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

use super::MetricDataPoint;

/// Central metric storage for the dashboard
pub struct MetricStore {
    /// Current metrics: hostname -> metric_name -> metric
    current_metrics: HashMap<String, HashMap<String, Metric>>,
    /// Historical metrics for trending
    historical_metrics: HashMap<String, Vec<MetricDataPoint>>,
    /// Last update timestamp per host
    last_update: HashMap<String, Instant>,
    /// 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_metrics: HashMap::new(),
            historical_metrics: HashMap::new(),
            last_update: HashMap::new(),
            max_metrics_per_host,
            history_retention: Duration::from_secs(history_retention_hours * 3600),
        }
    }

    /// Update metrics for a specific host
    pub fn update_metrics(&mut self, hostname: &str, metrics: Vec<Metric>) {
        let now = Instant::now();

        debug!("Updating {} metrics for host {}", metrics.len(), hostname);

        // Get or create host entry
        let host_metrics = self
            .current_metrics
            .entry(hostname.to_string())
            .or_insert_with(HashMap::new);

        // Get or create historical entry
        let host_history = self
            .historical_metrics
            .entry(hostname.to_string())
            .or_insert_with(Vec::new);

        // Update current metrics and add to history
        for metric in metrics {
            let metric_name = metric.name.clone();

            // Store current metric
            host_metrics.insert(metric_name.clone(), metric.clone());

            // Add to history
            host_history.push(MetricDataPoint { received_at: now });
        }

        // Update last update timestamp
        self.last_update.insert(hostname.to_string(), now);

        // Get metrics count before cleanup
        let metrics_count = host_metrics.len();

        // Cleanup old history and enforce limits
        self.cleanup_host_data(hostname);

        info!(
            "Updated metrics for {}: {} current metrics",
            hostname, metrics_count
        );
    }

    /// Get current metric for a specific host
    pub fn get_metric(&self, hostname: &str, metric_name: &str) -> Option<&Metric> {
        self.current_metrics.get(hostname)?.get(metric_name)
    }


    /// Get all current metrics for a host as a vector
    pub fn get_metrics_for_host(&self, hostname: &str) -> Vec<&Metric> {
        if let Some(metrics_map) = self.current_metrics.get(hostname) {
            metrics_map.values().collect()
        } else {
            Vec::new()
        }
    }

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

        self.last_update
            .iter()
            .filter_map(|(hostname, &last_update)| {
                if now.duration_since(last_update) <= timeout {
                    Some(hostname.clone())
                } else {
                    None
                }
            })
            .collect()
    }

    /// 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, metrics) in &self.current_metrics {
            if let Some(version_metric) = metrics.get("agent_version") {
                if let cm_dashboard_shared::MetricValue::String(version) = &version_metric.value {
                    versions.insert(hostname.clone(), 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))
        }
    }
}