"""
PostgreSQL database connection and session management for POS microservice.
Following SCM pattern with SQLAlchemy async engine.
"""
import logging
import ssl
from contextlib import asynccontextmanager
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker
from sqlalchemy import MetaData, text

from app.core.config import settings

logger = logging.getLogger(__name__)

# Database URL validation
DATABASE_URI = settings.POSTGRES_URI
if not DATABASE_URI:
    logger.error("POSTGRES_URI is empty or missing from settings")
    raise ValueError("POSTGRES_URI is not set. Check environment variables.")

# Parse and log connection details (with masked password)
def mask_connection_string(uri: str) -> str:
    """Mask password in connection string for safe logging"""
    if not uri:
        return "EMPTY"
    
    try:
        # Format: postgresql+asyncpg://user:password@host:port/database
        if "@" in uri:
            protocol_user_pass, host_db = uri.split("@", 1)
            
            if "://" in protocol_user_pass:
                protocol, user_pass = protocol_user_pass.split("://", 1)
                
                if ":" in user_pass:
                    user, _ = user_pass.split(":", 1)
                    masked_uri = f"{protocol}://{user}:***@{host_db}"
                else:
                    masked_uri = f"{protocol}://{user_pass}:***@{host_db}"
            else:
                masked_uri = f"{protocol_user_pass}:***@{host_db}"
        else:
            masked_uri = uri
        
        return masked_uri
    except Exception:
        return "INVALID_FORMAT"

def parse_connection_details(uri: str) -> dict:
    """Parse connection string to extract host, port, database"""
    try:
        # Extract host:port/database from URI
        if "@" in uri:
            _, host_db = uri.split("@", 1)
            
            if "/" in host_db:
                host_port, database = host_db.split("/", 1)
                
                if ":" in host_port:
                    host, port = host_port.split(":", 1)
                else:
                    host = host_port
                    port = "5432"
                
                return {
                    "host": host,
                    "port": port,
                    "database": database.split("?")[0]  # Remove query params
                }
    except Exception:
        pass
    
    return {"host": "unknown", "port": "unknown", "database": "unknown"}

masked_uri = mask_connection_string(DATABASE_URI)
conn_details = parse_connection_details(DATABASE_URI)

logger.info(
    "PostgreSQL connection configured",
    extra={
        "connection_string": masked_uri,
        "host": conn_details["host"],
        "port": conn_details["port"],
        "database": conn_details["database"],
        "ssl_mode": settings.POSTGRES_SSL_MODE
    }
)

# Build connect args including optional SSL
CONNECT_ARGS = {
    "server_settings": {
        "application_name": "cuatrolabs-pos-ms",
        "jit": "off"
    },
    "command_timeout": 60,
    "statement_cache_size": 0
}

mode = (settings.POSTGRES_SSL_MODE or "disable").lower()
if mode != "disable":
    ssl_context: ssl.SSLContext
    if mode == "verify-full":
        ssl_context = ssl.create_default_context(cafile=settings.POSTGRES_SSL_ROOT_CERT) if settings.POSTGRES_SSL_ROOT_CERT else ssl.create_default_context()
        if settings.POSTGRES_SSL_CERT and settings.POSTGRES_SSL_KEY:
            try:
                ssl_context.load_cert_chain(certfile=settings.POSTGRES_SSL_CERT, keyfile=settings.POSTGRES_SSL_KEY)
            except Exception as e:
                logger.warning("Failed to load client SSL cert/key for PostgreSQL", exc_info=e)
        ssl_context.check_hostname = True
        ssl_context.verify_mode = ssl.CERT_REQUIRED
    else:
        # sslmode=require: encrypt but don't verify server cert
        ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
        ssl_context.check_hostname = False
        ssl_context.verify_mode = ssl.CERT_NONE
    CONNECT_ARGS["ssl"] = ssl_context
    logger.info("PostgreSQL SSL enabled", extra={"ssl_mode": settings.POSTGRES_SSL_MODE})

async_engine = create_async_engine(
    DATABASE_URI,
    echo=settings.DEBUG,
    future=True,
    pool_size=10,
    max_overflow=20,
    pool_timeout=30,
    pool_recycle=3600,
    pool_pre_ping=True,
    connect_args=CONNECT_ARGS
)

# Create async session factory
async_session = sessionmaker(
    async_engine, 
    expire_on_commit=False, 
    class_=AsyncSession
)

# Metadata for table creation
metadata = MetaData()

logger.info("PostgreSQL configuration loaded successfully")

# ────────────────────────────────────────────────────────────────────────────────
# Lifecycle helpers
# ────────────────────────────────────────────────────────────────────────────────

async def connect_to_database() -> None:
    """Initialize database connection when the application starts."""
    import asyncio
    
    # Log connection details at startup (once per worker)
    print(f"\n{'='*70}")
    print(f"[POSTGRES] Starting Database Connection")
    print(f"{'='*70}")
    print(f"[POSTGRES] Connection String: {masked_uri}")
    print(f"[POSTGRES] Host: {conn_details['host']}")
    print(f"[POSTGRES] Port: {conn_details['port']}")
    print(f"[POSTGRES] Database: {conn_details['database']}")
    print(f"[POSTGRES] SSL Mode: {settings.POSTGRES_SSL_MODE}")
    print(f"{'='*70}\n")
    
    # Log connection attempt start
    logger.info(
        "Starting PostgreSQL connection attempts",
        extra={
            "max_retries": settings.POSTGRES_CONNECT_MAX_RETRIES,
            "initial_delay_ms": settings.POSTGRES_CONNECT_INITIAL_DELAY_MS,
            "backoff_multiplier": settings.POSTGRES_CONNECT_BACKOFF_MULTIPLIER
        }
    )
    print(f"[POSTGRES] Attempting to connect (max retries: {settings.POSTGRES_CONNECT_MAX_RETRIES})...")
    
    attempts = 0
    max_attempts = settings.POSTGRES_CONNECT_MAX_RETRIES
    delay = settings.POSTGRES_CONNECT_INITIAL_DELAY_MS / 1000.0
    last_error = None
    
    while attempts < max_attempts:
        try:
            async with async_engine.begin() as conn:
                await conn.execute(text("SELECT 1"))
            
            logger.info("Successfully connected to PostgreSQL database")
            print(f"[POSTGRES] ✅ Connection successful after {attempts + 1} attempt(s)")
            return
            
        except Exception as e:
            last_error = e
            attempts += 1
            
            error_msg = str(e)
            error_type = type(e).__name__
            
            logger.warning(
                "PostgreSQL connection attempt failed",
                extra={
                    "attempt": attempts,
                    "max_attempts": max_attempts,
                    "retry_delay_ms": int(delay * 1000),
                    "error_type": error_type,
                    "error_message": error_msg[:200]  # Truncate long errors
                }
            )
            
            print(f"[POSTGRES] ❌ Connection attempt {attempts}/{max_attempts} failed")
            print(f"[POSTGRES] Error: {error_type}: {error_msg[:150]}")
            
            if attempts < max_attempts:
                print(f"[POSTGRES] Retrying in {delay:.2f}s...")
                await asyncio.sleep(delay)
                delay = min(delay * settings.POSTGRES_CONNECT_BACKOFF_MULTIPLIER, 30.0)
    
    # All attempts failed
    logger.error(
        "Failed to connect to PostgreSQL after all retries",
        extra={
            "total_attempts": attempts,
            "final_error_type": type(last_error).__name__,
            "final_error": str(last_error)[:500]
        },
        exc_info=last_error
    )
    
    print(f"[POSTGRES] ❌ FATAL: Failed to connect after {attempts} attempts")
    print(f"[POSTGRES] Last error: {type(last_error).__name__}: {str(last_error)[:200]}")
    print(f"[POSTGRES] Please check:")
    print(f"[POSTGRES]   1. Database host is reachable: {conn_details['host']}")
    print(f"[POSTGRES]   2. Database credentials are correct")
    print(f"[POSTGRES]   3. SSL mode is appropriate: {settings.POSTGRES_SSL_MODE}")
    print(f"[POSTGRES]   4. Firewall allows connections to port {conn_details['port']}")
    
    raise last_error

async def disconnect_from_database() -> None:
    """Close database connection when the application shuts down."""
    try:
        await async_engine.dispose()
        logger.info("Successfully disconnected from PostgreSQL database")
    except Exception as e:
        logger.exception("Error disconnecting from PostgreSQL database")
        raise

async def enforce_trans_schema() -> None:
    """Enforce that all tables use the TRANS schema and validate schema compliance."""
    try:
        async with async_engine.begin() as conn:
            # Ensure trans schema exists
            await conn.execute(text("CREATE SCHEMA IF NOT EXISTS trans"))
            logger.info("✅ TRANS schema exists")
            
            # Validate that all models use trans schema
            from app.core.database import Base
            
            # Import all POS models to ensure they're registered with Base
            from app.sync.models import CustomerRef, StaffRef, CatalogueServiceRef
            
            # Validate schema compliance
            non_trans_tables = []
            for table in Base.metadata.tables.values():
                if table.schema != 'trans':
                    non_trans_tables.append(f"{table.name} (schema: {table.schema})")
            
            if non_trans_tables:
                error_msg = f"❌ SCHEMA VIOLATION: The following tables are not using 'trans' schema: {', '.join(non_trans_tables)}"
                logger.error(error_msg)
                print(f"\n{'='*80}")
                print(f"[SCHEMA ERROR] {error_msg}")
                print(f"{'='*80}\n")
                raise ValueError(error_msg)
            
            logger.info("✅ All POS tables correctly use 'trans' schema")
            print(f"[SCHEMA] ✅ All POS tables correctly use 'trans' schema")
            
    except Exception as e:
        logger.exception("Error enforcing TRANS schema")
        raise

async def create_tables() -> None:
    """Create all tables defined in models after enforcing schema compliance."""
    try:
        # First enforce schema compliance
        await enforce_trans_schema()
        
        from app.core.database import Base
        
        # Import all POS-specific model imports here as needed
        from app.sync.models import CustomerRef, StaffRef, CatalogueServiceRef
        
        async with async_engine.begin() as conn:
            # Create all tables (schema already validated)
            await conn.run_sync(Base.metadata.create_all)
        logger.info("✅ Database tables created successfully in TRANS schema")
        print(f"[SCHEMA] ✅ Database tables created successfully in TRANS schema")
    except Exception as e:
        logger.exception("Error creating database tables")
        raise

# ────────────────────────────────────────────────────────────────────────────────
# Legacy compatibility functions
# ────────────────────────────────────────────────────────────────────────────────

async def connect_to_postgres() -> None:
    """Legacy function name - calls connect_to_database"""
    await connect_to_database()

async def close_postgres_connection() -> None:
    """Legacy function name - calls disconnect_from_database"""
    await disconnect_from_database()

def get_postgres_engine():
    """Get PostgreSQL engine instance."""
    return async_engine

@asynccontextmanager
async def get_postgres_session():
    """
    Get PostgreSQL session context manager.
    
    Usage:
        async with get_postgres_session() as session:
            await session.execute(...)
            await session.commit()
    """
    if not async_session:
        logger.warning("PostgreSQL session maker not initialized")
        yield None
        return
    
    session = async_session()
    try:
        yield session
    except Exception as e:
        await session.rollback()
        logger.error(f"Session error, rolled back: {e}")
        raise
    finally:
        await session.close()

async def execute_postgres_query(query: str, params: dict = None):
    """
    Execute a raw SQL query.
    
    Args:
        query: SQL query string
        params: Query parameters dict
    """
    if not async_engine:
        logger.warning("PostgreSQL engine not available, skipping query")
        return None
    
    async with get_postgres_session() as session:
        if session is None:
            return None
        result = await session.execute(query, params or {})
        await session.commit()
        return result