use std::path::Path;

use crate::cache::CacheKey;

pub const NS_BLOB: u8 = b'B';
pub const NS_BLOB_SIZE: u8 = b'S';
pub const NS_BLOB_EXISTS: u8 = b'E';
pub const NS_COMMIT: u8 = b'C';
pub const NS_REV: u8 = b'r';
pub const NS_TREE_ENTRIES: u8 = b't';
pub const NS_LFS: u8 = b'l';

pub fn encode(ns: u8, suffix: &[u8]) -> CacheKey {
    let mut key = Vec::with_capacity(1 + suffix.len());
    key.push(ns);
    key.extend_from_slice(suffix);
    key
}

pub fn object_key(ns: u8, oid: &gix::ObjectId) -> CacheKey {
    encode(ns, oid.as_bytes())
}

pub fn rev_key(repo_dir: &Path, revision: &str) -> CacheKey {
    let path = repo_dir.as_os_str().as_encoded_bytes();
    let mut key = Vec::with_capacity(1 + 4 + path.len() + 1 + revision.len());
    key.push(NS_REV);
    key.extend_from_slice(&(path.len() as u32).to_le_bytes());
    key.extend_from_slice(path);
    key.push(0);
    key.extend_from_slice(revision.as_bytes());
    key
}

/// Key for a per-repository blob-existence probe. Blob *existence* is
/// repository-scoped (a given oid may be present in one repo's object store but
/// absent in another), unlike blob *content* which is content-addressed. The
/// canonicalised repo directory is therefore part of the key.
pub fn blob_exists_key(repo_dir: &Path, oid: &gix::ObjectId) -> CacheKey {
    let path = repo_dir.as_os_str().as_encoded_bytes();
    let oid_bytes = oid.as_bytes();
    let mut key = Vec::with_capacity(1 + 4 + path.len() + 1 + oid_bytes.len());
    key.push(NS_BLOB_EXISTS);
    key.extend_from_slice(&(path.len() as u32).to_le_bytes());
    key.extend_from_slice(path);
    key.push(0);
    key.extend_from_slice(oid_bytes);
    key
}