oxirs-gql 0.2.4

//! Real-Time Schema Synchronization for Federation
//!
//! This module provides real-time synchronization of GraphQL schemas across
//! federated services with conflict resolution and versioning support.

use anyhow::{anyhow, Result};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use std::time::{Duration, SystemTime};
use tokio::sync::{mpsc, RwLock};
use tokio::time::interval;
use tracing::{debug, info, warn};

use super::schema_stitcher::SchemaStitcher;
use super::service_discovery::{ServiceDiscovery, ServiceInfo};

/// Schema synchronization configuration
#[derive(Debug, Clone)]
pub struct SyncConfig {
    pub sync_interval: Duration,
    pub conflict_resolution: ConflictResolution,
    pub version_management: VersionManagement,
    pub change_detection: ChangeDetection,
    pub propagation_timeout: Duration,
    pub max_retry_attempts: usize,
    pub enable_rollback: bool,
    pub sync_priority: SyncPriority,
}

impl Default for SyncConfig {
    fn default() -> Self {
        Self {
            sync_interval: Duration::from_secs(30),
            conflict_resolution: ConflictResolution::LastWriterWins,
            version_management: VersionManagement::Semantic,
            change_detection: ChangeDetection::Hash,
            propagation_timeout: Duration::from_secs(10),
            max_retry_attempts: 3,
            enable_rollback: true,
            sync_priority: SyncPriority::Balanced,
        }
    }
}

/// Conflict resolution strategies
#[derive(Debug, Clone)]
pub enum ConflictResolution {
    LastWriterWins,
    FirstWriterWins,
    ManualResolution,
    MergeFields,
    VersionBased,
    PriorityBased,
}

/// Version management strategies
#[derive(Debug, Clone)]
pub enum VersionManagement {
    Semantic,
    Timestamp,
    Incremental,
    Hash,
}

/// Change detection methods
#[derive(Debug, Clone)]
pub enum ChangeDetection {
    Hash,
    Structural,
    Semantic,
    FieldLevel,
}

/// Synchronization priority
#[derive(Debug, Clone)]
pub enum SyncPriority {
    LatencyOptimized,
    ConsistencyFirst,
    Balanced,
    PerformanceFirst,
}

/// Schema change event
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SchemaChangeEvent {
    pub id: String,
    pub service_id: String,
    pub change_type: SchemaChangeType,
    pub affected_types: Vec<String>,
    pub affected_fields: Vec<String>,
    pub old_schema_hash: Option<String>,
    pub new_schema_hash: String,
    pub timestamp: SystemTime,
    pub version: String,
    pub metadata: HashMap<String, String>,
}

/// Types of schema changes
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SchemaChangeType {
    TypeAdded,
    TypeRemoved,
    TypeModified,
    FieldAdded,
    FieldRemoved,
    FieldModified,
    DirectiveAdded,
    DirectiveRemoved,
    DirectiveModified,
    ArgumentAdded,
    ArgumentRemoved,
    ArgumentModified,
}

/// Schema version information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SchemaVersion {
    pub version: String,
    pub hash: String,
    pub timestamp: SystemTime,
    pub service_id: String,
    pub compatible_versions: Vec<String>,
    pub breaking_changes: Vec<String>,
    pub schema_content: String,
}

/// Conflict information
#[derive(Debug, Clone)]
pub struct SchemaConflict {
    pub conflict_id: String,
    pub services: Vec<String>,
    pub conflict_type: ConflictType,
    pub description: String,
    pub possible_resolutions: Vec<ConflictResolution>,
    pub auto_resolvable: bool,
}

/// Types of schema conflicts
#[derive(Debug, Clone)]
pub enum ConflictType {
    TypeNameCollision,
    FieldTypeConflict,
    DirectiveConflict,
    IncompatibleChanges,
    VersionMismatch,
    NamespaceCollision,
}

/// Synchronization status
#[derive(Debug, Clone)]
pub struct SyncStatus {
    pub is_synchronized: bool,
    pub last_sync_time: Option<SystemTime>,
    pub pending_changes: usize,
    pub active_conflicts: usize,
    pub services_out_of_sync: Vec<String>,
    pub overall_health: SyncHealth,
}

/// Synchronization health status
#[derive(Debug, Clone, PartialEq)]
pub enum SyncHealth {
    Healthy,
    Warning,
    Critical,
    Failed,
}

/// Real-time schema synchronizer
pub struct RealTimeSchemaSynchronizer {
    config: SyncConfig,
    service_discovery: Arc<ServiceDiscovery>,
    schema_stitcher: Arc<SchemaStitcher>,
    schema_versions: Arc<RwLock<HashMap<String, SchemaVersion>>>,
    active_conflicts: Arc<RwLock<Vec<SchemaConflict>>>,
    change_subscribers: Arc<RwLock<Vec<mpsc::UnboundedSender<SchemaChangeEvent>>>>,
    sync_status: Arc<RwLock<SyncStatus>>,
    http_client: reqwest::Client,
}

impl RealTimeSchemaSynchronizer {
    /// Create a new real-time schema synchronizer
    pub fn new(
        config: SyncConfig,
        service_discovery: Arc<ServiceDiscovery>,
        schema_stitcher: Arc<SchemaStitcher>,
    ) -> Self {
        let http_client = reqwest::Client::builder()
            .timeout(config.propagation_timeout)
            .build()
            .expect("Failed to create HTTP client");

        Self {
            config,
            service_discovery,
            schema_stitcher,
            schema_versions: Arc::new(RwLock::new(HashMap::new())),
            active_conflicts: Arc::new(RwLock::new(Vec::new())),
            change_subscribers: Arc::new(RwLock::new(Vec::new())),
            sync_status: Arc::new(RwLock::new(SyncStatus {
                is_synchronized: false,
                last_sync_time: None,
                pending_changes: 0,
                active_conflicts: 0,
                services_out_of_sync: Vec::new(),
                overall_health: SyncHealth::Healthy,
            })),
            http_client,
        }
    }

    /// Start the real-time synchronization service
    pub async fn start(&self) -> Result<()> {
        info!("Starting real-time schema synchronization");

        // Start periodic sync
        self.start_periodic_sync().await;

        // Start change monitoring
        self.start_change_monitoring().await;

        // Perform initial synchronization
        self.perform_full_sync().await?;

        info!("Real-time schema synchronization started");
        Ok(())
    }

    /// Perform a full synchronization across all services
    pub async fn perform_full_sync(&self) -> Result<()> {
        info!("Performing full schema synchronization");

        let services = self.service_discovery.get_healthy_services().await;
        let mut changes = Vec::new();
        let mut conflicts = Vec::new();

        // Fetch current schemas from all services
        let mut service_schemas = HashMap::new();
        for service in &services {
            match self.fetch_service_schema(service).await {
                Ok(schema) => {
                    service_schemas.insert(service.id.clone(), schema);
                }
                Err(e) => {
                    warn!("Failed to fetch schema from service {}: {}", service.id, e);
                }
            }
        }

        // Detect changes and conflicts
        for (service_id, new_schema) in &service_schemas {
            if let Some(old_version) = self.get_schema_version(service_id).await {
                let change_events = self.detect_schema_changes(&old_version, new_schema).await?;
                changes.extend(change_events);
            }
        }

        // Detect conflicts between services
        let detected_conflicts = self.detect_conflicts(&service_schemas).await?;
        conflicts.extend(detected_conflicts);

        // Update stored versions
        for (service_id, schema) in service_schemas {
            self.update_schema_version(service_id, schema).await?;
        }

        // Resolve conflicts if possible
        if !conflicts.is_empty() {
            self.resolve_conflicts(&conflicts).await?;
        }

        // Notify subscribers of changes
        for change in changes {
            self.notify_change_subscribers(&change).await;
        }

        // Update sync status
        self.update_sync_status().await;

        info!("Full synchronization completed");
        Ok(())
    }

    /// Subscribe to schema change events
    pub async fn subscribe_to_changes(&self) -> mpsc::UnboundedReceiver<SchemaChangeEvent> {
        let (tx, rx) = mpsc::unbounded_channel();
        self.change_subscribers.write().await.push(tx);
        rx
    }

    /// Get current synchronization status
    pub async fn get_sync_status(&self) -> SyncStatus {
        self.sync_status.read().await.clone()
    }

    /// Get active conflicts
    pub async fn get_active_conflicts(&self) -> Vec<SchemaConflict> {
        self.active_conflicts.read().await.clone()
    }

    /// Manually resolve a conflict
    pub async fn resolve_conflict(
        &self,
        conflict_id: &str,
        resolution: ConflictResolution,
    ) -> Result<()> {
        info!("Manually resolving conflict: {}", conflict_id);

        let mut conflicts = self.active_conflicts.write().await;
        if let Some(pos) = conflicts.iter().position(|c| c.conflict_id == conflict_id) {
            let conflict = conflicts.remove(pos);

            // Apply the resolution
            match resolution {
                ConflictResolution::ManualResolution => {
                    // Implementation would depend on specific conflict type
                    info!("Manual resolution applied for conflict: {}", conflict_id);
                }
                _ => {
                    // Apply automatic resolution
                    self.apply_conflict_resolution(&conflict, &resolution)
                        .await?;
                }
            }
        } else {
            return Err(anyhow!("Conflict not found: {}", conflict_id));
        }

        self.update_sync_status().await;
        Ok(())
    }

    /// Start periodic synchronization
    async fn start_periodic_sync(&self) {
        let sync_interval = self.config.sync_interval;
        let _schema_stitcher = self.schema_stitcher.clone();

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

            loop {
                interval.tick().await;

                // Simple periodic sync implementation - would need full synchronizer logic
                debug!("Performing periodic sync");

                // For now, just log the sync attempt
                // In a full implementation, this would call the actual sync logic
            }
        });
    }

    /// Start change monitoring
    async fn start_change_monitoring(&self) {
        // In a real implementation, this would set up WebSocket connections
        // or webhook endpoints to receive real-time change notifications
        info!("Change monitoring started (stub implementation)");
    }

    /// Perform incremental synchronization
    #[allow(dead_code)]
    async fn perform_incremental_sync(&self) -> Result<()> {
        debug!("Performing incremental sync");

        let services = self.service_discovery.get_healthy_services().await;
        let mut has_changes = false;

        for service in services {
            if let Ok(current_schema) = self.fetch_service_schema(&service).await {
                if let Some(stored_version) = self.get_schema_version(&service.id).await {
                    let current_hash = self.calculate_schema_hash(&current_schema);

                    if current_hash != stored_version.hash {
                        info!("Schema change detected for service: {}", service.id);

                        let changes = self
                            .detect_schema_changes(&stored_version, &current_schema)
                            .await?;
                        for change in changes {
                            self.notify_change_subscribers(&change).await;
                        }

                        self.update_schema_version(service.id.clone(), current_schema)
                            .await?;
                        has_changes = true;
                    }
                }
            }
        }

        if has_changes {
            self.update_sync_status().await;
        }

        Ok(())
    }

    /// Fetch schema from a service
    async fn fetch_service_schema(&self, service: &ServiceInfo) -> Result<SchemaVersion> {
        let introspection_query = r#"
            query IntrospectionQuery {
                __schema {
                    queryType { name }
                    mutationType { name }
                    subscriptionType { name }
                    types {
                        ...FullType
                    }
                    directives {
                        name
                        description
                        locations
                        args {
                            ...InputValue
                        }
                    }
                }
            }

            fragment FullType on __Type {
                kind
                name
                description
                fields(includeDeprecated: true) {
                    name
                    description
                    args {
                        ...InputValue
                    }
                    type {
                        ...TypeRef
                    }
                    isDeprecated
                    deprecationReason
                }
                inputFields {
                    ...InputValue
                }
                interfaces {
                    ...TypeRef
                }
                enumValues(includeDeprecated: true) {
                    name
                    description
                    isDeprecated
                    deprecationReason
                }
                possibleTypes {
                    ...TypeRef
                }
            }

            fragment InputValue on __InputValue {
                name
                description
                type { ...TypeRef }
                defaultValue
            }

            fragment TypeRef on __Type {
                kind
                name
                ofType {
                    kind
                    name
                    ofType {
                        kind
                        name
                        ofType {
                            kind
                            name
                            ofType {
                                kind
                                name
                                ofType {
                                    kind
                                    name
                                    ofType {
                                        kind
                                        name
                                        ofType {
                                            kind
                                            name
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        "#;

        let request_body = serde_json::json!({
            "query": introspection_query
        });

        let response = self
            .http_client
            .post(&service.url)
            .json(&request_body)
            .send()
            .await?;

        let response_json: serde_json::Value = response.json().await?;
        let schema_content = serde_json::to_string(&response_json)?;
        let schema_hash = self.calculate_schema_hash_from_content(&schema_content);

        Ok(SchemaVersion {
            version: service
                .federation_version
                .clone()
                .unwrap_or_else(|| "1.0.0".to_string()),
            hash: schema_hash,
            timestamp: SystemTime::now(),
            service_id: service.id.clone(),
            compatible_versions: vec!["1.0.0".to_string()],
            breaking_changes: Vec::new(),
            schema_content,
        })
    }

    /// Detect schema changes between versions
    async fn detect_schema_changes(
        &self,
        old_version: &SchemaVersion,
        new_version: &SchemaVersion,
    ) -> Result<Vec<SchemaChangeEvent>> {
        let mut changes = Vec::new();

        // This is a simplified implementation
        // A real implementation would parse and compare the GraphQL schemas
        if old_version.hash != new_version.hash {
            changes.push(SchemaChangeEvent {
                id: uuid::Uuid::new_v4().to_string(),
                service_id: new_version.service_id.clone(),
                change_type: SchemaChangeType::TypeModified,
                affected_types: vec!["Unknown".to_string()],
                affected_fields: Vec::new(),
                old_schema_hash: Some(old_version.hash.clone()),
                new_schema_hash: new_version.hash.clone(),
                timestamp: SystemTime::now(),
                version: new_version.version.clone(),
                metadata: HashMap::new(),
            });
        }

        Ok(changes)
    }

    /// Detect conflicts between service schemas
    async fn detect_conflicts(
        &self,
        service_schemas: &HashMap<String, SchemaVersion>,
    ) -> Result<Vec<SchemaConflict>> {
        let mut conflicts = Vec::new();

        // Simple conflict detection - type name collisions
        let mut type_names: HashMap<String, Vec<String>> = HashMap::new();

        for service_id in service_schemas.keys() {
            // In a real implementation, we'd parse the schema and extract type names
            // For now, we'll use a simplified approach
            let type_name = format!("{service_id}Type");
            type_names
                .entry(type_name)
                .or_default()
                .push(service_id.clone());
        }

        for (type_name, services) in type_names {
            if services.len() > 1 {
                conflicts.push(SchemaConflict {
                    conflict_id: uuid::Uuid::new_v4().to_string(),
                    services,
                    conflict_type: ConflictType::TypeNameCollision,
                    description: format!("Type name collision detected for: {type_name}"),
                    possible_resolutions: vec![
                        ConflictResolution::MergeFields,
                        ConflictResolution::PriorityBased,
                    ],
                    auto_resolvable: true,
                });
            }
        }

        Ok(conflicts)
    }

    /// Resolve conflicts automatically
    async fn resolve_conflicts(&self, conflicts: &[SchemaConflict]) -> Result<()> {
        for conflict in conflicts {
            if conflict.auto_resolvable {
                let resolution = match self.config.conflict_resolution {
                    ConflictResolution::LastWriterWins => ConflictResolution::LastWriterWins,
                    ConflictResolution::MergeFields => ConflictResolution::MergeFields,
                    _ => ConflictResolution::LastWriterWins,
                };

                self.apply_conflict_resolution(conflict, &resolution)
                    .await?;
            } else {
                // Store for manual resolution
                self.active_conflicts.write().await.push(conflict.clone());
            }
        }

        Ok(())
    }

    /// Apply conflict resolution
    async fn apply_conflict_resolution(
        &self,
        conflict: &SchemaConflict,
        resolution: &ConflictResolution,
    ) -> Result<()> {
        match resolution {
            ConflictResolution::LastWriterWins => {
                info!(
                    "Applying last writer wins resolution for conflict: {}",
                    conflict.conflict_id
                );
                // Implementation would depend on specific conflict type
            }
            ConflictResolution::MergeFields => {
                info!(
                    "Applying merge fields resolution for conflict: {}",
                    conflict.conflict_id
                );
                // Implementation would merge conflicting fields
            }
            _ => {
                warn!("Unsupported resolution strategy: {:?}", resolution);
            }
        }

        Ok(())
    }

    /// Notify change subscribers
    async fn notify_change_subscribers(&self, change: &SchemaChangeEvent) {
        let subscribers = self.change_subscribers.read().await;

        for subscriber in subscribers.iter() {
            if let Err(e) = subscriber.send(change.clone()) {
                warn!("Failed to notify change subscriber: {}", e);
            }
        }
    }

    /// Update synchronization status
    async fn update_sync_status(&self) {
        let mut status = self.sync_status.write().await;
        let conflicts = self.active_conflicts.read().await;

        status.last_sync_time = Some(SystemTime::now());
        status.active_conflicts = conflicts.len();
        status.overall_health = if conflicts.is_empty() {
            SyncHealth::Healthy
        } else if conflicts.len() < 5 {
            SyncHealth::Warning
        } else {
            SyncHealth::Critical
        };

        status.is_synchronized = status.overall_health == SyncHealth::Healthy;
    }

    /// Get stored schema version for a service
    async fn get_schema_version(&self, service_id: &str) -> Option<SchemaVersion> {
        self.schema_versions.read().await.get(service_id).cloned()
    }

    /// Update stored schema version
    async fn update_schema_version(
        &self,
        service_id: String,
        version: SchemaVersion,
    ) -> Result<()> {
        self.schema_versions
            .write()
            .await
            .insert(service_id, version);
        Ok(())
    }

    /// Calculate schema hash
    #[allow(dead_code)]
    fn calculate_schema_hash(&self, schema: &SchemaVersion) -> String {
        self.calculate_schema_hash_from_content(&schema.schema_content)
    }

    /// Calculate schema hash from content
    fn calculate_schema_hash_from_content(&self, content: &str) -> String {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        content.hash(&mut hasher);
        format!("{:x}", hasher.finish())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::federation::service_discovery::ServiceDiscoveryConfig;
    use crate::types::Schema;

    #[tokio::test]
    async fn test_schema_synchronizer_creation() {
        let config = SyncConfig::default();
        let service_discovery = Arc::new(ServiceDiscovery::new(ServiceDiscoveryConfig::default()));
        let local_schema = Arc::new(Schema::new());
        let schema_stitcher = Arc::new(SchemaStitcher::new(local_schema));

        let synchronizer =
            RealTimeSchemaSynchronizer::new(config, service_discovery, schema_stitcher);

        let status = synchronizer.get_sync_status().await;
        assert!(!status.is_synchronized);
        assert_eq!(status.active_conflicts, 0);
    }

    #[tokio::test]
    async fn test_conflict_detection() {
        let config = SyncConfig::default();
        let service_discovery = Arc::new(ServiceDiscovery::new(ServiceDiscoveryConfig::default()));
        let local_schema = Arc::new(Schema::new());
        let schema_stitcher = Arc::new(SchemaStitcher::new(local_schema));

        let synchronizer =
            RealTimeSchemaSynchronizer::new(config, service_discovery, schema_stitcher);

        let mut service_schemas = HashMap::new();
        service_schemas.insert(
            "service1".to_string(),
            SchemaVersion {
                version: "1.0.0".to_string(),
                hash: "hash1".to_string(),
                timestamp: SystemTime::now(),
                service_id: "service1".to_string(),
                compatible_versions: Vec::new(),
                breaking_changes: Vec::new(),
                schema_content: "schema1".to_string(),
            },
        );

        let conflicts = synchronizer
            .detect_conflicts(&service_schemas)
            .await
            .expect("should succeed");
        // Should not have conflicts with single service
        assert_eq!(conflicts.len(), 0);
    }
}