"""
PostgreSQL Database Connector for Mitai Jinkendo (v9b)

Provides connection pooling and helper functions for database operations.
Compatible drop-in replacement for the previous SQLite get_db() pattern.
"""
import os
from contextlib import contextmanager
from typing import Optional, Dict, Any, List
import psycopg2
from psycopg2.extras import RealDictCursor
import psycopg2.pool


# Global connection pool
_pool: Optional[psycopg2.pool.SimpleConnectionPool] = None


def init_pool():
    """Initialize PostgreSQL connection pool."""
    global _pool
    if _pool is None:
        _pool = psycopg2.pool.SimpleConnectionPool(
            minconn=1,
            maxconn=10,
            host=os.getenv("DB_HOST", "postgres"),
            port=int(os.getenv("DB_PORT", "5432")),
            database=os.getenv("DB_NAME", "mitai"),
            user=os.getenv("DB_USER", "mitai"),
            password=os.getenv("DB_PASSWORD", "")
        )
        print(f"✓ PostgreSQL connection pool initialized ({os.getenv('DB_HOST', 'postgres')}:{os.getenv('DB_PORT', '5432')})")


@contextmanager
def get_db():
    """
    Context manager for database connections.

    Usage:
        with get_db() as conn:
            cur = conn.cursor()
            cur.execute("SELECT * FROM profiles")
            rows = cur.fetchall()

    Auto-commits on success, auto-rolls back on exception.
    """
    if _pool is None:
        init_pool()

    conn = _pool.getconn()
    try:
        yield conn
        conn.commit()
    except Exception:
        conn.rollback()
        raise
    finally:
        _pool.putconn(conn)


def get_cursor(conn):
    """
    Get cursor with RealDictCursor for dict-like row access.

    Returns rows as dictionaries: {'column_name': value, ...}
    Compatible with previous sqlite3.Row behavior.
    """
    return conn.cursor(cursor_factory=RealDictCursor)


def r2d(row) -> Optional[Dict[str, Any]]:
    """
    Convert row to dict (compatibility helper).

    Args:
        row: RealDictRow from psycopg2

    Returns:
        Dictionary or None if row is None
    """
    return dict(row) if row else None


def execute_one(conn, query: str, params: tuple = ()) -> Optional[Dict[str, Any]]:
    """
    Execute query and return one row as dict.

    Args:
        conn: Database connection from get_db()
        query: SQL query with %s placeholders
        params: Tuple of parameters

    Returns:
        Dictionary with column:value pairs, or None if no row found

    Example:
        profile = execute_one(conn, "SELECT * FROM profiles WHERE id=%s", (pid,))
        if profile:
            print(profile['name'])
    """
    with get_cursor(conn) as cur:
        cur.execute(query, params)
        row = cur.fetchone()
        return r2d(row)


def execute_all(conn, query: str, params: tuple = ()) -> List[Dict[str, Any]]:
    """
    Execute query and return all rows as list of dicts.

    Args:
        conn: Database connection from get_db()
        query: SQL query with %s placeholders
        params: Tuple of parameters

    Returns:
        List of dictionaries (one per row)

    Example:
        weights = execute_all(conn,
            "SELECT * FROM weight_log WHERE profile_id=%s ORDER BY date DESC",
            (pid,)
        )
        for w in weights:
            print(w['date'], w['weight'])
    """
    with get_cursor(conn) as cur:
        cur.execute(query, params)
        rows = cur.fetchall()
        return [r2d(r) for r in rows]


def execute_write(conn, query: str, params: tuple = ()) -> None:
    """
    Execute INSERT/UPDATE/DELETE query.

    Args:
        conn: Database connection from get_db()
        query: SQL query with %s placeholders
        params: Tuple of parameters

    Example:
        execute_write(conn,
            "UPDATE profiles SET name=%s WHERE id=%s",
            ("New Name", pid)
        )
    """
    with get_cursor(conn) as cur:
        cur.execute(query, params)


def init_db():
    """
    Initialize database with required data.

    Ensures critical data exists (e.g., pipeline master prompt).
    Safe to call multiple times - checks before inserting.
    Called automatically on app startup.
    """
    try:
        with get_db() as conn:
            cur = get_cursor(conn)

            # Check if table exists first
            cur.execute("""
                SELECT EXISTS (
                    SELECT FROM information_schema.tables
                    WHERE table_schema = 'public'
                    AND table_name = 'ai_prompts'
                ) as table_exists
            """)
            if not cur.fetchone()['table_exists']:
                print("⚠️  ai_prompts table doesn't exist yet - skipping pipeline prompt creation")
                return

            # Ensure "pipeline" master prompt exists
            cur.execute("SELECT COUNT(*) as count FROM ai_prompts WHERE slug='pipeline'")
            if cur.fetchone()['count'] == 0:
                cur.execute("""
                    INSERT INTO ai_prompts (slug, name, description, template, active, sort_order)
                    VALUES (
                        'pipeline',
                        'Mehrstufige Gesamtanalyse',
                        'Master-Schalter für die gesamte Pipeline. Deaktiviere diese Analyse, um die Pipeline komplett zu verstecken.',
                        'PIPELINE_MASTER',
                        true,
                        -10
                    )
                """)
                conn.commit()
                print("✓ Pipeline master prompt created")
    except Exception as e:
        print(f"⚠️  Could not create pipeline prompt: {e}")
        # Don't fail startup - prompt can be created manually