//! Sync service for encrypted backup and restore operations to cloud storage

use anyhow::{Result, anyhow};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use chrono::{DateTime, Utc};
use crate::services::EncryptionService;
use crate::config::ConfigManager;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BackupData {
    pub vectors: HashMap<String, Vec<f32>>,
    pub mappings: HashMap<String, String>,
    pub metadata: BackupMetadata,
    pub timestamp: DateTime<Utc>,
    pub version: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BackupMetadata {
    pub total_vectors: usize,
    pub total_mappings: usize,
    pub backup_size_bytes: usize,
    pub encryption_enabled: bool,
    pub cloud_provider: String,
    pub created_at: DateTime<Utc>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BackupOptions {
    pub cloud_provider: Option<String>,
    pub encryption_enabled: Option<bool>,
    pub include_vectors: bool,
    pub include_mappings: bool,
    pub include_metadata: bool,
    pub custom_path: Option<String>,
}

impl Default for BackupOptions {
    fn default() -> Self {
        Self {
            cloud_provider: None,
            encryption_enabled: None,
            include_vectors: true,
            include_mappings: true,
            include_metadata: true,
            custom_path: None,
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RestoreOptions {
    pub cloud_provider: Option<String>,
    pub backup_timestamp: Option<DateTime<Utc>>,
    pub custom_path: Option<String>,
    pub overwrite_existing: bool,
}

impl Default for RestoreOptions {
    fn default() -> Self {
        Self {
            cloud_provider: None,
            backup_timestamp: None,
            custom_path: None,
            overwrite_existing: false,
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SyncResult {
    pub success: bool,
    pub cloud_provider: String,
    pub operation: String,
    pub bytes_transferred: usize,
    pub duration_ms: u64,
    pub backup_path: Option<String>,
    pub error_message: Option<String>,
}

pub struct SyncService {
    encryption_service: Arc<EncryptionService>,
    config_manager: Arc<ConfigManager>,
    s3_client: Option<aws_sdk_s3::Client>,
}

impl SyncService {
    pub async fn new(
        encryption_service: Arc<EncryptionService>,
        config_manager: Arc<ConfigManager>,
    ) -> Result<Self> {
        let s3_client = Self::initialize_s3_client(&config_manager).await;
        
        Ok(Self {
            encryption_service,
            config_manager,
            s3_client,
        })
    }
    
    pub async fn initialize(&self) -> Result<()> {
        Ok(())
    }
    
    pub async fn shutdown(&self) -> Result<()> {
        Ok(())
    }

    pub async fn backup(&self, options: BackupOptions) -> Result<SyncResult> {
        let start_time = std::time::Instant::now();
        let cloud_provider = self.detect_cloud_provider(&options)?;
        
        // Create backup data
        let backup_data = self.create_backup_data(&options).await?;
        
        // Encrypt data if enabled
        let data_to_upload = if options.encryption_enabled.unwrap_or(true) {
            let serialized_data = serde_json::to_string(&backup_data)?;
            self.encryption_service.encrypt(&serialized_data).await?.into_bytes()
        } else {
            serde_json::to_vec(&backup_data)?
        };

        // Upload to cloud storage
        let backup_path = match cloud_provider.as_str() {
            "aws" | "s3" => self.backup_to_s3(&data_to_upload, &options).await?,
            "azure" => self.backup_to_azure(&data_to_upload, &options).await?,
            "gcp" => self.backup_to_gcs(&data_to_upload, &options).await?,
            _ => return Err(anyhow!("Unsupported cloud provider: {}", cloud_provider)),
        };

        let duration = start_time.elapsed();
        
        Ok(SyncResult {
            success: true,
            cloud_provider,
            operation: "backup".to_string(),
            bytes_transferred: data_to_upload.len(),
            duration_ms: duration.as_millis() as u64,
            backup_path: Some(backup_path),
            error_message: None,
        })
    }

    pub async fn restore(&self, options: RestoreOptions) -> Result<SyncResult> {
        let start_time = std::time::Instant::now();
        let cloud_provider = self.detect_cloud_provider_from_restore(&options)?;
        
        // Download from cloud storage
        let encrypted_data = match cloud_provider.as_str() {
            "aws" | "s3" => self.restore_from_s3(&options).await?,
            "azure" => self.restore_from_azure(&options).await?,
            "gcp" => self.restore_from_gcs(&options).await?,
            _ => return Err(anyhow!("Unsupported cloud provider: {}", cloud_provider)),
        };

        // Decrypt data
        let encrypted_str = String::from_utf8(encrypted_data.clone())?;
        let decrypted_data = self.encryption_service.decrypt(&encrypted_str).await?;
        
        // Deserialize backup data
        let backup_data: BackupData = serde_json::from_str(&decrypted_data)?;
        
        // Restore data (in a real implementation, this would restore to vector stores)
        self.apply_restore_data(&backup_data, &options).await?;

        let duration = start_time.elapsed();
        
        Ok(SyncResult {
            success: true,
            cloud_provider,
            operation: "restore".to_string(),
            bytes_transferred: encrypted_data.len(),
            duration_ms: duration.as_millis() as u64,
            backup_path: None,
            error_message: None,
        })
    }

    async fn create_backup_data(&self, options: &BackupOptions) -> Result<BackupData> {
        let mut vectors = HashMap::new();
        let mut mappings = HashMap::new();
        
        // In a real implementation, this would collect data from vector stores
        if options.include_vectors {
            // Placeholder: collect vectors from vector stores
            vectors.insert("sample_document_1".to_string(), vec![0.1, 0.2, 0.3]);
            vectors.insert("sample_document_2".to_string(), vec![0.4, 0.5, 0.6]);
        }
        
        if options.include_mappings {
            // Placeholder: collect mappings from storage
            mappings.insert("doc_id_1".to_string(), "sample_document_1".to_string());
            mappings.insert("doc_id_2".to_string(), "sample_document_2".to_string());
        }
        
        let metadata = BackupMetadata {
            total_vectors: vectors.len(),
            total_mappings: mappings.len(),
            backup_size_bytes: 0, // Will be calculated after serialization
            encryption_enabled: options.encryption_enabled.unwrap_or(true),
            cloud_provider: options.cloud_provider.clone().unwrap_or_else(|| "aws".to_string()),
            created_at: Utc::now(),
        };
        
        Ok(BackupData {
            vectors,
            mappings,
            metadata,
            timestamp: Utc::now(),
            version: "1.0".to_string(),
        })
    }

    async fn backup_to_s3(&self, data: &[u8], options: &BackupOptions) -> Result<String> {
        if let Some(ref client) = self.s3_client {
            let s3_config = self.config_manager.get_s3_config();
            let timestamp = Utc::now().format("%Y%m%d_%H%M%S");
            let key = options.custom_path.clone()
                .unwrap_or_else(|| format!("rag-backup-{}.bin", timestamp));
            
            let mut put_request = client
                .put_object()
                .bucket(&s3_config.bucket)
                .key(&key)
                .body(aws_sdk_s3::primitives::ByteStream::from(data.to_vec()));
            
            if s3_config.encryption_enabled {
                put_request = put_request.server_side_encryption(
                    aws_sdk_s3::types::ServerSideEncryption::Aes256
                );
            }
            
            put_request.send().await.map_err(|e| anyhow!("S3 upload failed: {}", e))?;
            
            Ok(format!("s3://{}/{}", s3_config.bucket, key))
        } else {
            Err(anyhow!("S3 client not initialized"))
        }
    }

    async fn backup_to_azure(&self, _data: &[u8], options: &BackupOptions) -> Result<String> {
        // Placeholder implementation for Azure Blob Storage
        let azure_config = self.config_manager.get_azure_blob_config();
        if !azure_config.enabled {
            return Err(anyhow!("Azure Blob Storage not configured"));
        }
        
        // In a real implementation, this would use Azure SDK
        let timestamp = Utc::now().format("%Y%m%d_%H%M%S");
        let blob_name = options.custom_path.clone()
            .unwrap_or_else(|| format!("rag-backup-{}.bin", timestamp));
        
        // Placeholder: Azure upload logic would go here
        Ok(format!("azure://{}/{}", azure_config.container_name, blob_name))
    }

    async fn backup_to_gcs(&self, _data: &[u8], options: &BackupOptions) -> Result<String> {
        // Placeholder implementation for Google Cloud Storage
        let gcs_config = self.config_manager.get_gcs_config();
        if !gcs_config.enabled {
            return Err(anyhow!("Google Cloud Storage not configured"));
        }
        
        // In a real implementation, this would use Google Cloud SDK
        let timestamp = Utc::now().format("%Y%m%d_%H%M%S");
        let object_name = options.custom_path.clone()
            .unwrap_or_else(|| format!("rag-backup-{}.bin", timestamp));
        
        // Placeholder: GCS upload logic would go here
        Ok(format!("gs://{}/{}", gcs_config.bucket_name, object_name))
    }

    async fn restore_from_s3(&self, options: &RestoreOptions) -> Result<Vec<u8>> {
        if let Some(ref client) = self.s3_client {
            let s3_config = self.config_manager.get_s3_config();
            let key = options.custom_path.clone()
                .unwrap_or_else(|| "latest-backup.bin".to_string());
            
            let response = client
                .get_object()
                .bucket(&s3_config.bucket)
                .key(&key)
                .send()
                .await
                .map_err(|e| anyhow!("S3 download failed: {}", e))?;
            
            let data = response.body.collect().await
                .map_err(|e| anyhow!("Failed to read S3 response body: {}", e))?
                .into_bytes()
                .to_vec();
            
            Ok(data)
        } else {
            Err(anyhow!("S3 client not initialized"))
        }
    }

    async fn restore_from_azure(&self, _options: &RestoreOptions) -> Result<Vec<u8>> {
        // Placeholder implementation for Azure Blob Storage
        let azure_config = self.config_manager.get_azure_blob_config();
        if !azure_config.enabled {
            return Err(anyhow!("Azure Blob Storage not configured"));
        }
        
        // Placeholder: Azure download logic would go here
        Ok(vec![]) // Placeholder data
    }

    async fn restore_from_gcs(&self, _options: &RestoreOptions) -> Result<Vec<u8>> {
        // Placeholder implementation for Google Cloud Storage
        let gcs_config = self.config_manager.get_gcs_config();
        if !gcs_config.enabled {
            return Err(anyhow!("Google Cloud Storage not configured"));
        }
        
        // Placeholder: GCS download logic would go here
        Ok(vec![]) // Placeholder data
    }

    async fn apply_restore_data(&self, backup_data: &BackupData, options: &RestoreOptions) -> Result<()> {
        // In a real implementation, this would restore data to vector stores
        println!("Restoring {} vectors and {} mappings", 
            backup_data.metadata.total_vectors,
            backup_data.metadata.total_mappings);
        
        if !options.overwrite_existing {
            // Check for conflicts and handle them
            println!("Checking for conflicts with existing data...");
        }
        
        // Placeholder: Restore logic would go here
        Ok(())
    }

    fn detect_cloud_provider(&self, options: &BackupOptions) -> Result<String> {
        if let Some(ref provider) = options.cloud_provider {
            return Ok(provider.clone());
        }
        
        self.detect_default_cloud()
    }

    fn detect_cloud_provider_from_restore(&self, options: &RestoreOptions) -> Result<String> {
        if let Some(ref provider) = options.cloud_provider {
            return Ok(provider.clone());
        }
        
        self.detect_default_cloud()
    }

    fn detect_default_cloud(&self) -> Result<String> {
        let s3_config = self.config_manager.get_s3_config();
        let azure_config = self.config_manager.get_azure_blob_config();
        let gcs_config = self.config_manager.get_gcs_config();
        
        if s3_config.enabled && !s3_config.bucket.is_empty() {
            return Ok("aws".to_string());
        }
        
        if azure_config.enabled && !azure_config.container_name.is_empty() {
            return Ok("azure".to_string());
        }
        
        if gcs_config.enabled && !gcs_config.bucket_name.is_empty() {
            return Ok("gcp".to_string());
        }
        
        // Default fallback
        Ok("aws".to_string())
    }

    async fn initialize_s3_client(config_manager: &ConfigManager) -> Option<aws_sdk_s3::Client> {
        let s3_config = config_manager.get_s3_config();
        
        if s3_config.enabled && !s3_config.bucket.is_empty() {
            let mut aws_config_builder = aws_config::defaults(aws_config::BehaviorVersion::latest())
                .region(aws_sdk_s3::config::Region::new(s3_config.region.clone()));
            
            // Configure S3 endpoint if provided (for LocalStack)
            if let Some(endpoint_url) = &s3_config.endpoint_url {
                aws_config_builder = aws_config_builder.endpoint_url(endpoint_url);
            }
            
            let aws_config = aws_config_builder.load().await;
            return Some(aws_sdk_s3::Client::new(&aws_config));
        }
        
        None
    }

    pub async fn list_backups(&self, cloud_provider: Option<String>) -> Result<Vec<String>> {
        let provider = cloud_provider.unwrap_or_else(|| self.detect_default_cloud().unwrap_or_else(|_| "aws".to_string()));
        
        match provider.as_str() {
            "aws" | "s3" => self.list_s3_backups().await,
            "azure" => self.list_azure_backups().await,
            "gcp" => self.list_gcs_backups().await,
            _ => Err(anyhow!("Unsupported cloud provider: {}", provider)),
        }
    }

    async fn list_s3_backups(&self) -> Result<Vec<String>> {
        if let Some(ref client) = self.s3_client {
            let s3_config = self.config_manager.get_s3_config();
            
            let response = client
                .list_objects_v2()
                .bucket(&s3_config.bucket)
                .prefix("rag-backup-")
                .send()
                .await
                .map_err(|e| anyhow!("S3 list failed: {}", e))?;
            
            let keys = response.contents()
                .iter()
                .filter_map(|obj| obj.key().map(|k| k.to_string()))
                .collect();
            
            Ok(keys)
        } else {
            Err(anyhow!("S3 client not initialized"))
        }
    }

    async fn list_azure_backups(&self) -> Result<Vec<String>> {
        // Placeholder implementation
        Ok(vec!["azure-backup-1.bin".to_string(), "azure-backup-2.bin".to_string()])
    }

    async fn list_gcs_backups(&self) -> Result<Vec<String>> {
        // Placeholder implementation
        Ok(vec!["gcs-backup-1.bin".to_string(), "gcs-backup-2.bin".to_string()])
    }

    pub fn get_supported_providers(&self) -> Vec<String> {
        vec!["aws".to_string(), "s3".to_string(), "azure".to_string(), "gcp".to_string()]
    }

    pub async fn delete_backup(&self, backup_path: &str, cloud_provider: Option<String>) -> Result<()> {
        let provider = cloud_provider.unwrap_or_else(|| self.detect_default_cloud().unwrap_or_else(|_| "aws".to_string()));
        
        match provider.as_str() {
            "aws" | "s3" => self.delete_s3_backup(backup_path).await,
            "azure" => self.delete_azure_backup(backup_path).await,
            "gcp" => self.delete_gcs_backup(backup_path).await,
            _ => Err(anyhow!("Unsupported cloud provider: {}", provider)),
        }
    }

    async fn delete_s3_backup(&self, backup_path: &str) -> Result<()> {
        if let Some(ref client) = self.s3_client {
            let s3_config = self.config_manager.get_s3_config();
            
            client
                .delete_object()
                .bucket(&s3_config.bucket)
                .key(backup_path)
                .send()
                .await
                .map_err(|e| anyhow!("S3 delete failed: {}", e))?;
            
            Ok(())
        } else {
            Err(anyhow!("S3 client not initialized"))
        }
    }

    async fn delete_azure_backup(&self, backup_path: &str) -> Result<()> {
        // Placeholder implementation
        println!("Would delete Azure backup: {}", backup_path);
        Ok(())
    }

    async fn delete_gcs_backup(&self, backup_path: &str) -> Result<()> {
        // Placeholder implementation
        println!("Would delete GCS backup: {}", backup_path);
        Ok(())
    }
}
