"""
Database connection and initialization module.
Manages SQLite database connection and table creation.
"""
import sqlite3
import os
from contextlib import contextmanager
from typing import Generator

# Database file path
DB_PATH = os.getenv("DATABASE_PATH", "annotation_platform.db")


@contextmanager
def get_db_connection() -> Generator[sqlite3.Connection, None, None]:
    """
    Context manager for database connections.
    Ensures proper connection cleanup.
    """
    conn = sqlite3.connect(DB_PATH)
    conn.row_factory = sqlite3.Row  # Enable column access by name
    conn.execute("PRAGMA foreign_keys = ON")  # Enable foreign key constraints
    try:
        yield conn
        conn.commit()
    except Exception:
        conn.rollback()
        raise
    finally:
        conn.close()


def init_database() -> None:
    """
    Initialize database and create tables if they don't exist.
    Creates projects, tasks, and annotations tables with proper relationships.
    """
    with get_db_connection() as conn:
        cursor = conn.cursor()
        
        # Enable foreign key constraints
        cursor.execute("PRAGMA foreign_keys = ON")
        
        # Create projects table
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS projects (
                id TEXT PRIMARY KEY,
                name TEXT NOT NULL,
                description TEXT,
                config TEXT NOT NULL,
                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
            )
        """)
        
        # Create tasks table
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS tasks (
                id TEXT PRIMARY KEY,
                project_id TEXT NOT NULL,
                name TEXT NOT NULL,
                data TEXT NOT NULL,
                status TEXT DEFAULT 'pending',
                assigned_to TEXT,
                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
                FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE
            )
        """)
        
        # Create annotations table
        cursor.execute("""
            CREATE TABLE IF NOT EXISTS annotations (
                id TEXT PRIMARY KEY,
                task_id TEXT NOT NULL,
                user_id TEXT NOT NULL,
                result TEXT NOT NULL,
                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
                FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE
            )
        """)
        
        conn.commit()


def get_db() -> sqlite3.Connection:
    """
    Get a database connection.
    Note: Caller is responsible for closing the connection.
    """
    conn = sqlite3.connect(DB_PATH)
    conn.row_factory = sqlite3.Row
    conn.execute("PRAGMA foreign_keys = ON")
    return conn