Add initial implementation of Docker Compose manager and example usage

- Introduced DockerComposeManager class for programmatically creating and managing Docker Compose YAML files.
- Added example script demonstrating usage of DockerComposeManager.
- Created tests for service creation, modification, and removal.
- Included project metadata in pyproject.toml and added linting instructions in copilot-instructions.md.

.github/copilot-instructions.md

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+This Python library is used to create Docker compose.yaml files from Python classes.
+
+It is designed to simplify the process of defining and managing Docker Compose configurations programmatically.
+
+Uses uv for Python dependency management. `uv sync`, `uv add <package>`.
+
+Ruff is used for linting and formatting. Use `ruff check .` to check the code and `ruff format .` to format it.

example/basic_example.py

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+"""Example usage of DockerComposeManager to generate a docker-compose.yaml file."""
+
+from compose import DockerComposeManager
+
+if __name__ == "__main__":
+    # Path to the compose file to generate
+    compose_path = "docker-compose.yaml"
+
+    # Create a DockerComposeManager instance
+    manager = DockerComposeManager(compose_path)
+
+    # Add a simple web service
+    manager.create_service(
+        name="web",
+        image="nginx:alpine",
+        ports=["8080:80"],
+        environment={"NGINX_HOST": "localhost"},
+    )
+
+    # Add a database service
+    manager.create_service(
+        name="db",
+        image="postgres:15-alpine",
+        environment={
+            "POSTGRES_USER": "user",
+            "POSTGRES_PASSWORD": "password",
+            "POSTGRES_DB": "exampledb",
+        },
+        ports=["5432:5432"],
+        volumes=["db_data:/var/lib/postgresql/data"],
+    )
+
+    # Save the compose file
+    manager.save()
+
+    print(f"docker-compose.yaml generated at {compose_path}")

pyproject.toml

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+[project]
+name = "compose"
+version = "0.1.0"
+description = "A simple Python package for managing Docker Compose files"
+readme = "README.md"
+requires-python = ">=3.13"
+dependencies = [
+    "pytest>=8.4.0",
+    "pyyaml>=6.0.2",
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"

src/compose/__init__.py

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+# Copyright (c) 2023, the Compose project contributors.
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+"""Docker Compose YAML file generator.
+
+This package provides utilities for programmatically creating and managing Docker Compose
+configuration files through Python classes, simplifying the process of defining
+and managing Docker Compose configurations.
+"""
+
+from pathlib import Path
+from types import TracebackType
+from typing import Any
+
+import yaml
+
+
+class DockerComposeManager:
+    """A class to create and modify Docker Compose YAML files programmatically.
+
+    Supports context manager usage for auto-saving.
+    """
+
+    def __init__(self, path: str, version: str = "3.8") -> None:
+        """Initialize the manager with a YAML file path. Loads existing file or creates a new one."""
+        self.path: str = path
+        self.version: str = version
+        self._data: dict[str, Any] = {}
+        self._dirty: bool = False
+        self._load()
+
+    def _load(self) -> None:
+        if Path(self.path).exists():
+            with Path(self.path).open("r", encoding="utf-8") as f:
+                self._data = yaml.safe_load(f) or {}
+        if not self._data:
+            self._data = {"version": self.version, "services": {}}
+        if "services" not in self._data:
+            self._data["services"] = {}
+        if not isinstance(self._data["services"], dict):
+            self._data["services"] = {}
+
+    def create_service(
+        self,
+        name: str,
+        image: str,
+        ports: list[str] | None = None,
+        environment: dict[str, str] | None = None,
+        **kwargs: object,
+    ) -> "DockerComposeManager":
+        """Create a new service in the compose file.
+
+        Returns:
+            DockerComposeManager: self (for chaining)
+
+        """
+        services = self._data["services"]
+        service: dict[str, Any] = {"image": image}
+        if ports is not None:
+            service["ports"] = ports
+        if environment is not None:
+            service["environment"] = environment
+        service.update(kwargs)
+        services[name] = service
+        self._dirty = True
+        return self
+
+    def modify_service(self, name: str, **kwargs: object) -> "DockerComposeManager":
+        """Modify an existing service. Raises KeyError if not found.
+
+        Args:
+            name (str): Name of the service to modify.
+            **kwargs: Key-value pairs to update in the service configuration.
+
+        Raises:
+            KeyError: If the service with the given name does not exist.
+
+        Returns:
+            DockerComposeManager: self (for chaining)
+
+        """
+        services: dict[str, dict[str, Any]] = self._data["services"]
+        if name not in services:
+            msg: str = f"Service '{name}' not found."
+            raise KeyError(msg)
+        services[name].update(kwargs)
+        self._dirty = True
+        return self
+
+    def remove_service(self, name: str) -> "DockerComposeManager":
+        """Remove a service from the compose file.
+
+        Returns:
+            DockerComposeManager: self (for chaining)
+
+        """
+        services: dict[str, dict[str, Any]] = self._data["services"]
+        if name in services:
+            del services[name]
+            self._dirty = True
+        return self
+
+    def save(self) -> None:
+        """Save the current state to the YAML file."""
+        with Path(self.path).open("w", encoding="utf-8") as f:
+            yaml.dump(self._data, f, sort_keys=False, indent=2)
+        self._dirty = False
+
+    def __enter__(self) -> "DockerComposeManager":
+        """Enter the context manager and return self.
+
+        Returns:
+            DockerComposeManager: The instance itself for context management.
+
+        """
+        return self
+
+    def __exit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> None:
+        """Exit the context manager and save the file if changes were made.
+
+        Args:
+            exc_type: The exception type if an exception was raised, None otherwise.
+            exc_val: The exception value if an exception was raised, None otherwise.
+            exc_tb: The traceback if an exception was raised, None otherwise.
+
+        """
+        if self._dirty:
+            self.save()

tests/test_compose_manager.py

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+from pathlib import Path
+
+import pytest
+import yaml
+
+from compose import DockerComposeManager
+
+
+def test_create_and_save_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    manager.create_service(
+        name="web",
+        image="nginx:latest",
+        ports=["80:80"],
+        environment={"ENV_VAR": "value"},
+    ).save()
+    # Check file exists and content
+    assert compose_file.exists()
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert "web" in data["services"]
+    assert data["services"]["web"]["image"] == "nginx:latest"
+    assert data["services"]["web"]["ports"] == ["80:80"]
+    assert data["services"]["web"]["environment"] == {"ENV_VAR": "value"}
+
+
+def test_modify_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    manager.create_service(name="web", image="nginx:latest").save()
+    manager.modify_service(name="web", image="nginx:1.19", ports=["8080:80"]).save()
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert data["services"]["web"]["image"] == "nginx:1.19"
+    assert data["services"]["web"]["ports"] == ["8080:80"]
+
+
+def test_remove_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    manager.create_service(name="web", image="nginx:latest").save()
+    manager.remove_service("web").save()
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert "web" not in data["services"]
+
+
+def test_context_manager(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    with DockerComposeManager(str(compose_file)) as manager:
+        manager.create_service(name="web", image="nginx:latest")
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert "web" in data["services"]
+
+
+def test_modify_nonexistent_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    with pytest.raises(KeyError):
+        manager.modify_service("notfound", image="nginx:latest")