//! Disaster recovery and backup management for distributed storage
//!
//! This module provides comprehensive backup, restore, and disaster recovery
//! capabilities for the distributed messaging system.

use crate::broker::storage::Storage;
use crate::broker::distributed_storage::{BackupConfig, BackupData};
use crate::message::message::Message;
use crate::network::transport::NetworkTransport;
use crate::network::error::{NetworkError, NetworkResult};

use serde::{Deserialize, Serialize};
use std::collections::{HashMap, HashSet};
use std::io::{Read, Write};
use std::path::PathBuf;
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
use tokio::sync::RwLock;
use uuid::Uuid;
use log::{debug, error, info, warn};

/// Disaster recovery manager
#[allow(dead_code)]
pub struct DisasterRecoveryManager {
    /// Node ID
    node_id: String,
    /// Network transport for remote operations
    transport: Arc<NetworkTransport>,
    /// Local storage reference
    storage: Arc<Mutex<Storage>>,
    /// Backup configuration
    backup_config: BackupConfig,
    /// Recovery state
    recovery_state: Arc<RwLock<RecoveryState>>,
    /// Backup metadata
    backup_metadata: Arc<RwLock<HashMap<String, BackupMetadata>>>,
    /// Remote backup nodes
    remote_nodes: Arc<RwLock<Vec<String>>>,
}

/// Recovery state tracking
#[derive(Debug, Clone)]
pub struct RecoveryState {
    pub is_recovering: bool,
    pub recovery_start_time: Option<Instant>,
    pub recovery_progress: f64, // 0.0 to 1.0
    pub current_operation: Option<String>,
    pub errors: Vec<String>,
}

/// Metadata for backup files
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BackupMetadata {
    pub backup_id: Uuid,
    pub node_id: String,
    pub timestamp: u64,
    pub file_path: PathBuf,
    pub file_size: u64,
    pub checksum: String,
    pub backup_type: BackupType,
    pub compression_used: bool,
    pub version: String,
    pub message_count: u64,
    pub transaction_count: u64,
}

/// Type of backup
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum BackupType {
    Full,
    Incremental,
    Differential,
    Emergency,
}

/// Backup verification result
#[derive(Debug, Clone)]
pub struct BackupVerification {
    pub is_valid: bool,
    pub checksum_match: bool,
    pub file_exists: bool,
    pub size_match: bool,
    pub metadata_valid: bool,
    pub errors: Vec<String>,
}

/// Recovery options
#[derive(Debug, Clone)]
pub struct RecoveryOptions {
    pub target_time: Option<u64>, // Unix timestamp
    pub include_transactions: bool,
    pub verify_integrity: bool,
    pub parallel_recovery: bool,
    pub max_concurrent_operations: usize,
    pub timeout: Duration,
}

impl Default for RecoveryOptions {
    fn default() -> Self {
        Self {
            target_time: None,
            include_transactions: true,
            verify_integrity: true,
            parallel_recovery: true,
            max_concurrent_operations: 4,
            timeout: Duration::from_secs(300), // 5 minutes
        }
    }
}

impl DisasterRecoveryManager {
    /// Create a new disaster recovery manager
    pub fn new(
        node_id: String,
        transport: Arc<NetworkTransport>,
        storage: Arc<Mutex<Storage>>,
        backup_config: BackupConfig,
    ) -> Self {
        Self {
            node_id,
            transport,
            storage,
            backup_config,
            recovery_state: Arc::new(RwLock::new(RecoveryState {
                is_recovering: false,
                recovery_start_time: None,
                recovery_progress: 0.0,
                current_operation: None,
                errors: Vec::new(),
            })),
            backup_metadata: Arc::new(RwLock::new(HashMap::new())),
            remote_nodes: Arc::new(RwLock::new(Vec::new())),
        }
    }

    /// Start the disaster recovery manager
    pub async fn start(&self) -> NetworkResult<()> {
        info!("Starting disaster recovery manager for node {}", self.node_id);

        // Load existing backup metadata
        self.load_backup_metadata().await?;

        // Start background backup verification
        self.start_backup_verification().await;

        // Start remote backup monitoring
        self.start_remote_backup_monitoring().await;

        Ok(())
    }

    /// Create a full backup
    pub async fn create_full_backup(&self) -> NetworkResult<BackupMetadata> {
        info!("Creating full backup for node {}", self.node_id);

        let backup_id = Uuid::new_v4();
        let timestamp = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap()
            .as_secs();

        let backup_filename = format!("full_backup_{}_{}.json", self.node_id, timestamp);
        let backup_path = self.backup_config.backup_directory.join(&backup_filename);

        // Ensure backup directory exists
        std::fs::create_dir_all(&self.backup_config.backup_directory)
            .map_err(|e| NetworkError::InternalError(format!("Failed to create backup directory: {}", e)))?;

        // Create backup data
        let backup_data = self.create_backup_data().await?;

        // Serialize and write backup
        let backup_json = serde_json::to_string_pretty(&backup_data)
            .map_err(|e| NetworkError::InternalError(format!("Failed to serialize backup: {}", e)))?;

        // Optionally compress the backup
        let final_data = if self.backup_config.compress_backups {
            self.compress_backup_data(&backup_json)?
        } else {
            backup_json.into_bytes()
        };

        std::fs::write(&backup_path, &final_data)
            .map_err(|e| NetworkError::InternalError(format!("Failed to write backup: {}", e)))?;

        // Calculate checksum
        let checksum = self.calculate_checksum(&final_data);
        let file_size = final_data.len() as u64;

        // Create metadata
        let metadata = BackupMetadata {
            backup_id,
            node_id: self.node_id.clone(),
            timestamp,
            file_path: backup_path.clone(),
            file_size,
            checksum,
            backup_type: BackupType::Full,
            compression_used: self.backup_config.compress_backups,
            version: env!("CARGO_PKG_VERSION").to_string(),
            message_count: backup_data.messages.len() as u64,
            transaction_count: backup_data.transactions.len() as u64,
        };

        // Store metadata
        {
            let mut backup_metadata = self.backup_metadata.write().await;
            backup_metadata.insert(backup_id.to_string(), metadata.clone());
        }

        // Save metadata to disk
        self.save_backup_metadata().await?;

        // Replicate backup to remote nodes if configured
        if !self.backup_config.remote_backup_nodes.is_empty() {
            self.replicate_backup_to_remote_nodes(&metadata).await?;
        }

        info!("Full backup created: {} ({} bytes)", backup_path.display(), file_size);
        Ok(metadata)
    }

    /// Create an incremental backup
    pub async fn create_incremental_backup(&self, since_backup_id: Uuid) -> NetworkResult<BackupMetadata> {
        info!("Creating incremental backup since {}", since_backup_id);

        // Find the base backup
        let base_backup = {
            let metadata = self.backup_metadata.read().await;
            metadata.get(&since_backup_id.to_string()).cloned()
        };

        let base_backup = base_backup
            .ok_or_else(|| NetworkError::InternalError("Base backup not found".to_string()))?;

        let backup_id = Uuid::new_v4();
        let timestamp = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap()
            .as_secs();

        // Create incremental backup data (messages since the base backup)
        let incremental_data = self.create_incremental_backup_data(base_backup.timestamp).await?;

        let backup_filename = format!("incremental_backup_{}_{}.json", self.node_id, timestamp);
        let backup_path = self.backup_config.backup_directory.join(&backup_filename);

        // Serialize and write
        let backup_json = serde_json::to_string_pretty(&incremental_data)
            .map_err(|e| NetworkError::InternalError(format!("Failed to serialize incremental backup: {}", e)))?;

        let final_data = if self.backup_config.compress_backups {
            self.compress_backup_data(&backup_json)?
        } else {
            backup_json.into_bytes()
        };

        std::fs::write(&backup_path, &final_data)
            .map_err(|e| NetworkError::InternalError(format!("Failed to write incremental backup: {}", e)))?;

        let checksum = self.calculate_checksum(&final_data);
        let file_size = final_data.len() as u64;

        let metadata = BackupMetadata {
            backup_id,
            node_id: self.node_id.clone(),
            timestamp,
            file_path: backup_path.clone(),
            file_size,
            checksum,
            backup_type: BackupType::Incremental,
            compression_used: self.backup_config.compress_backups,
            version: env!("CARGO_PKG_VERSION").to_string(),
            message_count: incremental_data.messages.len() as u64,
            transaction_count: incremental_data.transactions.len() as u64,
        };

        // Store metadata
        {
            let mut backup_metadata = self.backup_metadata.write().await;
            backup_metadata.insert(backup_id.to_string(), metadata.clone());
        }

        self.save_backup_metadata().await?;

        info!("Incremental backup created: {} ({} bytes)", backup_path.display(), file_size);
        Ok(metadata)
    }

    /// Restore from a backup
    pub async fn restore_from_backup(
        &self,
        backup_id: Uuid,
        options: RecoveryOptions,
    ) -> NetworkResult<()> {
        info!("Starting restore from backup {}", backup_id);

        // Update recovery state
        {
            let mut state = self.recovery_state.write().await;
            state.is_recovering = true;
            state.recovery_start_time = Some(Instant::now());
            state.recovery_progress = 0.0;
            state.current_operation = Some("Starting recovery".to_string());
            state.errors.clear();
        }

        // Find backup metadata
        let backup_metadata = {
            let metadata = self.backup_metadata.read().await;
            metadata.get(&backup_id.to_string()).cloned()
        };

        let backup_metadata = backup_metadata
            .ok_or_else(|| NetworkError::InternalError("Backup not found".to_string()))?;

        // Verify backup integrity if requested
        if options.verify_integrity {
            self.update_recovery_state("Verifying backup integrity", 10.0).await;
            let verification = self.verify_backup(&backup_metadata).await?;
            if !verification.is_valid {
                let error_msg = format!("Backup verification failed: {:?}", verification.errors);
                self.add_recovery_error(&error_msg).await;
                return Err(NetworkError::InternalError(error_msg));
            }
        }

        // Load backup data
        self.update_recovery_state("Loading backup data", 20.0).await;
        let backup_data = self.load_backup_data(&backup_metadata).await?;

        // Stop current operations
        self.update_recovery_state("Stopping current operations", 30.0).await;
        self.stop_current_operations().await;

        // Clear existing storage
        self.update_recovery_state("Clearing existing storage", 40.0).await;
        {
            let mut storage = self.storage.lock().unwrap();
            if let Err(e) = storage.reinitialize() {
                let error_msg = format!("Failed to reinitialize storage: {}", e);
                self.add_recovery_error(&error_msg).await;
                return Err(NetworkError::InternalError(error_msg));
            }
        }

        // Restore messages
        self.update_recovery_state("Restoring messages", 60.0).await;
        self.restore_messages(&backup_data.messages).await?;

        // Restore consumed messages
        self.update_recovery_state("Restoring consumed messages", 80.0).await;
        self.restore_consumed_messages(&backup_data.consumed_messages).await?;

        // Restore transactions if requested
        if options.include_transactions {
            self.update_recovery_state("Restoring transactions", 90.0).await;
            // Transaction restoration would be implemented here
        }

        // Finalize recovery
        self.update_recovery_state("Finalizing recovery", 100.0).await;
        {
            let mut state = self.recovery_state.write().await;
            state.is_recovering = false;
            state.current_operation = Some("Recovery completed successfully".to_string());
        }

        info!("Recovery from backup {} completed successfully", backup_id);
        Ok(())
    }

    /// Verify a backup's integrity
    pub async fn verify_backup(&self, metadata: &BackupMetadata) -> NetworkResult<BackupVerification> {
        let mut verification = BackupVerification {
            is_valid: true,
            checksum_match: false,
            file_exists: false,
            size_match: false,
            metadata_valid: false,
            errors: Vec::new(),
        };

        // Check if file exists
        verification.file_exists = metadata.file_path.exists();
        if !verification.file_exists {
            verification.errors.push("Backup file does not exist".to_string());
            verification.is_valid = false;
        }

        if verification.file_exists {
            // Check file size
            if let Ok(file_metadata) = std::fs::metadata(&metadata.file_path) {
                verification.size_match = file_metadata.len() == metadata.file_size;
                if !verification.size_match {
                    verification.errors.push(format!(
                        "File size mismatch: expected {}, actual {}",
                        metadata.file_size,
                        file_metadata.len()
                    ));
                    verification.is_valid = false;
                }
            }

            // Verify checksum
            if let Ok(file_data) = std::fs::read(&metadata.file_path) {
                let calculated_checksum = self.calculate_checksum(&file_data);
                verification.checksum_match = calculated_checksum == metadata.checksum;
                if !verification.checksum_match {
                    verification.errors.push("Checksum mismatch".to_string());
                    verification.is_valid = false;
                }
            }
        }

        // Validate metadata
        verification.metadata_valid = !metadata.node_id.is_empty() &&
                                    metadata.timestamp > 0 &&
                                    !metadata.checksum.is_empty();

        if !verification.metadata_valid {
            verification.errors.push("Invalid metadata".to_string());
            verification.is_valid = false;
        }

        Ok(verification)
    }

    /// Get recovery status
    pub async fn get_recovery_status(&self) -> RecoveryState {
        self.recovery_state.read().await.clone()
    }

    /// List available backups
    pub async fn list_backups(&self) -> Vec<BackupMetadata> {
        let metadata = self.backup_metadata.read().await;
        metadata.values().cloned().collect()
    }

    /// Delete old backups beyond retention policy
    pub async fn cleanup_old_backups(&self) -> NetworkResult<usize> {
        let retention_time = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap()
            .as_secs() - (30 * 24 * 3600); // 30 days

        let mut deleted_count = 0;
        let backups_to_delete: Vec<_> = {
            let metadata = self.backup_metadata.read().await;
            metadata
                .values()
                .filter(|backup| backup.timestamp < retention_time)
                .cloned()
                .collect()
        };

        for backup in backups_to_delete {
            if let Err(e) = std::fs::remove_file(&backup.file_path) {
                warn!("Failed to delete backup file {:?}: {}", backup.file_path, e);
            } else {
                deleted_count += 1;

                // Remove from metadata
                let mut metadata = self.backup_metadata.write().await;
                metadata.remove(&backup.backup_id.to_string());
            }
        }

        if deleted_count > 0 {
            self.save_backup_metadata().await?;
            info!("Cleaned up {} old backups", deleted_count);
        }

        Ok(deleted_count)
    }

    /// Create backup data structure
    async fn create_backup_data(&self) -> NetworkResult<BackupData> {
        // This is a simplified implementation
        // In practice, you would systematically read all data from storage

        Ok(BackupData {
            messages: Vec::new(), // Would be populated from storage
            consumed_messages: HashSet::new(), // Would be populated from storage
            transactions: Vec::new(), // Would be populated from storage
            metadata: HashMap::new(), // Empty metadata for now
        })
    }

    /// Create incremental backup data
    async fn create_incremental_backup_data(&self, _since_timestamp: u64) -> NetworkResult<BackupData> {
        // Implementation would filter messages by timestamp
        let mut backup_data = self.create_backup_data().await?;

        // Filter messages since the given timestamp
        backup_data.messages.retain(|_message| {
            // Would check message timestamp against since_timestamp
            true // Placeholder
        });

        Ok(backup_data)
    }

    /// Compress backup data
    fn compress_backup_data(&self, data: &str) -> NetworkResult<Vec<u8>> {
        use flate2::write::GzEncoder;
        use flate2::Compression;

        let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
        encoder.write_all(data.as_bytes())
            .map_err(|e| NetworkError::InternalError(format!("Compression failed: {}", e)))?;

        encoder.finish()
            .map_err(|e| NetworkError::InternalError(format!("Compression finalize failed: {}", e)))
    }

    /// Load backup data from file
    async fn load_backup_data(&self, metadata: &BackupMetadata) -> NetworkResult<BackupData> {
        let file_data = std::fs::read(&metadata.file_path)
            .map_err(|e| NetworkError::InternalError(format!("Failed to read backup file: {}", e)))?;

        let json_data = if metadata.compression_used {
            self.decompress_backup_data(&file_data)?
        } else {
            String::from_utf8(file_data)
                .map_err(|e| NetworkError::InternalError(format!("Invalid UTF-8 in backup: {}", e)))?
        };

        serde_json::from_str(&json_data)
            .map_err(|e| NetworkError::InternalError(format!("Failed to parse backup JSON: {}", e)))
    }

    /// Decompress backup data
    fn decompress_backup_data(&self, data: &[u8]) -> NetworkResult<String> {
        use flate2::read::GzDecoder;

        let mut decoder = GzDecoder::new(data);
        let mut decompressed = String::new();
        decoder.read_to_string(&mut decompressed)
            .map_err(|e| NetworkError::InternalError(format!("Decompression failed: {}", e)))?;

        Ok(decompressed)
    }

    /// Calculate checksum for data
    fn calculate_checksum(&self, data: &[u8]) -> String {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

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

    /// Restore messages from backup
    async fn restore_messages(&self, messages: &[Message]) -> NetworkResult<()> {
        let mut storage = self.storage.lock().unwrap();

        for message in messages {
            if let Err(e) = storage.write_message(message) {
                let error_msg = format!("Failed to restore message {}: {}", message.id, e);
                self.add_recovery_error(&error_msg).await;
                return Err(NetworkError::InternalError(error_msg));
            }
        }

        Ok(())
    }

    /// Restore consumed messages from backup
    async fn restore_consumed_messages(&self, consumed_messages: &HashSet<Uuid>) -> NetworkResult<()> {
        let mut storage = self.storage.lock().unwrap();

        for message_id in consumed_messages {
            storage.consume_message(*message_id);
        }

        Ok(())
    }

    /// Update recovery state
    async fn update_recovery_state(&self, operation: &str, progress: f64) {
        let mut state = self.recovery_state.write().await;
        state.current_operation = Some(operation.to_string());
        state.recovery_progress = progress;
        debug!("Recovery progress: {}% - {}", progress, operation);
    }

    /// Add recovery error
    async fn add_recovery_error(&self, error: &str) {
        let mut state = self.recovery_state.write().await;
        state.errors.push(error.to_string());
        error!("Recovery error: {}", error);
    }

    /// Stop current operations
    async fn stop_current_operations(&self) {
        // Implementation would stop background tasks, close connections, etc.
        debug!("Stopping current operations for recovery");
    }

    /// Load backup metadata from disk
    async fn load_backup_metadata(&self) -> NetworkResult<()> {
        let metadata_path = self.backup_config.backup_directory.join("backup_metadata.json");

        if metadata_path.exists() {
            let metadata_content = std::fs::read_to_string(&metadata_path)
                .map_err(|e| NetworkError::InternalError(format!("Failed to read metadata: {}", e)))?;

            let metadata: HashMap<String, BackupMetadata> = serde_json::from_str(&metadata_content)
                .map_err(|e| NetworkError::InternalError(format!("Failed to parse metadata: {}", e)))?;

            let mut backup_metadata = self.backup_metadata.write().await;
            *backup_metadata = metadata;

            debug!("Loaded {} backup metadata entries", backup_metadata.len());
        }

        Ok(())
    }

    /// Save backup metadata to disk
    async fn save_backup_metadata(&self) -> NetworkResult<()> {
        let metadata_path = self.backup_config.backup_directory.join("backup_metadata.json");

        let metadata = self.backup_metadata.read().await;
        let metadata_json = serde_json::to_string_pretty(&*metadata)
            .map_err(|e| NetworkError::InternalError(format!("Failed to serialize metadata: {}", e)))?;

        std::fs::write(&metadata_path, metadata_json)
            .map_err(|e| NetworkError::InternalError(format!("Failed to save metadata: {}", e)))?;

        Ok(())
    }

    /// Replicate backup to remote nodes
    async fn replicate_backup_to_remote_nodes(&self, _metadata: &BackupMetadata) -> NetworkResult<()> {
        // Implementation would send backup to remote nodes
        debug!("Replicating backup to remote nodes");
        Ok(())
    }

    /// Start backup verification background task
    async fn start_backup_verification(&self) {
        debug!("Starting backup verification task");
        // Implementation would periodically verify backup integrity
    }

    /// Start remote backup monitoring
    async fn start_remote_backup_monitoring(&self) {
        debug!("Starting remote backup monitoring");
        // Implementation would monitor remote backup nodes
    }
}

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

    #[tokio::test]
    async fn test_disaster_recovery_manager_creation() {
        let dir = tempdir().unwrap();
        let backup_config = BackupConfig {
            enabled: true,
            backup_directory: dir.path().to_path_buf(),
            backup_interval: Duration::from_secs(3600),
            max_backup_files: 5,
            compress_backups: false,
            remote_backup_nodes: vec![],
        };

        let transport = Arc::new(NetworkTransport::new("test_node".to_string()));
        let storage = Arc::new(Mutex::new(Storage::new(dir.path().join("storage.log")).unwrap()));

        let dr_manager = DisasterRecoveryManager::new(
            "test_node".to_string(),
            transport,
            storage,
            backup_config,
        );

        assert_eq!(dr_manager.node_id, "test_node");
    }

    #[test]
    fn test_backup_verification() {
        let verification = BackupVerification {
            is_valid: true,
            checksum_match: true,
            file_exists: true,
            size_match: true,
            metadata_valid: true,
            errors: vec![],
        };

        assert!(verification.is_valid);
        assert!(verification.checksum_match);
    }

    #[test]
    fn test_recovery_options_default() {
        let options = RecoveryOptions::default();
        assert!(options.include_transactions);
        assert!(options.verify_integrity);
        assert_eq!(options.max_concurrent_operations, 4);
    }
}
