crabllm-core 0.0.16

use crate::Error;
use std::{future::Future, pin::Pin};

/// Fixed-length prefix size in bytes for storage keys.
pub const PREFIX_LEN: usize = 4;

/// A fixed-length prefix that namespaces storage keys per extension.
///
/// The first `PREFIX_LEN` bytes of every key identify which extension
/// owns the data. The remaining bytes are the extension-specific key.
pub type Prefix = [u8; PREFIX_LEN];

/// Key-value pairs returned by `Storage::list`.
pub type KvPairs = Vec<(Vec<u8>, Vec<u8>)>;

/// A pinned, boxed, Send future. Used for dyn-compatible async trait methods.
pub type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;

/// Build a full storage key from a fixed-length prefix and a suffix.
pub fn storage_key(prefix: &Prefix, suffix: &[u8]) -> Vec<u8> {
    let mut key = Vec::with_capacity(PREFIX_LEN + suffix.len());
    key.extend_from_slice(prefix);
    key.extend_from_slice(suffix);
    key
}

/// Generic async key-value storage backend for extensions.
///
/// Keys are raw bytes. The first `PREFIX_LEN` bytes are a fixed-width
/// namespace prefix. All methods take `&self` and are dyn-compatible
/// via `BoxFuture`. Implementations must be `Send + Sync`.
pub trait Storage: Send + Sync {
    /// Get a value by key. Returns `None` if the key does not exist.
    fn get(&self, key: &[u8]) -> BoxFuture<'_, Result<Option<Vec<u8>>, Error>>;

    /// Set a key to a value, overwriting any existing value.
    fn set(&self, key: &[u8], value: Vec<u8>) -> BoxFuture<'_, Result<(), Error>>;

    /// Atomically increment a counter by `delta`, returning the new value.
    /// If the key does not exist, it is created with an initial value of `delta`.
    fn increment(&self, key: &[u8], delta: i64) -> BoxFuture<'_, Result<i64, Error>>;

    /// List all key-value pairs whose keys start with `prefix`.
    /// Returned in arbitrary order.
    fn list(&self, prefix: &Prefix) -> BoxFuture<'_, Result<KvPairs, Error>>;

    /// Delete a key. No-op if the key does not exist.
    fn delete(&self, key: &[u8]) -> BoxFuture<'_, Result<(), Error>>;
}