keep/src/services/compression_service.rs

use crate::compression_engine::{get_compression_engine, CompressionType};
use crate::services::error::CoreError;
use std::io::Read;
use std::path::PathBuf;
use std::str::FromStr;
use anyhow::anyhow;

//// Service for handling compression and decompression of item content.
///
/// Provides methods to read compressed item files either fully into memory
/// or as streaming readers. Supports various compression types via engines.
/// This service abstracts the underlying compression engines for consistent access.
///
/// # Examples
///
/// ```
/// let service = CompressionService::new();
/// let content = service.get_item_content(path, "gzip")?;
/// ```
pub struct CompressionService;

/// Service for handling compression and decompression of item content.
///
/// Provides methods to read compressed item files either fully into memory
/// or as streaming readers. Supports various compression types via engines.
///
/// # Examples
///
/// ```
/// let service = CompressionService::new();
/// let content = service.get_item_content(path, "gzip")?;
/// ```

impl CompressionService {
    /// Creates a new CompressionService instance.
    ///
    /// This is a simple constructor; no initialization is required beyond the static methods.
    ///
    /// # Returns
    ///
    /// * `CompressionService` - A new instance of the service.
    ///
    /// # Examples
    ///
    /// ```
    /// let service = CompressionService::new();
    /// ```
    pub fn new() -> Self {
        Self
    }

    /// Reads and decompresses the full content of an item file into memory.
    ///
    /// Loads the entire decompressed content as a byte vector. Suitable for small to medium files.
    ///
    /// # Arguments
    ///
    /// * `item_path` - Path to the compressed item file on disk.
    /// * `compression` - Compression type as string (e.g., "gzip", "lz4"); case-insensitive.
    ///
    /// # Returns
    ///
    /// * `Ok(Vec<u8>)` - The full decompressed content bytes.
    /// * `Err(CoreError)` - On failure (see errors).
    ///
    /// # Errors
    ///
    /// * `CoreError::Compression(String)` - If the compression type string is invalid.
    /// * `CoreError::Other(anyhow::Error)` - If the file cannot be opened, the engine fails, or reading encounters an I/O error.
    ///
    /// # Examples
    ///
    /// ```
    /// let content = service.get_item_content(item_path, "lz4")?;
    /// assert_eq!(content.len(), expected_size);
    /// ```
    pub fn get_item_content(&self, item_path: PathBuf, compression: &str) -> Result<Vec<u8>, CoreError> {
        let compression_type = CompressionType::from_str(compression)
            .map_err(|e| CoreError::Compression(e.to_string()))?;
        let engine = get_compression_engine(compression_type)
            .map_err(|e| CoreError::Other(anyhow!(e.to_string())))?;

        let mut reader = engine.open(item_path.clone())
            .map_err(|e| CoreError::Other(anyhow!("Failed to open item file {:?}: {}", item_path, e)))?;
        let mut content = Vec::new();
        reader.read_to_end(&mut content)?;
        Ok(content)
    }

    /// Opens a streaming reader for decompressing item content.
    ///
    /// Due to Send requirements in async contexts, this loads the full content into a Cursor.
    /// Warning: For very large files, this consumes significant memory; consider alternatives for streaming without loading all data.
    ///
    /// # Arguments
    ///
    /// * `item_path` - Path to the compressed item file on disk.
    /// * `compression` - Compression type as string (e.g., "gzip", "lz4"); case-insensitive.
    ///
    /// # Returns
    ///
    /// * `Ok(Box<dyn Read + Send>)` - A boxed reader that can be used for streaming decompressed data.
    /// * `Err(CoreError)` - On failure (see errors).
    ///
    /// # Errors
    ///
    /// * `CoreError::Compression(String)` - If the compression type string is invalid.
    /// * `CoreError::Other(anyhow::Error)` - If the file cannot be opened, the engine fails, or reading encounters an I/O error.
    ///
    /// # Examples
    ///
    /// ```
    /// let mut reader = service.stream_item_content(item_path, "gzip")?;
    /// let mut buf = [0; 1024];
    /// let n = reader.read(&mut buf)?;
    /// ```
    pub fn stream_item_content(
        &self,
        item_path: PathBuf,
        compression: &str,
    ) -> Result<Box<dyn Read + Send>, CoreError> {
        let compression_type = CompressionType::from_str(compression)
            .map_err(|e| CoreError::Compression(e.to_string()))?;
        let engine = get_compression_engine(compression_type)
            .map_err(|e| CoreError::Other(anyhow!(e.to_string())))?;

        let reader = engine.open(item_path.clone())
            .map_err(|e| CoreError::Other(anyhow!("Failed to open item file {:?}: {}", item_path, e)))?;
        // Since we can't guarantee the reader implements Send, we need to wrap it
        // We'll read the content into a buffer and return a Cursor which is Send
        // This is not ideal for large files, but it ensures Send is implemented
        let mut content = Vec::new();
        let mut temp_reader = reader;
        temp_reader.read_to_end(&mut content)?;
        Ok(Box::new(std::io::Cursor::new(content)))
    }
}

impl Default for CompressionService {
    fn default() -> Self {
        Self::new()
    }
}