"""
Automatic database migrations system
"""
import logging
from sqlalchemy import inspect
from .. import db

logger = logging.getLogger(__name__)

class Migration:
    """Base migration class"""
    # Higher version numbers run later
    version = 0
    description = "Base migration"
    
    def should_run(self, inspector):
        """Determine if this migration should run"""
        return True
    
    def run(self):
        """Execute the migration"""
        raise NotImplementedError

class AddFolderIdToFiles(Migration):
    """Add folder_id column to files table"""
    version = 1
    description = "Add folder_id column to files table"
    
    def should_run(self, inspector):
        """Check if folder_id column exists in files table"""
        if 'files' not in inspector.get_table_names():
            return False
            
        columns = [col['name'] for col in inspector.get_columns('files')]
        return 'folder_id' not in columns
    
    def run(self):
        """Add the folder_id column and foreign key constraint"""
        try:
            db.engine.execute('ALTER TABLE files ADD COLUMN folder_id INTEGER;')
            db.engine.execute('ALTER TABLE files ADD CONSTRAINT fk_files_folder_id FOREIGN KEY (folder_id) REFERENCES folders (id);')
            logger.info("Added folder_id column to files table")
            return True
        except Exception as e:
            logger.error(f"Error adding folder_id column: {str(e)}")
            return False

# Add all migrations here
MIGRATIONS = [
    AddFolderIdToFiles(),
    # Remove the Share table migration since we're not using it
]

def run_migrations():
    """Run all pending migrations"""
    logger.info("Checking for pending database migrations...")
    inspector = inspect(db.engine)
    
    # Sort migrations by version
    pending_migrations = sorted([m for m in MIGRATIONS if m.should_run(inspector)], 
                              key=lambda m: m.version)
    
    if not pending_migrations:
        logger.info("No pending migrations found.")
        return
    
    logger.info(f"Found {len(pending_migrations)} pending migrations.")
    
    success_count = 0
    for migration in pending_migrations:
        logger.info(f"Running migration {migration.version}: {migration.description}")
        try:
            success = migration.run()
            if success:
                success_count += 1
            else:
                logger.warning(f"Migration {migration.version} reported failure")
        except Exception as e:
            logger.error(f"Error in migration {migration.version}: {str(e)}")
    
    logger.info(f"Migration complete. {success_count}/{len(pending_migrations)} migrations successful.")