use crate::arn::TargetID;
use crate::store::{Key, Store};
use crate::{
    Event, StoreError, Target, error::NotificationError, notifier::EventNotifier, registry::TargetRegistry,
    rules::BucketNotificationConfig, stream,
};
use ecstore::config::{Config, KVS};
use std::collections::HashMap;
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::time::{Duration, Instant};
use tokio::sync::{RwLock, Semaphore, mpsc};
use tracing::{debug, error, info, warn};

/// Notify the system of monitoring indicators
pub struct NotificationMetrics {
    /// The number of events currently being processed
    processing_events: AtomicUsize,
    /// Number of events that have been successfully processed
    processed_events: AtomicUsize,
    /// Number of events that failed to handle
    failed_events: AtomicUsize,
    /// System startup time
    start_time: Instant,
}

impl Default for NotificationMetrics {
    fn default() -> Self {
        Self::new()
    }
}

impl NotificationMetrics {
    pub fn new() -> Self {
        NotificationMetrics {
            processing_events: AtomicUsize::new(0),
            processed_events: AtomicUsize::new(0),
            failed_events: AtomicUsize::new(0),
            start_time: Instant::now(),
        }
    }

    // Provide public methods to increase count
    pub fn increment_processing(&self) {
        self.processing_events.fetch_add(1, Ordering::Relaxed);
    }

    pub fn increment_processed(&self) {
        self.processing_events.fetch_sub(1, Ordering::Relaxed);
        self.processed_events.fetch_add(1, Ordering::Relaxed);
    }

    pub fn increment_failed(&self) {
        self.processing_events.fetch_sub(1, Ordering::Relaxed);
        self.failed_events.fetch_add(1, Ordering::Relaxed);
    }

    // Provide public methods to get count
    pub fn processing_count(&self) -> usize {
        self.processing_events.load(Ordering::Relaxed)
    }

    pub fn processed_count(&self) -> usize {
        self.processed_events.load(Ordering::Relaxed)
    }

    pub fn failed_count(&self) -> usize {
        self.failed_events.load(Ordering::Relaxed)
    }

    pub fn uptime(&self) -> Duration {
        self.start_time.elapsed()
    }
}

/// The notification system that integrates all components
pub struct NotificationSystem {
    /// The event notifier
    pub notifier: Arc<EventNotifier>,
    /// The target registry
    pub registry: Arc<TargetRegistry>,
    /// The current configuration
    pub config: Arc<RwLock<Config>>,
    /// Cancel sender for managing stream processing tasks
    stream_cancellers: Arc<RwLock<HashMap<TargetID, mpsc::Sender<()>>>>,
    /// Concurrent control signal quantity
    concurrency_limiter: Arc<Semaphore>,
    /// Monitoring indicators
    metrics: Arc<NotificationMetrics>,
}

impl NotificationSystem {
    /// Creates a new NotificationSystem
    pub fn new(config: Config) -> Self {
        NotificationSystem {
            notifier: Arc::new(EventNotifier::new()),
            registry: Arc::new(TargetRegistry::new()),
            config: Arc::new(RwLock::new(config)),
            stream_cancellers: Arc::new(RwLock::new(HashMap::new())),
            concurrency_limiter: Arc::new(Semaphore::new(
                std::env::var("RUSTFS_TARGET_STREAM_CONCURRENCY")
                    .ok()
                    .and_then(|s| s.parse().ok())
                    .unwrap_or(20),
            )), // Limit the maximum number of concurrent processing events to 20
            metrics: Arc::new(NotificationMetrics::new()),
        }
    }

    /// Initializes the notification system
    pub async fn init(&self) -> Result<(), NotificationError> {
        info!("Initialize notification system...");

        let config = self.config.read().await;
        debug!("Initializing notification system with config: {:?}", *config);
        let targets: Vec<Box<dyn Target + Send + Sync>> = self.registry.create_targets_from_config(&config).await?;

        info!("{} notification targets were created", targets.len());

        // Initiate event stream processing for each storage enabled target
        let mut cancellers = HashMap::new();
        for target in &targets {
            let target_id = target.id();
            info!("Initializing target: {}", target.id());
            // Initialize the target
            if let Err(e) = target.init().await {
                error!("Target {} Initialization failed:{}", target.id(), e);
                continue;
            }
            debug!("Target {} initialized successfully,enabled:{}", target_id, target.is_enabled());
            // Check if the target is enabled and has storage
            if target.is_enabled() {
                if let Some(store) = target.store() {
                    info!("Start event stream processing for target {}", target.id());

                    // The storage of the cloned target and the target itself
                    let store_clone = store.boxed_clone();
                    let target_box = target.clone_dyn();
                    let target_arc = Arc::from(target_box);

                    // Add a reference to the monitoring metrics
                    let metrics = self.metrics.clone();
                    let semaphore = self.concurrency_limiter.clone();

                    // Encapsulated enhanced version of start_event_stream
                    let cancel_tx = self.enhanced_start_event_stream(store_clone, target_arc, metrics, semaphore);

                    // Start event stream processing and save cancel sender
                    let target_id_clone = target_id.clone();
                    cancellers.insert(target_id, cancel_tx);
                    info!("Event stream processing for target {} is started successfully", target_id_clone);
                } else {
                    info!("Target {} No storage is configured, event stream processing is skipped", target_id);
                }
            } else {
                info!("Target {} is not enabled, event stream processing is skipped", target_id);
            }
        }

        // Update canceler collection
        *self.stream_cancellers.write().await = cancellers;
        // Initialize the bucket target
        self.notifier.init_bucket_targets(targets).await?;
        info!("Notification system initialized");
        Ok(())
    }

    /// Gets a list of Targets for all currently active (initialized).
    ///
    /// # Return
    /// A Vec containing all active Targets `TargetID`.
    pub async fn get_active_targets(&self) -> Vec<TargetID> {
        self.notifier.target_list().read().await.keys()
    }

    /// Accurately remove a Target and its related resources through TargetID.
    ///
    /// This process includes:
    /// 1. Stop the event stream associated with the Target (if present).
    /// 2. Remove the Target instance from the activity list of Notifier.
    /// 3. Remove the configuration item of the Target from the system configuration.
    ///
    /// # Parameters
    /// * `target_id` - The unique identifier of the Target to be removed.
    ///
    /// # return
    /// If successful, return `Ok(())`.
    pub async fn remove_target(&self, target_id: &TargetID, target_type: &str) -> Result<(), NotificationError> {
        info!("Attempting to remove target: {}", target_id);

        let Some(store) = ecstore::global::new_object_layer_fn() else {
            return Err(NotificationError::Io(std::io::Error::other("errServerNotInitialized")));
        };

        let mut new_config = ecstore::config::com::read_config_without_migrate(store.clone())
            .await
            .map_err(|e| NotificationError::Configuration(format!("Failed to read notification config: {}", e)))?;

        let mut changed = false;
        if let Some(targets_of_type) = new_config.0.get_mut(target_type) {
            if targets_of_type.remove(&target_id.name).is_some() {
                info!("Removed target {} from the configuration.", target_id);
                changed = true;
            }
            if targets_of_type.is_empty() {
                new_config.0.remove(target_type);
            }
        }

        if !changed {
            warn!("Target {} was not found in the configuration.", target_id);
            return Ok(());
        }

        if let Err(e) = ecstore::config::com::save_server_config(store, &new_config).await {
            error!("Failed to save config for target removal: {}", e);
            return Err(NotificationError::Configuration(format!("Failed to save config: {}", e)));
        }

        info!(
            "Configuration updated and persisted for target {} removal. Reloading system...",
            target_id
        );
        self.reload_config(new_config).await
    }

    /// Set or update a Target configuration.
    /// If the configuration is changed, the entire notification system will be automatically reloaded to apply the changes.
    ///
    /// # Arguments
    /// * `target_type` - Target type, such as "notify_webhook" or "notify_mqtt".
    /// * `target_name` - A unique name for a Target, such as "1".
    /// * `kvs` - The full configuration of the Target.
    ///
    /// # Returns
    /// Result<(), NotificationError>
    /// If the target configuration is successfully set, it returns Ok(()).
    /// If the target configuration is invalid, it returns Err(NotificationError::Configuration).
    pub async fn set_target_config(&self, target_type: &str, target_name: &str, kvs: KVS) -> Result<(), NotificationError> {
        info!("Setting config for target {} of type {}", target_name, target_type);
        // 1. Get the storage handle
        let Some(store) = ecstore::global::new_object_layer_fn() else {
            return Err(NotificationError::Io(std::io::Error::other("errServerNotInitialized")));
        };

        // 2. Read the latest configuration from storage
        let mut new_config = ecstore::config::com::read_config_without_migrate(store.clone())
            .await
            .map_err(|e| NotificationError::Configuration(format!("Failed to read notification config: {}", e)))?;

        // 3. Modify the configuration copy
        new_config
            .0
            .entry(target_type.to_string())
            .or_default()
            .insert(target_name.to_string(), kvs);

        // 4. Persist the new configuration
        if let Err(e) = ecstore::config::com::save_server_config(store, &new_config).await {
            error!("Failed to save notification config: {}", e);
            return Err(NotificationError::Configuration(format!("Failed to save notification config: {}", e)));
        }

        // 5. After the persistence is successful, the system will be reloaded to apply changes.
        match self.reload_config(new_config).await {
            Ok(_) => {
                info!(
                    "Target {} of type {} configuration updated and reloaded successfully",
                    target_name, target_type
                );
                Ok(())
            }
            Err(e) => {
                error!("Failed to reload config for target {} of type {}: {}", target_name, target_type, e);
                Err(NotificationError::Configuration(format!(
                    "Configuration saved, but failed to reload: {}",
                    e
                )))
            }
        }
    }

    /// Removes all notification configurations for a bucket.
    pub async fn remove_bucket_notification_config(&self, bucket_name: &str) {
        self.notifier.remove_rules_map(bucket_name).await;
    }

    /// Removes a Target configuration.
    /// If the configuration is successfully removed, the entire notification system will be automatically reloaded.
    ///
    /// # Arguments
    /// * `target_type` - Target type, such as "notify_webhook" or "notify_mqtt".
    /// * `target_name` - A unique name for a Target, such as "1".
    ///
    /// # Returns
    /// Result<(), NotificationError>
    ///
    /// If the target configuration is successfully removed, it returns Ok(()).
    /// If the target configuration does not exist, it returns Ok(()) without making any changes.
    pub async fn remove_target_config(&self, target_type: &str, target_name: &str) -> Result<(), NotificationError> {
        info!("Removing config for target {} of type {}", target_name, target_type);
        let Some(store) = ecstore::global::new_object_layer_fn() else {
            return Err(NotificationError::Io(std::io::Error::other("errServerNotInitialized")));
        };

        let mut new_config = ecstore::config::com::read_config_without_migrate(store.clone())
            .await
            .map_err(|e| NotificationError::Configuration(format!("Failed to read notification config: {}", e)))?;

        let mut changed = false;
        if let Some(targets) = new_config.0.get_mut(target_type) {
            if targets.remove(target_name).is_some() {
                changed = true;
            }
            if targets.is_empty() {
                new_config.0.remove(target_type);
            }
        }

        if !changed {
            info!("Target {} of type {} not found, no changes made.", target_name, target_type);
            return Ok(());
        }

        if let Err(e) = ecstore::config::com::save_server_config(store, &new_config).await {
            error!("Failed to save config for target removal: {}", e);
            return Err(NotificationError::Configuration(format!("Failed to save config: {}", e)));
        }

        info!(
            "Configuration updated and persisted for target {} removal. Reloading system...",
            target_name
        );
        self.reload_config(new_config).await
    }

    /// Enhanced event stream startup function, including monitoring and concurrency control
    fn enhanced_start_event_stream(
        &self,
        store: Box<dyn Store<Event, Error = StoreError, Key = Key> + Send>,
        target: Arc<dyn Target + Send + Sync>,
        metrics: Arc<NotificationMetrics>,
        semaphore: Arc<Semaphore>,
    ) -> mpsc::Sender<()> {
        // Event Stream Processing Using Batch Version
        stream::start_event_stream_with_batching(store, target, metrics, semaphore)
    }

    /// Reloads the configuration
    pub async fn reload_config(&self, new_config: Config) -> Result<(), NotificationError> {
        info!("Reload notification configuration starts");

        // Stop all existing streaming services
        let mut cancellers = self.stream_cancellers.write().await;
        for (target_id, cancel_tx) in cancellers.drain() {
            info!("Stop event stream processing for target {}", target_id);
            let _ = cancel_tx.send(()).await;
        }

        // Update the config
        {
            let mut config = self.config.write().await;
            *config = new_config.clone();
        }

        // Create a new target from configuration
        let targets: Vec<Box<dyn Target + Send + Sync>> = self
            .registry
            .create_targets_from_config(&new_config)
            .await
            .map_err(NotificationError::Target)?;

        info!("{} notification targets were created from the new configuration", targets.len());

        // Start new event stream processing for each storage enabled target
        let mut new_cancellers = HashMap::new();
        for target in &targets {
            let target_id = target.id();

            // Initialize the target
            if let Err(e) = target.init().await {
                error!("Target {} Initialization failed:{}", target_id, e);
                continue;
            }
            // Check if the target is enabled and has storage
            if target.is_enabled() {
                if let Some(store) = target.store() {
                    info!("Start new event stream processing for target {}", target_id);

                    // The storage of the cloned target and the target itself
                    let store_clone = store.boxed_clone();
                    let target_box = target.clone_dyn();
                    let target_arc = Arc::from(target_box);

                    // Add a reference to the monitoring metrics
                    let metrics = self.metrics.clone();
                    let semaphore = self.concurrency_limiter.clone();

                    // Encapsulated enhanced version of start_event_stream
                    let cancel_tx = self.enhanced_start_event_stream(store_clone, target_arc, metrics, semaphore);

                    // Start event stream processing and save cancel sender
                    // let cancel_tx = start_event_stream(store_clone, target_clone);
                    let target_id_clone = target_id.clone();
                    new_cancellers.insert(target_id, cancel_tx);
                    info!("Event stream processing of target {} is restarted successfully", target_id_clone);
                } else {
                    info!("Target {} No storage is configured, event stream processing is skipped", target_id);
                }
            } else {
                info!("Target {} disabled, event stream processing is skipped", target_id);
            }
        }

        // Update canceler collection
        *cancellers = new_cancellers;

        // Initialize the bucket target
        self.notifier.init_bucket_targets(targets).await?;
        info!("Configuration reloaded end");
        Ok(())
    }

    /// Loads the bucket notification configuration
    pub async fn load_bucket_notification_config(
        &self,
        bucket_name: &str,
        config: &BucketNotificationConfig,
    ) -> Result<(), NotificationError> {
        let arn_list = self.notifier.get_arn_list(&config.region).await;
        if arn_list.is_empty() {
            return Err(NotificationError::Configuration("No targets configured".to_string()));
        }
        info!("Available ARNs: {:?}", arn_list);
        // Validate the configuration against the available ARNs
        if let Err(e) = config.validate(&config.region, &arn_list) {
            debug!("Bucket notification config validation region:{} failed: {}", &config.region, e);
            if !e.to_string().contains("ARN not found") {
                return Err(NotificationError::BucketNotification(e.to_string()));
            } else {
                error!("{}", e);
            }
        }

        // let rules_map = config.to_rules_map();
        let rules_map = config.get_rules_map();
        self.notifier.add_rules_map(bucket_name, rules_map.clone()).await;
        info!("Loaded notification config for bucket: {}", bucket_name);
        Ok(())
    }

    /// Sends an event
    pub async fn send_event(&self, bucket_name: &str, event_name: &str, object_key: &str, event: Event) {
        self.notifier.send(bucket_name, event_name, object_key, event).await;
    }

    /// Obtain system status information
    pub fn get_status(&self) -> HashMap<String, String> {
        let mut status = HashMap::new();

        status.insert("uptime_seconds".to_string(), self.metrics.uptime().as_secs().to_string());
        status.insert("processing_events".to_string(), self.metrics.processing_count().to_string());
        status.insert("processed_events".to_string(), self.metrics.processed_count().to_string());
        status.insert("failed_events".to_string(), self.metrics.failed_count().to_string());

        status
    }

    // Add a method to shut down the system
    pub async fn shutdown(&self) {
        info!("Turn off the notification system");

        // Get the number of active targets
        let active_targets = self.stream_cancellers.read().await.len();
        info!("Stops {} active event stream processing tasks", active_targets);

        let mut cancellers = self.stream_cancellers.write().await;
        for (target_id, cancel_tx) in cancellers.drain() {
            info!("Stop event stream processing for target {}", target_id);
            let _ = cancel_tx.send(()).await;
        }
        // Wait for a short while to make sure the task has a chance to complete
        tokio::time::sleep(Duration::from_millis(500)).await;

        info!("Notify the system to be shut down completed");
    }
}

impl Drop for NotificationSystem {
    fn drop(&mut self) {
        // Asynchronous operation cannot be used here, but logs can be recorded.
        info!("Notify the system instance to be destroyed");
        let status = self.get_status();
        for (key, value) in status {
            info!("key:{}, value:{}", key, value);
        }

        info!("Notification system status at shutdown:");
    }
}

/// Loads configuration from a file
pub async fn load_config_from_file(path: &str, system: &NotificationSystem) -> Result<(), NotificationError> {
    let config_data = tokio::fs::read(path)
        .await
        .map_err(|e| NotificationError::Configuration(format!("Failed to read config file: {}", e)))?;

    let config = Config::unmarshal(config_data.as_slice())
        .map_err(|e| NotificationError::Configuration(format!("Failed to parse config: {}", e)))?;
    system.reload_config(config).await
}