link-assistant-router 0.87.0

//! Construction of the shared HTTP client used for every upstream call.

use std::env;
use std::time::Duration;

/// Seconds the router waits for the *next byte* from an upstream before it
/// fails the request.
///
/// This is a read timeout rather than a total one: a long agentic answer may
/// legitimately take many minutes, but a backend that has gone quiet will never
/// speak again. Without it a stalled upstream — as seen when a capped
/// `web_search` request was forwarded to Codex — leaves the client waiting
/// forever instead of receiving an error.
pub const DEFAULT_UPSTREAM_READ_TIMEOUT_SECS: u64 = 120;

/// Parse `UPSTREAM_READ_TIMEOUT_SECS`; `0` disables the bound.
#[must_use]
pub fn parse_upstream_read_timeout(value: Option<&str>) -> Option<Duration> {
    let seconds = value
        .and_then(|value| value.trim().parse::<u64>().ok())
        .unwrap_or(DEFAULT_UPSTREAM_READ_TIMEOUT_SECS);
    (seconds > 0).then(|| Duration::from_secs(seconds))
}

/// Build the shared upstream HTTP client with that bound applied.
///
/// # Errors
/// Propagates a `reqwest` client construction failure.
pub fn build_upstream_client() -> reqwest::Result<reqwest::Client> {
    let mut builder = reqwest::Client::builder().redirect(reqwest::redirect::Policy::none());
    if let Some(timeout) =
        parse_upstream_read_timeout(env::var("UPSTREAM_READ_TIMEOUT_SECS").ok().as_deref())
    {
        builder = builder.read_timeout(timeout);
    }
    builder.build()
}

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

    #[test]
    fn upstream_reads_are_bounded_unless_explicitly_disabled() {
        assert_eq!(
            parse_upstream_read_timeout(None),
            Some(Duration::from_secs(DEFAULT_UPSTREAM_READ_TIMEOUT_SECS))
        );
        assert_eq!(
            parse_upstream_read_timeout(Some("30")),
            Some(Duration::from_secs(30))
        );
        assert_eq!(parse_upstream_read_timeout(Some("0")), None);
        assert_eq!(
            parse_upstream_read_timeout(Some("not-a-number")),
            Some(Duration::from_secs(DEFAULT_UPSTREAM_READ_TIMEOUT_SECS))
        );
    }
}