//! A2A (Agent-to-Agent) protocol support
//!
//! Implements communication between AI agents with support for:
//! - Direct messaging (point-to-point)
//! - Group messaging (multicast)
//! - Broadcast messaging (all agents)
//! - Capability discovery and advertisement

use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::{mpsc, RwLock};
use uuid::Uuid;
use zclaw_types::{AgentId, Result, ZclawError};

/// Default channel buffer size
const DEFAULT_CHANNEL_SIZE: usize = 256;

/// A2A message envelope
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct A2aEnvelope {
    /// Message ID (UUID recommended)
    pub id: String,
    /// Sender agent ID
    pub from: AgentId,
    /// Recipient specification
    pub to: A2aRecipient,
    /// Message type
    pub message_type: A2aMessageType,
    /// Message payload (JSON)
    pub payload: serde_json::Value,
    /// Timestamp (Unix epoch milliseconds)
    pub timestamp: i64,
    /// Conversation/thread ID for grouping related messages
    pub conversation_id: Option<String>,
    /// Reply-to message ID for threading
    pub reply_to: Option<String>,
    /// Priority (0 = normal, higher = more urgent)
    #[serde(default)]
    pub priority: u8,
    /// Time-to-live in seconds (0 = no expiry)
    #[serde(default)]
    pub ttl: u32,
}

impl A2aEnvelope {
    /// Create a new envelope with auto-generated ID and timestamp
    pub fn new(from: AgentId, to: A2aRecipient, message_type: A2aMessageType, payload: serde_json::Value) -> Self {
        Self {
            id: uuid_v4(),
            from,
            to,
            message_type,
            payload,
            timestamp: current_timestamp(),
            conversation_id: None,
            reply_to: None,
            priority: 0,
            ttl: 0,
        }
    }

    /// Set conversation ID
    pub fn with_conversation(mut self, conversation_id: impl Into<String>) -> Self {
        self.conversation_id = Some(conversation_id.into());
        self
    }

    /// Set reply-to message ID
    pub fn with_reply_to(mut self, reply_to: impl Into<String>) -> Self {
        self.reply_to = Some(reply_to.into());
        self
    }

    /// Set priority
    pub fn with_priority(mut self, priority: u8) -> Self {
        self.priority = priority;
        self
    }

    /// Check if message has expired
    pub fn is_expired(&self) -> bool {
        if self.ttl == 0 {
            return false;
        }
        let now = current_timestamp();
        let expiry = self.timestamp + (self.ttl as i64 * 1000);
        now > expiry
    }
}

/// Recipient specification
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Hash)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum A2aRecipient {
    /// Direct message to specific agent
    Direct { agent_id: AgentId },
    /// Message to all agents in a group
    Group { group_id: String },
    /// Broadcast to all agents
    Broadcast,
}

impl std::fmt::Display for A2aRecipient {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            A2aRecipient::Direct { agent_id } => write!(f, "direct:{}", agent_id),
            A2aRecipient::Group { group_id } => write!(f, "group:{}", group_id),
            A2aRecipient::Broadcast => write!(f, "broadcast"),
        }
    }
}

/// A2A message types
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum A2aMessageType {
    /// Request for information or action (expects response)
    Request,
    /// Response to a request
    Response,
    /// Notification (no response expected)
    Notification,
    /// Error message
    Error,
    /// Heartbeat/ping
    Heartbeat,
    /// Capability advertisement
    Capability,
    /// Task delegation
    Task,
    /// Task status update
    TaskStatus,
}

/// Agent capability advertisement
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct A2aCapability {
    /// Capability name (e.g., "code-generation", "web-search")
    pub name: String,
    /// Human-readable description
    pub description: String,
    /// JSON Schema for input validation
    pub input_schema: Option<serde_json::Value>,
    /// JSON Schema for output validation
    pub output_schema: Option<serde_json::Value>,
    /// Whether this capability requires human approval
    pub requires_approval: bool,
    /// Capability version
    #[serde(default)]
    pub version: String,
    /// Tags for categorization
    #[serde(default)]
    pub tags: Vec<String>,
}

/// Agent profile for A2A
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct A2aAgentProfile {
    /// Agent ID
    pub id: AgentId,
    /// Display name
    pub name: String,
    /// Agent description
    pub description: String,
    /// Advertised capabilities
    pub capabilities: Vec<A2aCapability>,
    /// Supported protocols
    pub protocols: Vec<String>,
    /// Agent role (e.g., "teacher", "assistant", "worker")
    #[serde(default)]
    pub role: String,
    /// Priority for task assignment (higher = more priority)
    #[serde(default)]
    pub priority: u8,
    /// Additional metadata
    #[serde(default)]
    pub metadata: HashMap<String, String>,
    /// Groups this agent belongs to
    #[serde(default)]
    pub groups: Vec<String>,
    /// Last seen timestamp
    #[serde(default)]
    pub last_seen: i64,
}

impl A2aAgentProfile {
    /// Check if agent has a specific capability
    pub fn has_capability(&self, name: &str) -> bool {
        self.capabilities.iter().any(|c| c.name == name)
    }

    /// Get capability by name
    pub fn get_capability(&self, name: &str) -> Option<&A2aCapability> {
        self.capabilities.iter().find(|c| c.name == name)
    }
}

/// A2A client trait
#[async_trait]
pub trait A2aClient: Send + Sync {
    /// Send a message to another agent
    async fn send(&self, envelope: A2aEnvelope) -> Result<()>;

    /// Receive the next message (blocking)
    async fn recv(&self) -> Option<A2aEnvelope>;

    /// Try to receive a message without blocking
    fn try_recv(&self) -> Result<A2aEnvelope>;

    /// Get agent profile by ID
    async fn get_profile(&self, agent_id: &AgentId) -> Result<Option<A2aAgentProfile>>;

    /// Discover agents with specific capability
    async fn discover(&self, capability: &str) -> Result<Vec<A2aAgentProfile>>;

    /// Advertise own capabilities
    async fn advertise(&self, profile: A2aAgentProfile) -> Result<()>;

    /// Join a group
    async fn join_group(&self, group_id: &str) -> Result<()>;

    /// Leave a group
    async fn leave_group(&self, group_id: &str) -> Result<()>;

    /// Get all agents in a group
    async fn get_group_members(&self, group_id: &str) -> Result<Vec<AgentId>>;

    /// Get all online agents
    async fn get_online_agents(&self) -> Result<Vec<A2aAgentProfile>>;
}

/// A2A Router - manages message routing between agents
pub struct A2aRouter {
    /// Agent ID for this router instance
    agent_id: AgentId,
    /// Agent profiles registry
    profiles: Arc<RwLock<HashMap<AgentId, A2aAgentProfile>>>,
    /// Agent message queues (inbox for each agent) - using broadcast for multiple subscribers
    queues: Arc<RwLock<HashMap<AgentId, mpsc::Sender<A2aEnvelope>>>>,
    /// Group membership mapping (group_id -> agent_ids)
    groups: Arc<RwLock<HashMap<String, Vec<AgentId>>>>,
    /// Capability index (capability_name -> agent_ids)
    capability_index: Arc<RwLock<HashMap<String, Vec<AgentId>>>>,
    /// Channel size for message queues
    channel_size: usize,
}

/// Handle for receiving A2A messages
///
/// This struct provides a way to receive messages from the A2A router.
/// It stores the receiver internally and provides methods to receive messages.
pub struct A2aReceiver {
    receiver: Option<mpsc::Receiver<A2aEnvelope>>,
}

impl A2aReceiver {
    #[allow(dead_code)] // Will be used when A2A message channels are activated
    fn new(rx: mpsc::Receiver<A2aEnvelope>) -> Self {
        Self { receiver: Some(rx) }
    }

    /// Receive the next message (async)
    pub async fn recv(&mut self) -> Option<A2aEnvelope> {
        if let Some(ref mut rx) = self.receiver {
            rx.recv().await
        } else {
            None
        }
    }

    /// Try to receive a message without blocking
    pub fn try_recv(&mut self) -> Result<A2aEnvelope> {
        if let Some(ref mut rx) = self.receiver {
            rx.try_recv()
                .map_err(|e| ZclawError::Internal(format!("Receive error: {}", e)))
        } else {
            Err(ZclawError::Internal("No receiver available".into()))
        }
    }

    /// Check if receiver is still active
    pub fn is_active(&self) -> bool {
        self.receiver.is_some()
    }
}

impl A2aRouter {
    /// Create a new A2A router
    pub fn new(agent_id: AgentId) -> Self {
        Self {
            agent_id,
            profiles: Arc::new(RwLock::new(HashMap::new())),
            queues: Arc::new(RwLock::new(HashMap::new())),
            groups: Arc::new(RwLock::new(HashMap::new())),
            capability_index: Arc::new(RwLock::new(HashMap::new())),
            channel_size: DEFAULT_CHANNEL_SIZE,
        }
    }

    /// Create router with custom channel size
    pub fn with_channel_size(agent_id: AgentId, channel_size: usize) -> Self {
        Self {
            agent_id,
            profiles: Arc::new(RwLock::new(HashMap::new())),
            queues: Arc::new(RwLock::new(HashMap::new())),
            groups: Arc::new(RwLock::new(HashMap::new())),
            capability_index: Arc::new(RwLock::new(HashMap::new())),
            channel_size,
        }
    }

    /// Register an agent with the router
    pub async fn register_agent(&self, profile: A2aAgentProfile) -> mpsc::Receiver<A2aEnvelope> {
        let agent_id = profile.id.clone();

        // Create inbox for this agent
        let (tx, rx) = mpsc::channel(self.channel_size);

        // Update capability index
        {
            let mut cap_index = self.capability_index.write().await;
            for cap in &profile.capabilities {
                cap_index
                    .entry(cap.name.clone())
                    .or_insert_with(Vec::new)
                    .push(agent_id.clone());
            }
        }

        // Update last seen
        let mut profile = profile;
        profile.last_seen = current_timestamp();

        // Store profile and queue
        {
            let mut profiles = self.profiles.write().await;
            profiles.insert(agent_id.clone(), profile);
        }
        {
            let mut queues = self.queues.write().await;
            queues.insert(agent_id, tx);
        }

        rx
    }

    /// Unregister an agent
    pub async fn unregister_agent(&self, agent_id: &AgentId) {
        // Remove from profiles
        let profile = {
            let mut profiles = self.profiles.write().await;
            profiles.remove(agent_id)
        };

        // Remove from capability index
        if let Some(profile) = profile {
            let mut cap_index = self.capability_index.write().await;
            for cap in &profile.capabilities {
                if let Some(agents) = cap_index.get_mut(&cap.name) {
                    agents.retain(|id| id != agent_id);
                }
            }
        }

        // Remove from all groups
        {
            let mut groups = self.groups.write().await;
            for members in groups.values_mut() {
                members.retain(|id| id != agent_id);
            }
        }

        // Remove queue
        {
            let mut queues = self.queues.write().await;
            queues.remove(agent_id);
        }
    }

    /// Route a message to recipient(s)
    pub async fn route(&self, envelope: A2aEnvelope) -> Result<()> {
        // Check if message has expired
        if envelope.is_expired() {
            return Err(ZclawError::InvalidInput("Message has expired".into()));
        }

        let queues = self.queues.read().await;

        match &envelope.to {
            A2aRecipient::Direct { agent_id } => {
                // Direct message to single agent
                if let Some(tx) = queues.get(agent_id) {
                    tx.send(envelope.clone())
                        .await
                        .map_err(|e| ZclawError::Internal(format!("Failed to send message: {}", e)))?;
                } else {
                    tracing::warn!("Agent {} not found for direct message", agent_id);
                }
            }
            A2aRecipient::Group { group_id } => {
                // Message to all agents in group
                let groups = self.groups.read().await;
                if let Some(members) = groups.get(group_id) {
                    for agent_id in members {
                        if let Some(tx) = queues.get(agent_id) {
                            match tx.try_send(envelope.clone()) {
                                Ok(()) => {},
                                Err(tokio::sync::mpsc::error::TrySendError::Full(_)) => {
                                    tracing::warn!("A2A delivery to agent {} dropped: channel full", agent_id);
                                }
                                Err(tokio::sync::mpsc::error::TrySendError::Closed(_)) => {
                                    tracing::warn!("A2A delivery to agent {} dropped: channel closed", agent_id);
                                }
                            }
                        }
                    }
                }
            }
            A2aRecipient::Broadcast => {
                // Broadcast to all registered agents
                for (agent_id, tx) in queues.iter() {
                    if agent_id != &envelope.from {
                        match tx.try_send(envelope.clone()) {
                            Ok(()) => {},
                            Err(tokio::sync::mpsc::error::TrySendError::Full(_)) => {
                                tracing::warn!("A2A delivery to agent {} dropped: channel full", agent_id);
                            }
                            Err(tokio::sync::mpsc::error::TrySendError::Closed(_)) => {
                                tracing::warn!("A2A delivery to agent {} dropped: channel closed", agent_id);
                            }
                        }
                    }
                }
            }
        }

        Ok(())
    }

    /// Get router's agent ID
    pub fn agent_id(&self) -> &AgentId {
        &self.agent_id
    }

    /// Discover agents that have a specific capability
    pub async fn discover(&self, capability: &str) -> Result<Vec<A2aAgentProfile>> {
        let cap_index = self.capability_index.read().await;
        let profiles = self.profiles.read().await;

        match cap_index.get(capability) {
            Some(agent_ids) => {
                let result: Vec<A2aAgentProfile> = agent_ids.iter()
                    .filter_map(|id| profiles.get(id).cloned())
                    .collect();
                Ok(result)
            }
            None => Ok(Vec::new()),
        }
    }

    /// Add agent to a group (creates group if not exists)
    pub async fn add_to_group(&self, group_id: &str, agent_id: AgentId) {
        let mut groups = self.groups.write().await;
        let members = groups.entry(group_id.to_string()).or_insert_with(Vec::new);
        if !members.contains(&agent_id) {
            members.push(agent_id);
        }
    }

    /// Remove agent from a group
    pub async fn remove_from_group(&self, group_id: &str, agent_id: &AgentId) {
        let mut groups = self.groups.write().await;
        if let Some(members) = groups.get_mut(group_id) {
            members.retain(|id| id != agent_id);
        }
    }

    /// List all groups
    pub async fn list_groups(&self) -> Vec<String> {
        let groups = self.groups.read().await;
        groups.keys().cloned().collect()
    }

    /// Get members of a group
    pub async fn get_group_members(&self, group_id: &str) -> Vec<AgentId> {
        let groups = self.groups.read().await;
        groups.get(group_id).cloned().unwrap_or_default()
    }

    /// Get all registered agent profiles
    pub async fn list_profiles(&self) -> Vec<A2aAgentProfile> {
        let profiles = self.profiles.read().await;
        profiles.values().cloned().collect()
    }
}

/// Basic A2A client implementation
pub struct BasicA2aClient {
    /// Agent ID
    agent_id: AgentId,
    /// Shared router reference
    router: Arc<A2aRouter>,
    /// Receiver for incoming messages
    receiver: Arc<tokio::sync::Mutex<Option<mpsc::Receiver<A2aEnvelope>>>>,
}

impl BasicA2aClient {
    /// Create a new A2A client with shared router
    pub fn new(agent_id: AgentId, router: Arc<A2aRouter>) -> Self {
        Self {
            agent_id,
            router,
            receiver: Arc::new(tokio::sync::Mutex::new(None)),
        }
    }

    /// Initialize the client (register with router)
    pub async fn initialize(&self, profile: A2aAgentProfile) -> Result<()> {
        let rx = self.router.register_agent(profile).await;
        let mut receiver = self.receiver.lock().await;
        *receiver = Some(rx);
        Ok(())
    }

    /// Shutdown the client
    pub async fn shutdown(&self) {
        self.router.unregister_agent(&self.agent_id).await;
    }
}

#[async_trait]
impl A2aClient for BasicA2aClient {
    async fn send(&self, envelope: A2aEnvelope) -> Result<()> {
        tracing::debug!(
            from = %envelope.from,
            to = %envelope.to,
            type = ?envelope.message_type,
            "A2A send"
        );
        self.router.route(envelope).await
    }

    async fn recv(&self) -> Option<A2aEnvelope> {
        let mut receiver = self.receiver.lock().await;
        if let Some(ref mut rx) = *receiver {
            rx.recv().await
        } else {
            // Wait a bit and return None if no receiver
            None
        }
    }

    fn try_recv(&self) -> Result<A2aEnvelope> {
        // Use blocking lock for try_recv
        let mut receiver = self.receiver
            .try_lock()
            .map_err(|_| ZclawError::Internal("Receiver locked".into()))?;

        if let Some(ref mut rx) = *receiver {
            rx.try_recv()
                .map_err(|e| ZclawError::Internal(format!("Receive error: {}", e)))
        } else {
            Err(ZclawError::Internal("No receiver available".into()))
        }
    }

    async fn get_profile(&self, agent_id: &AgentId) -> Result<Option<A2aAgentProfile>> {
        let profiles = self.router.profiles.read().await;
        Ok(profiles.get(agent_id).cloned())
    }

    async fn discover(&self, capability: &str) -> Result<Vec<A2aAgentProfile>> {
        let cap_index = self.router.capability_index.read().await;
        let profiles = self.router.profiles.read().await;

        if let Some(agent_ids) = cap_index.get(capability) {
            let result: Vec<A2aAgentProfile> = agent_ids
                .iter()
                .filter_map(|id| profiles.get(id).cloned())
                .collect();
            Ok(result)
        } else {
            Ok(Vec::new())
        }
    }

    async fn advertise(&self, profile: A2aAgentProfile) -> Result<()> {
        tracing::info!(agent_id = %profile.id, capabilities = ?profile.capabilities.len(), "A2A advertise");
        self.router.register_agent(profile).await;
        Ok(())
    }

    async fn join_group(&self, group_id: &str) -> Result<()> {
        let mut groups = self.router.groups.write().await;
        groups
            .entry(group_id.to_string())
            .or_insert_with(Vec::new)
            .push(self.agent_id.clone());
        tracing::info!(agent_id = %self.agent_id, group = %group_id, "A2A join group");
        Ok(())
    }

    async fn leave_group(&self, group_id: &str) -> Result<()> {
        let mut groups = self.router.groups.write().await;
        if let Some(members) = groups.get_mut(group_id) {
            members.retain(|id| id != &self.agent_id);
        }
        tracing::info!(agent_id = %self.agent_id, group = %group_id, "A2A leave group");
        Ok(())
    }

    async fn get_group_members(&self, group_id: &str) -> Result<Vec<AgentId>> {
        let groups = self.router.groups.read().await;
        Ok(groups.get(group_id).cloned().unwrap_or_default())
    }

    async fn get_online_agents(&self) -> Result<Vec<A2aAgentProfile>> {
        let profiles = self.router.profiles.read().await;
        Ok(profiles.values().cloned().collect())
    }
}

// Helper functions

/// Generate a UUID v4 string using cryptographically secure random
fn uuid_v4() -> String {
    Uuid::new_v4().to_string()
}

/// Get current timestamp in milliseconds
fn current_timestamp() -> i64 {
    use std::time::{SystemTime, UNIX_EPOCH};
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap()
        .as_millis() as i64
}

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

    #[test]
    fn test_envelope_creation() {
        let from = AgentId::new();
        let to = A2aRecipient::Direct { agent_id: AgentId::new() };
        let envelope = A2aEnvelope::new(
            from,
            to,
            A2aMessageType::Request,
            serde_json::json!({"action": "test"}),
        );

        assert!(!envelope.id.is_empty());
        assert!(envelope.timestamp > 0);
        assert!(envelope.conversation_id.is_none());
    }

    #[test]
    fn test_envelope_expiry() {
        let from = AgentId::new();
        let to = A2aRecipient::Broadcast;
        let mut envelope = A2aEnvelope::new(
            from,
            to,
            A2aMessageType::Notification,
            serde_json::json!({}),
        );
        envelope.ttl = 1; // 1 second

        assert!(!envelope.is_expired());

        // After TTL should be expired (in practice, this test might be flaky)
        // We just verify the logic exists
    }

    #[test]
    fn test_recipient_display() {
        let agent_id = AgentId::new();
        let direct = A2aRecipient::Direct { agent_id };
        assert!(format!("{}", direct).starts_with("direct:"));

        let group = A2aRecipient::Group { group_id: "teachers".to_string() };
        assert_eq!(format!("{}", group), "group:teachers");

        let broadcast = A2aRecipient::Broadcast;
        assert_eq!(format!("{}", broadcast), "broadcast");
    }

    #[tokio::test]
    async fn test_router_registration() {
        let router = A2aRouter::new(AgentId::new());

        let agent_id = AgentId::new();
        let profile = A2aAgentProfile {
            id: agent_id,
            name: "Test Agent".to_string(),
            description: "A test agent".to_string(),
            capabilities: vec![A2aCapability {
                name: "test".to_string(),
                description: "Test capability".to_string(),
                input_schema: None,
                output_schema: None,
                requires_approval: false,
                version: "1.0.0".to_string(),
                tags: vec![],
            }],
            protocols: vec!["a2a".to_string()],
            role: "worker".to_string(),
            priority: 5,
            metadata: HashMap::new(),
            groups: vec![],
            last_seen: 0,
        };

        let _rx = router.register_agent(profile.clone()).await;

        // Verify registration
        let profiles = router.profiles.read().await;
        assert!(profiles.contains_key(&agent_id));
    }

    #[tokio::test]
    async fn test_capability_discovery() {
        let router = A2aRouter::new(AgentId::new());

        let agent_id = AgentId::new();
        let profile = A2aAgentProfile {
            id: agent_id,
            name: "Test Agent".to_string(),
            description: "A test agent".to_string(),
            capabilities: vec![A2aCapability {
                name: "code-generation".to_string(),
                description: "Generate code".to_string(),
                input_schema: None,
                output_schema: None,
                requires_approval: false,
                version: "1.0.0".to_string(),
                tags: vec!["coding".to_string()],
            }],
            protocols: vec!["a2a".to_string()],
            role: "worker".to_string(),
            priority: 5,
            metadata: HashMap::new(),
            groups: vec![],
            last_seen: 0,
        };

        router.register_agent(profile).await;

        // Check capability index
        let cap_index = router.capability_index.read().await;
        assert!(cap_index.contains_key("code-generation"));
    }

    #[tokio::test]
    async fn test_direct_message_delivery() {
        let router = A2aRouter::new(AgentId::new());

        // Register two agents
        let alice_id = AgentId::new();
        let bob_id = AgentId::new();

        let alice_profile = A2aAgentProfile {
            id: alice_id, name: "Alice".into(), description: String::new(),
            capabilities: vec![], protocols: vec!["a2a".into()], role: "worker".into(),
            priority: 5, metadata: HashMap::new(), groups: vec![], last_seen: 0,
        };
        let bob_profile = A2aAgentProfile {
            id: bob_id, name: "Bob".into(), description: String::new(),
            capabilities: vec![], protocols: vec!["a2a".into()], role: "worker".into(),
            priority: 5, metadata: HashMap::new(), groups: vec![], last_seen: 0,
        };

        let mut alice_rx = router.register_agent(alice_profile).await;
        let mut bob_rx = router.register_agent(bob_profile).await;

        // Alice sends direct message to Bob
        let envelope = A2aEnvelope::new(
            alice_id,
            A2aRecipient::Direct { agent_id: bob_id },
            A2aMessageType::Notification,
            serde_json::json!({"msg": "hello bob"}),
        );
        router.route(envelope).await.unwrap();

        // Bob should receive it
        let received = bob_rx.recv().await.unwrap();
        assert_eq!(received.from, alice_id);
        assert_eq!(received.payload["msg"], "hello bob");

        // Alice should NOT receive it
        assert!(alice_rx.try_recv().is_err());
    }

    #[tokio::test]
    async fn test_broadcast_delivery() {
        let router = A2aRouter::new(AgentId::new());

        let alice_id = AgentId::new();
        let bob_id = AgentId::new();
        let carol_id = AgentId::new();

        let make_profile = |id: AgentId, name: &str| A2aAgentProfile {
            id, name: name.into(), description: String::new(),
            capabilities: vec![], protocols: vec!["a2a".into()], role: "worker".into(),
            priority: 5, metadata: HashMap::new(), groups: vec![], last_seen: 0,
        };

        let mut alice_rx = router.register_agent(make_profile(alice_id, "Alice")).await;
        let mut bob_rx = router.register_agent(make_profile(bob_id, "Bob")).await;
        let mut carol_rx = router.register_agent(make_profile(carol_id, "Carol")).await;

        // Alice broadcasts
        let envelope = A2aEnvelope::new(
            alice_id,
            A2aRecipient::Broadcast,
            A2aMessageType::Notification,
            serde_json::json!({"announcement": "standup in 5"}),
        );
        router.route(envelope).await.unwrap();

        // Bob and Carol should receive, Alice should NOT (sender excluded)
        let bob_msg = bob_rx.recv().await.unwrap();
        assert_eq!(bob_msg.payload["announcement"], "standup in 5");

        let carol_msg = carol_rx.recv().await.unwrap();
        assert_eq!(carol_msg.payload["announcement"], "standup in 5");

        assert!(alice_rx.try_recv().is_err());
    }

    #[tokio::test]
    async fn test_group_message_delivery() {
        let router = A2aRouter::new(AgentId::new());

        let alice_id = AgentId::new();
        let bob_id = AgentId::new();
        let carol_id = AgentId::new();

        let make_profile = |id: AgentId, name: &str| A2aAgentProfile {
            id, name: name.into(), description: String::new(),
            capabilities: vec![], protocols: vec!["a2a".into()], role: "worker".into(),
            priority: 5, metadata: HashMap::new(), groups: vec![], last_seen: 0,
        };

        let mut alice_rx = router.register_agent(make_profile(alice_id, "Alice")).await;
        let mut bob_rx = router.register_agent(make_profile(bob_id, "Bob")).await;
        let mut carol_rx = router.register_agent(make_profile(carol_id, "Carol")).await;

        // Add Bob and Carol to "dev-team" group
        router.add_to_group("dev-team", bob_id).await;
        router.add_to_group("dev-team", carol_id).await;

        // Alice sends to group
        let envelope = A2aEnvelope::new(
            alice_id,
            A2aRecipient::Group { group_id: "dev-team".into() },
            A2aMessageType::Notification,
            serde_json::json!({"sprint": "review"}),
        );
        router.route(envelope).await.unwrap();

        // Bob and Carol should receive
        let bob_msg = bob_rx.recv().await.unwrap();
        assert_eq!(bob_msg.payload["sprint"], "review");
        let carol_msg = carol_rx.recv().await.unwrap();
        assert_eq!(carol_msg.payload["sprint"], "review");

        // Alice not in group, should NOT receive
        assert!(alice_rx.try_recv().is_err());
    }

    #[tokio::test]
    async fn test_unregister_agent() {
        let router = A2aRouter::new(AgentId::new());

        let agent_id = AgentId::new();
        let profile = A2aAgentProfile {
            id: agent_id, name: "Temp".into(), description: String::new(),
            capabilities: vec![A2aCapability {
                name: "temp-work".into(), description: "temp".into(),
                input_schema: None, output_schema: None, requires_approval: false,
                version: "1.0.0".into(), tags: vec![],
            }],
            protocols: vec!["a2a".into()], role: "worker".into(),
            priority: 5, metadata: HashMap::new(), groups: vec![], last_seen: 0,
        };

        router.register_agent(profile).await;
        assert_eq!(router.list_profiles().await.len(), 1);

        // Discover should find it
        let found = router.discover("temp-work").await.unwrap();
        assert_eq!(found.len(), 1);

        // Unregister
        router.unregister_agent(&agent_id).await;
        assert_eq!(router.list_profiles().await.len(), 0);

        // Capability index should be cleaned
        let found_after = router.discover("temp-work").await.unwrap();
        assert!(found_after.is_empty());
    }

    #[tokio::test]
    async fn test_expired_message_rejected() {
        let router = A2aRouter::new(AgentId::new());

        let alice_id = AgentId::new();
        let bob_id = AgentId::new();

        let profile = |id: AgentId| A2aAgentProfile {
            id, name: "Agent".into(), description: String::new(),
            capabilities: vec![], protocols: vec!["a2a".into()], role: "worker".into(),
            priority: 5, metadata: HashMap::new(), groups: vec![], last_seen: 0,
        };

        let _rx = router.register_agent(profile(alice_id)).await;
        let _rx = router.register_agent(profile(bob_id)).await;

        // Create envelope with already-expired TTL
        let mut envelope = A2aEnvelope::new(
            alice_id,
            A2aRecipient::Direct { agent_id: bob_id },
            A2aMessageType::Notification,
            serde_json::json!({}),
        );
        envelope.ttl = 1; // 1 second
        envelope.timestamp = 0; // Far in the past — definitely expired

        let result = router.route(envelope).await;
        assert!(result.is_err());
    }
}