monorepo/dezendorf/applications/python_web_framework/framework.py

#!/usr/bin/env python3

from __future__ import annotations

import time
from pathlib import Path

from flask import Flask, Response, render_template

_START_TIME = time.time()


def create_app(app_name: str, *, title: str | None = None) -> Flask:
    """Create a Flask app with shared web defaults for this monorepo."""
    template_dir = Path(__file__).with_name("templates")
    app = Flask(app_name, template_folder=str(template_dir))
    app.config["APP_TITLE"] = title or app_name
    register_default_routes(app)
    return app


def register_default_routes(app: Flask) -> None:
    @app.get("/")
    def index() -> str:
        return render_template("index.html", app_title=app.config["APP_TITLE"])

    @app.get("/healthz")
    def healthz() -> Response:
        uptime_seconds = max(0.0, time.time() - _START_TIME)
        lines = [
            "# HELP app_health Application health status (1 = healthy).",
            "# TYPE app_health gauge",
            f'app_health{{service="{app.name}"}} 1',
            "# HELP app_uptime_seconds Application uptime in seconds.",
            "# TYPE app_uptime_seconds gauge",
            f'app_uptime_seconds{{service="{app.name}"}} {uptime_seconds:.3f}',
            "",
        ]
        body = "\n".join(lines)
        return Response(body, status=200, headers={"Content-Type": "text/plain; version=0.0.4; charset=utf-8"})