sta/backend/src/infrastructure/modbus/client.rs

use async_trait::async_trait;
use std::result::Result as SResult;
use std::sync::Arc;
use tokio::sync::{Mutex, MutexGuard};
use tokio::time::error::Elapsed;
use tokio::time::{Duration, timeout};
use tokio_modbus::client::Context;

use crate::domain::relay::controller::{ControllerError, RelayController, Result};
use crate::domain::relay::types::{RelayId, RelayState};

use tokio_modbus::prelude::*;

/// Modbus TCP relay controller for real hardware communication.
///
/// This implementation communicates with physical Modbus relay hardware over TCP,
/// supporting 8-channel relay control via the Modbus protocol. It provides thread-safe
/// access using `Arc<Mutex>` and includes configurable timeout handling.
pub struct ModbusRelayController {
    ctx: Arc<Mutex<tokio_modbus::client::Context>>,
    timeout_duration: Duration,
}

impl std::fmt::Debug for ModbusRelayController {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ModbusRelayController")
            .field("timeout_duration", &self.timeout_duration)
            .field("ctx", &"<tokio_modbus::client::Context>")
            .finish()
    }
}

const ALL_ADDRS: tokio_modbus::Address = 0x0000;
const FIRMWARE_ADDR: tokio_modbus::Address = 0x8000;

impl ModbusRelayController {
    /// Creates a new Modbus relay controller connected to the specified device.
    ///
    /// Establishes a TCP connection to the Modbus device and configures timeout behavior.
    ///
    /// # Errors
    ///
    /// Returns `ControllerError::ConnectionError` if:
    /// - The host/port address is invalid
    /// - Connection to the Modbus device fails
    /// - The device is unreachable
    pub async fn new(host: &str, port: u16, slave_id: u8, timeout_secs: u64) -> Result<Self> {
        if slave_id != 1 {
            tracing::warn!("Device typically uses slave_id=1, got {slave_id}");
        }
        let socket_addr = format!("{host}:{port}")
            .parse()
            .map_err(|e| ControllerError::ConnectionError(format!("Invalid address: {e}")))?;
        let ctx = tcp::connect_slave(socket_addr, Slave(slave_id))
            .await
            .map_err(|e| ControllerError::ConnectionError(e.to_string()))?;
        Ok(Self {
            ctx: Arc::new(Mutex::new(ctx)),
            timeout_duration: Duration::from_secs(timeout_secs),
        })
    }

    async fn context(&self) -> MutexGuard<'_, Context> {
        self.ctx.lock().await
    }

    fn handle_modbus_result<T>(
        &self,
        result: SResult<SResult<SResult<T, ExceptionCode>, tokio_modbus::Error>, Elapsed>,
    ) -> Result<T> {
        result
            .map_err(|_| ControllerError::Timeout(self.timeout_duration.as_secs()))?
            .map_err(|e| ControllerError::ConnectionError(e.to_string()))?
            .map_err(|e| ControllerError::ModbusException(e.to_string()))
    }

    async fn read_coils_with_timeout(&self, addr: u16, count: u16) -> Result<Vec<bool>> {
        let result = timeout(
            self.timeout_duration,
            self.context().await.read_coils(addr, count),
        )
        .await;
        self.handle_modbus_result(result)
    }

    async fn write_single_coil_with_timeout(&self, addr: u16, value: bool) -> Result<()> {
        let result = timeout(
            self.timeout_duration,
            self.context().await.write_single_coil(addr, value),
        )
        .await;
        self.handle_modbus_result(result)
    }
}

#[async_trait]
impl RelayController for ModbusRelayController {
    async fn read_relay_state(&self, id: RelayId) -> Result<RelayState> {
        let addr = id.to_modbus_address();
        let coils = self.read_coils_with_timeout(addr, 1).await?;
        let state = RelayState::from(
            *coils
                .first()
                .ok_or_else(|| ControllerError::InvalidRelayId(id.as_u8()))?,
        );
        tracing::debug!(target: "modbus", relay_id = id.as_u8(), ?state, "Read relay state");
        Ok(state)
    }

    async fn write_relay_state(&self, id: RelayId, state: RelayState) -> Result<()> {
        let addr = id.to_modbus_address();
        let value: bool = state.into();
        self.write_single_coil_with_timeout(addr, value).await?;
        tracing::info!(target: "modbus", relay_id = id.as_u8(), ?state, "Wrote relay state");
        Ok(())
    }

    async fn read_all_states(&self) -> Result<Vec<RelayState>> {
        let coils = self.read_coils_with_timeout(ALL_ADDRS, 8).await?;
        let states: Vec<RelayState> = coils.into_iter().map(RelayState::from).collect();
        tracing::debug!(target: "modbus", "Read all relay states");
        Ok(states)
    }

    async fn write_all_states(&self, states: Vec<RelayState>) -> Result<()> {
        if states.len() != 8 {
            return Err(ControllerError::InvalidInput(format!(
                "Expected 8 relay states, got {}",
                states.len()
            )));
        }
        let coils: Vec<bool> = states.iter().map(|&s| s.into()).collect();
        let result = timeout(
            self.timeout_duration,
            self.context().await.write_multiple_coils(ALL_ADDRS, &coils),
        )
        .await;
        self.handle_modbus_result(result)?;
        tracing::info!(target: "modbus", "Wrote all relay states");
        Ok(())
    }

    async fn check_connection(&self) -> Result<()> {
        // Try reading first coil as health check
        self.read_coils_with_timeout(ALL_ADDRS, 1).await?;
        Ok(())
    }

    async fn get_firmware_version(&self) -> Result<Option<String>> {
        let result = timeout(
            self.timeout_duration,
            self.context()
                .await
                .read_holding_registers(FIRMWARE_ADDR, 1),
        )
        .await;
        let result = self.handle_modbus_result(result)?;
        if let Some(&version_raw) = result.first() {
            let version = f32::from(version_raw) / 100.0;
            Ok(Some(format!("v{version:.2}")))
        } else {
            Ok(None)
        }
    }
}

#[cfg(test)]
#[path = "client_test.rs"]
mod tests;