From c47cbfd2efb2f72133494b7b68940fe14410ccf8 Mon Sep 17 00:00:00 2001
From: Gavin D'souza <gavin18d@gmail.com>
Date: Tue, 13 Jul 2021 17:03:30 +0530
Subject: [PATCH] refactor: Set Language in HTTPHeader

Order of priority for setting language:
1. Form Dict => _lang
2. Cookie => preferred_language
3. Request Header => Accept-Language
4. User document => language
5. System Settings => language

Cookie is placed at #2 since the language picker in the navbar depends
on it. And the Accept-Language header sends values based on the client's locales.

---

Form Dict _lang now accepts language codes too. Previously, language
names were used...for whatever reason.
---
 frappe/auth.py      | 13 +++-----
 frappe/translate.py | 78 ++++++++++++++++++++++++++++++++-------------
 2 files changed, 59 insertions(+), 32 deletions(-)

diff --git a/frappe/auth.py b/frappe/auth.py
index a95c41906d..9135b139ae 100644
--- a/frappe/auth.py
+++ b/frappe/auth.py
@@ -5,13 +5,13 @@ from frappe import _
 import frappe
 import frappe.database
 import frappe.utils
-from frappe.utils import cint, flt, get_datetime, datetime, date_diff, today
+from frappe.utils import cint, get_datetime, datetime, date_diff, today
 import frappe.utils.user
 from frappe import conf
 from frappe.sessions import Session, clear_sessions, delete_session
 from frappe.modules.patch_handler import check_session_stopped
-from frappe.translate import get_lang_code, guess_language
-from frappe.utils.password import check_password, delete_login_failed_cache
+from frappe.translate import guess_language
+from frappe.utils.password import check_password
 from frappe.core.doctype.activity_log.activity_log import add_authentication_log
 from frappe.twofactor import (should_run_2fa, authenticate_for_2factor,
 	confirm_otp_token, get_cached_user_pass)
@@ -92,12 +92,7 @@ class HTTPRequest:
 				frappe.throw(_("Invalid Request"), frappe.CSRFTokenError)
 
 	def set_lang(self):
-		if frappe.form_dict._lang:
-			lang = get_lang_code(frappe.form_dict._lang)
-			if lang:
-				frappe.local.lang = lang
-		else:
-			frappe.local.lang = guess_language()
+		frappe.local.lang = guess_language()
 
 	def get_db_name(self):
 		"""get database name from conf"""
diff --git a/frappe/translate.py b/frappe/translate.py
index 8344436d94..c567d0615c 100644
--- a/frappe/translate.py
+++ b/frappe/translate.py
@@ -11,6 +11,7 @@ import io
 import itertools
 import json
 import operator
+import functools
 import os
 import re
 from csv import reader
@@ -21,36 +22,64 @@ from frappe.utils import is_html, strip, strip_html_tags
 
 
 def guess_language(lang_list=None):
-	"""Set `frappe.local.lang` from HTTP headers at beginning of request"""
+	"""Set `frappe.local.lang` from HTTP headers at beginning of request
+
+	Order of priority for setting language:
+	1. Form Dict => _lang
+	2. Cookie => preferred_language
+	3. Request Header => Accept-Language
+	4. User document => language
+	5. System Settings => language
+	"""
+
+	# fetch language from form_dict
+	if frappe.form_dict._lang:
+		language = get_lang_code(
+			frappe.form_dict._lang or get_parent_language(frappe.form_dict._lang)
+		)
+		if language:
+			return language
+
+	lang_set = set(lang_list or get_all_languages() or [])
+
+	# fetch language from cookie
 	preferred_language_cookie = frappe.request.cookies.get('preferred_language')
-	lang_codes = list(frappe.request.accept_languages.values())
 
 	if preferred_language_cookie:
-		lang_codes.append(preferred_language_cookie)
+		if preferred_language_cookie in lang_set:
+			return preferred_language_cookie
 
-	if not lang_codes:
-		return frappe.local.lang
+		parent_language = get_parent_language(language)
+		if parent_language in lang_set:
+			return parent_language
 
-	guess = None
-	if not lang_list:
-		lang_list = get_all_languages() or []
+	# fetch language from request headers
+	accept_language = list(frappe.request.accept_languages.values())
 
-	for l in lang_codes:
-		code = l.strip()
-		if not isinstance(code, str):
-			code = str(code, 'utf-8')
-		if code in lang_list or code == "en":
-			guess = code
-			break
+	for language in accept_language:
+		if language in lang_set:
+			return language
 
-		# check if parent language (pt) is setup, if variant (pt-BR)
-		if "-" in code:
-			code = code.split("-")[0]
-			if code in lang_list:
-				guess = code
-				break
+		parent_language = get_parent_language(language)
+		if parent_language in lang_set:
+			return parent_language
+
+	# fallback to language set in User or System Settings
+	return frappe.local.lang
+
+
+@functools.lru_cache(maxsize=None)
+def get_parent_language(lang: str) -> str:
+	"""If the passed language is a variant, return its parent
+
+	Eg:
+		1. zh-TW -> zh
+		2. sr-BA -> sr
+	"""
+	is_language_variant = "-" in lang
+	if is_language_variant:
+		return lang[:lang.index("-")]
 
-	return guess or frappe.local.lang
 
 def get_user_lang(user=None):
 	"""Set frappe.local.lang from user preferences on session beginning or resumption"""
@@ -75,7 +104,10 @@ def get_user_lang(user=None):
 	return lang
 
 def get_lang_code(lang):
-	return frappe.db.get_value('Language', {'language_name': lang}) or lang
+	return (
+		frappe.db.get_value("Language", {"name": lang})
+		or frappe.db.get_value("Language", {"language_name": lang})
+	)
 
 def set_default_language(lang):
 	"""Set Global default language"""