# `Localize.FormatCache`
[🔗](https://github.com/elixir-localize/localize/blob/v0.39.0/lib/localize/format_cache.ex#L1)

An ETS-backed cache for compiled format patterns.

Number format metadata and datetime format tokens are cached
here after first compilation. The cache is hard-bounded: when
inserting an entry would exceed the configured maximum, an
existing entry is evicted synchronously, keeping the cache at
or below the cap at all times.

The maximum number of entries defaults to 2,000 and can be
overridden with:

    config :localize, :format_cache_max_entries, 5_000

## Trust model

The ETS table is `:protected` — only the cache GenServer can
write to it; any process can read directly. This keeps the
cache from being polluted by other libraries running in the
same BEAM, and ensures the size invariant cannot be violated
by a non-owner write.

Writes go through `store/2`, which is a `GenServer.call` to the
owner. A miss-then-store pattern from a hot path therefore pays
one gen-server round-trip per *first-time* format compilation;
subsequent lookups are direct ETS reads with no synchronisation
cost.

# `child_spec`

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `clear`

```elixir
@spec clear() :: :ok
```

Clears all entries from the cache.

Routed through the GenServer so the operation respects the
table's `:protected` ownership. Intended for tests and
maintenance; production callers should not need this.

# `lookup`

```elixir
@spec lookup(term()) :: {:ok, term()} | :miss
```

Look up a compiled format pattern by its cache key.

### Arguments

* `key` is the cache key, typically a tuple like
  `{:localize, :number_format_meta, format_string}`.

### Returns

* `{:ok, value}` if the key is present.

* `:miss` if not cached or the table does not exist.

# `max_entries`

```elixir
@spec max_entries() :: pos_integer()
```

Returns the configured maximum number of cache entries.

# `size`

```elixir
@spec size() :: non_neg_integer()
```

Returns the current number of entries in the cache.

Primarily useful in tests; production callers should not need
to inspect the size directly.

# `store`

```elixir
@spec store(term(), term()) :: :ok
```

Store a compiled format pattern in the cache.

Routed through the cache GenServer so the size cap can be
enforced synchronously. If the table doesn't exist (e.g. during
a bare unit test), the call is a no-op.

### Arguments

* `key` is the cache key.

* `value` is the compiled artifact to cache.

### Returns

* `:ok`.

---

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