lean_ctx/proxy/
forward.rs

1use axum::{
2    body::Body,
3    extract::State,
4    http::{request::Parts, Request, StatusCode},
5    response::Response,
6};
7
8use super::ProxyState;
9
10const MAX_BODY_BYTES: usize = 10 * 1024 * 1024;
11
12pub type CompressFn = fn(&[u8]) -> (Vec<u8>, usize, usize);
13
14pub async fn forward_request(
15    State(state): State<ProxyState>,
16    req: Request<Body>,
17    upstream_base: &str,
18    default_path: &str,
19    compress_body: CompressFn,
20    provider_label: &str,
21    extra_stream_types: &[&str],
22) -> Result<Response, StatusCode> {
23    let (parts, body) = req.into_parts();
24    let body_bytes = axum::body::to_bytes(body, MAX_BODY_BYTES)
25        .await
26        .map_err(|_| StatusCode::BAD_REQUEST)?;
27
28    state.stats.record_request();
29
30    // Introspect the request for context analysis
31    if let Ok(parsed) = serde_json::from_slice::<serde_json::Value>(&body_bytes) {
32        let provider = match provider_label {
33            "Anthropic" => super::introspect::Provider::Anthropic,
34            "OpenAI" => super::introspect::Provider::OpenAi,
35            _ => super::introspect::Provider::Gemini,
36        };
37        let breakdown = super::introspect::analyze_request(&parsed, provider);
38        state.introspect.record(breakdown);
39    }
40
41    let (compressed_body, original_size, compressed_size) = compress_body(&body_bytes);
42
43    if compressed_size < original_size {
44        state
45            .stats
46            .record_compression(original_size, compressed_size);
47    }
48
49    let upstream_url = build_upstream_url(&parts, upstream_base, default_path);
50    let response = send_upstream(
51        &state,
52        &parts,
53        &upstream_url,
54        compressed_body,
55        provider_label,
56    )
57    .await?;
58
59    build_response(response, extra_stream_types).await
60}
61
62fn build_upstream_url(parts: &Parts, base: &str, default_path: &str) -> String {
63    format!(
64        "{base}{}",
65        parts
66            .uri
67            .path_and_query()
68            .map_or(default_path, axum::http::uri::PathAndQuery::as_str)
69    )
70}
71
72async fn send_upstream(
73    state: &ProxyState,
74    parts: &Parts,
75    url: &str,
76    body: Vec<u8>,
77    provider_label: &str,
78) -> Result<reqwest::Response, StatusCode> {
79    let mut req = state.client.request(parts.method.clone(), url);
80
81    const ALLOWED_HEADERS: &[&str] = &[
82        "authorization",
83        "x-api-key",
84        "content-type",
85        "accept",
86        "user-agent",
87        "anthropic-version",
88        "anthropic-beta",
89        "anthropic-dangerous-direct-browser-access",
90        "openai-organization",
91        "openai-beta",
92        "x-goog-api-key",
93        "x-goog-api-client",
94    ];
95    for (key, value) in &parts.headers {
96        let k = key.as_str().to_lowercase();
97        if ALLOWED_HEADERS.contains(&k.as_str()) {
98            req = req.header(key.clone(), value.clone());
99        }
100    }
101
102    req.body(body).send().await.map_err(|e| {
103        tracing::error!("lean-ctx proxy: {provider_label} upstream error: {e}");
104        StatusCode::BAD_GATEWAY
105    })
106}
107
108async fn build_response(
109    response: reqwest::Response,
110    extra_stream_types: &[&str],
111) -> Result<Response, StatusCode> {
112    let status = StatusCode::from_u16(response.status().as_u16()).unwrap_or(StatusCode::OK);
113    let resp_headers = response.headers().clone();
114
115    let is_stream = resp_headers
116        .get("content-type")
117        .and_then(|v| v.to_str().ok())
118        .is_some_and(|ct| {
119            ct.contains("text/event-stream") || extra_stream_types.iter().any(|t| ct.contains(t))
120        });
121
122    if is_stream {
123        let stream = response.bytes_stream();
124        let body = Body::from_stream(stream);
125        let mut resp = Response::builder().status(status);
126        for (k, v) in &resp_headers {
127            resp = resp.header(k, v);
128        }
129        return resp
130            .body(body)
131            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR);
132    }
133
134    let resp_bytes = response
135        .bytes()
136        .await
137        .map_err(|_| StatusCode::BAD_GATEWAY)?;
138
139    let mut resp = Response::builder().status(status);
140    for (k, v) in &resp_headers {
141        let ks = k.as_str().to_lowercase();
142        if ks == "transfer-encoding" || ks == "content-length" {
143            continue;
144        }
145        resp = resp.header(k, v);
146    }
147    resp.body(Body::from(resp_bytes))
148        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)
149}
lean_ctx/proxy/forward.rs

lean_ctx/proxy/
forward.rs
