"""
Create systemd service file in Linux from given JSON data file
Author: Ahmed Sadman Muhib
"""

"""
Sample JSON file:

{
    "service_name": "test_service",
    "description": "Netcore dev server",
    "package_path": "dotnet",
    "service_path": "/home/muhib/DevOps/loopdatetime/Output/BuildApp.dll",
    "service_url": "localhost:6000"
}
"""

import os
import json
import subprocess


class ServiceCreator:
    def __init__(self, data_file):
        self.data_file = data_file

        # check if given file is valid json
        if (not os.path.isfile(data_file)) or (
            not data_file.endswith(".json")
        ):
            raise Exception("Invalid data file. It should be JSON")

        self.data = self.parse_json_file()

    def parse_json_file(self):
        with open(self.data_file, "r") as f:
            data = json.load(f)
            return data

    def get_service_file_template(self):
        return """[Unit]
Description={desc}
After=network.target

[Service]
ExecStart={pkg} {service_path} {service_url}
Restart=on-failure

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

    def create_service_file(self):
        with open(
            "/etc/systemd/system/{}.service".format(self.data["service_name"]),
            "w",
        ) as f:

            template = self.get_service_file_template()

            f.write(
                template.format(
                    desc=self.data["description"],
                    pkg=self.data["package_path"],
                    service_path=self.data["service_path"],
                    service_url=self.data["service_url"],
                )
            )

    def restart_service(self):
        os.system(
            "sudo systemctl restart {}".format(self.data["service_name"])
        )

    def restart_daemon(self):
        """restart daemon and start the service"""

        os.system("sudo systemctl daemon-reload")
        os.system("sudo systemctl enable {}".format(self.data["service_name"]))
        os.system("sudo systemctl start {}".format(self.data["service_name"]))

    def create_or_restart_service(self):
        """Check if the service is running. If yes, then restart it. Otherwise,
        create a new service file and start the new service"""

        service_status = subprocess.Popen(
            ["sudo", "systemctl", "is-active", self.data["service_name"]],
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
        )

        output, stderr = service_status.communicate()
        output = output.decode("utf-8").strip()

        if output == "active":
            # service is running
            print("Restarting service...")
            self.restart_service()
            print("Done")
        else:
            # service is not running
            print("Creating service file...")
            self.create_service_file()
            print("Starting service...")
            self.restart_daemon()
            print("Done")


if __name__ == "__main__":
    sc = ServiceCreator("test.json")
    sc.create_or_restart_service()