# -*- coding: utf-8 -*-
"""
Systemd service unit file generator for Gunicorn.

**Single Responsibility:** Accept a ``ServiceConfig`` and render a production-
hardened systemd ``.service`` file.  Security best-practices (``--umask 007``,
``ProtectSystem``, dynamic worker count) are baked in by default.
"""

from __future__ import annotations

import textwrap

from core.interfaces import IServiceGenerator
from core.models import ServiceConfig


class SystemdServiceGenerator(IServiceGenerator):
    """Generates a systemd service unit for a Gunicorn-backed Django app."""

    _TEMPLATE = textwrap.dedent("""\
        # ──────────────────────────────────────────────────────────────────
        # Gunicorn service for {domain}
        # Auto-generated by hestia-django-gunicorn deployment engine
        # ──────────────────────────────────────────────────────────────────
        [Unit]
        Description=Gunicorn instance for {domain} (Django)
        After=network.target

        [Service]
        User={user}
        Group=www-data
        WorkingDirectory={web_dir}
        Environment="PATH={venv_bin}:/usr/local/bin:/usr/bin"
        Environment="PYTHONUNBUFFERED=1"
        {env_file_line}
        ExecStart={venv_bin}/gunicorn \\
                  --access-logfile - \\
                  --error-logfile - \\
                  --workers {workers} \\
                  --threads {threads} \\
                  --worker-class=gthread \\
                  --bind unix:{socket_path} \\
                  --umask {umask} \\
                  --log-level={log_level} \\
                  {wsgi_module}

        Restart=always
        RestartSec={restart_sec}
        ProtectSystem=full
        PrivateTmp=true
        NoNewPrivileges=true

        [Install]
        WantedBy=multi-user.target
    """)

    def generate(self, config: ServiceConfig) -> str:
        """Return the full text of a systemd ``.service`` unit file."""
        dc = config.domain_config
        pi = config.project_info

        venv_bin = str(pi.venv_path / "bin") if pi.venv_path else "/usr/bin"

        # Optional EnvironmentFile directive for projects with .env
        if pi.has_dot_env:
            env_file_line = f"EnvironmentFile={dc.web_dir}/.env"
        else:
            env_file_line = "# No .env found — environment variables from Environment= only"

        return self._TEMPLATE.format(
            domain=dc.domain,
            user=dc.user,
            web_dir=dc.web_dir,
            venv_bin=venv_bin,
            socket_path=dc.socket_path,
            workers=config.workers,
            threads=config.threads,
            umask=config.umask,
            log_level=config.log_level,
            restart_sec=config.restart_sec,
            wsgi_module=pi.wsgi_module,
            env_file_line=env_file_line,
        )