# chanora_cache

Disposable content-addressed blob cache for avatar and icon files. Wraps `cacache` for crash safety and integrity verification. Separated from `chanora_storage` because cache owns reconstructible, disposable blob data with different durability and backup semantics.

## Architecture

- **`BlobCache`** — async blob store backed by cacache's content-v2 / index-v2 on-disk layout.
- Keys are protocol identifiers prefixed by type: `av_<32-char-hex>` for avatars (MD5), `ic_<decimal>` for icons (CRC32).
- Cacache handles dedup and SSRI integrity verification on every read.
- Corrupt entries are automatically removed on read failure.
- LRU eviction by timestamp when total size exceeds the configured cap.

## Public API Summary

### Types

| Type | Role |
|---|---|
| `BlobCache` | Content-addressed blob cache |
| `BlobCacheError` | Io, InvalidKey |

### Key methods on `BlobCache`

- `new(cache_dir, max_bytes)` — create or open the cache. `max_bytes = 0` disables eviction.
- `put(prefix, key, data)` — store a blob (async)
- `get(prefix, key)` → `Option<Vec<u8>>` — read a blob, with integrity check (async)
- `remove(prefix, key)` — delete a specific blob (async)
- `clear()` — delete all blobs (async)
- `total_size()` → `u64` — sum of all blob sizes (async)
- `evict()` — remove oldest entries until under `max_bytes` cap (async)

### Constants

- `PREFIX_AVATAR` = `"av_"` — avatar key prefix
- `PREFIX_ICON` = `"ic_"` — icon key prefix

## Key validation

Avatar keys must be exactly 32 hex characters. Icon keys must be non-empty decimal digits. Unknown prefixes are rejected. This prevents malformed entries from polluting the cache.