//! Request/Reply IPC sample. This component will read requests from a channel,
//! than send replies on a separate channel. The requests is expected to be three u64 values:
//! a request id, and 2 values which the replier will add them up. The reply will be two
//! u64 values: the id of the request and the sum of the two values from request.
//! In order to start the replier type cargo run --example rep <reply_channel_id> <request_channel_id>
use kekbit::api::EncoderHandler;
use kekbit::api::Writer;
use kekbit::core::TickUnit::Secs;
use kekbit::core::*;
use kekbit::retry::*;

#[inline]
fn read_u64(data: &[u8], offset: usize) -> u64 {
    assert!(offset + 8 <= data.len());
    u64::from_le_bytes([
        data[offset],
        data[offset + 1],
        data[offset + 2],
        data[offset + 3],
        data[offset + 4],
        data[offset + 5],
        data[offset + 6],
        data[offset + 7],
    ])
}

fn main() {
    let args: Vec<u64> = std::env::args().skip(1).map(|id| id.parse().unwrap()).collect();
    assert!(args.len() == 2);
    let rep_id = 0xFEDC;
    let reply_channel_id = args[0];
    let req_channel_id = args[1];
    let timeout_secs = 10; //channel times out in 10 secs
    let tmp_dir = std::env::temp_dir().join("kekbit").join("req_rep");
    let max_msg_size = 1024;
    let metadata = Metadata::new(
        rep_id,
        reply_channel_id,
        max_msg_size * 1000,
        max_msg_size,
        timeout_secs,
        Secs,
    );
    //creates the channel where the replies will be sent together with the associated writer
    let mut writer = shm_writer(&tmp_dir, &metadata, EncoderHandler::default()).unwrap();
    //tries to connect to the channel where the requests are pushed
    let reader_rep = try_shm_reader(&tmp_dir, req_channel_id, 15000, 45);
    if reader_rep.is_err() {
        println!("Could not connect to request channel. Giving up..");
        std::process::exit(1);
    }
    let mut reader = reader_rep.unwrap();
    let mut msg_iter: RetryIter<ShmReader> = reader.try_iter().into();

    for read_res in &mut msg_iter {
        match read_res {
            ReadResult::Record(msg) => {
                let id = read_u64(&msg, 0);
                println!("Got request {}", id);
                let first = read_u64(&msg, 8);
                let second = read_u64(&msg, 16);
                //compute and sent the reply
                let res: u64 = first + second;
                let mut reply: [u8; 16] = [0; 16];
                reply[0..8].clone_from_slice(&id.to_le_bytes());
                reply[8..16].clone_from_slice(&res.to_le_bytes());
                writer.write(&reply).unwrap();
                println!("Reply for {} sent", id);
            }
            ReadResult::Nothing => {
                //just hold your breath
                std::thread::sleep(std::time::Duration::from_millis(20));
            }
            ReadResult::Failed(err) => {
                println!("Requests channel read error {:?}", err);
                break;
            }
        }
    }
}