cm-dashboard/agent/src/cache/mod.rs

use cm_dashboard_shared::{CacheConfig, Metric};
use std::collections::HashMap;
use std::fs;
use std::path::Path;
use std::sync::Arc;
use tokio::sync::RwLock;
use tracing::{info, warn, error};

/// Simple persistent cache for metrics
pub struct SimpleCache {
    metrics: RwLock<HashMap<String, Metric>>,
    persist_path: String,
}

impl SimpleCache {
    pub fn new(config: CacheConfig) -> Self {
        let cache = Self {
            metrics: RwLock::new(HashMap::new()),
            persist_path: config.persist_path,
        };
        
        // Clear cache file on startup to ensure fresh data
        cache.clear_cache_file();
        cache
    }

    /// Store metric in cache
    pub async fn store_metric(&self, metric: Metric) {
        let mut metrics = self.metrics.write().await;
        metrics.insert(metric.name.clone(), metric);
    }

    /// Get all cached metrics
    pub async fn get_all_cached_metrics(&self) -> Vec<Metric> {
        let metrics = self.metrics.read().await;
        metrics.values().cloned().collect()
    }

    /// Save cache to disk
    pub async fn save_to_disk(&self) {
        let metrics = self.metrics.read().await;
        
        // Create directory if needed
        if let Some(parent) = Path::new(&self.persist_path).parent() {
            if let Err(e) = fs::create_dir_all(parent) {
                warn!("Failed to create cache directory {}: {}", parent.display(), e);
                return;
            }
        }

        // Serialize and save
        match serde_json::to_string_pretty(&*metrics) {
            Ok(json) => {
                if let Err(e) = fs::write(&self.persist_path, json) {
                    error!("Failed to save cache to {}: {}", self.persist_path, e);
                }
            }
            Err(e) => {
                error!("Failed to serialize cache: {}", e);
            }
        }
    }

    /// Load cache from disk
    fn load_from_disk(&self) {
        match fs::read_to_string(&self.persist_path) {
            Ok(content) => {
                match serde_json::from_str::<HashMap<String, Metric>>(&content) {
                    Ok(loaded_metrics) => {
                        if let Ok(mut metrics) = self.metrics.try_write() {
                            *metrics = loaded_metrics;
                            info!("Loaded {} metrics from cache", metrics.len());
                        }
                    }
                    Err(e) => {
                        warn!("Failed to parse cache file {}: {}", self.persist_path, e);
                    }
                }
            }
            Err(_) => {
                info!("No cache file found at {}, starting fresh", self.persist_path);
            }
        }
    }

    /// Clear cache file on startup to ensure fresh data
    fn clear_cache_file(&self) {
        if Path::new(&self.persist_path).exists() {
            match fs::remove_file(&self.persist_path) {
                Ok(_) => info!("Cleared cache file {} on startup", self.persist_path),
                Err(e) => warn!("Failed to clear cache file {}: {}", self.persist_path, e),
            }
        }
    }
}


#[derive(Clone)]
pub struct MetricCacheManager {
    cache: Arc<SimpleCache>,
}

impl MetricCacheManager {
    pub fn new(config: CacheConfig) -> Self {
        Self {
            cache: Arc::new(SimpleCache::new(config)),
        }
    }

    pub async fn store_metric(&self, metric: Metric) {
        self.cache.store_metric(metric).await;
    }

    pub async fn cache_metric(&self, metric: Metric) {
        self.store_metric(metric).await;
    }

    pub async fn start_background_tasks(&self) {
        // No background tasks needed for simple cache
    }

    pub async fn get_all_cached_metrics(&self) -> Result<Vec<Metric>, anyhow::Error> {
        Ok(self.cache.get_all_cached_metrics().await)
    }

    pub async fn save_to_disk(&self) {
        self.cache.save_to_disk().await;
    }
}