use std::path::Path;

use anyhow::{Context, Result, bail};
use serde::Serialize;
use serde::de::DeserializeOwned;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::UnixStream;

/// Generic JSON-line request/response over a unix socket. One request, one
/// response, then drop. Used by both the agent and manager harnesses.
pub async fn request<Req, Resp>(socket: &Path, req: &Req) -> Result<Resp>
where
    Req: Serialize + ?Sized,
    Resp: DeserializeOwned,
{
    let stream = UnixStream::connect(socket)
        .await
        .with_context(|| format!("connect to {}", socket.display()))?;
    let (read, mut write) = stream.into_split();

    let mut payload = serde_json::to_string(req)?;
    payload.push('\n');
    write.write_all(payload.as_bytes()).await?;
    write.flush().await?;

    let mut reader = BufReader::new(read);
    let mut line = String::new();
    reader.read_line(&mut line).await?;
    if line.is_empty() {
        bail!("server closed connection without responding");
    }
    Ok(serde_json::from_str(line.trim())?)
}