fix: handle Range header in HEAD requests (#114)

## What I'm changing

The HEAD handler was ignoring Range headers entirely, always returning
200 OK with the full Content-Length. This caused clients issuing `HEAD
-H "Range: bytes=0-1023"` to receive incorrect responses missing 206
status, Content-Range, and Accept-Ranges headers.

## How I did it

- Extract range parsing into `parse_range_str`/`parse_range_header` in
utils/core.rs with comprehensive unit tests (13 test cases)
- Update HEAD handler to return 206 Partial Content with correct
Content-Range and Content-Length when a Range header is present
- Refactor GET handler to use the same shared parsing logic

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: alukach

src/main.rs

@@ -1,13 +1,14 @@
 mod apis;
 mod backends;
 mod utils;
-use crate::utils::core::{split_at_first_slash, StreamingResponse};
+use crate::utils::core::{split_at_first_slash, RangeRequest, StreamingResponse};
 use actix_cors::Cors;
 use actix_web::body::{BodySize, BoxBody, MessageBody};
 use actix_web::error::ErrorInternalServerError;
 use actix_web::{
-    delete, get, head, http::header::CONTENT_TYPE, http::header::RANGE, middleware, post, put, web,
-    App, HttpRequest, HttpResponse, HttpServer, Responder,
+    delete, get, head,
+    http::header::{CONTENT_TYPE, RANGE},
+    middleware, post, put, web, App, HttpRequest, HttpResponse, HttpServer, Responder,
 };
 
 use apis::source::{RepositoryPermission, SourceApi};
@@ -56,27 +57,11 @@ async fn get_object(
     user_identity: web::ReqData<UserIdentity>,
 ) -> Result<impl Responder, BackendError> {
     let (account_id, repository_id, key) = path.into_inner();
-    let headers = req.headers();
-    let mut range_start = 0;
-    let mut is_range_request = false;
-
-    let range = headers
+    let range_info: Option<RangeRequest> = req
+        .headers()
         .get(RANGE)
-        .and_then(|h| h.to_str().ok())
-        .and_then(|r| r.strip_prefix("bytes="))
-        .and_then(|bytes_range| bytes_range.split_once('-'))
-        .and_then(|(start, end)| {
-            start.parse::<u64>().ok().map(|s| {
-                range_start = s;
-                if end.is_empty() || end.parse::<u64>().is_ok() {
-                    is_range_request = true;
-                    Some(format!("bytes={start}-{end}"))
-                } else {
-                    None
-                }
-            })
-        })
-        .flatten();
+        .and_then(|v| String::from_utf8(v.as_ref().to_vec()).ok())
+        .and_then(|s| s.parse().ok());
 
     let client = api_client
         .get_backend_client(&account_id, &repository_id)
@@ -92,13 +77,13 @@ async fn get_object(
         .await?;
 
     // Found the repository, now try to get the object
-    let res = client.get_object(key.clone(), range).await?;
+    let res = client
+        .get_object(key.clone(), range_info.map(Into::into))
+        .await?;
 
-    let mut content_length = String::from("*");
-    // Remove this if statement to increase performance since it's making an extra request just to get the total content-length
-    // This is only needed for range requests and in theory, you can return a * in the Content-Range header to indicate that the content length is unknown
-    if is_range_request {
-        content_length = client
+    let mut total_content_length = String::from("*");
+    if range_info.is_some() {
+        total_content_length = client
             .head_object(key.clone())
             .await?
             .content_length
@@ -110,7 +95,7 @@ async fn get_object(
         .map(|result| result.map_err(|e| ErrorInternalServerError(e.to_string())));
 
     let streaming_response = StreamingResponse::new(stream, res.content_length);
-    let mut response = if is_range_request {
+    let mut response = if range_info.is_some() {
         HttpResponse::PartialContent()
     } else {
         HttpResponse::Ok()
@@ -124,15 +109,15 @@ async fn get_object(
         .insert_header(("Content-Length", res.content_length.to_string()))
         .insert_header(("ETag", res.etag));
 
-    if is_range_request {
+    if let Some(ref range) = range_info {
         response = response
             .insert_header((
                 "Content-Range",
                 format!(
                     "bytes {}-{}/{}",
-                    range_start,
-                    range_start + res.content_length - 1,
-                    content_length
+                    range.start,
+                    range.start + res.content_length - 1,
+                    total_content_length
                 ),
             ))
             .insert_header((
@@ -336,6 +321,7 @@ async fn post_handler(
 #[head("/{account_id}/{repository_id}/{key:.*}")]
 async fn head_object(
     api_client: web::Data<SourceApi>,
+    req: HttpRequest,
     path: web::Path<(String, String, String)>,
     user_identity: web::ReqData<UserIdentity>,
 ) -> Result<impl Responder, BackendError> {
@@ -355,15 +341,45 @@ async fn head_object(
         .await?;
 
     let res = client.head_object(key.clone()).await?;
-    Ok(HttpResponse::Ok()
-        .insert_header(("Accept-Ranges", "bytes"))
-        .insert_header(("Access-Control-Expose-Headers", "Accept-Ranges"))
-        .insert_header(("Content-Type", res.content_type))
-        .insert_header(("Last-Modified", res.last_modified))
-        .insert_header(("ETag", res.etag))
-        .body(BoxBody::new(FakeBody {
-            size: res.content_length as usize,
-        })))
+    let total_size = res.content_length;
+    let range_info: Option<RangeRequest> = req
+        .headers()
+        .get(RANGE)
+        .and_then(|v| v.to_str().ok())
+        .and_then(|s| s.parse().ok());
+
+    let response = if let Some(ref range) = range_info {
+        let end = range.end.unwrap();
+        let content_length = end - range.start + 1;
+        HttpResponse::PartialContent()
+            .insert_header(("Accept-Ranges", "bytes"))
+            .insert_header((
+                "Content-Range",
+                format!("bytes {}-{}/{}", range.start, end, total_size),
+            ))
+            .insert_header((
+                "Access-Control-Expose-Headers",
+                "Accept-Ranges, Content-Range",
+            ))
+            .insert_header(("Content-Type", res.content_type))
+            .insert_header(("Last-Modified", res.last_modified))
+            .insert_header(("ETag", res.etag))
+            .body(BoxBody::new(FakeBody {
+                size: content_length as usize,
+            }))
+    } else {
+        HttpResponse::Ok()
+            .insert_header(("Accept-Ranges", "bytes"))
+            .insert_header(("Access-Control-Expose-Headers", "Accept-Ranges"))
+            .insert_header(("Content-Type", res.content_type))
+            .insert_header(("Last-Modified", res.last_modified))
+            .insert_header(("ETag", res.etag))
+            .body(BoxBody::new(FakeBody {
+                size: total_size as usize,
+            }))
+    };
+
+    Ok(response)
 }
 
 #[derive(Deserialize)]

src/utils/core.rs

@@ -4,8 +4,8 @@ use actix_web::{
 };
 use futures::Stream;
 use pin_project_lite::pin_project;
-use std::pin::Pin;
 use std::task::{Context, Poll};
+use std::{pin::Pin, str::FromStr};
 
 pin_project! {
     pub struct StreamingResponse<S> {
@@ -97,3 +97,150 @@ pub fn split_at_first_slash(input: &str) -> (&str, &str) {
         None => (input, ""),
     }
 }
+
+/// Parsed range request information.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct RangeRequest {
+    /// The start byte offset
+    pub start: u64,
+    /// The end byte offset (inclusive), or `None` for open-ended ranges (e.g. "bytes=100-")
+    pub end: Option<u64>,
+}
+
+impl From<RangeRequest> for String {
+    fn from(r: RangeRequest) -> Self {
+        match r.end {
+            Some(end) => format!("bytes={}-{}", r.start, end),
+            None => format!("bytes={}-", r.start),
+        }
+    }
+}
+
+impl FromStr for RangeRequest {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let bytes_range = s.strip_prefix("bytes=").ok_or(())?;
+        let (start_str, end_str) = bytes_range.split_once('-').ok_or(())?;
+        let start = start_str.parse::<u64>().map_err(|_| ())?;
+
+        let end = if end_str.is_empty() {
+            None
+        } else {
+            let end = end_str.parse::<u64>().map_err(|_| ())?;
+            if start > end {
+                return Err(());
+            }
+            Some(end)
+        };
+
+        Ok(RangeRequest { start, end })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_range_full_range() {
+        let result: RangeRequest = "bytes=0-1023".parse().unwrap();
+        assert_eq!(
+            result,
+            RangeRequest {
+                start: 0,
+                end: Some(1023),
+            }
+        );
+    }
+
+    #[test]
+    fn test_parse_range_open_ended() {
+        let result = "bytes=100-".parse::<RangeRequest>().unwrap();
+        assert_eq!(
+            result,
+            RangeRequest {
+                start: 100,
+                end: None,
+            }
+        );
+    }
+
+    #[test]
+    fn test_parse_range_open_ended_no_total_size() {
+        // Without with_total_size, end remains None
+        let result: RangeRequest = "bytes=100-".parse().unwrap();
+        assert_eq!(result.end, None);
+    }
+
+    #[test]
+    fn test_parse_range_missing_prefix() {
+        assert!("invalid=0-100".parse::<RangeRequest>().is_err());
+    }
+
+    #[test]
+    fn test_parse_range_non_numeric_start() {
+        assert!("bytes=abc-100".parse::<RangeRequest>().is_err());
+    }
+
+    #[test]
+    fn test_parse_range_non_numeric_end() {
+        assert!("bytes=0-abc".parse::<RangeRequest>().is_err());
+    }
+
+    #[test]
+    fn test_parse_range_start_greater_than_end() {
+        assert!("bytes=500-100".parse::<RangeRequest>().is_err());
+    }
+
+    #[test]
+    fn test_parse_range_start_beyond_total_size() {
+        // Parsing succeeds; validation against total_size is the caller's responsibility
+        let result: RangeRequest = "bytes=1000-1023".parse().unwrap();
+        assert_eq!(result.start, 1000);
+        assert_eq!(result.end, Some(1023));
+    }
+
+    #[test]
+    fn test_parse_range_single_byte() {
+        let result: RangeRequest = "bytes=0-0".parse().unwrap();
+        assert_eq!(
+            result,
+            RangeRequest {
+                start: 0,
+                end: Some(0),
+            }
+        );
+    }
+
+    #[test]
+    fn test_parse_range_large_file() {
+        let rr: RangeRequest = "bytes=0-1023".parse().unwrap();
+        assert_eq!(rr.start, 0);
+        assert_eq!(rr.end, Some(1023));
+        assert_eq!(rr.end.unwrap() - rr.start + 1, 1024);
+    }
+
+    #[test]
+    fn test_parse_range_no_hyphen() {
+        assert!("bytes=100".parse::<RangeRequest>().is_err());
+    }
+
+    #[test]
+    fn test_parse_range_content_length_calculation() {
+        let result: RangeRequest = "bytes=0-1023".parse().unwrap();
+        assert_eq!(result.end.unwrap() - result.start + 1, 1024);
+    }
+
+    #[test]
+    fn test_parse_range_content_range_format() {
+        let result: RangeRequest = "bytes=0-1023".parse().unwrap();
+        let content_range = format!(
+            "bytes {}-{}/{}",
+            result.start,
+            result.end.unwrap(),
+            3515053862u64
+        );
+        assert_eq!(content_range, "bytes 0-1023/3515053862");
+    }
+}