import os
import re
import logging

from sqlalchemy import inspect
from sqlalchemy.sql import text
from alembic.config import Config
from alembic import command

import common.dependencies as DI


logger = logging.getLogger(__name__)

def get_old_versions():
    old_versions = list()
    migration_dir = 'components/dbo/alembic/versions'
    for file in os.listdir(migration_dir):
        if not file.endswith('.py'):
            continue
        file_path = os.path.join(migration_dir, file)
        with open(file_path, 'r', encoding='utf-8') as f:
            content = f.read()
            match = re.search(
                r"^(down_revision: Union\[str, None\] = )(None|'[^']*')",
                content,
                re.MULTILINE)
            if match:
                old_versions.append(match.group(2).replace("'", ""))
    return old_versions


def get_cur_version():
    session_factory = DI.get_db() 
    session: Session = session_factory() 
    
    try:
        inspector = inspect(session.bind)
        if 'alembic_version' not in inspector.get_table_names():
            return None
            
        result = session.execute(text("SELECT version_num FROM alembic_version")).scalar()
        return result
        
    finally:
        session.close()


def update():
    old_versions = get_old_versions()
    cur_version = get_cur_version()
    if cur_version not in old_versions and cur_version is not None:
        return


    logger.info(f"Updating the database from migration {cur_version}")
    config = Config("alembic.ini")
    command.upgrade(config, "head")