use cm_dashboard_shared::AgentData;
use std::collections::HashMap;
use std::time::{Duration, Instant};
use tracing::{debug, info, warn};

use super::MetricDataPoint;

/// ZMQ communication statistics per host
#[derive(Debug, Clone)]
pub struct ZmqStats {
    pub packets_received: u64,
    pub last_packet_time: Instant,
    pub last_packet_age_secs: f64,
}

/// Central metric storage for the dashboard
pub struct MetricStore {
    /// Current structured data: hostname -> AgentData
    current_agent_data: HashMap<String, AgentData>,
    /// Historical metrics for trending
    historical_metrics: HashMap<String, Vec<MetricDataPoint>>,
    /// Last heartbeat timestamp per host
    last_heartbeat: HashMap<String, Instant>,
    /// ZMQ communication statistics per host
    zmq_stats: HashMap<String, ZmqStats>,
    /// Configuration
    max_metrics_per_host: usize,
    history_retention: Duration,
}

impl MetricStore {
    pub fn new(max_metrics_per_host: usize, history_retention_hours: u64) -> Self {
        Self {
            current_agent_data: HashMap::new(),
            historical_metrics: HashMap::new(),
            last_heartbeat: HashMap::new(),
            zmq_stats: HashMap::new(),
            max_metrics_per_host,
            history_retention: Duration::from_secs(history_retention_hours * 3600),
        }
    }


    /// Store structured agent data directly
    pub fn store_agent_data(&mut self, agent_data: AgentData) {
        let now = Instant::now();
        let hostname = agent_data.hostname.clone();

        debug!("Storing structured data for host {}", hostname);

        // Store the structured data directly
        self.current_agent_data.insert(hostname.clone(), agent_data);

        // Update heartbeat timestamp
        self.last_heartbeat.insert(hostname.clone(), now);
        debug!("Updated heartbeat for host {}", hostname);

        // Update ZMQ stats
        let stats = self.zmq_stats.entry(hostname.clone()).or_insert(ZmqStats {
            packets_received: 0,
            last_packet_time: now,
            last_packet_age_secs: 0.0,
        });
        stats.packets_received += 1;
        stats.last_packet_time = now;
        stats.last_packet_age_secs = 0.0; // Just received

        // Add to history
        let host_history = self
            .historical_metrics
            .entry(hostname.clone())
            .or_insert_with(Vec::new);
        host_history.push(MetricDataPoint { received_at: now });

        // Cleanup old data
        self.cleanup_host_data(&hostname);

        info!("Stored structured data for {}", hostname);
    }




    /// Get current structured data for a host
    pub fn get_agent_data(&self, hostname: &str) -> Option<&AgentData> {
        self.current_agent_data.get(hostname)
    }

    /// Get connected hosts (hosts with recent heartbeats)
    pub fn get_connected_hosts(&self, timeout: Duration) -> Vec<String> {
        let now = Instant::now();

        self.last_heartbeat
            .iter()
            .filter_map(|(hostname, &last_heartbeat)| {
                if now.duration_since(last_heartbeat) <= timeout {
                    Some(hostname.clone())
                } else {
                    debug!("Host {} considered offline - last heartbeat was {:?} ago", 
                           hostname, now.duration_since(last_heartbeat));
                    None
                }
            })
            .collect()
    }

    /// Clean up data for offline hosts
    pub fn cleanup_offline_hosts(&mut self, timeout: Duration) {
        let now = Instant::now();
        let mut hosts_to_cleanup = Vec::new();

        // Find hosts that are offline (no recent heartbeat)
        for (hostname, &last_heartbeat) in &self.last_heartbeat {
            if now.duration_since(last_heartbeat) > timeout {
                hosts_to_cleanup.push(hostname.clone());
            }
        }

        // Clear data for offline hosts
        for hostname in hosts_to_cleanup {
            if let Some(_agent_data) = self.current_agent_data.remove(&hostname) {
                info!("Cleared structured data for offline host: {}", hostname);
            }
            // Keep heartbeat timestamp for reconnection detection
            // Don't remove from last_heartbeat to track when host was last seen
        }
    }

    /// Cleanup old data and enforce limits
    fn cleanup_host_data(&mut self, hostname: &str) {
        let now = Instant::now();

        // Cleanup historical data
        if let Some(history) = self.historical_metrics.get_mut(hostname) {
            // Remove old entries
            history.retain(|dp| now.duration_since(dp.received_at) <= self.history_retention);

            // Enforce size limit
            if history.len() > self.max_metrics_per_host {
                let excess = history.len() - self.max_metrics_per_host;
                history.drain(0..excess);
                warn!(
                    "Trimmed {} old metrics for host {} (size limit: {})",
                    excess, hostname, self.max_metrics_per_host
                );
            }
        }
    }

    /// Get agent versions from all hosts for cross-host comparison
    pub fn get_agent_versions(&self) -> HashMap<String, String> {
        let mut versions = HashMap::new();
        
        for (hostname, agent_data) in &self.current_agent_data {
            versions.insert(hostname.clone(), agent_data.agent_version.clone());
        }
        
        versions
    }

    /// Check for agent version mismatches across hosts
    pub fn get_version_mismatches(&self) -> Option<(String, Vec<String>)> {
        let versions = self.get_agent_versions();
        
        if versions.len() < 2 {
            return None; // Need at least 2 hosts to compare
        }
        
        // Find the most common version (assume it's the "current" version)
        let mut version_counts = HashMap::new();
        for version in versions.values() {
            *version_counts.entry(version.clone()).or_insert(0) += 1;
        }
        
        let most_common_version = version_counts
            .iter()
            .max_by_key(|(_, count)| *count)
            .map(|(version, _)| version.clone())?;
        
        // Find hosts with different versions
        let outdated_hosts: Vec<String> = versions
            .iter()
            .filter(|(_, version)| *version != &most_common_version)
            .map(|(hostname, _)| hostname.clone())
            .collect();
        
        if outdated_hosts.is_empty() {
            None
        } else {
            Some((most_common_version, outdated_hosts))
        }
    }
}