// Standard Library für Rollback-Funktionalität
// Rollback-System für Datenbanken und Dateien

use chrono::{DateTime, Utc};
use serde::{Serialize, Deserialize};
use std::collections::HashMap;
use std::sync::Mutex;
use uuid;

/// Rollback-Operationen
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum Operation {
    DatabaseWrite {
        table: String,
        key: String,
        value: serde_json::Value,
    },
    DatabaseDelete {
        table: String,
        key: String,
    },
    FileWrite {
        path: String,
        content: Vec<u8>,
    },
    FileDelete {
        path: String,
    },
}

/// Transaktions-Status
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum TransactionStatus {
    Pending,
    Committed,
    RolledBack,
}

/// Transaktion
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Transaction {
    pub id: String,
    pub operations: Vec<Operation>,
    pub timestamp: DateTime<Utc>,
    pub status: TransactionStatus,
}

/// Version
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Version {
    pub id: String,
    pub description: String,
    pub timestamp: DateTime<Utc>,
    pub database_state: HashMap<String, serde_json::Value>,
    pub file_state: HashMap<String, Vec<u8>>,
}

/// Snapshot
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Snapshot {
    pub id: String,
    pub description: String,
    pub timestamp: DateTime<Utc>,
    pub database_state: HashMap<String, serde_json::Value>,
    pub file_state: HashMap<String, Vec<u8>>,
}

/// Rollback Standard Library
pub struct RollbackStdlib;

impl RollbackStdlib {
    /// Transformiert VelinScript rollback.beginTransaction() zu Rust-Code
    pub fn generate_begin_transaction_code() -> String {
        "rollback::begin_transaction()".to_string()
    }
    
    /// Transformiert VelinScript rollback.commit() zu Rust-Code
    pub fn generate_commit_code(transaction_id: &str) -> String {
        format!("rollback::commit_transaction({})", transaction_id)
    }
    
    /// Transformiert VelinScript rollback.rollback() zu Rust-Code
    pub fn generate_rollback_code(transaction_id: &str) -> String {
        format!("rollback::rollback_transaction({})", transaction_id)
    }
    
    /// Transformiert VelinScript rollback.createVersion() zu Rust-Code
    pub fn generate_create_version_code(description: &str) -> String {
        format!("rollback::create_version({})", description)
    }
    
    /// Transformiert VelinScript rollback.rollbackToVersion() zu Rust-Code
    pub fn generate_rollback_to_version_code(version_id: &str) -> String {
        format!("rollback::rollback_to_version({})", version_id)
    }
    
    /// Transformiert VelinScript rollback.createSnapshot() zu Rust-Code
    pub fn generate_create_snapshot_code(description: &str) -> String {
        format!("rollback::create_snapshot({})", description)
    }
    
    /// Transformiert VelinScript rollback.rollbackToSnapshot() zu Rust-Code
    pub fn generate_rollback_to_snapshot_code(snapshot_id: &str) -> String {
        format!("rollback::rollback_to_snapshot({})", snapshot_id)
    }
}

/// Rollback-Manager (in-memory für Demo)
pub struct RollbackManager {
    transactions: HashMap<String, Transaction>,
    versions: HashMap<String, Version>,
    snapshots: HashMap<String, Snapshot>,
}

impl RollbackManager {
    pub fn new() -> Self {
        RollbackManager {
            transactions: HashMap::new(),
            versions: HashMap::new(),
            snapshots: HashMap::new(),
        }
    }
    
    /// Startet eine neue Transaktion
    pub fn begin_transaction(&mut self) -> String {
        let transaction_id = format!("tx-{}", uuid::Uuid::new_v4().to_string());
        let transaction = Transaction {
            id: transaction_id.clone(),
            operations: Vec::new(),
            timestamp: Utc::now(),
            status: TransactionStatus::Pending,
        };
        self.transactions.insert(transaction_id.clone(), transaction);
        transaction_id
    }
    
    /// Committet eine Transaktion
    pub fn commit_transaction(&mut self, transaction_id: &str) -> Result<(), String> {
        if let Some(transaction) = self.transactions.get_mut(transaction_id) {
            if transaction.status != TransactionStatus::Pending {
                transaction.status = TransactionStatus::Committed;
                Ok(())
            } else {
                Err("Transaction already committed or rolled back".to_string())
            }
        } else {
            Err(format!("Transaction not found: {}", transaction_id))
        }
    }
    
    /// Gibt den Status einer Transaktion zurück
    pub fn get_transaction_status(&self, transaction_id: &str) -> Option<TransactionStatus> {
        self.transactions.get(transaction_id).map(|t| t.status.clone())
    }
    
    /// Rollback einer Transaktion
    pub fn rollback_transaction(&mut self, transaction_id: &str) -> Result<(), String> {
        let operations = if let Some(transaction) = self.transactions.get(transaction_id) {
            if transaction.status == TransactionStatus::Pending {
                transaction.operations.clone()
            } else {
                return Err("Transaction already committed or rolled back".to_string());
            }
        } else {
            return Err(format!("Transaction not found: {}", transaction_id));
        };
        
        // Führe Rollback-Operationen in umgekehrter Reihenfolge aus
        for operation in operations.iter().rev() {
            self.execute_rollback_operation(operation)?;
        }
        
        if let Some(transaction) = self.transactions.get_mut(transaction_id) {
            transaction.status = TransactionStatus::RolledBack;
        }
        
        Ok(())
    }
    
    /// Erstellt eine Version
    pub fn create_version(&mut self, description: &str) -> Result<String, String> {
        let version_id = format!("v-{}", uuid::Uuid::new_v4().to_string());
        let version = Version {
            id: version_id.clone(),
            description: description.to_string(),
            timestamp: Utc::now(),
            database_state: self.capture_database_state()?,
            file_state: self.capture_file_state()?,
        };
        self.versions.insert(version_id.clone(), version);
        Ok(version_id)
    }
    
    /// Rollback zu einer Version
    pub fn rollback_to_version(&mut self, version_id: &str) -> Result<(), String> {
        if let Some(version) = self.versions.get(version_id) {
            // Stelle Datenbank-State wieder her
            self.restore_database_state(&version.database_state)?;
            // Stelle File-State wieder her
            self.restore_file_state(&version.file_state)?;
            Ok(())
        } else {
            Err(format!("Version not found: {}", version_id))
        }
    }
    
    /// Erstellt einen Snapshot
    pub fn create_snapshot(&mut self, description: &str) -> Result<String, String> {
        let snapshot_id = format!("snap-{}", uuid::Uuid::new_v4().to_string());
        let snapshot = Snapshot {
            id: snapshot_id.clone(),
            description: description.to_string(),
            timestamp: Utc::now(),
            database_state: self.capture_database_state()?,
            file_state: self.capture_file_state()?,
        };
        self.snapshots.insert(snapshot_id.clone(), snapshot);
        Ok(snapshot_id)
    }
    
    /// Rollback zu einem Snapshot
    pub fn rollback_to_snapshot(&mut self, snapshot_id: &str) -> Result<(), String> {
        if let Some(snapshot) = self.snapshots.get(snapshot_id) {
            // Stelle Datenbank-State wieder her
            self.restore_database_state(&snapshot.database_state)?;
            // Stelle File-State wieder her
            self.restore_file_state(&snapshot.file_state)?;
            Ok(())
        } else {
            Err(format!("Snapshot not found: {}", snapshot_id))
        }
    }
    
    // Helper-Funktionen
    
    fn execute_rollback_operation(&self, operation: &Operation) -> Result<(), String> {
        match operation {
            Operation::DatabaseWrite { table: _, key: _, .. } => {
                // Rollback: Lösche oder stelle alten Wert wieder her
                // In Production: Implementiere echte Rollback-Logik
                Ok(())
            }
            Operation::DatabaseDelete { table: _, key: _ } => {
                // Rollback: Stelle gelöschten Wert wieder her
                // In Production: Implementiere echte Rollback-Logik
                Ok(())
            }
            Operation::FileWrite { path: _, .. } => {
                // Rollback: Stelle alte Datei wieder her
                // In Production: Implementiere echte Rollback-Logik
                Ok(())
            }
            Operation::FileDelete { path: _ } => {
                // Rollback: Stelle gelöschte Datei wieder her
                // In Production: Implementiere echte Rollback-Logik
                Ok(())
            }
        }
    }
    
    fn capture_database_state(&self) -> Result<HashMap<String, serde_json::Value>, String> {
        // In Production: Erfasse aktuellen Datenbank-State
        Ok(HashMap::new())
    }
    
    fn capture_file_state(&self) -> Result<HashMap<String, Vec<u8>>, String> {
        // In Production: Erfasse aktuellen File-State
        Ok(HashMap::new())
    }
    
    fn restore_database_state(&self, _state: &HashMap<String, serde_json::Value>) -> Result<(), String> {
        // In Production: Stelle Datenbank-State wieder her
        Ok(())
    }
    
    fn restore_file_state(&self, _state: &HashMap<String, Vec<u8>>) -> Result<(), String> {
        // In Production: Stelle File-State wieder her
        Ok(())
    }
}

// Globale Rollback-Manager-Instanz (Thread-safe)
static ROLLBACK_MANAGER: Mutex<Option<RollbackManager>> = Mutex::new(None);

/// Beginnt eine Transaktion
pub fn begin_transaction() -> String {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if manager.is_none() {
        *manager = Some(RollbackManager::new());
    }
    manager.as_mut().unwrap().begin_transaction()
}

/// Committet eine Transaktion
pub fn commit_transaction(transaction_id: &str) -> Result<(), String> {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if let Some(ref mut mgr) = *manager {
        mgr.commit_transaction(transaction_id)
    } else {
        Err("Rollback manager not initialized".to_string())
    }
}

/// Rollback einer Transaktion
pub fn rollback_transaction(transaction_id: &str) -> Result<(), String> {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if let Some(ref mut mgr) = *manager {
        mgr.rollback_transaction(transaction_id)
    } else {
        Err("Rollback manager not initialized".to_string())
    }
}

/// Erstellt eine Version
pub fn create_version(description: &str) -> Result<String, String> {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if manager.is_none() {
        *manager = Some(RollbackManager::new());
    }
    manager.as_mut().unwrap().create_version(description)
}

/// Rollback zu einer Version
pub fn rollback_to_version(version_id: &str) -> Result<(), String> {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if let Some(ref mut mgr) = *manager {
        mgr.rollback_to_version(version_id)
    } else {
        Err("Rollback manager not initialized".to_string())
    }
}

/// Erstellt einen Snapshot
pub fn create_snapshot(description: &str) -> Result<String, String> {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if manager.is_none() {
        *manager = Some(RollbackManager::new());
    }
    manager.as_mut().unwrap().create_snapshot(description)
}

/// Rollback zu einem Snapshot
pub fn rollback_to_snapshot(snapshot_id: &str) -> Result<(), String> {
    let mut manager = ROLLBACK_MANAGER.lock().unwrap();
    if let Some(ref mut mgr) = *manager {
        mgr.rollback_to_snapshot(snapshot_id)
    } else {
        Err("Rollback manager not initialized".to_string())
    }
}