import logging
from pathlib import Path
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy import text


class MigrationRunner:
    MIGRATIONS_SCHEMA_NAME: str = "schema_migrations"

    def __init__(self, database_url: str) -> None:
        self.engine = create_async_engine(database_url)
        self.migrations_dir = Path("migrations/sql")
        logging.error(f"{database_url}")

    async def get_applied_migrations(self) -> set:
        """Get list of applied migrations"""
        async with self.engine.begin() as conn:
            # Create migrations list table if not exists
            await conn.execute(
                text(f"""
                CREATE TABLE IF NOT EXISTS {self.MIGRATIONS_SCHEMA_NAME} (
                  version VARCHAR(50) PRIMARY KEY,
                  applied_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
                );
            """)
            )

            # Receiving list of applied migrations
            result = await conn.execute(
                text(f"SELECT version FROM {self.MIGRATIONS_SCHEMA_NAME}")
            )
            return {row[0] for row in result.fetchall()}

    async def run_migrations(self):
        """Run all unapplied migrations"""
        applied = await self.get_applied_migrations()
        logging.info(f"Applied migrations: {applied}")

        # Getting all sql files from migrations_dir
        # TODO: (#ToLearn) Read about Path.glob function
        migration_files = sorted([file for file in self.migrations_dir.glob(".*sql")])

        for migration_file in migration_files:
            # TODO: (#ToLearn) Read about stem property
            migration_name = migration_file.stem

            if migration_name not in applied:
                logging.info(f"Applying migration: {migration_name}")
                await self._apply_migration(migration_file, migration_name)
            else:
                logging.info(f"Skipping migration: {migration_name} (already applied)")

    async def _apply_migration(self, migration_file: Path, migration_name: str):
        """Apply migrations from migrations/sql folder"""
        with open(migration_file, 'r', encoding='utf-8') as f:
            sql_content = f.read()
        
        async with self.engine.begin() as conn:
            try:
                statements = [s.strip() for s in sql_content.split(';') if s.strip()]
                
                for statement in statements:
                    if statement:
                        await conn.execute(text(statement))
                
                logging.info(f"Migration {migration_name} applied successfully")
                
            except Exception as e:
                logging.error(f"Error applying migration {migration_name}: {e}")
                raise