[WIP] feat: express JS

rockcraft/extensions/express.py

@@ -0,0 +1,121 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright 2024 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""An extension for the NodeJS based Javascript application extension."""
+from typing import Any, Dict, Tuple
+
+from overrides import override
+
+from .extension import Extension
+
+
+class ExpressJSFramework(Extension):
+    """An extension for constructing Javascript applications based on the ExpressJS framework."""
+
+    @staticmethod
+    @override
+    def get_supported_bases() -> Tuple[str, ...]:
+        """Return supported bases."""
+        return "bare", "ubuntu@22.04", "ubuntu:22.04", "ubuntu@24.04", "ubuntu:24.04"
+
+    @staticmethod
+    @override
+    def is_experimental(base: str | None) -> bool:
+        """Check if the extension is in an experimental state."""
+        return False
+
+    @property
+    @override
+    def framework(self) -> str:
+        """Return the framework name, i.e. expressjs."""
+        return "expressjs"
+
+    @override
+    def get_root_snippet(self) -> Dict[str, Any]:
+        """Fill in some default root components.
+
+        Default values:
+          - run_user: _daemon_
+          - build-base: ubuntu:22.04 (only if user specify bare without a build-base)
+          - platform: amd64
+          - services: a service to run the ExpressJS server
+          - parts: see ExpressJSFramework._gen_parts
+        """
+        snippet: Dict[str, Any] = {
+            "run-user": "_daemon_",
+            "services": {
+                "app": {
+                    "override": "replace",
+                    "command": "npm start",
+                    "startup": "enabled",
+                    "on-success": "shutdown",
+                    "on-failure": "shutdown",
+                    "working-dir": f"{self.framework}/app",
+                }
+            },
+        }
+        return snippet
+
+    @override
+    def get_part_snippet(self) -> dict[str, Any]:
+        """Return the part snippet to apply to existing parts.
+
+        This is unused but is required by the ABC.
+        """
+        return {}
+
+    @override
+    def get_parts_snippet(self) -> dict[str, Any]:
+        """Return the parts to add to parts.
+
+        This is unused but is required by the ABC.
+        """
+        return {}
+
+    def _gen_parts(self) -> dict:
+        """Generate the parts associated with this extension.
+
+        The parts generated are the following:
+        1. install-app: Install the application with npm installs.
+        2. install-dependencies: Install application host dependencies (e.g. pg lib)
+        """
+        ...
+
+    def _gen_install_app_part(self) -> dict:
+        """Generate the install app part using NPM plugin."""
+        ...
+
+    def _gen_install_dependencies_part(self) -> dict:
+        """Generate the install dependencies part using dump plugin."""
+        ...
+
+    @property
+    def _app_prime(self):
+        """Return the prime list for the ExpressJS proejct.
+
+        Use the paths generated by the
+        express-generator (https://expressjs.com/en/starter/generator.html) tool by default if no
+        user prime paths are provided. Use only user prime paths otherwise.
+        """
+        ...
+
+    def _check_project(self):
+        """Ensure this extension can apply to the current rockcraft project.
+
+        The ExpressJS framework assumes that:
+        - The npm start script exists.
+        """
+        ...