humpback-dds/src/translation.rs

use scpi::prelude::*;
use scpi::Context;
use scpi::error::Result;
use log::trace;
use arrayvec::{ArrayVec};

pub trait MqttScpiTranslator {
    // Convert an MQTT publish message into SCPI compatible command
    // The argument part/ MQTT message must follow SCPI standard for parameter formatting
    fn run_with_mqtt<FMT: Formatter>(&mut self, topic: &str, args: &str, response: &mut FMT) -> Result<()>;
}

impl<'a, T: Device> MqttScpiTranslator for Context<'a, T> {
    fn run_with_mqtt<FMT>(&mut self, topic: &str, args: &str, response: &mut FMT) -> Result<()>
    where
        FMT: Formatter,
    {
        // Create a fixed-size buffer to handle slice operation
        let mut buffer = ArrayVec::<[u8; 1024]>::new();

        // Copy MQTT topic, convert it into SCPI header format
        for i in topic.chars() {
            if i == '/' {
                // The topic separator is colon(':') in SCPI, and slash('/') in MQTT
                buffer.try_push(b':')
                        .map_err(|_| ErrorCode::OutOfMemory)?;
            } else {
                buffer.try_push(i as u8)
                        .map_err(|_| ErrorCode::OutOfMemory)?;
            }
        }

        // Place a space bar between header and parameter
        buffer.try_push(b' ')
                .map_err(|_| ErrorCode::OutOfMemory)?;

        // Copy the arguments into the buffer
        for i in args.chars() {
            buffer.try_push(i as u8)
                    .map_err(|_| ErrorCode::OutOfMemory)?;
        }

        // Pass the message to SCPI processing unit
        trace!("Translated MQTT message into SCPI. Translated command: {}",
                    core::str::from_utf8(buffer.as_slice()).unwrap());
        self.run(buffer.as_slice(), response)
    }
}