src/channel.rs

// SPF Smart Gateway - Channel Hub: Universal Agent Communication
// Copyright 2026 Joseph Stone - All Rights Reserved
//
// Real-time group messaging for SPF agent networks.
// Central hub (orchestrator) + WebSocket clients (agents) = instant duplex push.
// Role-agnostic: any agent can send/receive regardless of role.
//
// Architecture:
//   Hub node runs ChannelHub + WS server (/ws/channel/{id})
//   Agent nodes connect via WsChannelClient (tokio-tungstenite)
//   MCP tool (spf_channel) is the LLM control interface
//   HTTP API (/api/channel/*) for control plane operations
//
// State: static CHANNEL_HUB global (same pattern as CHAT_ENGINE in mcp.rs)
//        — avoids modifying ServerState, handle_tool_call signature, dispatch::call
//
// Depends on: nothing for CH-1 (core types). CH-2+ adds http.rs routes.

use serde::{Deserialize, Serialize};
use std::collections::{HashMap, VecDeque};
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Mutex;
use axum::extract::ws::{WebSocket, Message};
use futures_util::{SinkExt, StreamExt};

// ============================================================================
// GLOBAL STATE — static Mutex (same pattern as CHAT_ENGINE in mcp.rs)
// ============================================================================

/// Channel hub state — persists across tool calls.
/// Lazy-initialized on first access via get_or_insert_with().
pub static CHANNEL_HUB: Mutex<Option<ChannelHub>> = Mutex::new(None);

/// Monotonic message sequence counter — unique across all channels.
static MSG_SEQ: AtomicU64 = AtomicU64::new(0);

// ============================================================================
// MESSAGE FORMAT
// ============================================================================

/// Message type classification.
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum MessageType {
    /// Regular text message from an agent
    Text,
    /// System notification (join, leave, channel created)
    System,
    /// Tool result shared in channel
    ToolResult,
}

/// A single message in a channel.
/// Serialized as JSON for WebSocket transport and HTTP API responses.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChannelMessage {
    /// Unique message ID: "msg-{timestamp_ms}-{seq}"
    pub id: String,
    /// Channel this message belongs to
    pub channel_id: String,
    /// Sender's full pub_key hex
    pub from: String,
    /// Sender's human-readable name
    pub from_name: String,
    /// Message text content
    pub text: String,
    /// Timestamp (RFC3339)
    pub timestamp: String,
    /// Message type
    pub msg_type: MessageType,
}

/// Generate a unique message ID using timestamp + atomic counter.
/// Format: "msg-{timestamp_ms}-{seq}"
fn new_message_id() -> String {
    let ts = chrono::Utc::now().timestamp_millis();
    let seq = MSG_SEQ.fetch_add(1, Ordering::Relaxed);
    format!("msg-{}-{}", ts, seq)
}

// ============================================================================
// PARTICIPANT
// ============================================================================

/// A participant in a channel.
/// The ws_sender is Some when the participant has an active WebSocket connection
/// to the hub. None means they joined via HTTP but aren't listening via WS yet.
#[derive(Debug, Clone)]
pub struct Participant {
    /// Full pub_key hex
    pub key: String,
    /// Human-readable display name
    pub name: String,
    /// WebSocket sender handle — None if not connected via WS.
    /// Uses tokio mpsc so broadcast doesn't block on slow receivers.
    pub ws_sender: Option<tokio::sync::mpsc::UnboundedSender<String>>,
}

// ============================================================================
// CHANNEL
// ============================================================================

/// Maximum messages retained in memory per channel.
const MAX_CHANNEL_HISTORY: usize = 1000;

/// A single communication channel.
/// Holds participants and a bounded message history buffer.
pub struct Channel {
    /// Unique channel identifier
    pub id: String,
    /// Human-readable channel name
    pub name: String,
    /// Who created this channel (pub_key hex)
    pub created_by: String,
    /// Creation timestamp (RFC3339)
    pub created_at: String,
    /// Current participants
    pub participants: Vec<Participant>,
    /// Message history — bounded VecDeque, oldest evicted at MAX_CHANNEL_HISTORY
    pub messages: VecDeque<ChannelMessage>,
}

impl Channel {
    /// Create a new channel.
    pub fn new(id: String, name: String, created_by: String) -> Self {
        Self {
            id,
            name,
            created_by,
            created_at: chrono::Utc::now().to_rfc3339(),
            participants: Vec::new(),
            messages: VecDeque::new(),
        }
    }

    /// Add a participant. Returns false if already present.
    pub fn add_participant(&mut self, key: &str, name: &str) -> bool {
        if self.participants.iter().any(|p| p.key == key) {
            return false;
        }
        self.participants.push(Participant {
            key: key.to_string(),
            name: name.to_string(),
            ws_sender: None,
        });
        true
    }

    /// Remove a participant by key. Returns true if found and removed.
    pub fn remove_participant(&mut self, key: &str) -> bool {
        let before = self.participants.len();
        self.participants.retain(|p| p.key != key);
        self.participants.len() < before
    }

    /// Check if a key is a participant.
    pub fn has_participant(&self, key: &str) -> bool {
        self.participants.iter().any(|p| p.key == key)
    }

    /// Set the WS sender for a participant. Returns false if participant not found.
    pub fn set_ws_sender(
        &mut self,
        key: &str,
        sender: tokio::sync::mpsc::UnboundedSender<String>,
    ) -> bool {
        if let Some(p) = self.participants.iter_mut().find(|p| p.key == key) {
            p.ws_sender = Some(sender);
            true
        } else {
            false
        }
    }

    /// Clear the WS sender for a participant (on disconnect).
    pub fn clear_ws_sender(&mut self, key: &str) {
        if let Some(p) = self.participants.iter_mut().find(|p| p.key == key) {
            p.ws_sender = None;
        }
    }

    /// Add a message to history. Evicts oldest if over MAX_CHANNEL_HISTORY.
    pub fn push_message(&mut self, msg: ChannelMessage) {
        if self.messages.len() >= MAX_CHANNEL_HISTORY {
            self.messages.pop_front();
        }
        self.messages.push_back(msg);
    }

    /// Get last N messages from history.
    pub fn get_history(&self, limit: usize) -> Vec<&ChannelMessage> {
        let start = self.messages.len().saturating_sub(limit);
        self.messages.iter().skip(start).collect()
    }

    /// Broadcast a message to all participants with active WS connections.
    /// Skips the sender (don't echo back). Reaps dead senders on send failure.
    /// Returns the number of participants the message was delivered to.
    pub fn broadcast(&mut self, msg: &ChannelMessage) -> usize {
        let json = match serde_json::to_string(msg) {
            Ok(j) => j,
            Err(_) => return 0,
        };

        let mut delivered = 0;
        let mut dead_keys: Vec<String> = Vec::new();

        for participant in &self.participants {
            // Don't echo back to sender
            if participant.key == msg.from {
                continue;
            }
            if let Some(ref sender) = participant.ws_sender {
                if sender.send(json.clone()).is_ok() {
                    delivered += 1;
                } else {
                    dead_keys.push(participant.key.clone());
                }
            }
        }

        // Reap dead WS senders (not participants — they stay joined)
        for key in &dead_keys {
            self.clear_ws_sender(key);
        }

        delivered
    }

    /// Participant count.
    pub fn participant_count(&self) -> usize {
        self.participants.len()
    }

    /// Count of participants with active WS connections.
    pub fn connected_count(&self) -> usize {
        self.participants.iter().filter(|p| p.ws_sender.is_some()).count()
    }

    /// Message count.
    pub fn message_count(&self) -> usize {
        self.messages.len()
    }
}

// ============================================================================
// CHANNEL HUB — manages all channels
// ============================================================================

/// Central hub managing all communication channels.
/// One instance per node — orchestrator hosts the "real" hub,
/// worker nodes may run a local hub for testing.
pub struct ChannelHub {
    /// All channels indexed by ID
    channels: HashMap<String, Channel>,
    /// Monotonic channel ID counter
    next_id: u64,
}

impl ChannelHub {
    /// Create a new empty hub.
    pub fn new() -> Self {
        Self {
            channels: HashMap::new(),
            next_id: 1,
        }
    }

    /// Create a new channel. Returns the channel ID.
    /// The creator is automatically added as the first participant.
    pub fn create_channel(
        &mut self,
        name: &str,
        created_by: &str,
        created_by_name: &str,
    ) -> String {
        let id = format!("ch-{}", self.next_id);
        self.next_id += 1;

        let mut channel = Channel::new(id.clone(), name.to_string(), created_by.to_string());
        channel.add_participant(created_by, created_by_name);

        // System message: channel created
        let sys_msg = ChannelMessage {
            id: new_message_id(),
            channel_id: id.clone(),
            from: "system".to_string(),
            from_name: "System".to_string(),
            text: format!("Channel '{}' created by {}", name, created_by_name),
            timestamp: chrono::Utc::now().to_rfc3339(),
            msg_type: MessageType::System,
        };
        channel.push_message(sys_msg);

        self.channels.insert(id.clone(), channel);
        id
    }

    /// Join an existing channel. Returns Ok or Err if channel not found.
    pub fn join_channel(
        &mut self,
        channel_id: &str,
        key: &str,
        name: &str,
    ) -> Result<(), String> {
        let channel = self.channels.get_mut(channel_id)
            .ok_or_else(|| format!("Channel not found: {}", channel_id))?;

        if channel.has_participant(key) {
            return Ok(()); // Already joined — idempotent
        }

        channel.add_participant(key, name);

        // System message: participant joined
        let sys_msg = ChannelMessage {
            id: new_message_id(),
            channel_id: channel_id.to_string(),
            from: "system".to_string(),
            from_name: "System".to_string(),
            text: format!("{} joined the channel", name),
            timestamp: chrono::Utc::now().to_rfc3339(),
            msg_type: MessageType::System,
        };
        channel.broadcast(&sys_msg);
        channel.push_message(sys_msg);

        Ok(())
    }

    /// Leave a channel. Returns Ok or Err if channel/participant not found.
    pub fn leave_channel(
        &mut self,
        channel_id: &str,
        key: &str,
    ) -> Result<(), String> {
        let channel = self.channels.get_mut(channel_id)
            .ok_or_else(|| format!("Channel not found: {}", channel_id))?;

        let name = channel.participants.iter()
            .find(|p| p.key == key)
            .map(|p| p.name.clone())
            .unwrap_or_else(|| key[..8.min(key.len())].to_string());

        if !channel.remove_participant(key) {
            return Err(format!("Not a participant in channel {}", channel_id));
        }

        // System message: participant left
        let sys_msg = ChannelMessage {
            id: new_message_id(),
            channel_id: channel_id.to_string(),
            from: "system".to_string(),
            from_name: "System".to_string(),
            text: format!("{} left the channel", name),
            timestamp: chrono::Utc::now().to_rfc3339(),
            msg_type: MessageType::System,
        };
        channel.broadcast(&sys_msg);
        channel.push_message(sys_msg);

        Ok(())
    }

    /// Send a message to a channel. Broadcasts to all connected participants.
    /// Returns the created message or Err if channel not found / not a participant.
    pub fn send_message(
        &mut self,
        channel_id: &str,
        from: &str,
        from_name: &str,
        text: &str,
        msg_type: MessageType,
    ) -> Result<ChannelMessage, String> {
        let channel = self.channels.get_mut(channel_id)
            .ok_or_else(|| format!("Channel not found: {}", channel_id))?;

        if !channel.has_participant(from) {
            return Err(format!("Not a participant in channel {}", channel_id));
        }

        let msg = ChannelMessage {
            id: new_message_id(),
            channel_id: channel_id.to_string(),
            from: from.to_string(),
            from_name: from_name.to_string(),
            text: text.to_string(),
            timestamp: chrono::Utc::now().to_rfc3339(),
            msg_type,
        };

        let delivered = channel.broadcast(&msg);
        channel.push_message(msg.clone());

        eprintln!("[SPF-CHANNEL] {} → #{}: '{}' (delivered to {})",
            from_name, channel_id,
            text.chars().take(50).collect::<String>(),
            delivered);

        Ok(msg)
    }

    /// Get message history for a channel.
    pub fn get_history(
        &self,
        channel_id: &str,
        limit: usize,
    ) -> Result<Vec<&ChannelMessage>, String> {
        let channel = self.channels.get(channel_id)
            .ok_or_else(|| format!("Channel not found: {}", channel_id))?;
        Ok(channel.get_history(limit))
    }

    /// Get a mutable reference to a channel (for WS sender management).
    pub fn get_channel_mut(&mut self, channel_id: &str) -> Option<&mut Channel> {
        self.channels.get_mut(channel_id)
    }

    /// Get an immutable reference to a channel.
    pub fn get_channel(&self, channel_id: &str) -> Option<&Channel> {
        self.channels.get(channel_id)
    }

    /// Check if a channel exists.
    pub fn has_channel(&self, channel_id: &str) -> bool {
        self.channels.contains_key(channel_id)
    }

    /// List all channels with summary info.
    pub fn list_channels(&self) -> Vec<ChannelSummary> {
        self.channels.values().map(|ch| ChannelSummary {
            id: ch.id.clone(),
            name: ch.name.clone(),
            created_by: ch.created_by.clone(),
            created_at: ch.created_at.clone(),
            participants: ch.participants.iter().map(|p| ParticipantInfo {
                key: p.key.clone(),
                name: p.name.clone(),
                connected: p.ws_sender.is_some(),
            }).collect(),
            participant_count: ch.participant_count(),
            connected_count: ch.connected_count(),
            message_count: ch.message_count(),
        }).collect()
    }

    /// Total channel count.
    pub fn channel_count(&self) -> usize {
        self.channels.len()
    }

    /// Remove a channel entirely. Returns true if it existed.
    pub fn remove_channel(&mut self, channel_id: &str) -> bool {
        self.channels.remove(channel_id).is_some()
    }

    /// Register a WS sender for a participant in a channel.
    /// Auto-joins if not already a participant.
    /// Returns Ok or Err if channel not found.
    pub fn register_ws(
        &mut self,
        channel_id: &str,
        key: &str,
        name: &str,
        sender: tokio::sync::mpsc::UnboundedSender<String>,
    ) -> Result<(), String> {
        let channel = self.channels.get_mut(channel_id)
            .ok_or_else(|| format!("Channel not found: {}", channel_id))?;

        // Auto-join if not already a participant
        if !channel.has_participant(key) {
            channel.add_participant(key, name);
            let sys_msg = ChannelMessage {
                id: new_message_id(),
                channel_id: channel_id.to_string(),
                from: "system".to_string(),
                from_name: "System".to_string(),
                text: format!("{} joined the channel", name),
                timestamp: chrono::Utc::now().to_rfc3339(),
                msg_type: MessageType::System,
            };
            channel.broadcast(&sys_msg);
            channel.push_message(sys_msg);
        }

        channel.set_ws_sender(key, sender);
        eprintln!("[SPF-CHANNEL] WS registered: {} ({}) on #{}",
            name, &key[..8.min(key.len())], channel_id);
        Ok(())
    }

    /// Unregister a WS sender for a participant (on WS disconnect).
    /// Does NOT remove the participant — they stay joined.
    pub fn unregister_ws(&mut self, channel_id: &str, key: &str) {
        if let Some(channel) = self.channels.get_mut(channel_id) {
            channel.clear_ws_sender(key);
            eprintln!("[SPF-CHANNEL] WS disconnected: {} on #{}",
                &key[..8.min(key.len())], channel_id);
        }
    }
}

// ============================================================================
// CH-2: WEBSOCKET SERVER — hub-side WS handler for agent connections
// ============================================================================

/// WebSocket message envelope for channel protocol.
/// Agents send these over WS; hub parses and routes to ChannelHub methods.
#[derive(Debug, Deserialize)]
struct WsInbound {
    /// Action: "send", "join", "leave", "history"
    action: String,
    /// Message text (for "send")
    #[serde(default)]
    text: String,
    /// Message type (for "send") — defaults to "text"
    #[serde(default = "default_msg_type")]
    msg_type: MessageType,
    /// History limit (for "history") — defaults to 50
    #[serde(default = "default_history_limit")]
    limit: usize,
}

fn default_msg_type() -> MessageType { MessageType::Text }
fn default_history_limit() -> usize { 50 }

/// WebSocket outbound envelope — hub sends these to agents.
#[derive(Debug, Serialize)]
struct WsOutbound {
    /// "message", "system", "error", "history"
    #[serde(rename = "type")]
    resp_type: String,
    /// Payload — ChannelMessage for message/system, array for history, string for error
    data: serde_json::Value,
}

/// Handle a WebSocket connection for a channel.
/// Called after auth + upgrade in http.rs ws_channel_upgrade handler.
///
/// Protocol:
///   - Hub sends ChannelMessage JSON when other agents post
///   - Agent sends WsInbound JSON to send/join/leave/get history
///   - Hub auto-registers agent's WS sender on connect, unregisters on disconnect
///
/// Uses tokio::select! to simultaneously:
///   1. Forward hub broadcasts (mpsc rx) → WebSocket
///   2. Process agent commands (WebSocket rx) → ChannelHub
pub async fn handle_channel_ws(
    mut socket: WebSocket,
    channel_id: String,
    peer_key: String,
    peer_name: String,
) {
    // Create mpsc channel for hub → this WS connection
    let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel::<String>();

    // Register WS sender in hub (auto-joins if not already participant)
    // NOTE: MutexGuard is !Send — must drop before any .await
    let register_err: Option<String> = {
        let mut guard = CHANNEL_HUB.lock().unwrap();
        let hub = guard.get_or_insert_with(ChannelHub::new);
        match hub.register_ws(&channel_id, &peer_key, &peer_name, tx) {
            Ok(()) => None,
            Err(e) => Some(serde_json::to_string(&WsOutbound {
                resp_type: "error".to_string(),
                data: serde_json::Value::String(e),
            }).unwrap_or_default()),
        }
    }; // guard dropped here
    if let Some(err_json) = register_err {
        let _ = socket.send(Message::Text(err_json.into())).await;
        return;
    }

    eprintln!("[SPF-CHANNEL] WS connected: {} ({}) on #{}",
        peer_name, &peer_key[..8.min(peer_key.len())], channel_id);

    // Send recent history on connect so agent has context
    // NOTE: serialize inside lock, send outside lock (.await requires Send)
    let history_json: Option<String> = {
        let guard = CHANNEL_HUB.lock().unwrap();
        if let Some(hub) = guard.as_ref() {
            if let Ok(history) = hub.get_history(&channel_id, 50) {
                let msgs: Vec<&ChannelMessage> = history;
                let envelope = WsOutbound {
                    resp_type: "history".to_string(),
                    data: serde_json::to_value(&msgs).unwrap_or_default(),
                };
                serde_json::to_string(&envelope).ok()
            } else { None }
        } else { None }
    }; // guard dropped here
    if let Some(json) = history_json {
        let _ = socket.send(Message::Text(json.into())).await;
    }

    // Main loop: select between hub→agent (mpsc) and agent→hub (WS)
    loop {
        tokio::select! {
            // Hub broadcast → forward to agent via WS
            msg = rx.recv() => {
                match msg {
                    Some(text) => {
                        if socket.send(Message::Text(text.into())).await.is_err() {
                            break; // WS send failed — agent disconnected
                        }
                    }
                    None => break, // mpsc closed — hub dropped sender
                }
            }

            // Agent command → process via ChannelHub
            ws_msg = socket.recv() => {
                match ws_msg {
                    Some(Ok(Message::Text(text))) => {
                        let response = process_ws_command(
                            &text, &channel_id, &peer_key, &peer_name
                        );
                        if let Some(resp_json) = response {
                            if socket.send(Message::Text(resp_json.into())).await.is_err() {
                                break;
                            }
                        }
                    }
                    Some(Ok(Message::Ping(data))) => {
                        if socket.send(Message::Pong(data)).await.is_err() {
                            break;
                        }
                    }
                    Some(Ok(Message::Close(_))) | Some(Err(_)) | None => break,
                    _ => {} // Binary, Pong — ignore
                }
            }
        }
    }

    // Cleanup: unregister WS sender (participant stays joined)
    {
        let mut guard = CHANNEL_HUB.lock().unwrap();
        if let Some(hub) = guard.as_mut() {
            hub.unregister_ws(&channel_id, &peer_key);
        }
    }

    eprintln!("[SPF-CHANNEL] WS disconnected: {} ({}) from #{}",
        peer_name, &peer_key[..8.min(peer_key.len())], channel_id);
}

/// Process an inbound WS command from an agent.
/// Returns Some(json_string) if there's a response to send back, None otherwise.
fn process_ws_command(
    text: &str,
    channel_id: &str,
    peer_key: &str,
    peer_name: &str,
) -> Option<String> {
    let cmd: WsInbound = match serde_json::from_str(text) {
        Ok(c) => c,
        Err(e) => {
            return Some(serde_json::to_string(&WsOutbound {
                resp_type: "error".to_string(),
                data: serde_json::Value::String(format!("Invalid JSON: {}", e)),
            }).unwrap_or_default());
        }
    };

    let mut guard = CHANNEL_HUB.lock().unwrap();
    let hub = guard.get_or_insert_with(ChannelHub::new);

    match cmd.action.as_str() {
        "send" => {
            match hub.send_message(channel_id, peer_key, peer_name, &cmd.text, cmd.msg_type) {
                Ok(msg) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "ack".to_string(),
                    data: serde_json::to_value(&msg).unwrap_or_default(),
                }).unwrap_or_default()),
                Err(e) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "error".to_string(),
                    data: serde_json::Value::String(e),
                }).unwrap_or_default()),
            }
        }

        "history" => {
            match hub.get_history(channel_id, cmd.limit) {
                Ok(msgs) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "history".to_string(),
                    data: serde_json::to_value(&msgs).unwrap_or_default(),
                }).unwrap_or_default()),
                Err(e) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "error".to_string(),
                    data: serde_json::Value::String(e),
                }).unwrap_or_default()),
            }
        }

        "join" => {
            // Already joined via register_ws, but allow explicit re-join
            match hub.join_channel(channel_id, peer_key, peer_name) {
                Ok(()) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "system".to_string(),
                    data: serde_json::Value::String("Joined".to_string()),
                }).unwrap_or_default()),
                Err(e) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "error".to_string(),
                    data: serde_json::Value::String(e),
                }).unwrap_or_default()),
            }
        }

        "leave" => {
            match hub.leave_channel(channel_id, peer_key) {
                Ok(()) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "system".to_string(),
                    data: serde_json::Value::String("Left channel".to_string()),
                }).unwrap_or_default()),
                Err(e) => Some(serde_json::to_string(&WsOutbound {
                    resp_type: "error".to_string(),
                    data: serde_json::Value::String(e),
                }).unwrap_or_default()),
            }
        }

        other => {
            Some(serde_json::to_string(&WsOutbound {
                resp_type: "error".to_string(),
                data: serde_json::Value::String(format!("Unknown action: {}", other)),
            }).unwrap_or_default())
        }
    }
}

// ============================================================================
// CH-3: HTTP API HANDLERS — called from http.rs route handlers
// ============================================================================

/// POST /api/channel/create — Create a new channel.
/// Body: { "name": "ops", "key": "abc...", "name_display": "ALPHA" }
pub fn api_create_channel(name: &str, key: &str, display_name: &str) -> serde_json::Value {
    let mut guard = CHANNEL_HUB.lock().unwrap();
    let hub = guard.get_or_insert_with(ChannelHub::new);
    let id = hub.create_channel(name, key, display_name);
    serde_json::json!({
        "ok": true,
        "channel_id": id,
        "name": name,
        "created_by": display_name
    })
}

/// POST /api/channel/join — Join an existing channel.
/// Body: { "channel_id": "ch-1", "key": "abc...", "name": "BRAVO" }
pub fn api_join_channel(channel_id: &str, key: &str, name: &str) -> serde_json::Value {
    let mut guard = CHANNEL_HUB.lock().unwrap();
    let hub = guard.get_or_insert_with(ChannelHub::new);
    match hub.join_channel(channel_id, key, name) {
        Ok(()) => serde_json::json!({ "ok": true, "channel_id": channel_id }),
        Err(e) => serde_json::json!({ "ok": false, "error": e }),
    }
}

/// POST /api/channel/leave — Leave a channel.
/// Body: { "channel_id": "ch-1", "key": "abc..." }
pub fn api_leave_channel(channel_id: &str, key: &str) -> serde_json::Value {
    let mut guard = CHANNEL_HUB.lock().unwrap();
    let hub = guard.get_or_insert_with(ChannelHub::new);
    match hub.leave_channel(channel_id, key) {
        Ok(()) => serde_json::json!({ "ok": true, "channel_id": channel_id }),
        Err(e) => serde_json::json!({ "ok": false, "error": e }),
    }
}

/// POST /api/channel/send — Send a message.
/// Body: { "channel_id": "ch-1", "key": "abc...", "name": "ALPHA", "text": "hello", "msg_type": "text" }
pub fn api_send_message(
    channel_id: &str,
    key: &str,
    name: &str,
    text: &str,
    msg_type: MessageType,
) -> serde_json::Value {
    let mut guard = CHANNEL_HUB.lock().unwrap();
    let hub = guard.get_or_insert_with(ChannelHub::new);
    match hub.send_message(channel_id, key, name, text, msg_type) {
        Ok(msg) => serde_json::json!({
            "ok": true,
            "message": msg
        }),
        Err(e) => serde_json::json!({ "ok": false, "error": e }),
    }
}

/// GET /api/channel/list — List all channels.
pub fn api_list_channels() -> serde_json::Value {
    let guard = CHANNEL_HUB.lock().unwrap();
    match guard.as_ref() {
        Some(hub) => serde_json::json!({
            "ok": true,
            "channels": hub.list_channels(),
            "count": hub.channel_count()
        }),
        None => serde_json::json!({
            "ok": true,
            "channels": [],
            "count": 0
        }),
    }
}

/// GET /api/channel/:id/history — Get channel message history.
pub fn api_channel_history(channel_id: &str, limit: usize) -> serde_json::Value {
    let guard = CHANNEL_HUB.lock().unwrap();
    match guard.as_ref() {
        Some(hub) => match hub.get_history(channel_id, limit) {
            Ok(msgs) => serde_json::json!({
                "ok": true,
                "channel_id": channel_id,
                "messages": msgs,
                "count": msgs.len()
            }),
            Err(e) => serde_json::json!({ "ok": false, "error": e }),
        },
        None => serde_json::json!({ "ok": false, "error": "No channels exist" }),
    }
}

// ============================================================================
// CH-4: WEBSOCKET CLIENT — agent-side WS connection to hub
// ============================================================================

/// Message received from the hub via WebSocket.
/// Buffered in VecDeque for MCP tool polling (spf_channel listen action).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct InboundMessage {
    /// Envelope type from hub: "message", "system", "history", "ack", "error"
    #[serde(rename = "type")]
    pub msg_type: String,
    /// Payload — varies by type
    pub data: serde_json::Value,
}

/// A connected WS client to a remote channel hub.
/// One per channel connection. Holds:
///   - Background task handle (reads WS, buffers messages)
///   - mpsc sender to push outbound messages through WS
///   - VecDeque buffer of inbound messages for MCP polling
pub struct WsClientConnection {
    /// Channel ID on the hub
    pub channel_id: String,
    /// Hub URL (for display/reconnect)
    pub hub_url: String,
    /// Sender: MCP tool → background task → WS → hub
    pub outbound_tx: tokio::sync::mpsc::UnboundedSender<String>,
    /// Inbound message buffer: background task populates, MCP tool drains
    pub inbound: std::sync::Arc<std::sync::Mutex<VecDeque<InboundMessage>>>,
    /// Background task handle — abort on disconnect
    pub task_handle: tokio::task::JoinHandle<()>,
    /// Connected flag
    pub connected: std::sync::Arc<std::sync::atomic::AtomicBool>,
}

/// Global WS client manager — keyed by "hub_url#channel_id".
/// MCP tool accesses this to send/receive/connect/disconnect.
pub static WS_CLIENTS: Mutex<Option<HashMap<String, WsClientConnection>>> = Mutex::new(None);

/// Build a client key from hub URL and channel ID.
fn client_key(hub_url: &str, channel_id: &str) -> String {
    format!("{}#{}", hub_url, channel_id)
}

/// Connect to a remote channel hub via WebSocket.
/// Spawns a background tokio task that:
///   1. Reads from WS → buffers into inbound VecDeque
///   2. Reads from outbound mpsc → writes to WS
///
/// Returns Ok(client_key) on success.
/// Requires a tokio runtime handle (from ServerState.tokio_handle).
pub fn ws_client_connect(
    handle: &tokio::runtime::Handle,
    hub_url: &str,
    channel_id: &str,
    api_key: &str,
    peer_key: &str,
    peer_name: &str,
) -> Result<String, String> {
    let key = client_key(hub_url, channel_id);

    // Check if already connected
    {
        let guard = WS_CLIENTS.lock().unwrap();
        if let Some(clients) = guard.as_ref() {
            if let Some(conn) = clients.get(&key) {
                if conn.connected.load(std::sync::atomic::Ordering::Relaxed) {
                    return Ok(key);
                }
            }
        }
    }

    // Build WS URL: http→ws, https→wss
    let ws_url = format!(
        "{}/ws/channel/{}?key={}&name={}",
        hub_url.replace("http://", "ws://").replace("https://", "wss://"),
        channel_id,
        peer_key,
        urlencoding(peer_name),
    );

    let (outbound_tx, mut outbound_rx) = tokio::sync::mpsc::unbounded_channel::<String>();
    let inbound_buf: std::sync::Arc<std::sync::Mutex<VecDeque<InboundMessage>>>
        = std::sync::Arc::new(std::sync::Mutex::new(VecDeque::new()));
    let connected = std::sync::Arc::new(std::sync::atomic::AtomicBool::new(false));

    let inbound_clone = inbound_buf.clone();
    let connected_clone = connected.clone();
    let api_key_owned = api_key.to_string();
    let ws_url_owned = ws_url.clone();
    let key_clone = key.clone();
    let hub_url_owned = hub_url.to_string();
    let channel_id_owned = channel_id.to_string();

    const MAX_INBOUND_BUFFER: usize = 500;

    // Spawn background WS task on the tokio runtime
    let task_handle = handle.spawn(async move {
        // Build request with auth header
        let request = match http::Request::builder()
            .uri(&ws_url_owned)
            .header("x-spf-key", &api_key_owned)
            .header("sec-websocket-key", tokio_tungstenite::tungstenite::handshake::client::generate_key())
            .header("sec-websocket-version", "13")
            .header("connection", "Upgrade")
            .header("upgrade", "websocket")
            .header("host", extract_host(&hub_url_owned))
            .body(())
        {
            Ok(r) => r,
            Err(e) => {
                eprintln!("[SPF-CHANNEL-CLIENT] Request build error: {}", e);
                return;
            }
        };

        let ws_stream = match tokio_tungstenite::connect_async(request).await {
            Ok((stream, _)) => stream,
            Err(e) => {
                eprintln!("[SPF-CHANNEL-CLIENT] Connect failed to {}: {}", ws_url_owned, e);
                return;
            }
        };

        connected_clone.store(true, std::sync::atomic::Ordering::Relaxed);
        eprintln!("[SPF-CHANNEL-CLIENT] Connected to {} #{}", hub_url_owned, channel_id_owned);

        let (mut ws_sink, mut ws_stream_rx) = ws_stream.split();

        loop {
            tokio::select! {
                // Hub → agent: read from WS, buffer for MCP polling
                ws_msg = ws_stream_rx.next() => {
                    match ws_msg {
                        Some(Ok(tokio_tungstenite::tungstenite::Message::Text(text))) => {
                            if let Ok(msg) = serde_json::from_str::<InboundMessage>(&text) {
                                let mut buf = inbound_clone.lock().unwrap();
                                if buf.len() >= MAX_INBOUND_BUFFER {
                                    buf.pop_front(); // evict oldest
                                }
                                buf.push_back(msg);
                            }
                        }
                        Some(Ok(tokio_tungstenite::tungstenite::Message::Close(_))) => break,
                        Some(Err(e)) => {
                            eprintln!("[SPF-CHANNEL-CLIENT] WS error: {}", e);
                            break;
                        }
                        None => break,
                        _ => {} // Binary, Ping, Pong handled by tungstenite
                    }
                }

                // Agent → hub: forward outbound messages through WS
                out_msg = outbound_rx.recv() => {
                    match out_msg {
                        Some(text) => {
                            if ws_sink.send(tokio_tungstenite::tungstenite::Message::Text(text.into())).await.is_err() {
                                break;
                            }
                        }
                        None => break, // outbound channel closed
                    }
                }
            }
        }

        connected_clone.store(false, std::sync::atomic::Ordering::Relaxed);
        eprintln!("[SPF-CHANNEL-CLIENT] Disconnected from {} #{}", hub_url_owned, channel_id_owned);

        // Cleanup from global map
        let mut guard = WS_CLIENTS.lock().unwrap();
        if let Some(clients) = guard.as_mut() {
            clients.remove(&key_clone);
        }
    });

    // Register in global map
    let conn = WsClientConnection {
        channel_id: channel_id.to_string(),
        hub_url: hub_url.to_string(),
        outbound_tx,
        inbound: inbound_buf,
        task_handle,
        connected,
    };

    let mut guard = WS_CLIENTS.lock().unwrap();
    let clients = guard.get_or_insert_with(HashMap::new);
    clients.insert(key.clone(), conn);

    Ok(key)
}

/// Send a message through a connected WS client.
pub fn ws_client_send(
    client_key: &str,
    text: &str,
    msg_type: &str,
) -> Result<(), String> {
    let guard = WS_CLIENTS.lock().unwrap();
    let clients = guard.as_ref().ok_or("No client connections")?;
    let conn = clients.get(client_key).ok_or("Not connected")?;

    if !conn.connected.load(std::sync::atomic::Ordering::Relaxed) {
        return Err("Connection lost".to_string());
    }

    let cmd = serde_json::json!({
        "action": "send",
        "text": text,
        "msg_type": msg_type,
    });
    conn.outbound_tx.send(cmd.to_string())
        .map_err(|e| format!("Send failed: {}", e))
}

/// Drain inbound message buffer — returns all buffered messages.
/// Called by MCP tool `spf_channel listen` action.
pub fn ws_client_drain(client_key: &str) -> Result<Vec<InboundMessage>, String> {
    let guard = WS_CLIENTS.lock().unwrap();
    let clients = guard.as_ref().ok_or("No client connections")?;
    let conn = clients.get(client_key).ok_or("Not connected")?;

    let mut buf = conn.inbound.lock().unwrap();
    let messages: Vec<InboundMessage> = buf.drain(..).collect();
    Ok(messages)
}

/// Disconnect a WS client.
pub fn ws_client_disconnect(client_key: &str) -> Result<(), String> {
    let mut guard = WS_CLIENTS.lock().unwrap();
    let clients = guard.as_mut().ok_or("No client connections")?;

    if let Some(conn) = clients.remove(client_key) {
        conn.task_handle.abort();
        Ok(())
    } else {
        Err("Not connected".to_string())
    }
}

/// List all active WS client connections.
pub fn ws_client_list() -> Vec<serde_json::Value> {
    let guard = WS_CLIENTS.lock().unwrap();
    match guard.as_ref() {
        Some(clients) => clients.iter().map(|(key, conn)| {
            serde_json::json!({
                "key": key,
                "channel_id": conn.channel_id,
                "hub_url": conn.hub_url,
                "connected": conn.connected.load(std::sync::atomic::Ordering::Relaxed),
                "buffered": conn.inbound.lock().unwrap().len(),
            })
        }).collect(),
        None => Vec::new(),
    }
}

/// Simple URL-encode for query params (spaces, special chars).
fn urlencoding(s: &str) -> String {
    s.chars().map(|c| match c {
        'A'..='Z' | 'a'..='z' | '0'..='9' | '-' | '_' | '.' | '~' => c.to_string(),
        ' ' => "%20".to_string(),
        _ => format!("%{:02X}", c as u32),
    }).collect()
}

/// Extract host from URL for WebSocket Host header.
fn extract_host(url: &str) -> String {
    url.trim_start_matches("http://")
       .trim_start_matches("https://")
       .split('/')
       .next()
       .unwrap_or("localhost")
       .to_string()
}

// ============================================================================
// SUMMARY TYPES — for API responses
// ============================================================================

/// Channel summary for list/status responses.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChannelSummary {
    pub id: String,
    pub name: String,
    pub created_by: String,
    pub created_at: String,
    pub participants: Vec<ParticipantInfo>,
    pub participant_count: usize,
    pub connected_count: usize,
    pub message_count: usize,
}

/// Participant info for API responses.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ParticipantInfo {
    pub key: String,
    pub name: String,
    pub connected: bool,
}

// ============================================================================
// TESTS
// ============================================================================

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

    #[test]
    fn test_message_id_unique() {
        let id1 = new_message_id();
        let id2 = new_message_id();
        assert_ne!(id1, id2);
        assert!(id1.starts_with("msg-"));
    }

    #[test]
    fn test_create_channel() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");
        assert_eq!(id, "ch-1");
        assert!(hub.has_channel("ch-1"));
        assert_eq!(hub.channel_count(), 1);

        let ch = hub.get_channel("ch-1").unwrap();
        assert_eq!(ch.name, "ops");
        assert_eq!(ch.created_by, "key_aaa");
        assert_eq!(ch.participant_count(), 1);
        assert!(ch.has_participant("key_aaa"));
        assert_eq!(ch.message_count(), 1); // system "created" msg
    }

    #[test]
    fn test_join_leave() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");

        hub.join_channel(&id, "key_bbb", "BRAVO").unwrap();
        let ch = hub.get_channel(&id).unwrap();
        assert_eq!(ch.participant_count(), 2);
        assert!(ch.has_participant("key_bbb"));

        // Idempotent join
        hub.join_channel(&id, "key_bbb", "BRAVO").unwrap();
        assert_eq!(hub.get_channel(&id).unwrap().participant_count(), 2);

        hub.leave_channel(&id, "key_bbb").unwrap();
        assert_eq!(hub.get_channel(&id).unwrap().participant_count(), 1);
        assert!(!hub.get_channel(&id).unwrap().has_participant("key_bbb"));
    }

    #[test]
    fn test_join_nonexistent() {
        let mut hub = ChannelHub::new();
        let result = hub.join_channel("ch-999", "key_aaa", "ALPHA");
        assert!(result.is_err());
    }

    #[test]
    fn test_send_message() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");
        hub.join_channel(&id, "key_bbb", "BRAVO").unwrap();

        let msg = hub.send_message(&id, "key_aaa", "ALPHA", "hello team", MessageType::Text).unwrap();
        assert_eq!(msg.channel_id, id);
        assert_eq!(msg.from, "key_aaa");
        assert_eq!(msg.text, "hello team");
        assert_eq!(msg.msg_type, MessageType::Text);

        // 1 system (created) + 1 system (bravo joined) + 1 text
        assert_eq!(hub.get_channel(&id).unwrap().message_count(), 3);
    }

    #[test]
    fn test_send_not_participant() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");
        let result = hub.send_message(&id, "key_zzz", "STRANGER", "hi", MessageType::Text);
        assert!(result.is_err());
    }

    #[test]
    fn test_history_limit() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");

        for i in 0..10 {
            hub.send_message(&id, "key_aaa", "ALPHA", &format!("msg {}", i), MessageType::Text).unwrap();
        }

        let history = hub.get_history(&id, 3).unwrap();
        assert_eq!(history.len(), 3);
        assert!(history[2].text.contains("msg 9"));
    }

    #[test]
    fn test_eviction() {
        let mut channel = Channel::new("test".to_string(), "Test".to_string(), "key".to_string());
        for i in 0..(MAX_CHANNEL_HISTORY + 10) {
            channel.push_message(ChannelMessage {
                id: format!("msg-{}", i),
                channel_id: "test".to_string(),
                from: "key".to_string(),
                from_name: "Test".to_string(),
                text: format!("message {}", i),
                timestamp: "2026-04-07T00:00:00Z".to_string(),
                msg_type: MessageType::Text,
            });
        }
        assert_eq!(channel.message_count(), MAX_CHANNEL_HISTORY);
        assert!(channel.messages.front().unwrap().text.contains("message 10"));
    }

    #[test]
    fn test_list_channels() {
        let mut hub = ChannelHub::new();
        hub.create_channel("ops", "key_aaa", "ALPHA");
        hub.create_channel("research", "key_bbb", "BRAVO");

        let list = hub.list_channels();
        assert_eq!(list.len(), 2);
        let names: Vec<&str> = list.iter().map(|s| s.name.as_str()).collect();
        assert!(names.contains(&"ops"));
        assert!(names.contains(&"research"));
    }

    #[test]
    fn test_remove_channel() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("temp", "key_aaa", "ALPHA");
        assert!(hub.remove_channel(&id));
        assert!(!hub.has_channel(&id));
        assert!(!hub.remove_channel(&id));
    }

    #[test]
    fn test_ids_increment() {
        let mut hub = ChannelHub::new();
        assert_eq!(hub.create_channel("a", "k", "n"), "ch-1");
        assert_eq!(hub.create_channel("b", "k", "n"), "ch-2");
        assert_eq!(hub.create_channel("c", "k", "n"), "ch-3");
    }

    #[test]
    fn test_register_ws_auto_joins() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");

        let (tx, _rx) = tokio::sync::mpsc::unbounded_channel();
        hub.register_ws(&id, "key_bbb", "BRAVO", tx).unwrap();

        let ch = hub.get_channel(&id).unwrap();
        assert_eq!(ch.participant_count(), 2);
        assert!(ch.has_participant("key_bbb"));
        assert_eq!(ch.connected_count(), 1);
    }

    #[test]
    fn test_unregister_ws_keeps_participant() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");

        let (tx, _rx) = tokio::sync::mpsc::unbounded_channel();
        hub.register_ws(&id, "key_aaa", "ALPHA", tx).unwrap();
        assert_eq!(hub.get_channel(&id).unwrap().connected_count(), 1);

        hub.unregister_ws(&id, "key_aaa");
        let ch = hub.get_channel(&id).unwrap();
        assert_eq!(ch.connected_count(), 0);
        assert!(ch.has_participant("key_aaa"));
    }

    #[test]
    fn test_broadcast_skips_sender() {
        let mut hub = ChannelHub::new();
        let id = hub.create_channel("ops", "key_aaa", "ALPHA");

        let (tx_a, mut rx_a) = tokio::sync::mpsc::unbounded_channel();
        let (tx_b, mut rx_b) = tokio::sync::mpsc::unbounded_channel();

        hub.register_ws(&id, "key_aaa", "ALPHA", tx_a).unwrap();
        hub.register_ws(&id, "key_bbb", "BRAVO", tx_b).unwrap();

        // ALPHA sends — should NOT echo to ALPHA, SHOULD deliver to BRAVO
        hub.send_message(&id, "key_aaa", "ALPHA", "test", MessageType::Text).unwrap();

        // BRAVO should have received
        assert!(rx_b.try_recv().is_ok());
        // ALPHA should NOT have received (no echo)
        assert!(rx_a.try_recv().is_err());
    }
}