//! CycloneDDS backend implementation (native, optional)
//!
//! This backend uses the cyclonedds-rs crate for native DDS communication.
//! It requires CycloneDDS to be installed on the system.
//!
//! # System Requirements
//!
//! - CycloneDDS installed (https://github.com/eclipse-cyclonedds/cyclonedds)
//! - cyclonedds-rs Rust bindings
//!
//! # Building
//!
//! Enable the `dds-cyclone` feature:
//! ```bash
//! cargo build --features dds-cyclone
//! ```

use parking_lot::RwLock;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;

use super::super::{Go2Config, LowCmd, LowState, SportModeCmd};
use super::backend::DdsBackend;
use crate::comm::{bounded_channel, Receiver, Sender};
use crate::{Error, Result};

/// DDS backend using CycloneDDS (native implementation)
///
/// This backend provides maximum compatibility with the Unitree SDK2
/// by using the same underlying CycloneDDS library.
///
/// # Note
///
/// This is currently a stub implementation. Full implementation requires:
/// - cyclonedds-rs dependency
/// - CycloneDDS system library
/// - IDL-generated type bindings
pub struct CycloneDdsBackend {
    /// Flag indicating connection status
    connected: Arc<AtomicBool>,
    /// Channel for receiving state updates
    state_rx: Receiver<LowState>,
    /// Channel for sending state updates (used by reader thread)
    #[allow(dead_code)]
    state_tx: Sender<LowState>,
    /// Configuration
    #[allow(dead_code)]
    config: Go2Config,
    /// Placeholder for CycloneDDS participant
    #[allow(dead_code)]
    participant: Arc<RwLock<()>>,
}

impl DdsBackend for CycloneDdsBackend {
    fn new(config: &Go2Config) -> Result<Self>
    where
        Self: Sized,
    {
        let connected = Arc::new(AtomicBool::new(false));
        let (state_tx, state_rx) = bounded_channel::<LowState>(100);
        let participant = Arc::new(RwLock::new(()));

        // TODO: Initialize CycloneDDS participant when cyclonedds-rs is available
        //
        // Example implementation outline:
        // ```
        // let participant = cyclonedds::domain::DomainParticipant::new(0)?;
        // let subscriber = participant.create_subscriber()?;
        // let publisher = participant.create_publisher()?;
        //
        // // Create topics
        // let low_state_topic = participant.create_topic::<LowState>("rt/lowstate")?;
        // let low_cmd_topic = participant.create_topic::<LowCmd>("rt/lowcmd")?;
        // let sport_topic = participant.create_topic::<SportModeRequest>("rt/api/sport/request")?;
        //
        // // Create readers/writers
        // let state_reader = subscriber.create_datareader(&low_state_topic)?;
        // let cmd_writer = publisher.create_datawriter(&low_cmd_topic)?;
        // let sport_writer = publisher.create_datawriter(&sport_topic)?;
        // ```

        tracing::warn!(
            "CycloneDDS backend is not yet fully implemented. \
             Consider using the default dust-dds backend."
        );

        // For now, return an error indicating this is not yet implemented
        Err(Error::Config(
            "CycloneDDS backend requires cyclonedds-rs which is not yet integrated. \
             Use the default dust-dds backend instead."
                .into(),
        ))

        // When implemented, return:
        // Ok(Self {
        //     connected,
        //     state_rx,
        //     state_tx,
        //     config: config.clone(),
        //     participant,
        // })
    }

    fn publish_low_cmd(&self, _cmd: &LowCmd) -> Result<()> {
        if !self.is_connected() {
            return Err(Error::Connection("Not connected to robot".into()));
        }

        // TODO: Publish using CycloneDDS writer
        Err(Error::Config("CycloneDDS backend not implemented".into()))
    }

    fn publish_sport_cmd(&self, _cmd: &SportModeCmd) -> Result<()> {
        if !self.is_connected() {
            return Err(Error::Connection("Not connected to robot".into()));
        }

        // TODO: Publish using CycloneDDS writer
        Err(Error::Config("CycloneDDS backend not implemented".into()))
    }

    fn subscribe_state(&self) -> Receiver<LowState> {
        self.state_rx.clone()
    }

    fn is_connected(&self) -> bool {
        self.connected.load(Ordering::Relaxed)
    }

    fn disconnect(&self) {
        self.connected.store(false, Ordering::Relaxed);
        // TODO: Clean up CycloneDDS resources
    }
}

impl Drop for CycloneDdsBackend {
    fn drop(&mut self) {
        self.disconnect();
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_cyclone_backend_not_implemented() {
        let config = Go2Config::default();
        let result = CycloneDdsBackend::new(&config);
        assert!(result.is_err());
    }
}
