Die Webapp (main.py)

from contextlib import asynccontextmanager

from fastapi import FastAPI, Form, HTTPException, Request
from fastapi.responses import HTMLResponse, RedirectResponse
from fastapi.templating import Jinja2Templates
from pydantic import BaseModel

from db import pool


@asynccontextmanager
async def lifespan(app: FastAPI):
    pool.open()        # beim Start der App
    yield
    pool.close()       # beim Beenden


app = FastAPI(lifespan=lifespan)
templates = Jinja2Templates(directory='templates')


# ---------- HTML-Seiten ----------

@app.get('/', response_class=HTMLResponse)
def kundenliste(request: Request, q: str = ''):
    with pool.connection() as conn:
        kunden = conn.execute(
            'SELECT id, name, stadt, umsatz FROM kunden WHERE name ILIKE %s ORDER BY name',
            (f'%{q}%',),
        ).fetchall()
    return templates.TemplateResponse(request, 'kunden.html', {'kunden': kunden, 'q': q})


@app.post('/kunden')
def kunde_anlegen(name: str = Form(...), stadt: str = Form('')):
    with pool.connection() as conn:
        conn.execute(
            'INSERT INTO kunden (name, stadt) VALUES (%s, %s)',
            (name, stadt or None),
        )
    return RedirectResponse('/', status_code=303)     # zurück zur Liste


# ---------- JSON-API ----------

class KundeNeu(BaseModel):
    name: str
    stadt: str | None = None


@app.get('/api/kunden')
def api_liste():
    with pool.connection() as conn:
        return conn.execute('SELECT id, name, stadt, umsatz FROM kunden ORDER BY id').fetchall()


@app.get('/api/kunden/{kunden_id}')
def api_einzeln(kunden_id: int):
    with pool.connection() as conn:
        kunde = conn.execute(
            'SELECT id, name, stadt, umsatz FROM kunden WHERE id = %s', (kunden_id,)
        ).fetchone()
    if kunde is None:
        raise HTTPException(status_code=404, detail='Kunde nicht gefunden')
    return kunde


@app.post('/api/kunden', status_code=201)
def api_anlegen(kunde: KundeNeu):
    with pool.connection() as conn:
        return conn.execute(
            'INSERT INTO kunden (name, stadt) VALUES (%s, %s) RETURNING id, name, stadt',
            (kunde.name, kunde.stadt),
        ).fetchone()