### Writing controllers

Istio provides a few helper libraries to get started writing a controller. While these libraries help, there are still a lot of subtleties in correctly writing (and testing!) a controller properly.

To get started writing a controller, review the [Example Controller](../../pkg/kube/controllers/example_test.go).

### Controllers overview

@router.route("/items/")
def read_items(request: Request):
    return JSONResponse({"hello": "world"})


app.include_router(router)

client = TestClient(app)


def test_sub_router():
    response = client.get("/items/")
    assert response.status_code == 200, response.text

class Item(BaseModel):
    name: str
    description: str | None = None


app = FastAPI(separate_input_output_schemas=False)


@app.post("/items/")
def create_item(item: Item):
    return item


@app.get("/items/")
def read_items() -> list[Item]:
    return [
        Item(
            name="Portal Gun",
            description="Device to travel through the multi-rick-verse",
        ),
        Item(name="Plumbus"),

from fastapi import FastAPI

app = FastAPI()


@app.get("/users/{user_id}/items/{item_id}")
async def read_user_item(
    user_id: int, item_id: str, q: str | None = None, short: bool = False
):
    item = {"item_id": item_id, "owner_id": user_id}
    if q:
        item.update({"q": q})
    if not short:
        item.update(
            {"description": "This is an amazing item that has a long description"}
        )

class User(BaseModel):
    username: str
    email: str


@app.post("/items/", response_model=ResponseMessage, tags=["items"])
async def create_item(item: Item):
    return {"message": "Item received"}


@app.get("/items/", response_model=list[Item], tags=["items"])
async def get_items():
    return [
        {"name": "Plumbus", "price": 3},
        {"name": "Portal Gun", "price": 9001},
    ]

   */
  @JvmStatic
  fun fragmentBuffer(buffer: Buffer): Buffer {
    // Write each byte into a new buffer, then clone it so that the segments are shared.
    // Shared segments cannot be compacted so we'll get a long chain of short segments.
    val result = Buffer()
    while (!buffer.exhausted()) {
      val box = Buffer()
      box.write(buffer, 1)
      result.write(box.copy(), 1)
    }
    return result
  }

        requireNonNull(properties, "properties");
        Properties map = new Properties();
        for (String key : properties.keySet()) {
            map.put(key, properties.get(key));
        }
        return map;
    }

    @Nonnull
    public static BasicInterpolator createInterpolator(Collection<Map<String, String>> properties) {

        public void endElement(final String uri, final String localName, final String qName) {
            if ("field".equals(qName)) {
                if (fieldName != null) {
                    final Object obj = dataMap.get(fieldName);
                    if (obj == null) {
                        dataMap.put(fieldName, buffer.toString());
                    }
                    fieldName = null;
                }

        ) {
          response.close()
          latch.countDown()
        }
      },
    )
    latch.await()
    assertThat(call.isCanceled()).isTrue()
    assertThat(exceptionRef.get()).isNotNull()
  }

  @Test
  fun timeoutProcessing() {
    server.enqueue(
      MockResponse.Builder()
        .headersDelay(500, TimeUnit.MILLISECONDS)
        .build(),
    )
    val request =

    model_config = {"extra": "forbid"}

    limit: int = Field(100, gt=0, le=100)
    offset: int = Field(0, ge=0)
    order_by: Literal["created_at", "updated_at"] = "created_at"
    tags: list[str] = []


@app.get("/items/")
async def read_items(filter_query: Annotated[FilterParams, Query()]):