use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::collections::HashSet;
use std::fs;
use std::path::Path;
use std::sync::{Arc, Mutex, OnceLock};
use tracing::{debug, info, warn};

/// Shared instance for global access
static GLOBAL_TRACKER: OnceLock<Arc<Mutex<UserStoppedServiceTracker>>> = OnceLock::new();

/// Tracks services that have been stopped by user action
/// These services should be treated as OK status instead of Warning
#[derive(Debug)]
pub struct UserStoppedServiceTracker {
    /// Set of services stopped by user action
    user_stopped_services: HashSet<String>,
    /// Path to persistent storage file
    storage_path: String,
}

/// Serializable data structure for persistence
#[derive(Debug, Serialize, Deserialize)]
struct UserStoppedData {
    services: Vec<String>,
}

impl UserStoppedServiceTracker {
    /// Create new tracker with default storage path
    pub fn new() -> Self {
        Self::with_storage_path("/var/lib/cm-dashboard/user-stopped-services.json")
    }

    /// Initialize global instance (called by agent)
    pub fn init_global() -> Result<Self> {
        let tracker = Self::new();
        
        // Set global instance
        let global_instance = Arc::new(Mutex::new(tracker));
        if GLOBAL_TRACKER.set(global_instance).is_err() {
            warn!("Global service tracker was already initialized");
        }
        
        // Return a new instance for the agent to use
        Ok(Self::new())
    }

    /// Check if a service is user-stopped (global access for collectors)
    pub fn is_service_user_stopped(service_name: &str) -> bool {
        if let Some(global) = GLOBAL_TRACKER.get() {
            if let Ok(tracker) = global.lock() {
                tracker.is_user_stopped(service_name)
            } else {
                debug!("Failed to lock global service tracker");
                false
            }
        } else {
            debug!("Global service tracker not initialized");
            false
        }
    }

    /// Update global tracker (called by agent when tracker state changes)
    pub fn update_global(updated_tracker: &UserStoppedServiceTracker) {
        if let Some(global) = GLOBAL_TRACKER.get() {
            if let Ok(mut tracker) = global.lock() {
                tracker.user_stopped_services = updated_tracker.user_stopped_services.clone();
            } else {
                debug!("Failed to lock global service tracker for update");
            }
        } else {
            debug!("Global service tracker not initialized for update");
        }
    }

    /// Create new tracker with custom storage path
    pub fn with_storage_path<P: AsRef<Path>>(storage_path: P) -> Self {
        let storage_path = storage_path.as_ref().to_string_lossy().to_string();
        let mut tracker = Self {
            user_stopped_services: HashSet::new(),
            storage_path,
        };

        // Load existing data from storage
        if let Err(e) = tracker.load_from_storage() {
            warn!("Failed to load user-stopped services from storage: {}", e);
            info!("Starting with empty user-stopped services list");
        }

        tracker
    }


    /// Clear user-stopped flag for a service (when user starts it)
    pub fn clear_user_stopped(&mut self, service_name: &str) -> Result<()> {
        if self.user_stopped_services.remove(service_name) {
            info!("Cleared user-stopped flag for service '{}'", service_name);
            self.save_to_storage()?;
            debug!("Service '{}' user-stopped flag cleared and saved to storage", service_name);
        } else {
            debug!("Service '{}' was not marked as user-stopped", service_name);
        }
        Ok(())
    }

    /// Check if a service is marked as user-stopped
    pub fn is_user_stopped(&self, service_name: &str) -> bool {
        let is_stopped = self.user_stopped_services.contains(service_name);
        debug!("Service '{}' user-stopped status: {}", service_name, is_stopped);
        is_stopped
    }


    /// Save current state to persistent storage
    fn save_to_storage(&self) -> Result<()> {
        // Create parent directory if it doesn't exist
        if let Some(parent_dir) = Path::new(&self.storage_path).parent() {
            if !parent_dir.exists() {
                fs::create_dir_all(parent_dir)?;
                debug!("Created parent directory: {}", parent_dir.display());
            }
        }

        let data = UserStoppedData {
            services: self.user_stopped_services.iter().cloned().collect(),
        };

        let json_data = serde_json::to_string_pretty(&data)?;
        fs::write(&self.storage_path, json_data)?;

        debug!(
            "Saved {} user-stopped services to {}",
            data.services.len(),
            self.storage_path
        );
        Ok(())
    }

    /// Load state from persistent storage
    fn load_from_storage(&mut self) -> Result<()> {
        if !Path::new(&self.storage_path).exists() {
            debug!("Storage file {} does not exist, starting fresh", self.storage_path);
            return Ok(());
        }

        let json_data = fs::read_to_string(&self.storage_path)?;
        let data: UserStoppedData = serde_json::from_str(&json_data)?;

        self.user_stopped_services = data.services.into_iter().collect();

        info!(
            "Loaded {} user-stopped services from {}",
            self.user_stopped_services.len(),
            self.storage_path
        );

        if !self.user_stopped_services.is_empty() {
            debug!("User-stopped services: {:?}", self.user_stopped_services);
        }

        Ok(())
    }
}