armature-compression 0.1.0

//! Compression middleware implementation

use crate::{CompressionAlgorithm, CompressionConfig};
use armature_core::{Error, HttpRequest, HttpResponse, Middleware};
use async_trait::async_trait;
use std::future::Future;
use std::pin::Pin;

/// HTTP response compression middleware
///
/// This middleware compresses HTTP response bodies based on the client's
/// `Accept-Encoding` header and the configured compression algorithm.
///
/// # Example
///
/// ```rust,no_run
/// use armature_compression::{CompressionMiddleware, CompressionConfig};
///
/// // Create with default settings (auto-select algorithm)
/// let middleware = CompressionMiddleware::new();
///
/// // Create with custom configuration
/// let config = CompressionConfig::builder()
///     .min_size(1024)
///     .level(6)
///     .build();
/// let middleware = CompressionMiddleware::with_config(config);
/// ```
#[derive(Debug, Clone)]
pub struct CompressionMiddleware {
    config: CompressionConfig,
}

impl CompressionMiddleware {
    /// Create a new compression middleware with default settings
    pub fn new() -> Self {
        Self {
            config: CompressionConfig::default(),
        }
    }

    /// Create a compression middleware with custom configuration
    pub fn with_config(config: CompressionConfig) -> Self {
        Self { config }
    }

    /// Get a reference to the configuration
    pub fn config(&self) -> &CompressionConfig {
        &self.config
    }

    /// Determine the compression algorithm to use for a request
    fn select_algorithm(&self, accept_encoding: Option<&str>) -> CompressionAlgorithm {
        match self.config.algorithm {
            CompressionAlgorithm::Auto => {
                if let Some(encoding) = accept_encoding {
                    CompressionAlgorithm::select_from_accept_encoding(encoding)
                } else {
                    CompressionAlgorithm::None
                }
            }
            algo => algo,
        }
    }

    /// Check if a response should be compressed
    fn should_compress(&self, response: &HttpResponse) -> bool {
        // Don't compress error responses or empty bodies
        if response.status >= 400 || response.body.is_empty() {
            return false;
        }

        // Check size threshold
        if !self.config.should_compress_size(response.body.len()) {
            return false;
        }

        // Check if already encoded
        if !self.config.compress_encoded
            && let Some(encoding) = response.headers.get("Content-Encoding")
            && !encoding.is_empty()
            && encoding != "identity"
        {
            return false;
        }

        // Check content type
        if let Some(content_type) = response.headers.get("Content-Type") {
            self.config.should_compress_content_type(content_type)
        } else {
            // No content type header, compress by default for non-empty bodies
            true
        }
    }

    /// Compress the response body
    fn compress_response(
        &self,
        mut response: HttpResponse,
        algorithm: CompressionAlgorithm,
    ) -> HttpResponse {
        let level = self.config.effective_level();

        match algorithm.compress(&response.body, level) {
            Ok(compressed) => {
                // Only use compressed data if it's smaller
                if compressed.len() < response.body.len() {
                    response.body = compressed;

                    // Set Content-Encoding header
                    if let Some(encoding) = algorithm.encoding_name() {
                        response
                            .headers
                            .insert("Content-Encoding".to_string(), encoding.to_string());
                    }

                    // Update Content-Length
                    response.headers.insert(
                        "Content-Length".to_string(),
                        response.body.len().to_string(),
                    );

                    // Add Vary header to indicate response varies by Accept-Encoding
                    let vary = response.headers.entry("Vary".to_string()).or_default();
                    if !vary.contains("Accept-Encoding") {
                        if !vary.is_empty() {
                            vary.push_str(", ");
                        }
                        vary.push_str("Accept-Encoding");
                    }
                }
            }
            Err(e) => {
                // Log compression error but return original response
                tracing::warn!("Compression failed: {}", e);
            }
        }

        response
    }
}

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

#[async_trait]
impl Middleware for CompressionMiddleware {
    async fn handle(
        &self,
        req: HttpRequest,
        next: Box<
            dyn FnOnce(
                    HttpRequest,
                )
                    -> Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>>
                + Send,
        >,
    ) -> Result<HttpResponse, Error> {
        // Get Accept-Encoding header before passing request
        let accept_encoding = req
            .headers
            .get("Accept-Encoding")
            .or_else(|| req.headers.get("accept-encoding"))
            .cloned();

        // Call the next handler
        let response = next(req).await?;

        // Determine compression algorithm
        let algorithm = self.select_algorithm(accept_encoding.as_deref());

        // Check if we should compress
        if algorithm == CompressionAlgorithm::None || !self.should_compress(&response) {
            return Ok(response);
        }

        // Compress and return
        Ok(self.compress_response(response, algorithm))
    }
}

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

    fn create_response(body: &str, content_type: &str) -> HttpResponse {
        HttpResponse::new(200)
            .with_header("Content-Type".to_string(), content_type.to_string())
            .with_header("Content-Length".to_string(), body.len().to_string())
            .with_body(body.as_bytes().to_vec())
    }

    #[test]
    fn test_middleware_creation() {
        let middleware = CompressionMiddleware::new();
        assert_eq!(middleware.config().algorithm, CompressionAlgorithm::Auto);
    }

    #[test]
    fn test_should_compress() {
        let middleware = CompressionMiddleware::new();

        // Large JSON response should compress
        let response = create_response(&"x".repeat(1000), "application/json");
        assert!(middleware.should_compress(&response));

        // Small response should not compress
        let response = create_response("small", "application/json");
        assert!(!middleware.should_compress(&response));

        // Binary content should not compress
        let response = create_response(&"x".repeat(1000), "image/png");
        assert!(!middleware.should_compress(&response));

        // Error response should not compress
        let mut response = create_response(&"x".repeat(1000), "application/json");
        response.status = 500;
        assert!(!middleware.should_compress(&response));

        // Empty body should not compress
        let mut response = create_response("", "application/json");
        response.body = Vec::new();
        assert!(!middleware.should_compress(&response));
    }

    #[test]
    fn test_select_algorithm_auto() {
        let middleware = CompressionMiddleware::new();

        // No Accept-Encoding
        assert_eq!(
            middleware.select_algorithm(None),
            CompressionAlgorithm::None
        );

        #[cfg(feature = "gzip")]
        {
            assert_eq!(
                middleware.select_algorithm(Some("gzip")),
                CompressionAlgorithm::Gzip
            );
        }

        #[cfg(feature = "brotli")]
        {
            assert_eq!(
                middleware.select_algorithm(Some("br")),
                CompressionAlgorithm::Brotli
            );
        }

        #[cfg(all(feature = "gzip", feature = "brotli"))]
        {
            // Brotli should be preferred over gzip
            assert_eq!(
                middleware.select_algorithm(Some("gzip, br")),
                CompressionAlgorithm::Brotli
            );
        }
    }

    #[cfg(feature = "gzip")]
    #[test]
    fn test_select_algorithm_specific() {
        let config = CompressionConfig::builder().gzip().build();
        let middleware = CompressionMiddleware::with_config(config);

        // Should always use gzip regardless of Accept-Encoding
        assert_eq!(
            middleware.select_algorithm(Some("br")),
            CompressionAlgorithm::Gzip
        );
    }

    #[cfg(feature = "gzip")]
    #[test]
    fn test_compress_response() {
        let middleware = CompressionMiddleware::with_config(
            CompressionConfig::builder().gzip().min_size(10).build(),
        );

        // Use a large repetitive string that compresses well
        let body = "Hello, World! ".repeat(100);
        let response = create_response(&body, "text/plain");

        let compressed = middleware.compress_response(response, CompressionAlgorithm::Gzip);

        // Check headers
        assert_eq!(
            compressed.headers.get("Content-Encoding"),
            Some(&"gzip".to_string())
        );
        assert!(
            compressed
                .headers
                .get("Vary")
                .unwrap()
                .contains("Accept-Encoding")
        );

        // Compressed body should be smaller
        assert!(compressed.body.len() < body.len());
    }

    #[cfg(feature = "gzip")]
    #[test]
    fn test_vary_header_appended() {
        let middleware = CompressionMiddleware::with_config(
            CompressionConfig::builder().gzip().min_size(10).build(),
        );

        // Use a repetitive string that compresses well
        let body = "Hello, World! ".repeat(100);
        let mut response = create_response(&body, "text/plain");
        response
            .headers
            .insert("Vary".to_string(), "Origin".to_string());

        let compressed = middleware.compress_response(response, CompressionAlgorithm::Gzip);
        let vary = compressed.headers.get("Vary").unwrap();
        assert!(vary.contains("Origin"));
        assert!(vary.contains("Accept-Encoding"));
    }
}