From a44df63a9119148adda806bae077f96330192bfb Mon Sep 17 00:00:00 2001
From: Ankush Menat <ankush@iwebnotes.com>
Date: Mon, 1 Mar 2021 17:12:53 +0530
Subject: [PATCH] fix: Add warning for invalid GST invoice numbers

GST Invoice numbers should be 16 characters alphanumeric with dash(/) or
slash(-) only. Add check for doc.name before saving and warn about
naming series.
---
 erpnext/hooks.py                |  3 +++
 erpnext/regional/india/utils.py | 16 +++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/erpnext/hooks.py b/erpnext/hooks.py
index 59639ffc43..f87769c182 100644
--- a/erpnext/hooks.py
+++ b/erpnext/hooks.py
@@ -278,6 +278,9 @@ doc_events = {
 	('Sales Invoice', 'Sales Order', 'Delivery Note', 'Purchase Invoice', 'Purchase Order', 'Purchase Receipt'): {
 		'validate': ['erpnext.regional.india.utils.set_place_of_supply']
 	},
+	('Sales Invoice', 'Purchase Invoice'): {
+		'validate': ['erpnext.regional.india.utils.validate_document_name']
+	},
 	"Contact": {
 		"on_trash": "erpnext.support.doctype.issue.issue.update_issue",
 		"after_insert": "erpnext.telephony.doctype.call_log.call_log.link_existing_conversations",
diff --git a/erpnext/regional/india/utils.py b/erpnext/regional/india/utils.py
index cb30605291..7980d0b9ff 100644
--- a/erpnext/regional/india/utils.py
+++ b/erpnext/regional/india/utils.py
@@ -2,7 +2,7 @@ from __future__ import unicode_literals
 import frappe, re, json
 from frappe import _
 import erpnext
-from frappe.utils import cstr, flt, date_diff, nowdate, round_based_on_smallest_currency_fraction, money_in_words
+from frappe.utils import cstr, flt, date_diff, nowdate, round_based_on_smallest_currency_fraction, money_in_words, getdate
 from erpnext.regional.india import states, state_numbers
 from erpnext.controllers.taxes_and_totals import get_itemised_tax, get_itemised_taxable_amount
 from erpnext.controllers.accounts_controller import get_taxes_and_charges
@@ -148,6 +148,20 @@ def get_itemised_tax_breakup_data(doc, account_wise=False):
 def set_place_of_supply(doc, method=None):
 	doc.place_of_supply = get_place_of_supply(doc, doc.doctype)
 
+def validate_document_name(doc, method=None):
+	"""Validate GST invoice number requirements."""
+	country = frappe.get_cached_value("Company", doc.company, "country")
+
+	if country != "India" or getdate(doc.posting_date) < getdate("2021-04-01"):
+		return
+
+	if len(doc.name) > 16:
+		frappe.throw(_("Maximum length of document number should be 16 characters as per GST rules. Please change the naming series."))
+
+	gst_doc_name_pattern = re.compile(r"^[a-zA-Z0-9\-/]+$")
+	if not gst_doc_name_pattern.match(doc.name):
+		frappe.throw(_("Document name should only contain alphanumeric values, dash(-) and slash(/) characters as per GST rules. Please change the naming series."))
+
 # don't remove this function it is used in tests
 def test_method():
 	'''test function'''