# Fan-out & Routing

## FanoutNode

Reads one item and pushes a copy to each of N output channels. All downstream nodes receive every item.

```cpp
auto fan = make_fanout<Image, 2>(/*capacity=*/8);

net.connect("src",  src.output<0>(),  "fan",   fan.input<0>())
   .connect("fan",  fan.output<0>(),  "nodeA", nodeA.input<0>())
   .connect("fan",  fan.output<1>(),  "nodeB", nodeB.input<0>());
```

If one downstream channel overflows, that output drops the item independently — the other outputs are unaffected.

See `examples/11_static_fanout`.

## RouterNode

Reads one item and pushes it to exactly one of N outputs, chosen by a selector function:

```cpp
auto router = make_router<Frame, 3>(
    [](const Frame& f) -> std::size_t { return f.stream_id % 3; });

net.connect("src",    src.output<0>(),     "router", router.input<0>())
   .connect("router", router.output<0>(),  "nodeA",  nodeA.input<0>())
   .connect("router", router.output<1>(),  "nodeB",  nodeB.input<0>())
   .connect("router", router.output<2>(),  "nodeC",  nodeC.input<0>());
```

If the selector returns `>= N` the item is silently dropped.

## FilterNode

Reads one item and passes it downstream only when a predicate returns `true`:

```cpp
auto filt = make_filter<Frame>([](const Frame& f) { return f.valid; });

net.connect("src",  src.output<0>(),  "filt", filt.input<0>())
   .connect("filt", filt.output<0>(), "dst",  dst.input<0>());
```