Payroll Period - validate dates and overlap

erpnext/hr/doctype/payroll_period/payroll_period.py

@@ -4,11 +4,45 @@
 
 from __future__ import unicode_literals
 import frappe
-from frappe.utils import date_diff, getdate
+from frappe import _
+from frappe.utils import date_diff, getdate, formatdate
 from frappe.model.document import Document
 
 class PayrollPeriod(Document):
-	pass
+	def validate(self):
+		self.validate_dates()
+		self.validate_overlap()
+
+	def validate_dates(self):
+		if getdate(self.start_date) > getdate(self.end_date):
+			frappe.throw(_("End date can not be less than start date"))
+
+	def validate_overlap(self):
+		query = """
+			select name
+			from `tab{0}`
+			where name != %(name)s
+			and company = %(company)s and (start_date between %(start_date)s and %(end_date)s \
+				or end_date between %(start_date)s and %(end_date)s \
+				or (start_date < %(start_date)s and end_date > %(end_date)s))
+			"""
+		if not self.name:
+			# hack! if name is null, it could cause problems with !=
+			self.name = "New "+self.doctype
+
+		overlap_doc = frappe.db.sql(query.format(self.doctype),{
+				"start_date": self.start_date,
+				"end_date": self.end_date,
+				"name": self.name,
+				"company": self.company
+			}, as_dict = 1)
+
+		if overlap_doc:
+			msg = _("A {0} exists between {1} and {2} (").format(self.doctype,
+				formatdate(self.start_date), formatdate(self.end_date)) \
+				+ """ <b><a href="#Form/{0}/{1}">{1}</a></b>""".format(self.doctype, overlap_doc[0].name) \
+				+ _(") for {0}").format(self.company)
+			frappe.throw(msg)
 
 def get_payroll_period_days(start_date, end_date, company):
 	payroll_period_dates = frappe.db.sql("""