module net

import strings

const (
    crlf              = '\r\n'
    msg_peek          = 0x02
    max_read          = 400
    max_read_line_len = 1048576
)

// get_blocking returns whether the connection is in a blocking state,
// that is calls to .read_line, C.recv etc will block till there is new
// data arrived, instead of returning immediately.
pub fn (mut con TcpConn) get_blocking() bool {
    // flags := C.fcntl(con.sock.handle, C.F_GETFL, 0)
    // return 0 == flags & C.O_NONBLOCK
    return con.is_blocking
}

// set_blocking will change the state of the connection to either blocking,
// when state is true, or non blocking (false).
// The default for `net` tcp connections is the non blocking mode.
// Calling .read_line will set the connection to blocking mode.
pub fn (mut con TcpConn) set_blocking(state bool) ! {
    con.is_blocking = state
    $if windows {
        mut t := u32(0)
        if !con.is_blocking {
            t = 1
        }
        socket_error(C.ioctlsocket(con.sock.handle, fionbio, &t))!
    } $else {
        mut flags := C.fcntl(con.sock.handle, C.F_GETFL, 0)
        if state {
            flags &= ~C.O_NONBLOCK
        } else {
            flags |= C.O_NONBLOCK
        }
        socket_error(C.fcntl(con.sock.handle, C.F_SETFL, flags))!
    }
}

// read_line is a *simple*, *non customizable*, blocking line reader.
// It will return a line, ending with LF, or just '', on EOF.
// Note: if you want more control over the buffer, please use a buffered IO
// reader instead: `io.new_buffered_reader({reader: io.make_reader(con)})`
pub fn (mut con TcpConn) read_line() string {
    return con.read_line_max(net.max_read_line_len)
}

// read_line_max is a *simple*, *non customizable*, blocking line reader.
// It will return a line, ending with LF, '' on EOF.
// It stops reading, when the result line length exceeds max_line_len.
[manualfree]
pub fn (mut con TcpConn) read_line_max(max_line_len int) string {
    if !con.is_blocking {
        con.set_blocking(true) or {}
    }
    mut buf := [net.max_read]u8{} // where C.recv will store the network data
    mut res := strings.new_builder(net.max_read) // The final result, including the ending \n.
    defer {
        unsafe { res.free() }
    }
    bstart := unsafe { &buf[0] }
    for {
        n := C.recv(con.sock.handle, bstart, net.max_read - 1, net.msg_peek | msg_nosignal)
        if n <= 0 {
            return res.str()
        }
        buf[n] = `\0`
        mut eol_idx := -1
        mut lend := n
        for i in 0 .. n {
            if buf[i] == `\n` {
                eol_idx = i
                lend = i + 1
                buf[lend] = `\0`
                break
            }
        }
        if eol_idx > 0 {
            // At this point, we are sure that recv returned valid data,
            // that contains *at least* one line.
            // Ensure that the block till the first \n (including it)
            // is removed from the socket's receive queue, so that it does
            // not get read again.
            C.recv(con.sock.handle, bstart, lend, msg_nosignal)
            unsafe { res.write_ptr(bstart, lend) }
            break
        }
        // recv returned a buffer without \n in it, just store it for now:
        C.recv(con.sock.handle, bstart, n, msg_nosignal)
        unsafe { res.write_ptr(bstart, lend) }
        if res.len > max_line_len {
            break
        }
    }
    return res.str()
}