armature-core 0.7.0

// Middleware system for request/response processing

use crate::logging::{debug, trace};
use crate::{Error, HttpRequest, HttpResponse};
use async_trait::async_trait;
use std::collections::HashMap;
use std::future::Future;
use std::pin::Pin;
use std::sync::Arc;

/// Type alias for the next handler in the middleware chain
pub type Next = Box<
    dyn FnOnce(HttpRequest) -> Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>>
        + Send,
>;

/// Type alias for handler functions
pub type HandlerFn = Arc<
    dyn Fn(HttpRequest) -> Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>>
        + Send
        + Sync,
>;

/// Middleware trait for processing requests before they reach the handler
#[async_trait]
pub trait Middleware: Send + Sync {
    /// Process the request and optionally pass to next middleware
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error>;
}

/// Middleware chain executor
#[derive(Clone)]
pub struct MiddlewareChain {
    middlewares: Arc<Vec<Arc<dyn Middleware>>>,
}

impl MiddlewareChain {
    pub fn new() -> Self {
        Self {
            middlewares: Arc::new(Vec::new()),
        }
    }

    /// Add a middleware to the chain
    pub fn use_middleware<M: Middleware + 'static>(&mut self, middleware: M) {
        let mut mws = (*self.middlewares).clone();
        mws.push(Arc::new(middleware));
        self.middlewares = Arc::new(mws);
    }

    /// Execute the middleware chain with a handler
    pub async fn apply(&self, req: HttpRequest, handler: HandlerFn) -> Result<HttpResponse, Error> {
        // Fast path: with no middleware there is no chain to build, so call the
        // handler directly and skip the per-index recursion and boxing.
        if self.middlewares.is_empty() {
            trace!("No middleware registered, calling handler directly");
            return handler(req).await;
        }

        debug!(
            middleware_count = self.middlewares.len(),
            path = %req.path,
            method = %req.method,
            "Executing middleware chain"
        );
        self.execute_from(0, req, handler).await
    }

    fn execute_from(
        &self,
        index: usize,
        req: HttpRequest,
        handler: HandlerFn,
    ) -> Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>> {
        if index >= self.middlewares.len() {
            // No more middleware, call the handler
            trace!("Middleware chain complete, calling handler");
            handler(req)
        } else {
            let middleware = self.middlewares[index].clone();
            let chain = self.clone();
            let handler_clone = handler.clone();

            trace!(middleware_index = index, "Executing middleware");
            Box::pin(async move {
                middleware
                    .handle(
                        req,
                        Box::new(move |req| chain.execute_from(index + 1, req, handler_clone)),
                    )
                    .await
            })
        }
    }
}

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

// ========== Built-in Middleware ==========

/// CORS (Cross-Origin Resource Sharing) middleware
pub struct CorsMiddleware {
    pub allow_origin: String,
    pub allow_methods: String,
    pub allow_headers: String,
    pub allow_credentials: bool,
    pub max_age: u32,
}

impl CorsMiddleware {
    pub fn new() -> Self {
        Self {
            allow_origin: "*".to_string(),
            allow_methods: "GET, POST, PUT, DELETE, OPTIONS, PATCH".to_string(),
            allow_headers: "Content-Type, Authorization, Accept".to_string(),
            allow_credentials: false,
            max_age: 86400, // 24 hours
        }
    }

    pub fn allow_origin(mut self, origin: &str) -> Self {
        self.allow_origin = origin.to_string();
        self
    }

    pub fn allow_methods(mut self, methods: &str) -> Self {
        self.allow_methods = methods.to_string();
        self
    }

    pub fn allow_headers(mut self, headers: &str) -> Self {
        self.allow_headers = headers.to_string();
        self
    }

    pub fn allow_credentials(mut self, allow: bool) -> Self {
        self.allow_credentials = allow;
        self
    }
}

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

#[async_trait]
impl Middleware for CorsMiddleware {
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        // Handle preflight requests
        if req.method == "OPTIONS" {
            let mut headers = HashMap::new();
            headers.insert(
                "Access-Control-Allow-Origin".to_string(),
                self.allow_origin.clone(),
            );
            headers.insert(
                "Access-Control-Allow-Methods".to_string(),
                self.allow_methods.clone(),
            );
            headers.insert(
                "Access-Control-Allow-Headers".to_string(),
                self.allow_headers.clone(),
            );
            headers.insert(
                "Access-Control-Max-Age".to_string(),
                self.max_age.to_string(),
            );

            if self.allow_credentials {
                headers.insert(
                    "Access-Control-Allow-Credentials".to_string(),
                    "true".to_string(),
                );
            }

            return Ok(HttpResponse::with_status_and_headers(204, headers));
        }

        // Process request and add CORS headers to response
        let mut response = next(req).await?;

        response.headers.insert(
            "Access-Control-Allow-Origin".to_string(),
            self.allow_origin.clone(),
        );
        if self.allow_credentials {
            response.headers.insert(
                "Access-Control-Allow-Credentials".to_string(),
                "true".to_string(),
            );
        }

        Ok(response)
    }
}

/// Logging middleware
pub struct LoggerMiddleware {
    pub log_body: bool,
}

impl LoggerMiddleware {
    pub fn new() -> Self {
        Self { log_body: false }
    }

    pub fn with_body(mut self) -> Self {
        self.log_body = true;
        self
    }
}

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

#[async_trait]
impl Middleware for LoggerMiddleware {
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        let start = std::time::Instant::now();
        let method = req.method.clone();
        let path = req.path.clone();

        if self.log_body && !req.body.is_empty() {
            println!("→ {} {} (body: {} bytes)", method, path, req.body.len());
        } else {
            println!("→ {} {}", method, path);
        }

        let result = next(req).await;
        let duration = start.elapsed();

        match &result {
            Ok(response) => {
                println!(
                    "← {} {} - {} ({:?})",
                    method, path, response.status, duration
                );
            }
            Err(e) => {
                println!("← {} {} - Error: {} ({:?})", method, path, e, duration);
            }
        }

        result
    }
}

/// Request ID middleware
pub struct RequestIdMiddleware;

#[async_trait]
impl Middleware for RequestIdMiddleware {
    async fn handle(&self, mut req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        // Generate or use existing request ID
        let request_id = req
            .headers
            .get("x-request-id")
            .cloned()
            .unwrap_or_else(|| uuid::Uuid::new_v4().to_string());

        req.headers
            .insert("x-request-id".to_string(), request_id.clone());

        let mut response = next(req).await?;
        response
            .headers
            .insert("x-request-id".to_string(), request_id);

        Ok(response)
    }
}

/// Body size limit middleware
pub struct BodySizeLimitMiddleware {
    max_size: usize,
}

impl BodySizeLimitMiddleware {
    pub fn new(max_size: usize) -> Self {
        Self { max_size }
    }
}

#[async_trait]
impl Middleware for BodySizeLimitMiddleware {
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        if req.body.len() > self.max_size {
            return Err(Error::PayloadTooLarge(format!(
                "Request body exceeds maximum size of {} bytes",
                self.max_size
            )));
        }

        next(req).await
    }
}

// TimeoutMiddleware is now defined in the `timeout` module with more features.
// Re-exported from crate::timeout::{TimeoutMiddleware, ConfigurableTimeoutMiddleware, TimeoutConfig}

/// Security headers middleware
pub struct SecurityHeadersMiddleware {
    hsts_enabled: bool,
    nosniff_enabled: bool,
    xss_protection_enabled: bool,
    frame_options: Option<String>,
}

impl SecurityHeadersMiddleware {
    pub fn new() -> Self {
        Self {
            hsts_enabled: true,
            nosniff_enabled: true,
            xss_protection_enabled: true,
            frame_options: Some("DENY".to_string()),
        }
    }

    pub fn with_hsts(mut self, enabled: bool) -> Self {
        self.hsts_enabled = enabled;
        self
    }

    pub fn with_frame_options(mut self, value: &str) -> Self {
        self.frame_options = Some(value.to_string());
        self
    }
}

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

#[async_trait]
impl Middleware for SecurityHeadersMiddleware {
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        let mut response = next(req).await?;

        if self.hsts_enabled {
            response.headers.insert(
                "Strict-Transport-Security".to_string(),
                "max-age=31536000; includeSubDomains".to_string(),
            );
        }

        if self.nosniff_enabled {
            response
                .headers
                .insert("X-Content-Type-Options".to_string(), "nosniff".to_string());
        }

        if self.xss_protection_enabled {
            response
                .headers
                .insert("X-XSS-Protection".to_string(), "1; mode=block".to_string());
        }

        if let Some(frame_opts) = &self.frame_options {
            response
                .headers
                .insert("X-Frame-Options".to_string(), frame_opts.clone());
        }

        Ok(response)
    }
}

/// Gzip-compression middleware.
///
/// Compresses response bodies larger than `min_size` with gzip when the client's
/// `Accept-Encoding` permits it, setting `Content-Encoding: gzip` and merging
/// `Accept-Encoding` into `Vary` — merged rather than overwritten, so a
/// pre-existing `Vary` (e.g. `Vary: Origin` from CORS middleware upstream)
/// survives. Small bodies, bodies that are already content-encoded, and
/// clients that do not accept gzip are passed through unchanged (but still
/// gain `Vary`).
pub struct CompressionMiddleware {
    min_size: usize,
    level: crate::micro::CompressionLevel,
}

impl CompressionMiddleware {
    pub fn new() -> Self {
        Self {
            min_size: 1024, // Only compress responses > 1KB
            level: crate::micro::CompressionLevel::Default,
        }
    }

    pub fn with_min_size(mut self, size: usize) -> Self {
        self.min_size = size;
        self
    }

    /// Set the gzip compression level.
    pub fn with_level(mut self, level: crate::micro::CompressionLevel) -> Self {
        self.level = level;
        self
    }
}

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

#[async_trait]
impl Middleware for CompressionMiddleware {
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        // Negotiate before `req` is consumed by the handler.
        let client_accepts_gzip = crate::micro::accepts_gzip(&req);
        let mut response = next(req).await?;

        // Advertise Accept-Encoding as a cache-varying dimension regardless of
        // whether we compress this particular response. Merges with any
        // pre-existing `Vary` (e.g. `Vary: Origin` from CORS middleware
        // upstream) instead of clobbering it.
        crate::micro::add_vary_accept_encoding(&mut response);

        let already_encoded = response.headers.contains_key("Content-Encoding");
        if client_accepts_gzip && !already_encoded && response.body_ref().len() > self.min_size {
            response = crate::micro::apply_gzip_offload(response, self.level).await;
        }

        Ok(response)
    }
}

/// HTTP Request/Response Logging Middleware
///
/// Automatically logs HTTP requests and responses with configurable detail level.
/// Logs include method, path, status code, duration, and optional request/response bodies.
///
/// # Examples
///
/// ```no_run
/// use armature_core::{MiddlewareChain, LoggingMiddleware};
///
/// let mut chain = MiddlewareChain::new();
/// chain.use_middleware(LoggingMiddleware::new());
/// ```
pub struct LoggingMiddleware {
    /// Log request bodies
    pub log_request_body: bool,
    /// Log response bodies
    pub log_response_body: bool,
    /// Maximum body size to log (in bytes)
    pub max_body_size: usize,
}

impl LoggingMiddleware {
    /// Create a new logging middleware with default settings
    pub fn new() -> Self {
        Self {
            log_request_body: false,
            log_response_body: false,
            max_body_size: 1024, // 1KB
        }
    }

    /// Enable request body logging
    pub fn with_request_body(mut self, enable: bool) -> Self {
        self.log_request_body = enable;
        self
    }

    /// Enable response body logging
    pub fn with_response_body(mut self, enable: bool) -> Self {
        self.log_response_body = enable;
        self
    }

    /// Set maximum body size to log
    pub fn with_max_body_size(mut self, size: usize) -> Self {
        self.max_body_size = size;
        self
    }
}

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

#[async_trait]
impl Middleware for LoggingMiddleware {
    async fn handle(&self, req: HttpRequest, next: Next) -> Result<HttpResponse, Error> {
        use std::time::Instant;

        let start = Instant::now();
        let method = req.method.clone();
        let path = req.path.clone();

        // Log request
        if self.log_request_body && !req.body.is_empty() {
            let body_preview = if req.body.len() > self.max_body_size {
                format!(
                    "{}... ({} bytes)",
                    String::from_utf8_lossy(&req.body[..self.max_body_size]),
                    req.body.len()
                )
            } else {
                String::from_utf8_lossy(&req.body).to_string()
            };

            crate::logging::info!(
                method = %method,
                path = %path,
                body = %body_preview,
                "HTTP request received"
            );
        } else {
            crate::logging::info!(
                method = %method,
                path = %path,
                "HTTP request received"
            );
        }

        // Process request
        let result = next(req).await;
        let duration = start.elapsed();

        // Log response
        match &result {
            Ok(response) => {
                if self.log_response_body && !response.body.is_empty() {
                    let body_preview = if response.body.len() > self.max_body_size {
                        format!(
                            "{}... ({} bytes)",
                            String::from_utf8_lossy(&response.body[..self.max_body_size]),
                            response.body.len()
                        )
                    } else {
                        String::from_utf8_lossy(&response.body).to_string()
                    };

                    crate::logging::info!(
                        method = %method,
                        path = %path,
                        status = response.status,
                        duration_ms = duration.as_millis(),
                        body = %body_preview,
                        "HTTP response sent"
                    );
                } else {
                    crate::logging::info!(
                        method = %method,
                        path = %path,
                        status = response.status,
                        duration_ms = duration.as_millis(),
                        "HTTP response sent"
                    );
                }
            }
            Err(err) => {
                crate::logging::error!(
                    method = %method,
                    path = %path,
                    duration_ms = duration.as_millis(),
                    error = %err,
                    "HTTP request failed"
                );
            }
        }

        result
    }
}

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

    #[tokio::test]
    async fn test_middleware_chain() {
        let mut chain = MiddlewareChain::new();
        chain.use_middleware(LoggerMiddleware::new());

        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let handler = Arc::new(|_req: HttpRequest| {
            Box::pin(async { Ok(HttpResponse::ok()) })
                as Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>>
        });

        let result = chain.apply(req, handler).await;

        assert!(result.is_ok());
    }

    #[tokio::test]
    async fn test_empty_chain_calls_handler_directly() {
        // With no middleware registered, apply() must still invoke the handler
        // and return its response unchanged.
        let chain = MiddlewareChain::new();
        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let handler = Arc::new(|_req: HttpRequest| {
            Box::pin(async { Ok(HttpResponse::ok().with_body(b"direct".to_vec())) })
                as Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>>
        });

        let response = chain.apply(req, handler).await.unwrap();
        assert_eq!(response.status, 200);
        assert_eq!(response.body, b"direct");
    }

    #[tokio::test]
    async fn test_cors_middleware() {
        let cors = CorsMiddleware::new().allow_origin("https://example.com");
        let req = HttpRequest::new("GET".to_string(), "/api".to_string());

        let result = cors
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_ok());
        let response = result.unwrap();
        assert_eq!(
            response.headers.get("Access-Control-Allow-Origin"),
            Some(&"https://example.com".to_string())
        );
    }

    #[tokio::test]
    async fn test_body_size_limit() {
        let middleware = BodySizeLimitMiddleware::new(10);
        let mut req = HttpRequest::new("POST".to_string(), "/api".to_string());
        req.body = vec![0; 20]; // 20 bytes, exceeds limit

        let result = middleware
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_err());
    }

    #[tokio::test]
    async fn test_request_id_middleware() {
        let middleware = RequestIdMiddleware;
        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let result = middleware
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_ok());
        let response = result.unwrap();
        assert!(response.headers.contains_key("x-request-id"));
    }

    #[tokio::test]
    async fn test_security_headers_middleware() {
        let middleware = SecurityHeadersMiddleware::new();
        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let result = middleware
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_ok());
        let response = result.unwrap();
        assert!(response.headers.contains_key("X-Content-Type-Options"));
        assert!(response.headers.contains_key("X-Frame-Options"));
    }

    #[tokio::test]
    async fn test_timeout_middleware() {
        use crate::timeout::TimeoutMiddleware;

        let middleware = TimeoutMiddleware::new(5);
        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let result = middleware
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_ok());
    }

    #[test]
    fn test_cors_middleware_builder() {
        let cors = CorsMiddleware::new()
            .allow_origin("https://example.com")
            .allow_credentials(true);

        assert_eq!(cors.allow_origin, "https://example.com");
        assert!(cors.allow_credentials);
    }

    #[test]
    fn test_body_size_limit_creation() {
        let middleware = BodySizeLimitMiddleware::new(1024);
        assert_eq!(middleware.max_size, 1024);
    }

    #[test]
    fn test_logger_middleware_creation() {
        let _middleware = LoggerMiddleware::new();
        // Just test that it can be created
    }

    #[tokio::test]
    async fn test_compression_middleware() {
        let middleware = CompressionMiddleware::new();
        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let result = middleware
            .handle(
                req,
                Box::new(|_req| {
                    Box::pin(async {
                        Ok(HttpResponse::ok().with_body(b"test response body".to_vec()))
                    })
                }),
            )
            .await;

        assert!(result.is_ok());
    }

    fn gunzip(data: &[u8]) -> Vec<u8> {
        use std::io::Read;
        let mut decoder = flate2::read::GzDecoder::new(data);
        let mut out = Vec::new();
        decoder.read_to_end(&mut out).expect("valid gzip stream");
        out
    }

    /// Regression: a body above `min_size` is actually gzip-compressed (not just
    /// flagged) when the client accepts gzip. The old stub only set an
    /// `X-Compression-Eligible` header and never compressed.
    #[tokio::test]
    async fn test_compression_middleware_gzips_large_body() {
        let middleware = CompressionMiddleware::new().with_min_size(16);
        let mut req = HttpRequest::new("GET".to_string(), "/test".to_string());
        req.headers.insert("accept-encoding", "gzip");

        let original = vec![b'z'; 4096];
        let expected = original.clone();
        let response = middleware
            .handle(
                req,
                Box::new(move |_req| {
                    Box::pin(async move { Ok(HttpResponse::ok().with_body(original)) })
                }),
            )
            .await
            .unwrap();

        assert_eq!(
            response.headers.get("Content-Encoding").map(String::as_str),
            Some("gzip")
        );
        assert_eq!(
            response.headers.get("Vary").map(String::as_str),
            Some("Accept-Encoding")
        );
        assert!(response.body_ref().len() < expected.len());
        assert_eq!(gunzip(response.body_ref()), expected);
        // The stale eligibility-flag header must be gone.
        assert!(response.headers.get("X-Compression-Eligible").is_none());
    }

    /// Regression: `HttpResponse` stores its body in one of two places — the
    /// legacy `body: Vec<u8>` field, or the zero-copy `body_bytes:
    /// Option<Bytes>` storage set by `with_bytes_body` (used by static-file
    /// serving, `FastResponse`, and `ResponseBuilder::build()`), which takes
    /// precedence when present and leaves `body` empty. A body-storage-naive
    /// call site that only reads/writes the legacy `body` field would see an
    /// empty `Vec`, "successfully" gzip-encode zero bytes, and then wipe out
    /// the real content in `body_bytes` when installing the (bogus, empty)
    /// compressed result. This proves a `body_bytes`-backed body above the
    /// offload threshold is read and compressed correctly by
    /// `CompressionMiddleware` too (it shares `apply_gzip_offload` with
    /// `micro::Compress`).
    #[tokio::test]
    async fn test_compression_middleware_handles_bytes_backed_body_above_offload_threshold() {
        let middleware = CompressionMiddleware::new().with_min_size(16);
        let mut req = HttpRequest::new("GET".to_string(), "/test".to_string());
        req.headers.insert("accept-encoding", "gzip");

        let original: Vec<u8> = (0..(crate::micro::GZIP_OFFLOAD_THRESHOLD * 4))
            .map(|i| (i.wrapping_mul(2654435761) >> 13) as u8)
            .collect();
        assert!(original.len() > crate::micro::GZIP_OFFLOAD_THRESHOLD);
        let bytes_body = bytes::Bytes::from(original.clone());

        let response = middleware
            .handle(
                req,
                Box::new(move |_req| {
                    Box::pin(async move { Ok(HttpResponse::ok().with_bytes_body(bytes_body)) })
                }),
            )
            .await
            .unwrap();

        assert_eq!(
            response.headers.get("Content-Encoding").map(String::as_str),
            Some("gzip")
        );
        assert!(
            !response.body_ref().is_empty(),
            "compressed body must not be empty"
        );
        assert_eq!(gunzip(response.body_ref()), original);
    }

    /// Below `min_size`, the body must pass through uncompressed.
    #[tokio::test]
    async fn test_compression_middleware_respects_min_size() {
        let middleware = CompressionMiddleware::new().with_min_size(1024);
        let mut req = HttpRequest::new("GET".to_string(), "/test".to_string());
        req.headers.insert("accept-encoding", "gzip");

        let small = b"tiny".to_vec();
        let response = middleware
            .handle(
                req,
                Box::new(move |_req| {
                    Box::pin(async move { Ok(HttpResponse::ok().with_body(small)) })
                }),
            )
            .await
            .unwrap();

        assert!(response.headers.get("Content-Encoding").is_none());
        assert_eq!(response.body_ref(), b"tiny");
    }

    /// Without `Accept-Encoding: gzip`, a large body is left uncompressed.
    #[tokio::test]
    async fn test_compression_middleware_skips_without_accept_encoding() {
        let middleware = CompressionMiddleware::new().with_min_size(16);
        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let original = vec![b'q'; 4096];
        let expected = original.clone();
        let response = middleware
            .handle(
                req,
                Box::new(move |_req| {
                    Box::pin(async move { Ok(HttpResponse::ok().with_body(original)) })
                }),
            )
            .await
            .unwrap();

        assert!(response.headers.get("Content-Encoding").is_none());
        assert_eq!(response.body_ref(), expected.as_slice());
    }

    /// Regression: a pre-existing `Vary` header (e.g. `Vary: Origin` set by
    /// CORS middleware upstream) must be preserved, not clobbered, when
    /// `CompressionMiddleware` adds its own `Accept-Encoding` dimension.
    #[tokio::test]
    async fn test_compression_middleware_merges_vary_with_existing_value() {
        let middleware = CompressionMiddleware::new().with_min_size(16);
        let mut req = HttpRequest::new("GET".to_string(), "/test".to_string());
        req.headers.insert("accept-encoding", "gzip");

        let original = vec![b'z'; 4096];
        let response = middleware
            .handle(
                req,
                Box::new(move |_req| {
                    Box::pin(async move {
                        let mut resp = HttpResponse::ok().with_body(original);
                        resp.headers
                            .insert("Vary".to_string(), "Origin".to_string());
                        Ok(resp)
                    })
                }),
            )
            .await
            .unwrap();

        let vary = response.headers.get("Vary").cloned().unwrap_or_default();
        let tokens: Vec<&str> = vary.split(',').map(str::trim).collect();
        assert!(
            tokens.contains(&"Origin"),
            "Vary lost pre-existing Origin token: {vary}"
        );
        assert!(
            tokens
                .iter()
                .any(|t| t.eq_ignore_ascii_case("Accept-Encoding")),
            "Vary missing Accept-Encoding token: {vary}"
        );
    }

    /// A body larger than the gzip offload threshold is encoded on the
    /// `spawn_blocking` path; the result must be byte-identical to inline
    /// encoding, so gzip-decoding it reproduces the original exactly.
    #[tokio::test]
    async fn test_compression_middleware_offloads_large_body_and_round_trips() {
        let threshold = crate::micro::GZIP_OFFLOAD_THRESHOLD;
        let middleware = CompressionMiddleware::new().with_min_size(16);
        let mut req = HttpRequest::new("GET".to_string(), "/test".to_string());
        req.headers.insert("accept-encoding", "gzip");

        // Well past the offload threshold, non-repeating so it does not trivially
        // collapse to nothing.
        let original: Vec<u8> = (0..(threshold * 4))
            .map(|i| (i.wrapping_mul(2654435761) >> 13) as u8)
            .collect();
        assert!(original.len() > threshold);
        let expected = original.clone();

        let response = middleware
            .handle(
                req,
                Box::new(move |_req| {
                    Box::pin(async move { Ok(HttpResponse::ok().with_body(original)) })
                }),
            )
            .await
            .unwrap();

        assert_eq!(
            response.headers.get("Content-Encoding").map(String::as_str),
            Some("gzip")
        );
        assert_eq!(gunzip(response.body_ref()), expected);
    }

    #[tokio::test]
    async fn test_middleware_chain_multiple() {
        let mut chain = MiddlewareChain::new();
        chain.use_middleware(LoggerMiddleware::new());
        chain.use_middleware(RequestIdMiddleware);
        chain.use_middleware(SecurityHeadersMiddleware::new());

        let req = HttpRequest::new("GET".to_string(), "/test".to_string());

        let handler = Arc::new(|_req: HttpRequest| {
            Box::pin(async { Ok(HttpResponse::ok()) })
                as Pin<Box<dyn Future<Output = Result<HttpResponse, Error>> + Send>>
        });

        let result = chain.apply(req, handler).await;

        assert!(result.is_ok());
        let response = result.unwrap();
        assert!(response.headers.contains_key("x-request-id"));
        assert!(response.headers.contains_key("X-Content-Type-Options"));
    }

    #[tokio::test]
    async fn test_cors_preflight() {
        let cors = CorsMiddleware::new().allow_origin("https://example.com");

        let mut req = HttpRequest::new("OPTIONS".to_string(), "/api".to_string());
        req.headers
            .insert("Origin".to_string(), "https://example.com".to_string());
        req.headers.insert(
            "Access-Control-Request-Method".to_string(),
            "POST".to_string(),
        );

        let result = cors
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_ok());
        let response = result.unwrap();
        assert!(response.headers.contains_key("Access-Control-Allow-Origin"));
        assert!(
            response
                .headers
                .contains_key("Access-Control-Allow-Methods")
        );
    }

    #[tokio::test]
    async fn test_body_size_within_limit() {
        let middleware = BodySizeLimitMiddleware::new(100);
        let mut req = HttpRequest::new("POST".to_string(), "/api".to_string());
        req.body = vec![0; 50]; // 50 bytes, within limit

        let result = middleware
            .handle(
                req,
                Box::new(|_req| Box::pin(async { Ok(HttpResponse::ok()) })),
            )
            .await;

        assert!(result.is_ok());
    }

    #[test]
    fn test_cors_default_origin() {
        let cors = CorsMiddleware::new();
        assert_eq!(cors.allow_origin, "*");
    }
}