"""
Database Migration Script: Add Metadata Support

This script updates the documents table to add:
- metadata (JSONB) column for storing extracted metadata
- doc_id (TEXT) column for grouping chunks from the same document

Run this script after deploying the metadata extraction feature.
"""

import os
import sys
from pathlib import Path

# Add parent directory to path to import backend modules
project_root = Path(__file__).parent.parent.parent
sys.path.insert(0, str(project_root))

from dotenv import load_dotenv
import psycopg2

load_dotenv()

# Get database connection from environment
DATABASE_URL = os.getenv("POSTGRESQL_URL")

def get_connection():
    """
    Establish a direct PostgreSQL connection.
    """
    if not DATABASE_URL:
        raise ValueError(
            "PostgreSQL connection string not configured. "
            "Set POSTGRESQL_URL in your .env file."
        )
    return psycopg2.connect(DATABASE_URL)


def migrate_database():
    """
    Add metadata and doc_id columns to the documents table.
    """
    print("🔄 Starting database migration: Adding metadata support...")
    
    try:
        conn = get_connection()
        cur = conn.cursor()
        
        # Check if columns already exist
        cur.execute("""
            SELECT column_name 
            FROM information_schema.columns 
            WHERE table_name = 'documents' 
            AND column_name IN ('metadata', 'doc_id');
        """)
        existing_columns = {row[0] for row in cur.fetchall()}
        
        # Add metadata column if it doesn't exist
        if 'metadata' not in existing_columns:
            print("  ➕ Adding 'metadata' JSONB column...")
            cur.execute("""
                ALTER TABLE documents 
                ADD COLUMN metadata JSONB;
            """)
            print("  ✅ 'metadata' column added successfully")
        else:
            print("  ✓ 'metadata' column already exists")
        
        # Add doc_id column if it doesn't exist
        if 'doc_id' not in existing_columns:
            print("  ➕ Adding 'doc_id' TEXT column...")
            cur.execute("""
                ALTER TABLE documents 
                ADD COLUMN doc_id TEXT;
            """)
            print("  ✅ 'doc_id' column added successfully")
        else:
            print("  ✓ 'doc_id' column already exists")
        
        # Create index on doc_id for faster lookups (optional but recommended)
        try:
            print("  ➕ Creating index on 'doc_id'...")
            cur.execute("""
                CREATE INDEX IF NOT EXISTS documents_doc_id_idx 
                ON documents (doc_id);
            """)
            print("  ✅ Index on 'doc_id' created successfully")
        except Exception as e:
            print(f"  ⚠️  Index creation skipped (may already exist): {e}")
        
        # Create GIN index on metadata for JSONB queries (optional but recommended)
        try:
            print("  ➕ Creating GIN index on 'metadata'...")
            cur.execute("""
                CREATE INDEX IF NOT EXISTS documents_metadata_idx 
                ON documents USING GIN (metadata);
            """)
            print("  ✅ GIN index on 'metadata' created successfully")
        except Exception as e:
            print(f"  ⚠️  GIN index creation skipped (may already exist): {e}")
        
        conn.commit()
        cur.close()
        conn.close()
        
        print("\n✅ Database migration completed successfully!")
        print("\nThe documents table now supports:")
        print("  - metadata (JSONB): Stores extracted metadata (title, summary, tags, topics, etc.)")
        print("  - doc_id (TEXT): Groups chunks from the same document")
        print("\nNew documents will automatically have metadata extracted during ingestion.")
        
        return True
        
    except Exception as e:
        print(f"\n❌ Migration failed: {e}")
        print("\nTroubleshooting:")
        print("  1. Ensure PostgreSQL is running")
        print("  2. Check POSTGRESQL_URL in your .env file")
        print("  3. Verify you have permissions to alter the table")
        print("  4. Check if the documents table exists")
        return False


def verify_migration():
    """
    Verify that the migration was successful by checking column existence.
    """
    print("\n🔍 Verifying migration...")
    
    try:
        conn = get_connection()
        cur = conn.cursor()
        
        cur.execute("""
            SELECT column_name, data_type 
            FROM information_schema.columns 
            WHERE table_name = 'documents' 
            AND column_name IN ('metadata', 'doc_id')
            ORDER BY column_name;
        """)
        
        columns = cur.fetchall()
        
        if len(columns) == 2:
            print("  ✅ Both columns exist:")
            for col_name, col_type in columns:
                print(f"     - {col_name}: {col_type}")
            return True
        else:
            print(f"  ⚠️  Found {len(columns)} column(s), expected 2")
            for col_name, col_type in columns:
                print(f"     - {col_name}: {col_type}")
            return False
            
    except Exception as e:
        print(f"  ❌ Verification failed: {e}")
        return False
    finally:
        try:
            cur.close()
            conn.close()
        except:
            pass


if __name__ == "__main__":
    print("=" * 60)
    print("Database Migration: Add Metadata Support")
    print("=" * 60)
    print()
    
    # Check if database connection is available
    try:
        conn = get_connection()
        conn.close()
        print("✓ Database connection successful\n")
    except Exception as e:
        print(f"❌ Cannot connect to database: {e}")
        print("\nPlease check:")
        print("  1. PostgreSQL is running")
        print("  2. POSTGRESQL_URL is set in .env file")
        print("  3. Database credentials are correct")
        sys.exit(1)
    
    # Run migration
    success = migrate_database()
    
    if success:
        # Verify migration
        verify_migration()
        print("\n" + "=" * 60)
        print("Migration completed! You can now use metadata extraction.")
        print("=" * 60)
    else:
        print("\n" + "=" * 60)
        print("Migration failed. Please check the errors above.")
        print("=" * 60)
        sys.exit(1)