chore: establish development baseline

infrastructure/src/cas.rs

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+//! CAS 存储实现占位

infrastructure/src/cas/filesystem.rs

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+//! CAS 文件系统实现
+//!
+//! 基于文件系统的内容寻址存储实现
+
+use async_trait::async_trait;
+use bat_core::repositories::cas_repository::{CasRepository, ObjectId};
+use blake3::Hasher;
+use std::path::PathBuf;
+use tokio::fs;
+use tokio::io::AsyncWriteExt;
+
+/// 文件系统 CAS Repository
+///
+/// 使用文件系统存储对象，目录结构：
+/// ```text
+/// cas_root/
+/// ├── objects/
+/// │   ├── ab/
+/// │   │   ├── cd/
+/// │   │   │   └── abcd1234...
+/// └── refs.db (SQLite)
+/// ```
+pub struct FileSystemCasRepository {
+    /// CAS 根目录
+    root: PathBuf,
+}
+
+impl FileSystemCasRepository {
+    /// 创建新的文件系统 CAS Repository
+    ///
+    /// # 参数
+    ///
+    /// - `root`: CAS 根目录
+    ///
+    /// # 示例
+    ///
+    /// ```rust,ignore
+    /// let repo = FileSystemCasRepository::new("/path/to/cas");
+    /// ```
+    pub fn new(root: impl Into<PathBuf>) -> Self {
+        Self {
+            root: root.into(),
+        }
+    }
+
+    /// 计算对象 Hash
+    fn compute_hash(data: &[u8]) -> ObjectId {
+        let mut hasher = Hasher::new();
+        hasher.update(data);
+        hasher.finalize().to_hex().to_string()
+    }
+
+    /// 获取对象路径
+    fn object_path(&self, id: &ObjectId) -> PathBuf {
+        let prefix1 = &id[0..2];
+        let prefix2 = &id[2..4];
+        self.root
+            .join("objects")
+            .join(prefix1)
+            .join(prefix2)
+            .join(id)
+    }
+
+    /// 初始化存储
+    pub async fn init(&self) -> bat_core::Result<()> {
+        fs::create_dir_all(self.root.join("objects"))
+            .await
+            .map_err(bat_core::Error::Io)?;
+        Ok(())
+    }
+}
+
+#[async_trait]
+impl CasRepository for FileSystemCasRepository {
+    async fn store(&self, data: &[u8]) -> bat_core::Result<ObjectId> {
+        let hash = Self::compute_hash(data);
+        let path = self.object_path(&hash);
+
+        // 如果对象已存在，直接返回
+        if path.exists() {
+            return Ok(hash);
+        }
+
+        // 创建父目录
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent)
+                .await
+                .map_err(bat_core::Error::Io)?;
+        }
+
+        // 写入对象
+        let mut file = fs::File::create(&path)
+            .await
+            .map_err(bat_core::Error::Io)?;
+        file.write_all(data)
+            .await
+            .map_err(bat_core::Error::Io)?;
+        file.sync_all()
+            .await
+            .map_err(bat_core::Error::Io)?;
+
+        Ok(hash)
+    }
+
+    async fn get(&self, id: &ObjectId) -> bat_core::Result<Vec<u8>> {
+        let path = self.object_path(id);
+
+        if !path.exists() {
+            return Err(bat_core::Error::NotFound(format!("Object not found: {}", id)));
+        }
+
+        let data = fs::read(&path)
+            .await
+            .map_err(bat_core::Error::Io)?;
+
+        // 验证 Hash
+        let computed_hash = Self::compute_hash(&data);
+        if &computed_hash != id {
+            return Err(bat_core::Error::InvalidArgument(format!(
+                "Hash mismatch: expected {}, got {}",
+                id, computed_hash
+            )));
+        }
+
+        Ok(data)
+    }
+
+    async fn exists(&self, id: &ObjectId) -> bool {
+        self.object_path(id).exists()
+    }
+
+    async fn add_reference(&self, _id: &ObjectId) -> bat_core::Result<u64> {
+        // TODO: Phase 1 Week 3 - 实现引用计数
+        Ok(1)
+    }
+
+    async fn remove_reference(&self, _id: &ObjectId) -> bat_core::Result<u64> {
+        // TODO: Phase 1 Week 3 - 实现引用计数
+        Ok(0)
+    }
+
+    async fn get_reference_count(&self, _id: &ObjectId) -> bat_core::Result<u64> {
+        // TODO: Phase 1 Week 3 - 实现引用计数
+        Ok(1)
+    }
+
+    async fn gc(&self) -> bat_core::Result<u64> {
+        // TODO: Phase 1 Week 3 - 实现垃圾回收
+        Ok(0)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::TempDir;
+
+    #[tokio::test]
+    async fn test_store_and_get() {
+        let temp_dir = TempDir::new().unwrap();
+        let repo = FileSystemCasRepository::new(temp_dir.path());
+        repo.init().await.unwrap();
+
+        let data = b"Hello, World!";
+        let id = repo.store(data).await.unwrap();
+
+        let retrieved = repo.get(&id).await.unwrap();
+        assert_eq!(data, retrieved.as_slice());
+    }
+
+    #[tokio::test]
+    async fn test_exists() {
+        let temp_dir = TempDir::new().unwrap();
+        let repo = FileSystemCasRepository::new(temp_dir.path());
+        repo.init().await.unwrap();
+
+        let data = b"Test data";
+        let id = repo.store(data).await.unwrap();
+
+        assert!(repo.exists(&id).await);
+        assert!(!repo.exists(&"nonexistent".to_string()).await);
+    }
+
+    #[tokio::test]
+    async fn test_deduplication() {
+        let temp_dir = TempDir::new().unwrap();
+        let repo = FileSystemCasRepository::new(temp_dir.path());
+        repo.init().await.unwrap();
+
+        let data = b"Duplicate data";
+        let id1 = repo.store(data).await.unwrap();
+        let id2 = repo.store(data).await.unwrap();
+
+        assert_eq!(id1, id2);
+    }
+
+    #[test]
+    fn test_compute_hash() {
+        let data = b"test";
+        let hash = FileSystemCasRepository::compute_hash(data);
+        assert!(!hash.is_empty());
+        assert_eq!(hash.len(), 64); // BLAKE3 produces 32 bytes = 64 hex chars
+    }
+}

infrastructure/src/lib.rs

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+//! # BAT Infrastructure - 基础设施层
+//!
+//! 提供技术实现
+//!
+//! 包含：
+//! - CAS 存储实现
+//! - 下载器
+//! - 解析器
+
+#![warn(missing_docs)]
+#![warn(clippy::all)]
+
+pub mod cas;
+
+/// Infrastructure 版本号
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");