Move compression into the request builder

codex-rs/codex-api/src/requests/body.rs

@@ -0,0 +1,40 @@
+use crate::error::ApiError;
+use crate::provider::RequestCompression;
+use bytes::Bytes;
+use codex_client::Body;
+use http::HeaderMap;
+use http::HeaderValue;
+use http::header::CONTENT_ENCODING;
+use serde_json::Value;
+use std::time::Instant;
+use tracing::info;
+use zstd::stream::encode_all;
+
+pub(crate) fn encode_body(body: &Value, compression: RequestCompression) -> Result<Body, ApiError> {
+    match compression {
+        RequestCompression::None => Ok(Body::Json(body.clone())),
+        RequestCompression::Zstd => {
+            let json = serde_json::to_vec(body).map_err(|err| {
+                ApiError::Stream(format!("failed to encode request body as json: {err}"))
+            })?;
+            let started_at = Instant::now();
+            let compressed = encode_all(json.as_slice(), 0).map_err(|err| {
+                ApiError::Stream(format!("failed to compress request body: {err}"))
+            })?;
+            let elapsed = started_at.elapsed();
+            info!(
+                input_bytes = json.len(),
+                output_bytes = compressed.len(),
+                elapsed_ms = elapsed.as_millis(),
+                "compressed request body"
+            );
+            Ok(Body::Bytes(Bytes::from(compressed)))
+        }
+    }
+}
+
+pub(crate) fn insert_compression_headers(headers: &mut HeaderMap, compression: RequestCompression) {
+    if matches!(compression, RequestCompression::Zstd) {
+        headers.insert(CONTENT_ENCODING, HeaderValue::from_static("zstd"));
+    }
+}