suture-core 0.8.0

//! Blob Store — the primary CAS interface for storing and retrieving blobs.
//!
//! Blobs are stored on disk using a content-addressed scheme:
//! - Hash is split into a 2-char prefix directory and 62-char filename
//! - This creates 256 buckets, avoiding any single directory having too many files
//! - Blobs are optionally Zstd-compressed
//!
//! # Thread Safety
//!
//! `BlobStore` is `Send + Sync` and can be shared across threads via `Arc`.
//! File operations are the primary bottleneck; the store itself holds no mutable
//! state beyond the root path.

use crate::cas::compressor::{self, is_zstd_compressed};
use crate::cas::hasher;
use crate::cas::pack::{PackCache, PackError, PackFile, PackIndex};
use std::fs;
use std::io;
use std::path::PathBuf;
use std::sync::Mutex;
use suture_common::Hash;
use thiserror::Error;

/// Errors that can occur during CAS operations.
#[derive(Error, Debug)]
pub enum CasError {
    #[error("blob not found: {0}")]
    BlobNotFound(String),

    #[error("hash mismatch: expected {expected}, got {actual}")]
    HashMismatch { expected: String, actual: String },

    #[error("I/O error: {0}")]
    Io(#[from] io::Error),

    #[error("compression error: {0}")]
    CompressionError(String),

    #[error("decompression error: {0}")]
    DecompressionError(String),

    #[error("decompressed data too large: {max} bytes max")]
    DecompressionTooLarge { max: usize },

    #[error("blob already exists: {0}")]
    AlreadyExists(String),

    #[error("invalid path: {0}")]
    InvalidPath(String),

    #[error("pack error: {0}")]
    Pack(#[from] PackError),
}

/// The Content Addressable Storage blob store.
///
/// Stores blobs indexed by BLAKE3 hash on the local filesystem.
/// Provides deduplication, optional compression, and integrity verification.
///
/// # Thread Safety
///
/// `BlobStore` is `Send + Sync` and can be shared across threads via `Arc`.
/// The pack index cache uses `Mutex` for interior mutability.
pub struct BlobStore {
    /// Root directory containing the `objects/` subdirectory.
    root: PathBuf,
    /// Whether to compress blobs with Zstd.
    compress: bool,
    /// Zstd compression level (1-22).
    compression_level: i32,
    /// Whether to verify blob hashes on read. Default: true.
    /// Set to false for hot paths where performance matters more than
    /// per-read integrity verification (content addressing already
    /// provides correctness by construction).
    verify_on_read: bool,
    /// Cached pack indices, loaded lazily on first pack access.
    /// Invalidated when `repack()` creates new pack files.
    pack_cache: Mutex<Option<PackCache>>,
}

impl BlobStore {
    /// Create a new BlobStore rooted at the given directory.
    ///
    /// Creates the `objects/` subdirectory if it doesn't exist.
    pub fn new(root: impl Into<PathBuf>) -> Result<Self, CasError> {
        let root = root.into();
        let objects_dir = root.join("objects");
        fs::create_dir_all(&objects_dir)?;
        Ok(Self {
            root,
            compress: true,
            compression_level: compressor::DEFAULT_COMPRESSION_LEVEL,
            verify_on_read: true,
            pack_cache: Mutex::new(None),
        })
    }

    /// Create a BlobStore backed by a temporary directory.
    ///
    /// Useful for testing and in-memory repository usage. The temporary
    /// directory is cleaned up when the BlobStore is dropped.
    pub fn open_in_memory() -> Result<Self, CasError> {
        let root = tempfile::tempdir().map_err(CasError::Io)?.keep();
        let objects_dir = root.join("objects");
        fs::create_dir_all(&objects_dir)?;
        Ok(Self {
            root,
            compress: true,
            compression_level: compressor::DEFAULT_COMPRESSION_LEVEL,
            verify_on_read: true,
            pack_cache: Mutex::new(None),
        })
    }

    /// Create a BlobStore with compression disabled (for testing).
    pub fn new_uncompressed(root: impl Into<PathBuf>) -> Result<Self, CasError> {
        let mut store = Self::new(root)?;
        store.compress = false;
        Ok(store)
    }

    /// Set whether to verify blob hashes on read.
    ///
    /// When disabled, `get_blob()` skips the BLAKE3 hash verification
    /// step, saving O(n) computation per read. The content-addressed
    /// storage scheme already provides correctness by construction
    /// (the filename is the hash), so this is safe for performance-critical
    /// paths like `snapshot_head()` which may read many blobs in sequence.
    pub fn set_verify_on_read(&mut self, verify: bool) {
        self.verify_on_read = verify;
    }

    /// Check whether hash verification is enabled on read.
    pub fn verify_on_read(&self) -> bool {
        self.verify_on_read
    }

    /// Store a blob, returning its BLAKE3 hash.
    ///
    /// If a blob with the same hash already exists, this is a no-op
    /// (deduplication). Returns the hash either way.
    pub fn put_blob(&self, data: &[u8]) -> Result<Hash, CasError> {
        let hash = hasher::hash_bytes(data);
        let blob_path = self.blob_path(&hash);

        // Deduplication: if blob already exists, return immediately
        if blob_path.exists() {
            return Ok(hash);
        }

        // Ensure the prefix directory exists
        if let Some(parent) = blob_path.parent() {
            fs::create_dir_all(parent)?;
        }

        // Write blob (optionally compressed)
        if self.compress {
            let compressed = compressor::compress(data, self.compression_level)?;
            fs::write(&blob_path, &compressed)?;
        } else {
            fs::write(&blob_path, data)?;
        }

        Ok(hash)
    }

    /// Store a blob, returning an error if it already exists.
    pub fn put_blob_new(&self, data: &[u8]) -> Result<Hash, CasError> {
        let hash = hasher::hash_bytes(data);
        let blob_path = self.blob_path(&hash);

        if blob_path.exists() {
            return Err(CasError::AlreadyExists(hash.to_hex()));
        }

        if let Some(parent) = blob_path.parent() {
            fs::create_dir_all(parent)?;
        }

        if self.compress {
            let compressed = compressor::compress(data, self.compression_level)?;
            fs::write(&blob_path, &compressed)?;
        } else {
            fs::write(&blob_path, data)?;
        }

        Ok(hash)
    }

    /// Store a blob with an explicit hash (used when receiving blobs from a remote).
    ///
    /// Verifies the data matches the expected hash before storing.
    pub fn put_blob_with_hash(&self, data: &[u8], expected_hash: &Hash) -> Result<(), CasError> {
        let blob_path = self.blob_path(expected_hash);

        if blob_path.exists() {
            return Ok(());
        }

        hasher::verify_hash(data, expected_hash)?;

        if let Some(parent) = blob_path.parent() {
            fs::create_dir_all(parent)?;
        }

        if self.compress {
            let compressed = compressor::compress(data, self.compression_level)?;
            fs::write(&blob_path, &compressed)?;
        } else {
            fs::write(&blob_path, data)?;
        }

        Ok(())
    }

    /// Retrieve a blob by its BLAKE3 hash.
    ///
    /// Tries loose objects first, then pack files.
    /// Decompresses if necessary and verifies the hash of the result
    /// (unless verification was disabled via `set_verify_on_read(false)`).
    pub fn get_blob(&self, hash: &Hash) -> Result<Vec<u8>, CasError> {
        // Try loose blob first
        let blob_path = self.blob_path(hash);
        if blob_path.exists() {
            let raw = fs::read(&blob_path)?;
            let data = if is_zstd_compressed(&raw) {
                compressor::decompress(&raw)?
            } else {
                raw
            };
            if self.verify_on_read {
                hasher::verify_hash(&data, hash)?;
            }
            return Ok(data);
        }

        // Fall back to pack files
        if let Ok(data) = self.get_blob_packed(hash) {
            return Ok(data);
        }

        Err(CasError::BlobNotFound(hash.to_hex()))
    }

    /// Check if a blob exists in the store.
    ///
    /// Checks loose objects first, then pack files.
    /// This does NOT verify the blob's integrity — it only checks for existence.
    pub fn has_blob(&self, hash: &Hash) -> bool {
        self.blob_path(hash).exists() || self.has_blob_packed(hash)
    }

    /// Delete a blob from the store.
    ///
    /// The caller is responsible for ensuring no patches reference this blob.
    pub fn delete_blob(&self, hash: &Hash) -> Result<(), CasError> {
        let blob_path = self.blob_path(hash);
        fs::remove_file(&blob_path).map_err(|e| {
            if e.kind() == io::ErrorKind::NotFound {
                CasError::BlobNotFound(hash.to_hex())
            } else {
                CasError::Io(e)
            }
        })
    }

    /// Get the total number of blobs in the store.
    pub fn blob_count(&self) -> Result<u64, CasError> {
        let objects_dir = self.root.join("objects");
        let mut count = 0u64;
        if objects_dir.exists() {
            for entry in fs::read_dir(&objects_dir)? {
                let entry = entry?;
                if entry.file_type()?.is_dir() {
                    let dir_name = entry.file_name();
                    if dir_name == "pack" {
                        continue;
                    }
                    for sub_entry in fs::read_dir(entry.path())? {
                        let sub_entry = sub_entry?;
                        if sub_entry.file_type()?.is_file() {
                            count += 1;
                        }
                    }
                }
            }
        }
        Ok(count)
    }

    /// Get the total size of all blobs in the store (compressed).
    pub fn total_size(&self) -> Result<u64, CasError> {
        let objects_dir = self.root.join("objects");
        let mut total = 0u64;
        if objects_dir.exists() {
            for entry in fs::read_dir(&objects_dir)? {
                let entry = entry?;
                if entry.file_type()?.is_dir() {
                    let dir_name = entry.file_name();
                    if dir_name == "pack" {
                        continue;
                    }
                    for sub_entry in fs::read_dir(entry.path())? {
                        let sub_entry = sub_entry?;
                        if sub_entry.file_type()?.is_file() {
                            total += sub_entry.metadata()?.len();
                        }
                    }
                }
            }
        }
        Ok(total)
    }

    /// List all blob hashes in the store.
    pub fn list_blobs(&self) -> Result<Vec<Hash>, CasError> {
        let objects_dir = self.root.join("objects");
        let mut hashes = Vec::new();
        if !objects_dir.exists() {
            return Ok(hashes);
        }
        for entry in fs::read_dir(&objects_dir)? {
            let entry = entry?;
            if entry.file_type()?.is_dir() {
                let dir_name = entry.file_name();
                if dir_name == "pack" {
                    continue;
                }
                let prefix = dir_name.to_string_lossy().to_string();
                for sub_entry in fs::read_dir(entry.path())? {
                    let sub_entry = sub_entry?;
                    if sub_entry.file_type()?.is_file() {
                        let suffix = sub_entry.file_name().to_string_lossy().to_string();
                        let hex = format!("{prefix}{suffix}");
                        if let Ok(hash) = Hash::from_hex(&hex) {
                            hashes.push(hash);
                        }
                    }
                }
            }
        }
        Ok(hashes)
    }

    /// Get the path to the objects directory.
    pub fn objects_dir(&self) -> PathBuf {
        self.root.join("objects")
    }

    /// Get the path to the pack directory.
    pub fn pack_dir(&self) -> PathBuf {
        self.root.join("objects").join("pack")
    }

    /// Ensure pack cache is loaded, then call `f` with a reference to it.
    ///
    /// On first access, reads all `.idx` files from the pack directory.
    /// Subsequent calls return the cached data without disk I/O.
    /// Call `invalidate_pack_cache()` after `repack()` to force a reload.
    fn with_pack_cache<F, R>(&self, f: F) -> Result<R, CasError>
    where
        F: FnOnce(&PackCache) -> R,
    {
        let mut guard = self
            .pack_cache
            .lock()
            .map_err(|e| CasError::CompressionError(format!("pack cache lock poisoned: {e}")))?;
        if guard.is_none() {
            *guard = Some(PackCache::load_all(&self.pack_dir()).map_err(CasError::Pack)?);
        }
        Ok(f(guard.as_ref().unwrap()))
    }

    /// Invalidate the pack cache (call after repack or external pack changes).
    pub fn invalidate_pack_cache(&self) {
        if let Ok(mut guard) = self.pack_cache.lock() {
            *guard = None;
        }
    }

    /// Retrieve a blob from pack files only (not loose objects).
    pub fn get_blob_packed(&self, hash: &Hash) -> Result<Vec<u8>, CasError> {
        // Find which pack file contains this blob
        let pack_path = self.with_pack_cache(|cache| cache.find(hash).map(|(p, _)| p.clone()))?;
        let pack_path = pack_path.ok_or_else(|| CasError::BlobNotFound(hash.to_hex()))?;

        let idx_path = pack_path.with_extension("idx");
        let index = PackIndex::load(&idx_path).map_err(CasError::Pack)?;
        let data = PackFile::read_blob(&pack_path, &index, hash).map_err(CasError::Pack)?;
        Ok(data)
    }

    /// Check if a blob exists in any pack file.
    pub fn has_blob_packed(&self, hash: &Hash) -> bool {
        self.with_pack_cache(|cache| cache.find(hash).is_some())
            .unwrap_or(false)
    }

    /// List all blob hashes stored in pack files.
    pub fn list_blobs_packed(&self) -> Result<Vec<Hash>, CasError> {
        self.with_pack_cache(|cache| cache.all_hashes())
    }

    /// Repack loose blobs into a pack file if the count exceeds the threshold.
    ///
    /// Returns the number of blobs that were packed. If the loose blob count
    /// is at or below the threshold, no packing occurs and 0 is returned.
    /// After successful packing, the loose blobs are removed.
    pub fn repack(&self, threshold: usize) -> Result<usize, CasError> {
        let loose_hashes = self.list_blobs()?;
        if loose_hashes.len() <= threshold {
            return Ok(0);
        }

        let mut objects = Vec::with_capacity(loose_hashes.len());
        for hash in &loose_hashes {
            let data = self.get_blob(hash)?;
            objects.push((*hash, data));
        }

        let (pack_path, _idx_path) = PackFile::create(&self.pack_dir(), &objects)?;
        let _ = pack_path;

        for hash in &loose_hashes {
            let _ = self.delete_blob(hash);
        }

        // Invalidate pack cache since we created new pack files
        self.invalidate_pack_cache();

        Ok(loose_hashes.len())
    }

    /// Get the on-disk path for a given hash.
    fn blob_path(&self, hash: &Hash) -> PathBuf {
        let hex = hash.to_hex();
        let prefix = &hex[..2];
        let suffix = &hex[2..];
        self.root.join("objects").join(prefix).join(suffix)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use tempfile::TempDir;

    fn make_store() -> (TempDir, BlobStore) {
        let dir = tempfile::tempdir().unwrap();
        let store = BlobStore::new_uncompressed(dir.path()).unwrap();
        (dir, store)
    }

    #[test]
    fn test_put_and_get_blob() {
        let (_dir, store) = make_store();
        let data = b"hello, suture!";
        let hash = store.put_blob(data).unwrap();

        let retrieved = store.get_blob(&hash).unwrap();
        assert_eq!(data.as_slice(), retrieved.as_slice());
    }

    #[test]
    fn test_deduplication() {
        let (_dir, store) = make_store();
        let data = b"deduplicate me";

        let h1 = store.put_blob(data).unwrap();
        let h2 = store.put_blob(data).unwrap();
        assert_eq!(h1, h2);

        assert_eq!(store.blob_count().unwrap(), 1, "Only one copy should exist");
    }

    #[test]
    fn test_has_blob() {
        let (_dir, store) = make_store();
        let hash = store.put_blob(b"exists").unwrap();

        assert!(store.has_blob(&hash));
        let missing = Hash::from_hex(&"f".repeat(64)).unwrap();
        assert!(!store.has_blob(&missing));
    }

    #[test]
    fn test_get_nonexistent_blob() {
        let (_dir, store) = make_store();
        let missing = Hash::from_hex(&"a".repeat(64)).unwrap();
        let result = store.get_blob(&missing);
        assert!(matches!(result, Err(CasError::BlobNotFound(_))));
    }

    #[test]
    fn test_delete_blob() {
        let (_dir, store) = make_store();
        let hash = store.put_blob(b"delete me").unwrap();
        assert!(store.has_blob(&hash));

        store.delete_blob(&hash).unwrap();
        assert!(!store.has_blob(&hash));
    }

    #[test]
    fn test_delete_nonexistent_blob() {
        let (_dir, store) = make_store();
        let missing = Hash::from_hex(&"b".repeat(64)).unwrap();
        let result = store.delete_blob(&missing);
        assert!(matches!(result, Err(CasError::BlobNotFound(_))));
    }

    #[test]
    fn test_put_blob_new_rejects_duplicate() {
        let (_dir, store) = make_store();
        let data = b"duplicate";
        store.put_blob(data).unwrap();
        let result = store.put_blob_new(data);
        assert!(matches!(result, Err(CasError::AlreadyExists(_))));
    }

    #[test]
    fn test_blob_count_and_list() {
        let (_dir, store) = make_store();
        store.put_blob(b"one").unwrap();
        store.put_blob(b"two").unwrap();
        store.put_blob(b"three").unwrap();

        assert_eq!(store.blob_count().unwrap(), 3);
        assert_eq!(store.list_blobs().unwrap().len(), 3);
    }

    #[test]
    fn test_large_blob() {
        let (_dir, store) = make_store();
        // 10 MB blob
        let data: Vec<u8> = (0..10_000_000).map(|i| (i % 256) as u8).collect();
        let hash = store.put_blob(&data).unwrap();

        let retrieved = store.get_blob(&hash).unwrap();
        assert_eq!(data.len(), retrieved.len());
        assert_eq!(data, retrieved);
    }

    #[test]
    fn test_hash_integrity() {
        let (_dir, store) = make_store();
        let data = b"integrity check";
        let hash = store.put_blob(data).unwrap();

        // Manually corrupt the stored blob
        let blob_path = store.blob_path(&hash);
        let mut corrupted = fs::read(&blob_path).unwrap();
        corrupted[0] = corrupted[0].wrapping_add(1);
        fs::write(&blob_path, &corrupted).unwrap();

        // Getting the corrupted blob should fail integrity check
        let result = store.get_blob(&hash);
        assert!(matches!(result, Err(CasError::HashMismatch { .. })));
    }

    #[test]
    fn test_compressed_store() {
        let dir = tempfile::tempdir().unwrap();
        let store = BlobStore::new(dir.path()).unwrap();

        let data = b"this will be compressed";
        let hash = store.put_blob(data).unwrap();

        // Verify the stored file is actually compressed
        let blob_path = store.blob_path(&hash);
        let raw = fs::read(&blob_path).unwrap();
        assert!(is_zstd_compressed(&raw), "Blob should be Zstd-compressed");

        // Verify round-trip
        let retrieved = store.get_blob(&hash).unwrap();
        assert_eq!(data.as_slice(), retrieved.as_slice());
    }

    mod proptests {
        use super::*;
        use proptest::prelude::*;

        proptest! {
            #[test]
            fn put_get_roundtrip(data in proptest::collection::vec(proptest::num::u8::ANY, 0..1024)) {
                let dir = tempfile::tempdir().unwrap();
                let store = BlobStore::new_uncompressed(dir.path()).unwrap();
                let hash = store.put_blob(&data).unwrap();
                let retrieved = store.get_blob(&hash).unwrap();
                prop_assert_eq!(data, retrieved);
            }

            #[test]
            fn content_addressing(
                data1 in proptest::collection::vec(proptest::num::u8::ANY, 0..512),
                data2 in proptest::collection::vec(proptest::num::u8::ANY, 0..512)
            ) {
                let dir = tempfile::tempdir().unwrap();
                let store = BlobStore::new_uncompressed(dir.path()).unwrap();

                let hash1 = store.put_blob(&data1).unwrap();
                let hash2 = store.put_blob(&data2).unwrap();

                if data1 == data2 {
                    prop_assert_eq!(hash1, hash2, "same data must produce same hash");
                } else {
                    prop_assert_ne!(hash1, hash2, "different data must produce different hashes");
                }
            }

            #[test]
            fn put_twice_idempotent(data in proptest::collection::vec(proptest::num::u8::ANY, 0..1024)) {
                let dir = tempfile::tempdir().unwrap();
                let store = BlobStore::new_uncompressed(dir.path()).unwrap();

                let hash1 = store.put_blob(&data).unwrap();
                let hash2 = store.put_blob(&data).unwrap();
                prop_assert_eq!(hash1, hash2);
                prop_assert_eq!(store.blob_count().unwrap(), 1);
            }
        }
    }

    mod pack_tests {
        use super::*;

        #[test]
        fn test_get_blob_from_pack() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let hash1 = store.put_blob(b"packed blob one").unwrap();
            let hash2 = store.put_blob(b"packed blob two").unwrap();

            let packed = store.repack(0).unwrap();
            assert_eq!(packed, 2);

            assert_eq!(store.blob_count().unwrap(), 0);

            let data1 = store.get_blob(&hash1).unwrap();
            assert_eq!(data1, b"packed blob one".to_vec());

            let data2 = store.get_blob(&hash2).unwrap();
            assert_eq!(data2, b"packed blob two".to_vec());
        }

        #[test]
        fn test_has_blob_checks_packs() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let hash = store.put_blob(b"check me in packs").unwrap();
            store.repack(0).unwrap();

            assert!(store.has_blob(&hash));
            assert!(!store.has_blob(&Hash::from_hex(&"c".repeat(64)).unwrap()));
        }

        #[test]
        fn test_get_blob_packed_not_found() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let missing = Hash::from_hex(&"d".repeat(64)).unwrap();
            let result = store.get_blob_packed(&missing);
            assert!(matches!(result, Err(CasError::BlobNotFound(_))));
        }

        #[test]
        fn test_list_blobs_packed() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            store.put_blob(b"alpha").unwrap();
            store.put_blob(b"beta").unwrap();
            store.repack(0).unwrap();

            let packed = store.list_blobs_packed().unwrap();
            assert_eq!(packed.len(), 2);
        }

        #[test]
        fn test_repack_below_threshold() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            store.put_blob(b"only one").unwrap();

            let packed = store.repack(10).unwrap();
            assert_eq!(packed, 0);
            assert_eq!(store.blob_count().unwrap(), 1);
        }

        #[test]
        fn test_repack_at_threshold() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            store.put_blob(b"one").unwrap();
            store.put_blob(b"two").unwrap();

            let packed = store.repack(2).unwrap();
            assert_eq!(packed, 0);
            assert_eq!(store.blob_count().unwrap(), 2);

            let packed = store.repack(1).unwrap();
            assert_eq!(packed, 2);
            assert_eq!(store.blob_count().unwrap(), 0);
        }

        #[test]
        fn test_loose_priority_over_packed() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let hash = store.put_blob(b"original data").unwrap();
            store.repack(0).unwrap();

            // Re-store the same hash as a loose blob
            let blob_path = store.blob_path(&hash);
            if let Some(parent) = blob_path.parent() {
                fs::create_dir_all(parent).unwrap();
            }
            fs::write(&blob_path, b"original data").unwrap();

            let data = store.get_blob(&hash).unwrap();
            assert_eq!(data, b"original data".to_vec());

            // Delete the loose blob; should still find in pack
            store.delete_blob(&hash).unwrap();
            let data = store.get_blob(&hash).unwrap();
            assert_eq!(data, b"original data".to_vec());
        }

        #[test]
        fn test_has_blob_packed() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let hash = store.put_blob(b"packed check").unwrap();
            assert!(!store.has_blob_packed(&hash));

            store.repack(0).unwrap();
            assert!(store.has_blob_packed(&hash));
        }

        #[test]
        fn test_repack_multiple_times() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            store.put_blob(b"first batch one").unwrap();
            store.put_blob(b"first batch two").unwrap();
            store.repack(0).unwrap();

            store.put_blob(b"second batch").unwrap();
            store.repack(0).unwrap();

            let all = store.list_blobs_packed().unwrap();
            assert_eq!(all.len(), 3);
        }

        #[test]
        fn test_pack_cache_avoids_repeated_disk_reads() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let hash = store.put_blob(b"cache me").unwrap();
            store.repack(0).unwrap();

            // First access: loads cache from disk
            assert!(store.has_blob_packed(&hash));
            // Cache should now be populated
            {
                let guard = store.pack_cache.lock().unwrap();
                assert!(
                    guard.is_some(),
                    "pack cache should be populated after first access"
                );
            }

            // Second access: uses cached data (no disk I/O)
            assert!(store.has_blob_packed(&hash));

            // Third access: also cached
            let data = store.get_blob_packed(&hash).unwrap();
            assert_eq!(data, b"cache me".to_vec());
        }

        #[test]
        fn test_invalidate_pack_cache() {
            let dir = tempfile::tempdir().unwrap();
            let store = BlobStore::new_uncompressed(dir.path()).unwrap();

            let hash = store.put_blob(b"invalidate test").unwrap();
            store.repack(0).unwrap();

            // Populate cache
            assert!(store.has_blob_packed(&hash));
            assert!(store.pack_cache.lock().unwrap().is_some());

            // Invalidate
            store.invalidate_pack_cache();
            assert!(store.pack_cache.lock().unwrap().is_none());

            // Next access reloads from disk
            assert!(store.has_blob_packed(&hash));
            assert!(store.pack_cache.lock().unwrap().is_some());
        }
    }
}