mod stats;
mod telemetry;

use stats::ReceiveStats;
use telemetry::TelemetryFrame;

use std::io::Write;

const DEFAULT_BIND_ADDR: &str = "127.0.0.1:5005";
const BUFFER_SIZE: usize = 65535;

fn print_banner(bind_addr: &str) {
    println!("========================================");
    println!("  rusty-telemetry listener");
    println!("  Phase 1 - UDP JSON receiver");
    println!("========================================");
    println!("  Bind: {}", bind_addr);
    println!("========================================");
    println!();
}

#[tokio::main]
async fn main() {
    let bind_addr =
        std::env::var("RUSTY_TELEMETRY_BIND").unwrap_or_else(|_| DEFAULT_BIND_ADDR.to_string());

    print_banner(&bind_addr);

    let socket = match tokio::net::UdpSocket::bind(&bind_addr).await {
        Ok(s) => {
            let local_addr = s.local_addr().unwrap();
            println!("[INFO] Listening on {}", local_addr);
            s
        }
        Err(e) => {
            eprintln!("[ERROR] Failed to bind UDP socket: {}", e);
            std::process::exit(1);
        }
    };

    let mut buf = vec![0u8; BUFFER_SIZE];
    let mut stats = ReceiveStats::new();
    let stdout = std::io::stdout();

    loop {
        match socket.recv_from(&mut buf).await {
            Ok((len, src)) => {
                stats.record(len);

                let text = match std::str::from_utf8(&buf[..len]) {
                    Ok(s) => s,
                    Err(e) => {
                        eprintln!("[WARN] Invalid UTF-8 from {}: {}", src, e);
                        continue;
                    }
                };

                let frame: TelemetryFrame = match serde_json::from_str(text) {
                    Ok(f) => f,
                    Err(e) => {
                        eprintln!("[WARN] JSON parse error from {}: {}", src, e);
                        continue;
                    }
                };

                {
                    let mut handle = stdout.lock();
                    let _ = writeln!(handle, "{}", frame);
                    let _ = writeln!(handle, "  [{}] {}", src, stats);
                    let _ = writeln!(handle);
                }
            }
            Err(e) => {
                eprintln!("[ERROR] Receive error: {}", e);
            }
        }
    }
}