Added the initial application with the main account list, the pagination, the query, the permission, the localization, the documentation, the test case, and a test demonstration site.

2023-01-29 22:28:27 +08:00
parent 9c83ad97c1
commit 14638f574e
45 changed files with 3302 additions and 0 deletions
--- a/tests/babel-utils-testsite.py
+++ b/tests/babel-utils-testsite.py
@ -0,0 +1,133 @@
+#! env python3
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/28
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The translation management utilities for the test site.
+
+"""
+import os
+import re
+from pathlib import Path
+from time import strftime
+
+import click
+from babel.messages.frontend import CommandLineInterface
+from opencc import OpenCC
+
+root_dir: Path = Path(__file__).parent.parent
+translation_dir: Path = root_dir / "tests" / "testsite" / "translations"
+domain: str = "messages"
+
+
+@click.group()
+def main() -> None:
+    """Manages the message translation."""
+
+
+@click.command("extract")
+def babel_extract() -> None:
+    """Extracts the messages for translation."""
+    os.chdir(root_dir)
+    cfg: Path = translation_dir / "babel.cfg"
+    pot: Path = translation_dir / f"{domain}.pot"
+    zh_hant: Path = translation_dir / "zh_Hant" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    zh_hans: Path = translation_dir / "zh_Hans" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    CommandLineInterface().run([
+        "pybabel", "extract", "-F", str(cfg), "-k", "lazy_gettext", "-k", "A_",
+        "-o", str(pot), str(Path("tests") / "testsite")])
+    if not zh_hant.exists():
+        zh_hant.touch()
+    if not zh_hans.exists():
+        zh_hans.touch()
+    CommandLineInterface().run([
+        "pybabel", "update", "-i", str(pot), "-D", domain,
+        "-d", translation_dir])
+
+
+@click.command("compile")
+def babel_compile() -> None:
+    """Compiles the translated messages."""
+    __convert_chinese()
+    __update_rev_date()
+    CommandLineInterface().run([
+        "pybabel", "compile", "-D", domain, "-d", translation_dir])
+
+
+def __convert_chinese() -> None:
+    """Updates the Simplified Chinese translation according to the Traditional
+    Chinese translation.
+
+    :return: None.
+    """
+    cc: OpenCC = OpenCC("tw2sp")
+    zh_hant: Path = translation_dir / "zh_Hant" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    zh_hans: Path = translation_dir / "zh_Hans" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    now: str = strftime("%Y-%m-%d %H:%M%z")
+    with open(zh_hant, "r") as f:
+        content: str = f.read()
+    content = cc.convert(content)
+    content = re.sub(r"^# Chinese \\(Traditional\\) translations ",
+                     "# Chinese (Simplified) translations ", content)
+    content = re.sub(r"\n\"PO-Revision-Date: [^\n]*\"\n",
+                     f"\n\"PO-Revision-Date: {now}\\\\n\"\n",
+                     content)
+    content = content.replace("\n\"Language-Team: zh_Hant",
+                              "\n\"Language-Team: zh_Hans")
+    content = content.replace("\n\"Language: zh_Hant\\n\"\n",
+                              "\n\"Language: zh_Hans\\n\"\n")
+    content = content.replace("\nmsgstr \"zh-Hant\"\n",
+                              "\nmsgstr \"zh-Hans\"\n")
+    zh_hans.parent.mkdir(exist_ok=True)
+    with open(zh_hans, "w") as f:
+        f.write(content)
+
+
+def __update_rev_date() -> None:
+    """Updates the revision dates in the PO files.
+
+    :return: None.
+    """
+    for language_dir in translation_dir.glob("*"):
+        po_file: Path = language_dir / "LC_MESSAGES" / f"{domain}.po"
+        if po_file.is_file():
+            __update_file_rev_date(po_file)
+
+
+def __update_file_rev_date(file: Path) -> None:
+    """Updates the revision date of a PO file
+
+    :param file: The PO file.
+    :return: None.
+    """
+    now = strftime("%Y-%m-%d %H:%M%z")
+    with open(file, "r+") as f:
+        content = f.read()
+        content = re.sub(r"\n\"PO-Revision-Date: [^\n]*\"\n",
+                         f"\n\"PO-Revision-Date: {now}\\\\n\"\n",
+                         content)
+        f.seek(0)
+        f.write(content)
+
+
+main.add_command(babel_extract)
+main.add_command(babel_compile)
+
+if __name__ == '__main__':
+    main()
--- a/tests/babel-utils.py
+++ b/tests/babel-utils.py
@ -0,0 +1,133 @@
+#! env python3
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/28
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The translation management utilities.
+
+"""
+import os
+import re
+from pathlib import Path
+from time import strftime
+
+import click
+from babel.messages.frontend import CommandLineInterface
+from opencc import OpenCC
+
+root_dir: Path = Path(__file__).parent.parent
+translation_dir: Path = root_dir / "src" / "accounting" / "translations"
+domain: str = "accounting"
+
+
+@click.group()
+def main() -> None:
+    """Manages the message translation."""
+
+
+@click.command("extract")
+def babel_extract() -> None:
+    """Extracts the messages for translation."""
+    os.chdir(root_dir)
+    cfg: Path = translation_dir / "babel.cfg"
+    pot: Path = translation_dir / f"{domain}.pot"
+    zh_hant: Path = translation_dir / "zh_Hant" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    zh_hans: Path = translation_dir / "zh_Hans" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    CommandLineInterface().run([
+        "pybabel", "extract", "-F", str(cfg), "-k", "lazy_gettext", "-k", "A_",
+        "-o", str(pot), "src"])
+    if not zh_hant.exists():
+        zh_hant.touch()
+    if not zh_hans.exists():
+        zh_hans.touch()
+    CommandLineInterface().run([
+        "pybabel", "update", "-i", str(pot), "-D", domain,
+        "-d", translation_dir])
+
+
+@click.command("compile")
+def babel_compile() -> None:
+    """Compiles the translated messages."""
+    __convert_chinese()
+    __update_rev_date()
+    CommandLineInterface().run([
+        "pybabel", "compile", "-D", domain, "-d", translation_dir])
+
+
+def __convert_chinese() -> None:
+    """Updates the Simplified Chinese translation according to the Traditional
+    Chinese translation.
+
+    :return: None.
+    """
+    cc: OpenCC = OpenCC("tw2sp")
+    zh_hant: Path = translation_dir / "zh_Hant" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    zh_hans: Path = translation_dir / "zh_Hans" / "LC_MESSAGES"\
+        / f"{domain}.po"
+    now: str = strftime("%Y-%m-%d %H:%M%z")
+    with open(zh_hant, "r") as f:
+        content: str = f.read()
+    content = cc.convert(content)
+    content = re.sub(r"^# Chinese \\(Traditional\\) translations ",
+                     "# Chinese (Simplified) translations ", content)
+    content = re.sub(r"\n\"PO-Revision-Date: [^\n]*\"\n",
+                     f"\n\"PO-Revision-Date: {now}\\\\n\"\n",
+                     content)
+    content = content.replace("\n\"Language-Team: zh_Hant",
+                              "\n\"Language-Team: zh_Hans")
+    content = content.replace("\n\"Language: zh_Hant\\n\"\n",
+                              "\n\"Language: zh_Hans\\n\"\n")
+    content = content.replace("\nmsgstr \"zh-Hant\"\n",
+                              "\nmsgstr \"zh-Hans\"\n")
+    zh_hans.parent.mkdir(exist_ok=True)
+    with open(zh_hans, "w") as f:
+        f.write(content)
+
+
+def __update_rev_date() -> None:
+    """Updates the revision dates in the PO files.
+
+    :return: None.
+    """
+    for language_dir in translation_dir.glob("*"):
+        po_file: Path = language_dir / "LC_MESSAGES" / f"{domain}.po"
+        if po_file.is_file():
+            __update_file_rev_date(po_file)
+
+
+def __update_file_rev_date(file: Path) -> None:
+    """Updates the revision date of a PO file
+
+    :param file: The PO file.
+    :return: None.
+    """
+    now = strftime("%Y-%m-%d %H:%M%z")
+    with open(file, "r+") as f:
+        content = f.read()
+        content = re.sub(r"\n\"PO-Revision-Date: [^\n]*\"\n",
+                         f"\n\"PO-Revision-Date: {now}\\\\n\"\n",
+                         content)
+        f.seek(0)
+        f.write(content)
+
+
+main.add_command(babel_extract)
+main.add_command(babel_compile)
+
+if __name__ == '__main__':
+    main()
--- a/tests/test_base_account.py
+++ b/tests/test_base_account.py
@ -0,0 +1,113 @@
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/26
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+"""The test for the base account management.
+
+"""
+import unittest
+
+import httpx
+from click.testing import Result
+from flask import Flask
+from flask.testing import FlaskCliRunner
+
+from testlib import get_csrf_token
+from testsite import create_app
+
+
+class BaseAccountTestCase(unittest.TestCase):
+    """The base account test case."""
+
+    def setUp(self) -> None:
+        """Sets up the test.
+        This is run once per test.
+
+        :return: None.
+        """
+        self.app: Flask = create_app(is_testing=True)
+
+        runner: FlaskCliRunner = self.app.test_cli_runner()
+        with self.app.app_context():
+            result: Result = runner.invoke(args="init-db")
+            self.assertEqual(result.exit_code, 0)
+        self.client: httpx.Client = httpx.Client(app=self.app,
+                                                 base_url="https://testserver")
+        self.client.headers["Referer"] = "https://testserver"
+        self.csrf_token: str = get_csrf_token(self, self.client, "/login")
+
+    def test_init(self) -> None:
+        """Tests the "accounting-init-base" console command.
+
+        :return: None.
+        """
+        from accounting.base_account.models import BaseAccount, BaseAccountL10n
+        runner: FlaskCliRunner = self.app.test_cli_runner()
+        result: Result = runner.invoke(args="accounting-init-base")
+        self.assertEqual(result.exit_code, 0)
+        with self.app.app_context():
+            accounts: list[BaseAccount] = BaseAccount.query.all()
+            l10n: list[BaseAccountL10n] = BaseAccountL10n.query.all()
+        self.assertEqual(len(accounts), 527)
+        self.assertEqual(len(l10n), 527 * 2)
+        l10n_keys: set[str] = {f"{x.account_code}-{x.locale}" for x in l10n}
+        for account in accounts:
+            self.assertIn(f"{account.code}-zh_Hant", l10n_keys)
+            self.assertIn(f"{account.code}-zh_Hant", l10n_keys)
+
+        list_uri: str = "/accounting/base-accounts"
+        response: httpx.Response
+
+        self.__logout()
+        response = self.client.get(list_uri)
+        self.assertEqual(response.status_code, 403)
+
+        self.__logout()
+        self.__login_as("viewer")
+        response = self.client.get(list_uri)
+        self.assertEqual(response.status_code, 200)
+
+        self.__logout()
+        self.__login_as("editor")
+        response = self.client.get(list_uri)
+        self.assertEqual(response.status_code, 200)
+
+        self.__logout()
+        self.__login_as("nobody")
+        response = self.client.get(list_uri)
+        self.assertEqual(response.status_code, 403)
+
+    def __logout(self) -> None:
+        """Logs out the currently logged-in user.
+
+        :return: None.
+        """
+        response: httpx.Response = self.client.post(
+            "/logout", data={"csrf_token": self.csrf_token})
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(response.headers["Location"], "/")
+
+    def __login_as(self, username: str) -> None:
+        """Logs in as a specific user.
+
+        :param username: The username.
+        :return: None.
+        """
+        response: httpx.Response = self.client.post(
+            "/login", data={"csrf_token": self.csrf_token,
+                            "username": username})
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(response.headers["Location"], "/")
--- a/tests/testlib.py
+++ b/tests/testlib.py
@ -0,0 +1,56 @@
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/27
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The common test libraries.
+
+"""
+from html.parser import HTMLParser
+from unittest import TestCase
+
+import httpx
+
+
+def get_csrf_token(test_case: TestCase, client: httpx.Client, uri: str) -> str:
+    """Returns the CSRF token from a form in a URI.
+
+    :param test_case: The test case.
+    :param client: The httpx client.
+    :param uri: The URI.
+    :return: The CSRF token.
+    """
+
+    class CsrfParser(HTMLParser):
+        """The CSRF token parser."""
+
+        def __init__(self):
+            """Constructs the CSRF token parser."""
+            super().__init__()
+            self.csrf_token: str | None = None
+            """The CSRF token."""
+
+        def handle_starttag(self, tag: str,
+                            attrs: list[tuple[str, str | None]]) -> None:
+            """Handles when a start tag is found."""
+            attrs_dict: dict[str, str] = dict(attrs)
+            if attrs_dict.get("name") == "csrf_token":
+                self.csrf_token = attrs_dict["value"]
+
+    response: httpx.Response = client.get(uri)
+    test_case.assertEqual(response.status_code, 200)
+    parser: CsrfParser = CsrfParser()
+    parser.feed(response.text)
+    test_case.assertIsNotNone(parser.csrf_token)
+    return parser.csrf_token
--- a/tests/testsite/init.py
+++ b/tests/testsite/init.py
@ -0,0 +1,96 @@
+# The Mia! Accounting Flask Demonstration Website.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/27
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The Mia! Accounting Flask demonstration website.
+
+"""
+import typing as t
+from secrets import token_urlsafe
+
+import click
+from flask import Flask, Blueprint, render_template
+from flask.cli import with_appcontext
+from flask_babel_js import BabelJS
+from flask_sqlalchemy import SQLAlchemy
+from flask_wtf import CSRFProtect
+
+bp: Blueprint = Blueprint("home", __name__)
+babel_js: BabelJS = BabelJS()
+csrf: CSRFProtect = CSRFProtect()
+db: SQLAlchemy = SQLAlchemy()
+
+
+def create_app(is_testing: bool = False) -> Flask:
+    """Create and configure the application.
+
+    :param is_testing: True if we are running for testing, or False otherwise.
+    :return: The application.
+    """
+    import accounting
+
+    app: Flask = Flask(__name__)
+    db_uri: str = "sqlite:///" if is_testing else "sqlite:///local.sqlite"
+    app.config.from_mapping({
+        "SECRET_KEY": token_urlsafe(32),
+        "SQLALCHEMY_DATABASE_URI": db_uri,
+        "BABEL_DEFAULT_LOCALE": "en",
+        "ALL_LINGUAS": "zh_Hant|正體中文,en|English,zh_Hans|简体中文",
+    })
+    if is_testing:
+        app.config["TESTING"] = True
+
+    babel_js.init_app(app)
+    csrf.init_app(app)
+    db.init_app(app)
+
+    app.register_blueprint(bp, url_prefix="/")
+    app.cli.add_command(init_db_command)
+
+    from . import locale
+    locale.init_app(app)
+
+    from . import auth
+    auth.init_app(app)
+
+    can_view: t.Callable[[], bool] = lambda: auth.current_user() is not None \
+        and auth.current_user().username in ["viewer", "editor"]
+    can_edit: t.Callable[[], bool] = lambda: auth.current_user() is not None \
+        and auth.current_user().username == "editor"
+    accounting.init_app(app, can_view_func=can_view, can_edit_func=can_edit)
+
+    return app
+
+
+@click.command("init-db")
+@with_appcontext
+def init_db_command() -> None:
+    """Initializes the database."""
+    db.create_all()
+    from .auth import User
+    for username in ["viewer", "editor", "nobody"]:
+        if User.query.filter(User.username == username).first() is None:
+            db.session.add(User(username=username))
+    db.session.commit()
+    click.echo("Database initialized successfully.")
+
+
+@bp.get("/", endpoint="home")
+def get_home() -> str:
+    """Returns the home page.
+
+    :return: The home page.
+    """
+    return render_template("home.html")
--- a/tests/testsite/auth.py
+++ b/tests/testsite/auth.py
@ -0,0 +1,92 @@
+# The Mia! Accounting Flask Demonstration Website.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/27
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The authentication for the Mia! Accounting Flask demonstration website.
+
+"""
+from flask import Blueprint, render_template, Flask, redirect, url_for, \
+    session, request, g
+
+from . import db
+
+bp: Blueprint = Blueprint("auth", __name__, url_prefix="/")
+
+
+class User(db.Model):
+    """A user."""
+    __tablename__ = "users"
+    """The table name."""
+    id = db.Column(db.Integer, nullable=False, primary_key=True,
+                   autoincrement=True)
+    """The ID"""
+    username = db.Column(db.String, nullable=False, unique=True)
+    """The username."""
+
+
+@bp.get("login", endpoint="login-form")
+def show_login_form() -> str:
+    """Shows the login form.
+
+    :return: The login form.
+    """
+    return render_template("login.html")
+
+
+@bp.post("login", endpoint="login")
+def login() -> redirect:
+    """Logs in the user.
+
+    :return: The redirection to the home page.
+    """
+    if request.form.get("username") not in ["viewer", "editor", "nobody"]:
+        return redirect(url_for("auth.login"))
+    session["user"] = request.form.get("username")
+    return redirect(url_for("home.home"))
+
+
+@bp.post("logout", endpoint="logout")
+def logout() -> redirect:
+    """Logs out the user.
+
+    :return: The redirection to the home page.
+    """
+    if "user" in session:
+        del session["user"]
+    return redirect(url_for("home.home"))
+
+
+def current_user() -> User | None:
+    """Returns the current user.
+
+    :return: The current user, or None if the user did not log in.
+    """
+    if not hasattr(g, "user"):
+        if "user" not in session:
+            g.user = None
+        else:
+            g.user = User.query.filter(
+                User.username == session["user"]).first()
+    return g.user
+
+
+def init_app(app: Flask) -> None:
+    """Initialize the localization.
+
+    :param app: The Flask application.
+    :return: None.
+    """
+    app.register_blueprint(bp)
+    app.jinja_env.globals["current_user"] = current_user
--- a/tests/testsite/locale.py
+++ b/tests/testsite/locale.py
@ -0,0 +1,97 @@
+# The Mia! Accounting Flask Demonstration Website.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/1/2
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The localization for the Mia! Accounting Flask demonstration website.
+
+"""
+from babel import Locale
+from flask import request, session, current_app, Blueprint, Response, \
+    redirect, url_for, Flask
+from flask_babel import Babel
+from werkzeug.datastructures import LanguageAccept
+
+bp: Blueprint = Blueprint("locale", __name__, url_prefix="/")
+
+
+def get_locale():
+    """Returns the locale of the user
+
+    :return: The locale of the user.
+    """
+    all_linguas: dict[str, str] = get_all_linguas()
+    if "locale" in session and session["locale"] in all_linguas:
+        return session["locale"]
+    return __fix_accept_language(request.accept_languages)\
+        .best_match(all_linguas.keys())
+
+
+def __fix_accept_language(accept: LanguageAccept) -> LanguageAccept:
+    """Fixes the accept-language so that territory variants may be matched to
+    script variants.  For example, zh_TW, zh_HK to zh_Hant, and zh_CN, zh_SG to
+    zh_Hans.  This is to solve the issue that Flask only recognizes the script
+    variants, like zh_Hant and zh_Hans.
+
+    :param accept: The original HTTP accept languages.
+    :return: The fixed HTTP accept languages
+    """
+    accept_list: list[tuple[str, float]] = list(accept)
+    to_add: list[tuple[str, float]] = []
+    for pair in accept_list:
+        locale: Locale = Locale.parse(pair[0].replace("-", "_"))
+        if locale.script is not None:
+            tag: str = f"{locale.language}-{locale.script}"
+            if tag not in accept:
+                to_add.append((tag, pair[1]))
+    accept_list.extend(to_add)
+    return LanguageAccept(accept_list)
+
+
+@bp.post("/locale", endpoint="set-locale")
+def set_locale() -> Response:
+    """Sets the locale for the user.
+
+    :return: The response.
+    """
+    all_linguas: dict[str, str] = get_all_linguas()
+    if "locale" in request.form and request.form["locale"] in all_linguas:
+        session["locale"] = request.form["locale"]
+    if "next" in request.form:
+        return redirect(request.form["next"])
+    return redirect(url_for("home.home"))
+
+
+def get_all_linguas() -> dict[str, str]:
+    """Returns all the available languages.
+
+    :return: All the available languages, as a dictionary of the language code
+        and their local names.
+    """
+    return {y[0]: y[1] for y in
+            [x.split("|") for x in
+             current_app.config["ALL_LINGUAS"].split(",")]}
+
+
+def init_app(app: Flask) -> None:
+    """Initialize the localization.
+
+    :param app: The Flask application.
+    :return: None.
+    """
+    babel = Babel()
+    babel.init_app(app, locale_selector=get_locale)
+    app.register_blueprint(bp)
+    app.jinja_env.globals["get_locale"] = get_locale
+    app.jinja_env.globals["get_all_linguas"] = get_all_linguas
--- a/tests/testsite/templates/base.html
+++ b/tests/testsite/templates/base.html
@ -0,0 +1,134 @@
+{#
+The Mia! Accounting Flask Demonstration Website
+base.html: The side-wide layout template
+
+ Copyright (c) 2023 imacat.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+Author: imacat@mail.imacat.idv.tw (imacat)
+First written: 2023/1/27
+#}
+<!doctype html>
+<html xmlns="http://www.w3.org/1999/xhtml" lang="{{ _("en") }}">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="author" content="{{ "imacat" }}" />
+  <link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.3/dist/css/bootstrap.min.css">
+  <link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@6.2.1/css/all.min.css">
+  {% block styles %}{% endblock %}
+  <script src="{{ url_for("babel_catalog") }}"></script>
+  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.3/dist/js/bootstrap.bundle.min.js"></script>
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/decimal.js/9.0.0/decimal.min.js"></script>
+  {% block scripts %}{% endblock %}
+  <title>{% block title %}{% endblock %}</title>
+</head>
+<body>
+
+<nav class="navbar navbar-expand-lg bg-body-tertiary bg-dark navbar-dark">
+  <div class="container-fluid">
+    <a class="navbar-brand" href="{{ url_for("home.home") }}">
+      <i class="fa-solid fa-house"></i>
+      {{ _("Home") }}
+    </a>
+    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#collapsible-navbar" aria-controls="collapsible-navbar" aria-expanded="false" aria-label="Toggle navigation">
+      <span class="navbar-toggler-icon"></span>
+    </button>
+
+    <div id="collapsible-navbar" class="collapse navbar-collapse">
+      <ul class="navbar-nav me-auto mb-2 mb-lg-0">
+        {% include "/accounting/include/nav.html" %}
+      </ul>
+
+      <!-- The right side -->
+      <ul class="navbar-nav d-flex">
+        {% if current_user() is not none %}
+          <li class="nav-item dropdown">
+            <span class="nav-link dropdown-toggle" data-bs-toggle="dropdown">
+              <i class="fa-solid fa-user"></i>
+              {{ current_user().username }}
+            </span>
+            <ul class="dropdown-menu dropdown-menu-end">
+              <li>
+                <form action="{{ url_for("auth.logout") }}" method="post">
+                  <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">
+                  <button class="btn dropdown-item" type="submit">
+                    <i class="fa-solid fa-right-from-bracket"></i>
+                    {{ _("Log Out") }}
+                  </button>
+                </form>
+              </li>
+            </ul>
+          </li>
+        {% else %}
+          <li class="nav-item">
+            <a class="nav-link" href="{{ url_for("auth.login") }}">
+              <i class="fa-solid fa-right-to-bracket"></i>
+              {{ _("Log In") }}
+            </a>
+          </li>
+        {% endif %}
+        <li class="nav-item dropdown">
+          <span class="nav-link dropdown-toggle" data-bs-toggle="dropdown">
+            <i class="fa-solid fa-language"></i>
+          </span>
+          <form action="{{ url_for("locale.set-locale") }}" method="post">
+            <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">
+            <input type="hidden" name="next" value="{{ request.full_path if request.query_string else request.path }}">
+            <ul class="dropdown-menu dropdown-menu-end">
+              {% for locale_code, locale_name in get_all_linguas().items() %}
+                <li>
+                  <button class="dropdown-item {% if locale_code == get_locale() %} active {% endif %}" type="submit" name="locale" value="{{ locale_code }}">
+                    {{ locale_name }}
+                  </button>
+                </li>
+              {% endfor %}
+            </ul>
+          </form>
+        </li>
+      </ul>
+    </div>
+  </div>
+</nav>
+
+<div class="container">
+
+<h1>{% block header %}{% endblock %}</h1>
+
+{% with messages = get_flashed_messages(with_categories=true) %}
+  {% if messages %}
+    {% for category, message in messages %}
+      {% if category == "success" %}
+          <div class="alert alert-success alert-dismissible fade show" role="alert">
+            {{ message }}
+            <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
+          </div>
+      {% elif category == "error" %}
+        <div class="alert alert-danger alert-dismissible fade show" role="alert">
+          <strong>{{ _("Error:") }}</strong> {{ message }}
+          <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
+        </div>
+      {% endif %}
+    {% endfor %}
+  {% endif %}
+{% endwith %}
+
+<main class="pb-5">
+  {% block content %}{% endblock %}
+</main>
+
+</div>
+
+</body>
+</html>
--- a/tests/testsite/templates/home.html
+++ b/tests/testsite/templates/home.html
@ -0,0 +1,24 @@
+{#
+The Mia! Accounting Flask Demonstration Website
+home.html: The home page.
+
+ Copyright (c) 2023 imacat.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+Author: imacat@mail.imacat.idv.tw (imacat)
+First written: 2023/1/27
+#}
+{% extends "base.html" %}
+
+{% block header %}{% block title %}{{ _("Home") }}{% endblock %}{% endblock %}
--- a/tests/testsite/templates/login.html
+++ b/tests/testsite/templates/login.html
@ -0,0 +1,35 @@
+{#
+The Mia! Accounting Flask Demonstration Website
+login.html: The login page.
+
+ Copyright (c) 2023 imacat.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+Author: imacat@mail.imacat.idv.tw (imacat)
+First written: 2023/1/27
+#}
+{% extends "base.html" %}
+
+{% block header %}{% block title %}{{ _("Log In") }}{% endblock %}{% endblock %}
+
+{% block content %}
+
+<form action="{{ url_for("auth.login") }}" method="post">
+  <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">
+  <button class="btn btn-primary" type="submit" name="username" value="viewer">{{ _("Viewer") }}</button>
+  <button class="btn btn-primary" type="submit" name="username" value="editor">{{ _("Editor") }}</button>
+  <button class="btn btn-primary" type="submit" name="username" value="nobody">{{ _("Nobody") }}</button>
+</form>
+
+{% endblock %}
--- a/tests/testsite/translations/babel.cfg
+++ b/tests/testsite/translations/babel.cfg
@ -0,0 +1,3 @@
+[python: **.py]
+[jinja2: **/templates/**.html]
+[javascript: **/static/js/**.js]
--- a/tests/testsite/translations/zh_Hant/LC_MESSAGES/messages.po
+++ b/tests/testsite/translations/zh_Hant/LC_MESSAGES/messages.po
@ -0,0 +1,54 @@
+# Chinese (Traditional) translations for the Mia! Accounting Flask
+# Demonstration website.
+# Copyright (C) 2023 imacat
+# This file is distributed under the same license as the Mia! Accounting
+# Flask Demonstration project.
+# imacat <imacat@mail.imacat.idv.tw>, 2023.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: Mia! Accounting Flask Demonstration 0.0.0\n"
+"Report-Msgid-Bugs-To: imacat@mail.imacat.idv.tw\n"
+"POT-Creation-Date: 2023-01-28 13:42+0800\n"
+"PO-Revision-Date: 2023-01-28 13:42+0800\n"
+"Last-Translator: imacat <imacat@mail.imacat.idv.tw>\n"
+"Language: zh_Hant\n"
+"Language-Team: zh_Hant <imacat@mail.imacat.idv.tw>\n"
+"Plural-Forms: nplurals=1; plural=0;\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=utf-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Generated-By: Babel 2.11.0\n"
+
+#: tests/testsite/templates/base.html:23
+msgid "en"
+msgstr "zh-Hant"
+
+#: tests/testsite/templates/base.html:43 tests/testsite/templates/home.html:24
+msgid "Home"
+msgstr "首頁"
+
+#: tests/testsite/templates/base.html:68
+msgid "Log Out"
+msgstr ""
+
+#: tests/testsite/templates/base.html:78 tests/testsite/templates/login.html:24
+msgid "Log In"
+msgstr "登入"
+
+#: tests/testsite/templates/base.html:119
+msgid "Error:"
+msgstr "錯誤："
+
+#: tests/testsite/templates/login.html:30
+msgid "Viewer"
+msgstr "讀報表者"
+
+#: tests/testsite/templates/login.html:31
+msgid "Editor"
+msgstr "記帳者"
+
+#: tests/testsite/templates/login.html:32
+msgid "Nobody"
+msgstr "沒有權限者"
+