import net
import time

fn echo_server(mut c net.UdpConn) {
    mut count := 0
    for {
        eprintln('> echo_server loop count: ${count}')
        mut buf := []u8{len: 100}
        read, addr := c.read(mut buf) or { continue }
        eprintln('Server got addr ${addr}, read: ${read} | buf: ${buf}')
        c.write_to(addr, buf[..read]) or {
            println('Server: connection dropped')
            return
        }
        count++
        // Normally, after responding, the test will end, but there are sometimes  cases,
        // when the echo_server continued looping, printing messages constantly.
        // The sleep here, is a small precaution against spamming the CI with log messages,
        // when there are network problems, and it allows easier root cause diagnostic, when
        // they do happen:
        time.sleep(1000 * time.millisecond)
    }
}

const server_addr = '127.0.0.1:40003'

fn echo() ! {
    mut c := net.dial_udp(server_addr) or { panic('could not net.dial_udp: ${err}') }
    defer {
        c.close() or {}
    }
    data := 'Hello from vlib/net!'

    c.write_string(data) or { panic('could not write_string: ${err}') }

    mut buf := []u8{len: 100, init: 0}
    read, addr := c.read(mut buf) or { panic('could not read: ${err}') }

    assert read == data.len
    println('Got address ${addr}')
    // Can't test this here because loopback addresses
    // are mapped to other addresses
    // assert addr.str() == '127.0.0.1:30001'

    for i := 0; i < read; i++ {
        assert buf[i] == data[i]
    }

    println('Got "${buf.bytestr()}"')

    c.close()!
}

fn test_udp() {
    mut l := net.listen_udp(server_addr) or { panic('could not listen_udp: ${err}') }

    spawn echo_server(mut l)
    echo() or { panic('could not echo: ${err}') }

    l.close() or {}
}