oxirs-stream 0.2.4

//! # Enhanced GraphQL Subscription System
//!
//! Advanced GraphQL subscription features for real-time RDF stream updates:
//! - Window-based subscriptions
//! - Advanced filtering and pattern matching
//! - Subscription lifecycle management
//! - Subscription groups and namespaces
//! - Connection pooling and resilience

use anyhow::{anyhow, Result};
use chrono::{DateTime, Duration as ChronoDuration, Utc};
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, HashSet, VecDeque};
use std::sync::Arc;
use std::time::Duration;
use tokio::sync::{broadcast, RwLock};
use tokio::time::interval;
use tracing::{debug, info};

use crate::StreamEvent;

/// Enhanced GraphQL subscription manager
pub struct GraphQLSubscriptionManager {
    /// Active subscriptions
    subscriptions: Arc<RwLock<HashMap<String, EnhancedSubscription>>>,
    /// Subscription groups
    groups: Arc<RwLock<HashMap<String, SubscriptionGroup>>>,
    /// Window buffers
    windows: Arc<RwLock<HashMap<String, SubscriptionWindow>>>,
    /// Event broadcaster
    event_tx: broadcast::Sender<SubscriptionEvent>,
    /// Configuration
    config: SubscriptionConfig,
    /// Statistics
    stats: Arc<RwLock<SubscriptionStats>>,
}

/// Subscription configuration
#[derive(Debug, Clone)]
pub struct SubscriptionConfig {
    /// Maximum concurrent subscriptions
    pub max_subscriptions: usize,
    /// Maximum subscriptions per client
    pub max_subscriptions_per_client: usize,
    /// Default window size
    pub default_window_size: Duration,
    /// Enable windowing
    pub enable_windowing: bool,
    /// Enable advanced filtering
    pub enable_advanced_filtering: bool,
    /// Heartbeat interval
    pub heartbeat_interval: Duration,
    /// Subscription timeout
    pub subscription_timeout: Duration,
}

impl Default for SubscriptionConfig {
    fn default() -> Self {
        Self {
            max_subscriptions: 10000,
            max_subscriptions_per_client: 100,
            default_window_size: Duration::from_secs(60),
            enable_windowing: true,
            enable_advanced_filtering: true,
            heartbeat_interval: Duration::from_secs(30),
            subscription_timeout: Duration::from_secs(300),
        }
    }
}

/// Enhanced subscription with lifecycle management
#[derive(Debug, Clone)]
pub struct EnhancedSubscription {
    /// Subscription identifier
    pub id: String,
    /// Client identifier
    pub client_id: String,
    /// GraphQL query
    pub query: String,
    /// Variables
    pub variables: HashMap<String, serde_json::Value>,
    /// Advanced filters
    pub filters: Vec<AdvancedFilter>,
    /// Window specification
    pub window: Option<WindowSpec>,
    /// Lifecycle state
    pub state: SubscriptionState,
    /// Metadata
    pub metadata: SubscriptionMetadata,
    /// Statistics
    pub stats: SubscriptionStatistics,
}

/// Subscription lifecycle state
#[derive(Debug, Clone, PartialEq)]
pub enum SubscriptionState {
    /// Subscription is active
    Active,
    /// Subscription is paused (buffering updates)
    Paused,
    /// Subscription is in reconnection mode
    Reconnecting {
        attempts: u32,
        next_retry: DateTime<Utc>,
    },
    /// Subscription is throttled
    Throttled { until: DateTime<Utc> },
    /// Subscription is terminated
    Terminated {
        reason: String,
        timestamp: DateTime<Utc>,
    },
}

/// Advanced filtering options
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AdvancedFilter {
    /// Time-based filter
    TimeRange {
        start: Option<DateTime<Utc>>,
        end: Option<DateTime<Utc>>,
    },
    /// Value-based filter
    ValueFilter {
        field: String,
        operator: FilterOperator,
        value: serde_json::Value,
    },
    /// Pattern matching filter
    PatternMatch {
        field: String,
        pattern: String,
        case_sensitive: bool,
    },
    /// Geospatial filter
    GeoFilter {
        latitude: f64,
        longitude: f64,
        radius_km: f64,
    },
    /// Semantic filter (RDF-specific)
    SemanticFilter {
        subject_pattern: Option<String>,
        predicate_pattern: Option<String>,
        object_pattern: Option<String>,
    },
    /// Aggregation filter
    AggregationFilter {
        function: AggregationFunction,
        threshold: f64,
    },
    /// Composite filter
    CompositeFilter {
        operator: LogicalOperator,
        filters: Vec<Box<AdvancedFilter>>,
    },
}

/// Filter operators
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub enum FilterOperator {
    Equal,
    NotEqual,
    LessThan,
    LessThanOrEqual,
    GreaterThan,
    GreaterThanOrEqual,
    Contains,
    StartsWith,
    EndsWith,
    In,
    NotIn,
}

/// Aggregation functions for filtering
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub enum AggregationFunction {
    Count,
    Sum,
    Average,
    Min,
    Max,
    StdDev,
}

/// Logical operators for composite filters
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub enum LogicalOperator {
    And,
    Or,
    Not,
    Xor,
}

/// Window specification for subscriptions
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct WindowSpec {
    /// Window type
    pub window_type: WindowType,
    /// Size (time or count)
    pub size: WindowSize,
    /// Slide interval (for sliding windows)
    pub slide: Option<WindowSize>,
    /// Trigger conditions
    pub triggers: Vec<WindowTrigger>,
}

/// Window types
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub enum WindowType {
    Tumbling,
    Sliding,
    Session,
    Global,
}

/// Window size specification
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum WindowSize {
    Time(Duration),
    Count(usize),
    Bytes(usize),
}

/// Window trigger conditions
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum WindowTrigger {
    /// Trigger on time interval
    TimeInterval(Duration),
    /// Trigger on event count
    EventCount(usize),
    /// Trigger on watermark
    Watermark,
    /// Trigger on specific event type
    EventType(String),
    /// Custom trigger condition
    Custom(String),
}

/// Subscription metadata
#[derive(Debug, Clone)]
pub struct SubscriptionMetadata {
    /// Creation timestamp
    pub created_at: DateTime<Utc>,
    /// Last activity timestamp
    pub last_activity: DateTime<Utc>,
    /// Tags for organization
    pub tags: Vec<String>,
    /// Priority level
    pub priority: SubscriptionPriority,
    /// Namespace
    pub namespace: Option<String>,
    /// Group membership
    pub groups: Vec<String>,
}

/// Subscription priority
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum SubscriptionPriority {
    Low = 1,
    Normal = 2,
    High = 3,
    Critical = 4,
}

/// Subscription statistics
#[derive(Debug, Clone, Default)]
pub struct SubscriptionStatistics {
    /// Total events received
    pub events_received: u64,
    /// Total updates sent
    pub updates_sent: u64,
    /// Total bytes sent
    pub bytes_sent: u64,
    /// Average latency (ms)
    pub avg_latency_ms: f64,
    /// Max latency (ms)
    pub max_latency_ms: f64,
    /// Error count
    pub error_count: u64,
    /// Last error
    pub last_error: Option<String>,
}

/// Subscription group for managing related subscriptions
#[derive(Debug, Clone)]
pub struct SubscriptionGroup {
    /// Group identifier
    pub id: String,
    /// Group name
    pub name: String,
    /// Member subscription IDs
    pub members: HashSet<String>,
    /// Group-level filters
    pub filters: Vec<AdvancedFilter>,
    /// Group configuration
    pub config: GroupConfig,
}

/// Group configuration
#[derive(Debug, Clone)]
pub struct GroupConfig {
    /// Enable shared windowing
    pub shared_windowing: bool,
    /// Enable load balancing
    pub load_balancing: bool,
    /// Maximum members
    pub max_members: usize,
}

/// Subscription window buffer
pub struct SubscriptionWindow {
    /// Window identifier
    pub id: String,
    /// Associated subscription ID
    pub subscription_id: String,
    /// Window specification
    pub spec: WindowSpec,
    /// Event buffer
    pub buffer: VecDeque<WindowedEvent>,
    /// Window state
    pub state: WindowState,
}

/// Windowed event
#[derive(Debug, Clone)]
pub struct WindowedEvent {
    pub event: StreamEvent,
    pub timestamp: DateTime<Utc>,
    pub sequence_id: u64,
}

/// Window state
#[derive(Debug, Clone)]
pub struct WindowState {
    /// Window start time
    pub start_time: DateTime<Utc>,
    /// Window end time
    pub end_time: Option<DateTime<Utc>>,
    /// Event count
    pub event_count: usize,
    /// Total bytes
    pub total_bytes: usize,
    /// Is window closed
    pub is_closed: bool,
}

/// Subscription event
#[derive(Debug, Clone)]
pub enum SubscriptionEvent {
    /// New update available
    Update {
        subscription_id: String,
        data: serde_json::Value,
        timestamp: DateTime<Utc>,
    },
    /// Subscription state changed
    StateChanged {
        subscription_id: String,
        old_state: SubscriptionState,
        new_state: SubscriptionState,
    },
    /// Heartbeat
    Heartbeat {
        subscription_id: String,
        timestamp: DateTime<Utc>,
    },
    /// Error occurred
    Error {
        subscription_id: String,
        error: String,
        timestamp: DateTime<Utc>,
    },
}

/// Overall statistics
#[derive(Debug, Clone, Default)]
pub struct SubscriptionStats {
    pub total_subscriptions: usize,
    pub active_subscriptions: usize,
    pub paused_subscriptions: usize,
    pub reconnecting_subscriptions: usize,
    pub total_events_processed: u64,
    pub total_updates_sent: u64,
    pub avg_processing_time_ms: f64,
}

impl GraphQLSubscriptionManager {
    /// Create a new subscription manager
    pub fn new(config: SubscriptionConfig) -> Self {
        let (event_tx, _) = broadcast::channel(10000);

        let manager = Self {
            subscriptions: Arc::new(RwLock::new(HashMap::new())),
            groups: Arc::new(RwLock::new(HashMap::new())),
            windows: Arc::new(RwLock::new(HashMap::new())),
            event_tx,
            config,
            stats: Arc::new(RwLock::new(SubscriptionStats::default())),
        };

        // Start background tasks
        manager.start_heartbeat_task();
        manager.start_cleanup_task();

        manager
    }

    /// Register a new subscription
    pub async fn register_subscription(
        &self,
        subscription: EnhancedSubscription,
    ) -> Result<String> {
        let mut subscriptions = self.subscriptions.write().await;

        // Check limits
        if subscriptions.len() >= self.config.max_subscriptions {
            return Err(anyhow!("Maximum subscriptions limit reached"));
        }

        // Check per-client limit
        let client_count = subscriptions
            .values()
            .filter(|s| s.client_id == subscription.client_id)
            .count();

        if client_count >= self.config.max_subscriptions_per_client {
            return Err(anyhow!("Client subscription limit reached"));
        }

        let id = subscription.id.clone();

        // Create window if needed
        if self.config.enable_windowing {
            if let Some(window_spec) = &subscription.window {
                self.create_window(&id, window_spec.clone()).await?;
            }
        }

        subscriptions.insert(id.clone(), subscription);

        // Update stats
        let mut stats = self.stats.write().await;
        stats.total_subscriptions = subscriptions.len();
        stats.active_subscriptions = subscriptions
            .values()
            .filter(|s| s.state == SubscriptionState::Active)
            .count();

        info!("Registered GraphQL subscription: {}", id);
        Ok(id)
    }

    /// Unregister a subscription
    pub async fn unregister_subscription(&self, subscription_id: &str) -> Result<()> {
        let mut subscriptions = self.subscriptions.write().await;
        subscriptions
            .remove(subscription_id)
            .ok_or_else(|| anyhow!("Subscription not found"))?;

        // Remove window
        self.windows.write().await.remove(subscription_id);

        // Update stats
        let mut stats = self.stats.write().await;
        stats.total_subscriptions = subscriptions.len();
        stats.active_subscriptions = subscriptions
            .values()
            .filter(|s| s.state == SubscriptionState::Active)
            .count();

        info!("Unregistered GraphQL subscription: {}", subscription_id);
        Ok(())
    }

    /// Pause a subscription
    pub async fn pause_subscription(&self, subscription_id: &str) -> Result<()> {
        let mut subscriptions = self.subscriptions.write().await;
        let subscription = subscriptions
            .get_mut(subscription_id)
            .ok_or_else(|| anyhow!("Subscription not found"))?;

        let old_state = subscription.state.clone();
        subscription.state = SubscriptionState::Paused;

        // Emit state change event
        let _ = self.event_tx.send(SubscriptionEvent::StateChanged {
            subscription_id: subscription_id.to_string(),
            old_state,
            new_state: SubscriptionState::Paused,
        });

        info!("Paused subscription: {}", subscription_id);
        Ok(())
    }

    /// Resume a paused subscription
    pub async fn resume_subscription(&self, subscription_id: &str) -> Result<()> {
        let mut subscriptions = self.subscriptions.write().await;
        let subscription = subscriptions
            .get_mut(subscription_id)
            .ok_or_else(|| anyhow!("Subscription not found"))?;

        let old_state = subscription.state.clone();
        subscription.state = SubscriptionState::Active;
        subscription.metadata.last_activity = Utc::now();

        // Emit state change event
        let _ = self.event_tx.send(SubscriptionEvent::StateChanged {
            subscription_id: subscription_id.to_string(),
            old_state,
            new_state: SubscriptionState::Active,
        });

        info!("Resumed subscription: {}", subscription_id);
        Ok(())
    }

    /// Process stream event
    pub async fn process_event(&self, event: &StreamEvent) -> Result<()> {
        let subscriptions = self.subscriptions.read().await;

        for (sub_id, subscription) in subscriptions.iter() {
            // Only process for active subscriptions
            if subscription.state != SubscriptionState::Active {
                continue;
            }

            // Apply filters
            if !self.apply_filters(event, &subscription.filters).await? {
                continue;
            }

            // Handle windowing
            if self.config.enable_windowing && subscription.window.is_some() {
                self.add_to_window(sub_id, event).await?;
            } else {
                // Send immediate update
                self.send_update(sub_id, event).await?;
            }
        }

        let mut stats = self.stats.write().await;
        stats.total_events_processed += 1;

        Ok(())
    }

    /// Apply filters to event
    async fn apply_filters(
        &self,
        _event: &StreamEvent,
        filters: &[AdvancedFilter],
    ) -> Result<bool> {
        if !self.config.enable_advanced_filtering || filters.is_empty() {
            return Ok(true);
        }

        // Simplified filter logic - in production, implement full filter evaluation
        for filter in filters {
            match filter {
                AdvancedFilter::TimeRange { start, end } => {
                    let now = Utc::now();
                    if let Some(start) = start {
                        if &now < start {
                            return Ok(false);
                        }
                    }
                    if let Some(end) = end {
                        if &now > end {
                            return Ok(false);
                        }
                    }
                }
                _ => {
                    // Other filter types would be evaluated here
                }
            }
        }

        Ok(true)
    }

    /// Create window for subscription
    async fn create_window(&self, subscription_id: &str, spec: WindowSpec) -> Result<()> {
        let window = SubscriptionWindow {
            id: uuid::Uuid::new_v4().to_string(),
            subscription_id: subscription_id.to_string(),
            spec,
            buffer: VecDeque::new(),
            state: WindowState {
                start_time: Utc::now(),
                end_time: None,
                event_count: 0,
                total_bytes: 0,
                is_closed: false,
            },
        };

        self.windows
            .write()
            .await
            .insert(subscription_id.to_string(), window);

        Ok(())
    }

    /// Add event to window
    async fn add_to_window(&self, subscription_id: &str, event: &StreamEvent) -> Result<()> {
        let mut windows = self.windows.write().await;
        if let Some(window) = windows.get_mut(subscription_id) {
            let windowed_event = WindowedEvent {
                event: event.clone(),
                timestamp: Utc::now(),
                sequence_id: window.state.event_count as u64,
            };

            window.buffer.push_back(windowed_event);
            window.state.event_count += 1;

            // Check triggers
            self.check_window_triggers(window).await?;
        }

        Ok(())
    }

    /// Check if window triggers should fire
    async fn check_window_triggers(&self, window: &mut SubscriptionWindow) -> Result<()> {
        for trigger in &window.spec.triggers {
            match trigger {
                WindowTrigger::EventCount(count) if window.state.event_count >= *count => {
                    // Trigger window emission
                    debug!("Window trigger fired: event count {}", count);
                }
                WindowTrigger::TimeInterval(duration) => {
                    let elapsed = Utc::now() - window.state.start_time;
                    if elapsed > ChronoDuration::from_std(*duration)? {
                        debug!("Window trigger fired: time interval {:?}", duration);
                    }
                }
                _ => {}
            }
        }

        Ok(())
    }

    /// Send update to subscription
    async fn send_update(&self, subscription_id: &str, event: &StreamEvent) -> Result<()> {
        // Convert event to GraphQL data
        let data = self.convert_event_to_graphql(event)?;

        // Emit update event
        let _ = self.event_tx.send(SubscriptionEvent::Update {
            subscription_id: subscription_id.to_string(),
            data,
            timestamp: Utc::now(),
        });

        // Update subscription statistics
        let mut subscriptions = self.subscriptions.write().await;
        if let Some(subscription) = subscriptions.get_mut(subscription_id) {
            subscription.stats.updates_sent += 1;
            subscription.metadata.last_activity = Utc::now();
        }

        Ok(())
    }

    /// Convert stream event to GraphQL data
    fn convert_event_to_graphql(&self, event: &StreamEvent) -> Result<serde_json::Value> {
        // Simplified conversion - in production, implement full event mapping
        Ok(serde_json::json!({
            "type": format!("{:?}", event),
            "timestamp": Utc::now().to_rfc3339(),
        }))
    }

    /// Start heartbeat task
    fn start_heartbeat_task(&self) {
        let subscriptions = self.subscriptions.clone();
        let event_tx = self.event_tx.clone();
        let interval_duration = self.config.heartbeat_interval;

        tokio::spawn(async move {
            let mut interval_timer = interval(interval_duration);

            loop {
                interval_timer.tick().await;

                let subs = subscriptions.read().await;
                for (sub_id, subscription) in subs.iter() {
                    if subscription.state == SubscriptionState::Active {
                        let _ = event_tx.send(SubscriptionEvent::Heartbeat {
                            subscription_id: sub_id.clone(),
                            timestamp: Utc::now(),
                        });
                    }
                }
            }
        });
    }

    /// Start cleanup task
    fn start_cleanup_task(&self) {
        let subscriptions = self.subscriptions.clone();
        let timeout = self.config.subscription_timeout;

        tokio::spawn(async move {
            let mut interval_timer = interval(Duration::from_secs(60));

            loop {
                interval_timer.tick().await;

                let mut subs = subscriptions.write().await;
                let now = Utc::now();

                // Remove timed-out subscriptions
                subs.retain(|_, subscription| {
                    let inactive_duration = now - subscription.metadata.last_activity;
                    inactive_duration
                        < ChronoDuration::from_std(timeout)
                            .expect("timeout should be valid chrono Duration")
                });
            }
        });
    }

    /// Get statistics
    pub async fn get_stats(&self) -> SubscriptionStats {
        self.stats.read().await.clone()
    }

    /// Subscribe to events
    pub fn subscribe(&self) -> broadcast::Receiver<SubscriptionEvent> {
        self.event_tx.subscribe()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[tokio::test]
    async fn test_subscription_config_defaults() {
        let config = SubscriptionConfig::default();
        assert_eq!(config.max_subscriptions, 10000);
        assert!(config.enable_windowing);
    }

    #[tokio::test]
    async fn test_subscription_states() {
        let state = SubscriptionState::Active;
        assert_eq!(state, SubscriptionState::Active);

        let state = SubscriptionState::Paused;
        assert_eq!(state, SubscriptionState::Paused);
    }

    #[tokio::test]
    async fn test_filter_operators() {
        assert_eq!(FilterOperator::Equal, FilterOperator::Equal);
        assert_ne!(FilterOperator::Equal, FilterOperator::NotEqual);
    }

    #[tokio::test]
    async fn test_window_types() {
        let window = WindowSpec {
            window_type: WindowType::Tumbling,
            size: WindowSize::Time(Duration::from_secs(60)),
            slide: None,
            triggers: vec![WindowTrigger::EventCount(100)],
        };

        assert_eq!(window.window_type, WindowType::Tumbling);
    }

    #[tokio::test]
    async fn test_subscription_priority() {
        assert!(SubscriptionPriority::Critical > SubscriptionPriority::High);
        assert!(SubscriptionPriority::High > SubscriptionPriority::Normal);
        assert!(SubscriptionPriority::Normal > SubscriptionPriority::Low);
    }
}