//! WebSocket client for real-time updates
//!
//! Connects to the project-lifecycle API WebSocket endpoint
//! and receives real-time events for project and task updates

use anyhow::Result;
use serde::{Deserialize, Serialize};
use tokio::sync::mpsc;

/// Project event from WebSocket
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ProjectEvent {
    /// Task was created
    TaskCreated {
        /// Project ID
        project_id: String,
        /// Task ID
        task_id: String,
    },
    /// Task was updated
    TaskUpdated {
        /// Project ID
        project_id: String,
        /// Task ID
        task_id: String,
    },
    /// Task was deleted
    TaskDeleted {
        /// Project ID
        project_id: String,
        /// Task ID
        task_id: String,
    },
    /// Task was completed
    TaskCompleted {
        /// Project ID
        project_id: String,
        /// Task ID
        task_id: String,
    },
    /// Project was updated
    ProjectUpdated {
        /// Project ID
        project_id: String,
    },
    /// Connection established
    Connected,
    /// Ping message
    Ping,
}

/// WebSocket connection state
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[allow(dead_code)] // Prepared for future use
pub enum ConnectionState {
    /// Disconnected
    Disconnected,
    /// Connecting
    Connecting,
    /// Connected
    Connected,
    /// Error state
    Error,
}

/// Connect to WebSocket and send events to channel
///
/// This is a placeholder implementation. When the API server adds WebSocket support,
/// this function will be implemented using tokio-tungstenite.
///
/// # Arguments
/// * `ws_url` - WebSocket URL (e.g., "ws://localhost:3000/ws")
/// * `tx` - Channel to send events
///
/// # Example
/// ```no_run
/// use tokio::sync::mpsc;
/// use syntaxis_tui::websocket::{connect_websocket, ProjectEvent};
///
/// #[tokio::main]
/// async fn main() {
///     let (tx, mut rx) = mpsc::channel(100);
///
///     tokio::spawn(async move {
///         connect_websocket("ws://localhost:3000/ws", tx).await.ok();
///     });
///
///     while let Some(event) = rx.recv().await {
///         println!("Event: {:?}", event);
///     }
/// }
/// ```
pub async fn connect_websocket(ws_url: &str, tx: mpsc::Sender<ProjectEvent>) -> Result<()> {
    tracing::info!("WebSocket connection requested to: {}", ws_url);

    // TODO: Implement actual WebSocket connection when API server supports it
    // For now, this is a placeholder that logs the connection attempt

    // Simulated implementation (to be replaced with tokio-tungstenite):
    /*
    use tokio_tungstenite::{connect_async, tungstenite::Message};
    use futures_util::StreamExt;

    let (ws_stream, _) = connect_async(ws_url).await?;
    tracing::info!("WebSocket connected");

    let (_, mut read) = ws_stream.split();

    // Send connected event
    tx.send(ProjectEvent::Connected).await?;

    while let Some(msg) = read.next().await {
        match msg? {
            Message::Text(text) => {
                if let Ok(event) = serde_json::from_str::<ProjectEvent>(&text) {
                    tx.send(event).await?;
                }
            },
            Message::Close(_) => {
                tracing::info!("WebSocket connection closed");
                break;
            },
            Message::Ping(_) => {
                // Pong is sent automatically
            },
            _ => {},
        }
    }
    */

    // Placeholder: Just log that WebSocket is not yet implemented
    tracing::warn!("WebSocket support is not yet implemented. Real-time updates are disabled.");

    // Send a connected event anyway for testing
    tx.send(ProjectEvent::Connected).await?;

    Ok(())
}

/// Reconnect to WebSocket with exponential backoff
///
/// Attempts to reconnect to the WebSocket with increasing delays
/// between attempts (up to a maximum delay).
pub async fn connect_with_retry(
    ws_url: &str,
    tx: mpsc::Sender<ProjectEvent>,
    max_retries: usize,
) -> Result<()> {
    let mut retry_count = 0;
    let mut delay_ms = 1000; // Start with 1 second

    loop {
        match connect_websocket(ws_url, tx.clone()).await {
            Ok(()) => {
                tracing::info!("WebSocket connected successfully");
                return Ok(());
            }
            Err(e) => {
                retry_count += 1;
                if retry_count >= max_retries {
                    tracing::error!(
                        "WebSocket connection failed after {} retries: {}",
                        max_retries,
                        e
                    );
                    return Err(e);
                }

                tracing::warn!(
                    "WebSocket connection failed (attempt {}/{}), retrying in {}ms: {}",
                    retry_count,
                    max_retries,
                    delay_ms,
                    e
                );

                tokio::time::sleep(tokio::time::Duration::from_millis(delay_ms)).await;

                // Exponential backoff (max 30 seconds)
                delay_ms = (delay_ms * 2).min(30_000);
            }
        }
    }
}

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

    #[test]
    fn test_connection_state() {
        let state = ConnectionState::Disconnected;
        assert_eq!(state, ConnectionState::Disconnected);

        let state = ConnectionState::Connected;
        assert_eq!(state, ConnectionState::Connected);
    }

    #[test]
    fn test_project_event_serialization() {
        let event = ProjectEvent::TaskCreated {
            project_id: "proj-1".to_string(),
            task_id: "task-1".to_string(),
        };

        // Test serialization
        let json = serde_json::to_string(&event).unwrap();
        assert!(json.contains("task_created"));
        assert!(json.contains("proj-1"));
        assert!(json.contains("task-1"));

        // Test deserialization
        let deserialized: ProjectEvent = serde_json::from_str(&json).unwrap();
        match deserialized {
            ProjectEvent::TaskCreated {
                project_id,
                task_id,
            } => {
                assert_eq!(project_id, "proj-1");
                assert_eq!(task_id, "task-1");
            }
            _ => panic!("Wrong event type"),
        }
    }

    #[tokio::test]
    async fn test_websocket_placeholder() {
        let (tx, mut rx) = mpsc::channel(10);

        // Spawn connection task
        let handle =
            tokio::spawn(async move { connect_websocket("ws://localhost:3000/ws", tx).await });

        // Should receive a Connected event (from placeholder implementation)
        let event = tokio::time::timeout(tokio::time::Duration::from_secs(1), rx.recv())
            .await
            .unwrap();

        assert!(matches!(event, Some(ProjectEvent::Connected)));

        // Clean up
        handle.await.unwrap().ok();
    }
}
