# `ADK.Plugin.Cache`
[🔗](https://github.com/zeroasterisk/adk-elixir/blob/main/lib/adk/plugin/cache.ex#L1)

A simple in-memory response cache plugin using ETS.

Caches agent run results keyed by user content, with configurable TTL
and maximum cache size with LRU-style eviction.

## Configuration

    # Default — 5-minute TTL, hash of user message as key
    ADK.Plugin.register({ADK.Plugin.Cache, []})

    # Custom — 1-minute TTL, custom key function, max 500 entries
    ADK.Plugin.register({ADK.Plugin.Cache,
      ttl_ms: 60_000,
      max_size: 500,
      key_fn: fn context -> {context.user_id, context.user_content} end
    })

## Options

- `:ttl_ms` — cache entry TTL in milliseconds. Default `300_000` (5 minutes).
- `:key_fn` — function `context -> key` for cache lookup. Default uses
  `:erlang.phash2/1` on the user message text.
- `:max_size` — max entries before oldest eviction. Default `1000`.

## Behaviour

- `init/1` — creates an ETS table with a unique name.
- `before_run/2` — computes cache key; returns cached events on hit (not expired).
- `after_run/3` — stores result in cache with timestamp; evicts oldest if over max size.

# `config`

```elixir
@type config() :: [
  ttl_ms: pos_integer(),
  key_fn: (ADK.Context.t() -> term()),
  max_size: pos_integer()
]
```

# `state`

```elixir
@type state() :: %{
  ttl_ms: pos_integer(),
  key_fn: (ADK.Context.t() -> term()),
  max_size: pos_integer(),
  table: :ets.tid()
}
```

---

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