From c03fac0e37462112891829c85ad9ea2819b35e18 Mon Sep 17 00:00:00 2001
From: rm-dr <96270320+rm-dr@users.noreply.github.com>
Date: Wed, 11 Mar 2026 10:43:17 -0700
Subject: [PATCH] `/item` range requests

---
 crates/pile-dataset/src/serve/item.rs | 100 +++++++++++++++++++++++---
 1 file changed, 92 insertions(+), 8 deletions(-)

diff --git a/crates/pile-dataset/src/serve/item.rs b/crates/pile-dataset/src/serve/item.rs
index ae0ab5a..df50488 100644
--- a/crates/pile-dataset/src/serve/item.rs
+++ b/crates/pile-dataset/src/serve/item.rs
@@ -1,13 +1,13 @@
 use axum::{
 	body::Body,
 	extract::{Query, State},
-	http::{StatusCode, header},
+	http::{HeaderMap, StatusCode, header},
 	response::{IntoResponse, Response},
 };
 use pile_config::Label;
-use pile_value::value::AsyncReader;
+use pile_value::value::{AsyncReader, AsyncSeekReader};
 use serde::Deserialize;
-use std::{sync::Arc, time::Instant};
+use std::{io::SeekFrom, sync::Arc, time::Instant};
 use tokio::sync::mpsc;
 use tokio_stream::wrappers::ReceiverStream;
 use tracing::debug;
@@ -21,6 +21,24 @@ pub struct ItemQuery {
 	key: String,
 }
 
+/// Parse a `Range: bytes=...` header value.
+/// Returns `(start, end)` where either may be `None` (suffix form has `None` start).
+fn parse_byte_range(s: &str) -> Option<(Option<u64>, Option<u64>)> {
+	let spec = s.strip_prefix("bytes=")?;
+	if spec.contains(',') {
+		return None; // multiple ranges not supported
+	}
+	if let Some(suffix) = spec.strip_prefix('-') {
+		return Some((None, Some(suffix.parse().ok()?)));
+	}
+	let mut parts = spec.splitn(2, '-');
+	let start: u64 = parts.next()?.parse().ok()?;
+	let end = parts
+		.next()
+		.and_then(|e| if e.is_empty() { None } else { e.parse().ok() });
+	Some((Some(start), end))
+}
+
 /// Fetch the raw bytes of an item by source and key
 #[utoipa::path(
 	get,
@@ -31,14 +49,17 @@ pub struct ItemQuery {
 	),
 	responses(
 		(status = 200, description = "Raw item bytes"),
+		(status = 206, description = "Partial content"),
 		(status = 400, description = "Invalid source label"),
 		(status = 404, description = "Item not found"),
+		(status = 416, description = "Range not satisfiable"),
 		(status = 500, description = "Internal server error"),
 	)
 )]
 pub async fn item_get(
 	State(state): State<Arc<Datasets>>,
 	Query(params): Query<ItemQuery>,
+	headers: HeaderMap,
 ) -> Response {
 	let start = Instant::now();
 	debug!(
@@ -63,6 +84,43 @@ pub async fn item_get(
 		Err(e) => return (StatusCode::INTERNAL_SERVER_ERROR, format!("{e:?}")).into_response(),
 	};
 
+	let total = match reader.seek(SeekFrom::End(0)).await {
+		Ok(n) => n,
+		Err(e) => return (StatusCode::INTERNAL_SERVER_ERROR, format!("{e:?}")).into_response(),
+	};
+
+	let range = headers
+		.get(header::RANGE)
+		.and_then(|v| v.to_str().ok())
+		.and_then(parse_byte_range);
+
+	// Resolve (byte_start, byte_end, content_length, is_range)
+	let (byte_start, byte_end, length, is_range) = match range {
+		Some((Some(s), e)) => {
+			let e = e
+				.unwrap_or(total.saturating_sub(1))
+				.min(total.saturating_sub(1));
+			if s >= total || s > e {
+				return (
+					StatusCode::RANGE_NOT_SATISFIABLE,
+					[(header::CONTENT_RANGE, format!("bytes */{total}"))],
+				)
+					.into_response();
+			}
+			(s, e, e - s + 1, true)
+		}
+		Some((None, Some(suffix))) => {
+			let s = total.saturating_sub(suffix);
+			let e = total.saturating_sub(1);
+			(s, e, total.saturating_sub(s), true)
+		}
+		_ => (0, total.saturating_sub(1), total, false),
+	};
+
+	if let Err(e) = reader.seek(SeekFrom::Start(byte_start)).await {
+		return (StatusCode::INTERNAL_SERVER_ERROR, format!("{e:?}")).into_response();
+	}
+
 	debug!(
 		message = "Served /item",
 		source = params.source,
@@ -73,13 +131,17 @@ pub async fn item_get(
 	let (tx, rx) = mpsc::channel::<Result<Vec<u8>, std::io::Error>>(8);
 
 	tokio::spawn(async move {
-		// 1MiB chunks
-		let mut buf = vec![0u8; 65536 * 8];
-
+		let mut buf = vec![0u8; 65536];
+		let mut remaining = length;
 		loop {
-			match reader.read(&mut buf).await {
+			if remaining == 0 {
+				break;
+			}
+			let to_read = (buf.len() as u64).min(remaining) as usize;
+			match reader.read(&mut buf[..to_read]).await {
 				Ok(0) => break,
 				Ok(n) => {
+					remaining -= n as u64;
 					if tx.send(Ok(buf[..n].to_vec())).await.is_err() {
 						break;
 					}
@@ -93,5 +155,27 @@ pub async fn item_get(
 	});
 
 	let body = Body::from_stream(ReceiverStream::new(rx));
-	(StatusCode::OK, [(header::CONTENT_TYPE, mime)], body).into_response()
+	let status = if is_range {
+		StatusCode::PARTIAL_CONTENT
+	} else {
+		StatusCode::OK
+	};
+
+	let mut builder = axum::http::Response::builder()
+		.status(status)
+		.header(header::CONTENT_TYPE, mime)
+		.header(header::ACCEPT_RANGES, "bytes")
+		.header(header::CONTENT_LENGTH, length);
+
+	if is_range {
+		builder = builder.header(
+			header::CONTENT_RANGE,
+			format!("bytes {byte_start}-{byte_end}/{total}"),
+		);
+	}
+
+	builder
+		.body(body)
+		.map(IntoResponse::into_response)
+		.unwrap_or_else(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("{e:?}")).into_response())
 }