# `Opsmaru.Incus.SimpleStreams.CacheAdapter`
[🔗](https://github.com/upmaru/opsmaru-incus/blob/v0.1.0/lib/opsmaru/incus/simple_streams/cache_adapter.ex#L1)

Explicit host-owned catalog cache, the counterpart of the pinned client's
`CachePath`. Shared code never writes files.

Entries are index and products JSON bodies named by their file name inside a
namespace, the hex SHA-256 of the stream URL, as the pinned cache directory
lays them out. `read/3` returns the body and its age in milliseconds; the
library applies the expiry (one hour unless `cache_expiry:` says otherwise).
A fresh entry is used without a request; a failed request or non-200 reply
falls back to any entry, expired or not; a fresh 200 body replaces it; and a
404 while downloading an image file invalidates the namespace.

Failures are ignored as natively: an error or exception from `read/3` is a
miss and one from `write/4` or `invalidate/2` leaves the result unchanged.
Callbacks run in the bounded request worker. Fixture success is not installed
cache acceptance.

# `invalidate`

```elixir
@callback invalidate(term(), String.t()) :: :ok | {:error, term()}
```

# `read`

```elixir
@callback read(term(), String.t(), String.t()) ::
  {:ok, binary(), non_neg_integer()} | :miss | {:error, term()}
```

# `write`

```elixir
@callback write(term(), String.t(), String.t(), binary()) :: :ok | {:error, term()}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*