refactor:

- current_invoice _start and end should be determined by trial period or billing period
- adds new functions to get billing period data

erpnext/accounts/doctype/subscriptions/subscriptions.py

@@ -5,7 +5,7 @@
 from __future__ import unicode_literals
 import frappe
 from frappe.model.document import Document
-from frappe.utils.data import now, nowdate, getdate, cint, add_days, date_diff, get_last_day, get_first_day
+from frappe.utils.data import now, nowdate, getdate, cint, add_days, date_diff, get_last_day, get_first_day, add_to_date
 from frappe import _
 
 
@@ -25,17 +25,58 @@ class Subscriptions(Document):
 		if self.trial_period_start and self.is_trialling():
 			self.current_invoice_start = self.trial_period_start
 		elif not date:
-			current_invoice = self.get_current_invoice()
+			self.current_invoice_start = nowdate()
-			if not current_invoice:
-				self.current_invoice_start = nowdate()
-			else:
-				self.current_invoice_start = current_invoice.posting_date
 
 	def set_current_invoice_end(self):
 		if self.is_trialling():
 			self.current_invoice_end = self.trial_period_end
 		else:
-			self.current_invoice_end = get_last_day(self.current_invoice_start)
+			billing_cycle_info = self.get_billing_cycle()
+			if billing_cycle_info:
+				self.current_invoice_end = add_to_date(self.current_invoice_start, **billing_cycle_info)
+			else:
+				self.current_invoice_end = get_last_day(self.current_invoice_start)
+
+	def get_billing_cycle(self):
+		return self.get_billing_cycle_data()
+
+	def validate_plans_billing_cycle(self, billing_cycle_data):
+		if billing_cycle_data and len(billing_cycle_data) != 1:
+			frappe.throw(_('You can only have Plans with the same billing cycle in a Subscription'))
+
+	def get_billing_cycle_and_interval(self):
+		plan_names = [plan.plan for plan in self.plans]
+		billing_info = frappe.db.sql(
+			'select distinct `billing_interval`, `billing_interval_count` '
+			'from `tabSubscription Plan` '
+			'where name in %s',
+			(plan_names,), as_dict=1
+		)
+
+		return billing_info
+
+	def get_billing_cycle_data(self):
+		billing_info = self.get_billing_cycle_and_interval()
+
+		self.validate_plans_billing_cycle(billing_info)
+
+		if billing_info:
+			data = dict()
+			interval = billing_info[0]['billing_interval']
+			interval_count = billing_info[0]['billing_interval_count']
+			if interval not in ['Day', 'Week']:
+				data['days'] = -1
+			if interval == 'Day':
+				data['days'] = interval_count - 1
+			elif interval == 'Month':
+				data['months'] = interval_count
+			elif interval == 'Year':
+				data['years'] == interval_count
+			# todo: test week
+			elif interval == 'Week':
+				data['days'] = interval_count * 7 - 1
+
+			return data
 
 	def before_save(self):
 		self.set_status()
@@ -89,6 +130,7 @@ class Subscriptions(Document):
 
 	def validate(self):
 		self.validate_trial_period()
+		self.validate_plans_billing_cycle(self.get_billing_cycle_and_interval())
 
 	def validate_trial_period(self):
 		if self.trial_period_start and self.trial_period_end: