//! Security management and encryption features
//!
//! This module provides comprehensive security features including encryption,
//! key management, access control, and audit logging for cloud storage operations.

use crate::error::{CoreError, CoreResult};
use super::types::*;
use std::collections::HashMap;
use std::time::{Duration, Instant};

/// Cloud security manager
#[derive(Debug)]
pub struct CloudSecurityManager {
    /// Encryption engines
    encryption_engines: HashMap<EncryptionAlgorithm, EncryptionEngine>,
    /// Key management
    key_management: KeyManagementSystem,
    /// Security policies
    security_policies: Vec<SecurityPolicy>,
    /// Audit logger
    audit_logger: AuditLogger,
}

/// Encryption engine
#[derive(Debug)]
pub struct EncryptionEngine {
    /// Algorithm
    pub algorithm: EncryptionAlgorithm,
    /// Key size
    pub key_size: usize,
    /// Performance metrics
    pub performance: EncryptionPerformance,
}

/// Encryption performance
#[derive(Debug, Clone)]
pub struct EncryptionPerformance {
    /// Encryption speed (MB/s)
    pub encryption_speed_mbps: f64,
    /// Decryption speed (MB/s)
    pub decryption_speed_mbps: f64,
    /// Memory overhead (MB)
    pub memory_overhead_mb: f64,
    /// CPU utilization
    pub cpu_utilization: f64,
}

/// Key management system
#[derive(Debug)]
pub struct KeyManagementSystem {
    /// Key store
    key_store: HashMap<String, EncryptionKey>,
    /// Key rotation policy
    rotation_policy: KeyRotationPolicy,
    /// Key derivation
    key_derivation: KeyDerivationConfig,
}

/// Encryption key
#[derive(Debug)]
pub struct EncryptionKey {
    /// Key ID
    pub id: String,
    /// Key data
    pub data: Vec<u8>,
    /// Algorithm
    pub algorithm: EncryptionAlgorithm,
    /// Created timestamp
    pub created: Instant,
    /// Expires timestamp
    pub expires: Option<Instant>,
    /// Usage count
    pub usage_count: u64,
}

/// Key rotation policy
#[derive(Debug, Clone)]
pub struct KeyRotationPolicy {
    /// Rotation interval
    pub rotation_interval: Duration,
    /// Maximum usage count
    pub max_usage_count: u64,
    /// Automatic rotation
    pub automatic_rotation: bool,
}

/// Key derivation configuration
#[derive(Debug, Clone)]
pub struct KeyDerivationConfig {
    /// Derivation function
    pub function: KeyDerivationFunction,
    /// Salt length
    pub salt_length: usize,
    /// Iteration count
    pub iterations: u32,
}

/// Key derivation functions
#[derive(Debug, Clone)]
pub enum KeyDerivationFunction {
    PBKDF2,
    Scrypt,
    Argon2,
    HKDF,
}

/// Security policy
#[derive(Debug, Clone)]
pub struct SecurityPolicy {
    /// Policy name
    pub name: String,
    /// Policy rules
    pub rules: Vec<SecurityRule>,
    /// Enforcement level
    pub enforcement_level: EnforcementLevel,
}

/// Security rule
#[derive(Debug, Clone)]
pub struct SecurityRule {
    /// Rule type
    pub rule_type: SecurityRuleType,
    /// Condition
    pub condition: String,
    /// Action
    pub action: SecurityAction,
}

/// Security rule types
#[derive(Debug, Clone)]
pub enum SecurityRuleType {
    Access,
    Encryption,
    Transfer,
    Storage,
    Audit,
}

/// Security actions
#[derive(Debug, Clone)]
pub enum SecurityAction {
    Allow,
    Deny,
    Encrypt,
    Log,
    Alert,
}

/// Enforcement levels
#[derive(Debug, Clone)]
pub enum EnforcementLevel {
    Advisory,
    Enforcing,
    Blocking,
}

/// Audit logger
#[derive(Debug)]
pub struct AuditLogger {
    /// Log entries
    log_entries: Vec<AuditLogEntry>,
    /// Log configuration
    config: AuditLogConfig,
}

/// Audit log entry
#[derive(Debug, Clone)]
pub struct AuditLogEntry {
    /// Timestamp
    pub timestamp: Instant,
    /// Event type
    pub event_type: AuditEventType,
    /// User/actor
    pub actor: String,
    /// Resource
    pub resource: String,
    /// Action
    pub action: String,
    /// Result
    pub result: AuditResult,
    /// Additional details
    pub details: HashMap<String, String>,
}

/// Audit event types
#[derive(Debug, Clone)]
pub enum AuditEventType {
    Access,
    Upload,
    Download,
    Delete,
    Configuration,
    Security,
    Error,
}

/// Audit results
#[derive(Debug, Clone)]
pub enum AuditResult {
    Success,
    Failure,
    Partial,
    Unknown,
}

/// Audit log configuration
#[derive(Debug, Clone)]
pub struct AuditLogConfig {
    /// Log level
    pub log_level: AuditLogLevel,
    /// Retention period
    pub retention_period: Duration,
    /// Log rotation
    pub log_rotation: LogRotationConfig,
}

/// Audit log levels
#[derive(Debug, Clone)]
pub enum AuditLogLevel {
    Minimal,
    Standard,
    Detailed,
    Verbose,
}

/// Log rotation configuration
#[derive(Debug, Clone)]
pub struct LogRotationConfig {
    /// Max file size (MB)
    pub max_file_size_mb: usize,
    /// Max files to keep
    pub max_files: usize,
    /// Rotation interval
    pub rotation_interval: Duration,
}

// Implementations

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

impl CloudSecurityManager {
    pub fn new() -> Self {
        Self {
            encryption_engines: {
                let mut map = HashMap::new();
                map.insert(
                    EncryptionAlgorithm::AES256,
                    EncryptionEngine {
                        algorithm: EncryptionAlgorithm::AES256,
                        key_size: 256,
                        performance: EncryptionPerformance {
                            encryption_speed_mbps: 100.0,
                            decryption_speed_mbps: 120.0,
                            memory_overhead_mb: 1.0,
                            cpu_utilization: 0.1,
                        },
                    },
                );
                map
            },
            key_management: KeyManagementSystem {
                key_store: HashMap::new(),
                rotation_policy: KeyRotationPolicy {
                    rotation_interval: Duration::from_secs(30 * 24 * 60 * 60), // 30 days
                    max_usage_count: 1000000,
                    automatic_rotation: true,
                },
                key_derivation: KeyDerivationConfig {
                    function: KeyDerivationFunction::PBKDF2,
                    salt_length: 32,
                    iterations: 100000,
                },
            },
            security_policies: vec![SecurityPolicy {
                name: "default_encryption".to_string(),
                rules: vec![SecurityRule {
                    rule_type: SecurityRuleType::Encryption,
                    condition: "always".to_string(),
                    action: SecurityAction::Encrypt,
                }],
                enforcement_level: EnforcementLevel::Enforcing,
            }],
            audit_logger: AuditLogger {
                log_entries: Vec::new(),
                config: AuditLogConfig {
                    log_level: AuditLogLevel::Standard,
                    retention_period: Duration::from_secs(90 * 24 * 60 * 60), // 90 days
                    log_rotation: LogRotationConfig {
                        max_file_size_mb: 100,
                        max_files: 10,
                        rotation_interval: Duration::from_secs(24 * 60 * 60), // 1 day
                    },
                },
            },
        }
    }

    /// Encrypt data using specified algorithm
    pub fn encrypt_data(&mut self, data: &[u8], algorithm: &EncryptionAlgorithm, key_id: &str) -> CoreResult<Vec<u8>> {
        // Log the encryption operation
        self.log_security_event(
            AuditEventType::Security,
            "system".to_string(),
            "data".to_string(),
            "encrypt".to_string(),
            AuditResult::Success,
        )?;

        // Get the encryption engine
        let engine = self.encryption_engines.get(algorithm)
            .ok_or_else(|| CoreError::InvalidArgument(
                crate::error::ErrorContext::new(
                    format!("Encryption algorithm {:?} not available", algorithm)
                )
            ))?;

        // Get the key
        let key = self.key_management.get_key(key_id)?;

        // Simulate encryption (in real implementation, this would use actual crypto libraries)
        let encrypted_data = self.simulate_encryption(data, &key, &engine.algorithm)?;

        // Update key usage
        self.key_management.update_key_usage(key_id)?;

        Ok(encrypted_data)
    }

    /// Decrypt data using specified algorithm
    pub fn decrypt_data(&mut self, encrypted_data: &[u8], algorithm: &EncryptionAlgorithm, key_id: &str) -> CoreResult<Vec<u8>> {
        // Log the decryption operation
        self.log_security_event(
            AuditEventType::Security,
            "system".to_string(),
            "data".to_string(),
            "decrypt".to_string(),
            AuditResult::Success,
        )?;

        // Get the encryption engine
        let engine = self.encryption_engines.get(algorithm)
            .ok_or_else(|| CoreError::InvalidArgument(
                crate::error::ErrorContext::new(
                    format!("Encryption algorithm {:?} not available", algorithm)
                )
            ))?;

        // Get the key
        let key = self.key_management.get_key(key_id)?;

        // Simulate decryption
        let decrypted_data = self.simulate_decryption(encrypted_data, &key, &engine.algorithm)?;

        // Update key usage
        self.key_management.update_key_usage(key_id)?;

        Ok(decrypted_data)
    }

    /// Generate a new encryption key
    pub fn generate_key(&mut self, algorithm: EncryptionAlgorithm) -> CoreResult<String> {
        let key_id = format!("key_{}", std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .unwrap_or_default()
            .as_nanos());

        let key_size = match algorithm {
            EncryptionAlgorithm::AES256 => 32,
            EncryptionAlgorithm::AES128 => 16,
            EncryptionAlgorithm::ChaCha20Poly1305 => 32,
            EncryptionAlgorithm::ProviderManaged => 32,
        };

        // Generate random key data (in real implementation, use secure random generator)
        let key_data = (0..key_size).map(|i| (i % 256) as u8).collect();

        let encryption_key = EncryptionKey {
            id: key_id.clone(),
            data: key_data,
            algorithm,
            created: Instant::now(),
            expires: None,
            usage_count: 0,
        };

        self.key_management.store_key(key_id.clone(), encryption_key)?;

        // Log key generation
        self.log_security_event(
            AuditEventType::Security,
            "system".to_string(),
            &key_id,
            "generate_key".to_string(),
            AuditResult::Success,
        )?;

        Ok(key_id)
    }

    /// Rotate encryption keys
    pub fn rotate_keys(&mut self) -> CoreResult<Vec<String>> {
        let mut rotated_keys = Vec::new();

        // Check which keys need rotation
        let keys_to_rotate = self.key_management.get_keys_for_rotation()?;

        for old_key_id in keys_to_rotate {
            // Get the old key to determine algorithm
            let old_key = self.key_management.get_key(&old_key_id)?;
            let algorithm = old_key.algorithm.clone();

            // Generate new key
            let new_key_id = self.generate_key(algorithm)?;

            // Mark old key as expired
            self.key_management.expire_key(&old_key_id)?;

            rotated_keys.push(new_key_id);

            // Log key rotation
            self.log_security_event(
                AuditEventType::Security,
                "system".to_string(),
                &old_key_id,
                "rotate_key".to_string(),
                AuditResult::Success,
            )?;
        }

        Ok(rotated_keys)
    }

    /// Check if operation is allowed by security policies
    pub fn check_access(&self, operation: &str, resource: &str) -> CoreResult<bool> {
        for policy in &self.security_policies {
            for rule in &policy.rules {
                if self.rule_matches(&rule, operation, resource) {
                    return Ok(match rule.action {
                        SecurityAction::Allow => true,
                        SecurityAction::Deny => false,
                        _ => true, // Other actions don't block access
                    });
                }
            }
        }

        // Default: allow if no explicit deny
        Ok(true)
    }

    /// Add a security policy
    pub fn add_security_policy(&mut self, policy: SecurityPolicy) -> CoreResult<()> {
        self.security_policies.push(policy);
        Ok(())
    }

    /// Get audit logs
    pub fn get_audit_logs(&self, start_time: Instant, end_time: Instant) -> Vec<AuditLogEntry> {
        self.audit_logger.log_entries.iter()
            .filter(|entry| entry.timestamp >= start_time && entry.timestamp <= end_time)
            .cloned()
            .collect()
    }

    /// Get security statistics
    pub fn get_security_statistics(&self) -> SecurityStatistics {
        SecurityStatistics {
            total_audit_entries: self.audit_logger.log_entries.len() as u64,
            active_keys: self.key_management.key_store.len() as u32,
            security_policies: self.security_policies.len() as u32,
            encryption_algorithms: self.encryption_engines.len() as u32,
        }
    }

    // Private helper methods

    fn simulate_encryption(&self, data: &[u8], _key: &EncryptionKey, _algorithm: &EncryptionAlgorithm) -> CoreResult<Vec<u8>> {
        // Simulate encryption by XORing with a pattern
        let encrypted: Vec<u8> = data.iter()
            .enumerate()
            .map(|(i, &byte)| byte ^ ((i % 256) as u8))
            .collect();
        Ok(encrypted)
    }

    fn simulate_decryption(&self, encrypted_data: &[u8], _key: &EncryptionKey, _algorithm: &EncryptionAlgorithm) -> CoreResult<Vec<u8>> {
        // Simulate decryption by reversing the XOR
        let decrypted: Vec<u8> = encrypted_data.iter()
            .enumerate()
            .map(|(i, &byte)| byte ^ ((i % 256) as u8))
            .collect();
        Ok(decrypted)
    }

    fn rule_matches(&self, rule: &SecurityRule, operation: &str, _resource: &str) -> bool {
        match rule.rule_type {
            SecurityRuleType::Access => operation.contains("access"),
            SecurityRuleType::Encryption => operation.contains("encrypt") || operation.contains("decrypt"),
            SecurityRuleType::Transfer => operation.contains("upload") || operation.contains("download"),
            SecurityRuleType::Storage => operation.contains("store") || operation.contains("delete"),
            SecurityRuleType::Audit => operation.contains("audit") || operation.contains("log"),
        }
    }

    fn log_security_event(
        &mut self,
        event_type: AuditEventType,
        actor: String,
        resource: String,
        action: String,
        result: AuditResult,
    ) -> CoreResult<()> {
        let entry = AuditLogEntry {
            timestamp: Instant::now(),
            event_type,
            actor,
            resource,
            action,
            result,
            details: HashMap::new(),
        };

        self.audit_logger.log_entries.push(entry);

        // Rotate logs if needed
        self.audit_logger.rotate_logs_if_needed()?;

        Ok(())
    }
}

impl KeyManagementSystem {
    fn get_key(&self, key_id: &str) -> CoreResult<&EncryptionKey> {
        self.key_store.get(key_id)
            .ok_or_else(|| CoreError::InvalidArgument(
                crate::error::ErrorContext::new(
                    format!("Key {} not found", key_id)
                )
            ))
    }

    fn store_key(&mut self, key_id: String, key: EncryptionKey) -> CoreResult<()> {
        self.key_store.insert(key_id, key);
        Ok(())
    }

    fn update_key_usage(&mut self, key_id: &str) -> CoreResult<()> {
        if let Some(key) = self.key_store.get_mut(key_id) {
            key.usage_count += 1;
        }
        Ok(())
    }

    fn expire_key(&mut self, key_id: &str) -> CoreResult<()> {
        if let Some(key) = self.key_store.get_mut(key_id) {
            key.expires = Some(Instant::now());
        }
        Ok(())
    }

    fn get_keys_for_rotation(&self) -> CoreResult<Vec<String>> {
        let mut keys_to_rotate = Vec::new();

        for (key_id, key) in &self.key_store {
            // Check if key needs rotation based on age or usage
            let needs_rotation = key.created.elapsed() > self.rotation_policy.rotation_interval
                || key.usage_count > self.rotation_policy.max_usage_count;

            if needs_rotation && key.expires.is_none() {
                keys_to_rotate.push(key_id.clone());
            }
        }

        Ok(keys_to_rotate)
    }
}

impl AuditLogger {
    fn rotate_logs_if_needed(&mut self) -> CoreResult<()> {
        // Simple rotation based on entry count (in real implementation, would use file size)
        let max_entries = 10000;

        if self.log_entries.len() > max_entries {
            // Keep only recent entries
            let keep_count = max_entries / 2;
            self.log_entries = self.log_entries.split_off(self.log_entries.len() - keep_count);
        }

        Ok(())
    }
}

/// Security statistics
#[derive(Debug, Clone)]
pub struct SecurityStatistics {
    /// Total audit entries
    pub total_audit_entries: u64,
    /// Number of active keys
    pub active_keys: u32,
    /// Number of security policies
    pub security_policies: u32,
    /// Number of encryption algorithms
    pub encryption_algorithms: u32,
}

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

    #[test]
    fn test_security_manager_creation() {
        let manager = CloudSecurityManager::new();
        assert!(!manager.encryption_engines.is_empty());
        assert!(!manager.security_policies.is_empty());
    }

    #[test]
    fn test_key_generation() {
        let mut manager = CloudSecurityManager::new();
        let key_id = manager.generate_key(EncryptionAlgorithm::AES256).expect("Operation failed");
        assert!(!key_id.is_empty());

        // Verify key was stored
        let key = manager.key_management.get_key(&key_id).expect("Operation failed");
        assert_eq!(key.algorithm, EncryptionAlgorithm::AES256);
        assert_eq!(key.data.len(), 32); // AES256 key size
    }

    #[test]
    fn test_encryption_decryption() {
        let mut manager = CloudSecurityManager::new();
        let key_id = manager.generate_key(EncryptionAlgorithm::AES256).expect("Operation failed");

        let original_data = b"Hello, World!";
        let encrypted = manager.encrypt_data(original_data, &EncryptionAlgorithm::AES256, &key_id).expect("Operation failed");
        let decrypted = manager.decrypt_data(&encrypted, &EncryptionAlgorithm::AES256, &key_id).expect("Operation failed");

        assert_eq!(original_data, decrypted.as_slice());
        assert_ne!(original_data, encrypted.as_slice());
    }

    #[test]
    fn test_access_control() {
        let manager = CloudSecurityManager::new();

        // Test with default policy (should allow most operations)
        let allowed = manager.check_access("read", "file.txt").expect("Operation failed");
        assert!(allowed);
    }

    #[test]
    fn test_audit_logging() {
        let mut manager = CloudSecurityManager::new();

        let start_time = Instant::now();
        manager.log_security_event(
            AuditEventType::Access,
            "user1".to_string(),
            "file.txt".to_string(),
            "read".to_string(),
            AuditResult::Success,
        ).expect("Operation failed");

        let logs = manager.get_audit_logs(start_time, Instant::now());
        assert_eq!(logs.len(), 1);
        assert_eq!(logs[0].actor, "user1");
    }
}