency == "Monthly" else _("Holidays this Week.")
	frappe.sendmail(
		sender=sender_email,
		recipients=[employee_email],
		subject=_("Upcoming Holidays Reminder"),
		template="holiday_reminder",
		args=dict(
			reminder_text=_("Hey {}! This email is to remind you about the upcoming holidays.").format(
				employee_doc.get("first_name")
			),
			message=_("Below is the list of upcoming holidays for you:"),
			advance_holiday_reminder=True,
			holidays=holidays,
			frequency=frequency[:-2],
		),
		header=email_header,
	)


# ------------------
# BIRTHDAY REMINDERS
# ------------------
def send_birthday_reminders():
	"""Send Employee birthday reminders if no 'Stop Birthday Reminders' is not set."""

	to_send = int(frappe.db.get_single_value("HR Settings", "send_birthday_reminders"))
	if not to_send:
		return

	sender = get_sender_email()
	employees_born_today = get_employees_who_are_born_today()

	for company, birthday_persons in employees_born_today.items():
		employee_emails = get_all_employee_emails(company)
		birthday_person_emails = [get_employee_email(doc) for doc in birthday_persons]
		recipients = list(set(employee_emails) - set(birthday_person_emails))

		reminder_text, message = get_birthday_reminder_text_and_message(birthday_persons)
		send_birthday_reminder(recipients, reminder_text, birthday_persons, message, sender)

		if len(birthday_persons) > 1:
			# special email for people sharing birthdays
			for person in birthday_persons:
				person_email = person["user_id"] or person["personal_email"] or person["company_email"]
				others = [d for d in birthday_persons if d != person]
				reminder_text, message = get_birthday_reminder_text_and_message(others)
				send_birthday_reminder(person_email, reminder_text, others, message, sender)


def get_birthday_reminder_text_and_message(birthday_persons):
	if len(birthday_persons) == 1:
		birthday_person_text = birthday_persons[0]["name"]
	else:
		# converts ["Jim", "Rim", "Dim"] to Jim, Rim & Dim
		person_names = [d["name"] for d in birthday_persons]
		birthday_person_text = comma_sep(person_names, frappe._("{0} & {1}"), False)

	reminder_text = _("Today is {0}'s birthday 🎉").format(birthday_person_text)
	message = _("A friendly reminder of an important date for our team.")
	message += "<br>"
	message += _("Everyone, let’s congratulate {0} on their birthday.").format(birthday_person_text)

	return reminder_text, message


def send_birthday_reminder(recipients, reminder_text, birthday_persons, message, sender=None):
	frappe.sendmail(
		sender=sender,
		recipients=recipients,
		subject=_("Birthday Reminder"),
		template="birthday_reminder",
		args=dict(
			reminder_text=reminder_text,
			birthday_persons=birthday_persons,
			message=message,
		),
		header=_("Birthday Reminder 🎂"),
	)


def get_employees_who_are_born_today():
	"""Get all employee born today & group them based on their company"""
	return get_employees_having_an_event_today("birthday")


def get_employees_having_an_event_today(event_type):
	"""Get all employee who have `event_type` today
	& group them based on their company. `event_type`
	can be `birthday` or `work_anniversary`"""

	from collections import defaultdict

	# Set column based on event type
	if event_type == "birthday":
		condition_column = "date_of_birth"
	elif event_type == "work_anniversary":
		condition_column = "date_of_joining"
	else:
		return

	employees_born_today = frappe.db.multisql(
		{
			"mariadb": f"""
			SELECT `personal_email`, `company`, `company_email`, `user_id`, `employee_name` AS 'name', `image`, `date_of_joining`
			FROM `tabEmployee`
			WHERE
				DAY({condition_column}) = DAY(%(today)s)
			AND
				MONTH({condition_column}) = MONTH(%(today)s)
			AND
				YEAR({condition_column}) < YEAR(%(today)s)
			AND
				`status` = 'Active'
		""",
			"postgres": f"""
			SELECT "personal_email", "company", "company_email", "user_id", "employee_name" AS 'name', "image"
			FROM "tabEmployee"
			WHERE
				DATE_PART('day', {condition_column}) = date_part('day', %(today)s)
			AND
				DATE_PART('month', {condition_column}) = date_part('month', %(today)s)
			AND
				DATE_PART('year', {condition_column}) < date_part('year', %(today)s)
			AND
				"status" = 'Active'
		""",
		},
		dict(today=today(), condition_column=condition_column),
		as_dict=1,
	)

	grouped_employees = defaultdict(lambda: [])

	for employee_doc in employees_born_today:
		grouped_employees[employee_doc.get("company")].append(employee_doc)

	return grouped_employees


# --------------------------
# WORK ANNIVERSARY REMINDERS
# --------------------------
def send_work_anniversary_reminders():
	"""Send Employee Work Anniversary Reminders if 'Send Work Anniversary Reminders' is checked"""
	to_send = int(frappe.db.get_single_value("HR Settings", "send_work_anniversary_reminders"))
	if not to_send:
		return

	sender = get_sender_email()
	employees_joined_today = get_employees_having_an_event_today("work_anniversary")

	message = _("A friendly reminder of an important date for our team.")
	message += "<br>"
	message += _("Everyone, let’s congratulate them on their work anniversary!")

	for company, anniversary_persons in employees_joined_today.items():
		employee_emails = get_all_employee_emails(company)
		anniversary_person_emails = [get_employee_email(doc) for doc in anniversary_persons]
		recipients = list(set(employee_emails) - set(anniversary_person_emails))

		reminder_text = get_work_anniversary_reminder_text(anniversary_persons)
		send_work_anniversary_reminder(recipients, reminder_text, anniversary_persons, message, sender)

		if len(anniversary_persons) > 1:
			# email for people sharing work anniversaries
			for person in anniversary_persons:
				person_email = person["user_id"] or person["personal_email"] or person["company_email"]
				others = [d for d in anniversary_persons if d != person]
				reminder_text = get_work_anniversary_reminder_text(others)
				send_work_anniversary_reminder(person_email, reminder_text, others, message, sender)


def get_work_anniversary_reminder_text(anniversary_persons: list) -> str:
	if len(anniversary_persons) == 1:
		anniversary_person = anniversary_persons[0]["name"]
		completed_years = getdate().year - anniversary_persons[0]["date_of_joining"].year
		return _("Today {0} completed {1} year(s) at our Company! 🎉").format(
			_(anniversary_person), completed_years
		)

	names_grouped_by_years = {}

	for person in anniversary_persons:
		# Number of years completed at the company
		completed_years = getdate().year - person["date_of_joining"].year
		names_grouped_by_years.setdefault(completed_years, []).append(person["name"])

	person_names_with_years = [
		_("{0} completed {1} year(s)").format(comma_sep(person_names, _("{0} & {1}"), False), years)
		for years, person_names in names_grouped_by_years.items()
	]

	# converts ["Jim", "Rim", "Dim"] to Jim, Rim & Dim
	anniversary_person = comma_sep(person_names_with_years, _("{0} & {1}"), False)
	return _("Today {0} at our Company! 🎉").format(_(anniversary_person))


def send_work_anniversary_reminder(
	recipients,
	reminder_text,
	anniversary_persons,
	message,
	sender=None,
):
	frappe.sendmail(
		sender=sender,
		recipients=recipients,
		subject=_("Work Anniversary Reminder"),
		template="anniversary_reminder",
		args=dict(
			reminder_text=reminder_text,
			anniversary_persons=anniversary_persons,
			message=message,
		),
		header=_("Work Anniversary Reminder"),
	)


def get_sender_email() -> str | None:
	return frappe.db.get_single_value("HR Settings", "sender_email")