Custom MCP Server on Databricks Apps

from typing import Any
from hatchling.builders.hooks.plugin.interface import BuildHookInterface
from pathlib import Path
import shutil


class AppsBuildHook(BuildHookInterface):
    """Hook to create a Databricks Apps-compatible build.

    This hook is used to create a Databricks Apps-compatible build of the project.

    The following steps are performed:
    - Remove the ./.build folder if it exists.
    - Copy the artifact_path to the ./.build folder.
    - Write the name of the artifact to a requirements.txt file in the ./.build folder.
    - The resulting build directory is printed to the console.

    """

    def finalize(
        self, version: str, build_data: dict[str, Any], artifact_path: str
    ) -> None:
        self.app.display_info(
            f"Running Databricks Apps build hook for project {self.metadata.name} in directory {Path.cwd()}"
        )
        # remove the ./.build folder if it exists
        build_dir = Path(".build")
        self.app.display_info(f"Resulting build directory: {build_dir.absolute()}")

        if build_dir.exists():
            self.app.display_info(f"Removing {build_dir}")
            shutil.rmtree(build_dir)
            self.app.display_info(f"Removed {build_dir}")
        else:
            self.app.display_info(f"{build_dir} does not exist, skipping removal")

        # copy the artifact_path to the ./.build folder
        build_dir.mkdir(exist_ok=True)
        self.app.display_info(f"Copying {artifact_path} to {build_dir}")
        shutil.copy(artifact_path, build_dir)

        # write the name of the artifact to a requirements.txt file in the ./.build folder
        requirements_file = build_dir / "requirements.txt"

        requirements_file.write_text(Path(artifact_path).name, encoding="utf-8")

        app_file = Path("app.yaml")
        if app_file.exists():
            self.app.display_info(f"Copying {app_file} to {build_dir}")
            shutil.copy(app_file, build_dir)
        else:
            self.app.display_info(f"{app_file} does not exist, skipping copy")

        # Copy the resources folder for WAF measures
        resources_dir = Path("resources")
        if resources_dir.exists():
            self.app.display_info(f"Copying {resources_dir} to {build_dir}")
            shutil.copytree(resources_dir, build_dir / "resources")
        else:
            self.app.display_info(f"{resources_dir} does not exist, skipping copy")

        self.app.display_info(
            f"Apps-compatible build written to {build_dir.absolute()}"
        )