{ config, pkgs, ... }:

let
  # (Optional) name your Compose app’s directory on the VM:
  composeDir = "/etc/docker-compose-app";

in {
  # 1) Install Docker engine and Docker‐Compose binary:
  environment.systemPackages = with pkgs; [
    docker
    docker-compose      # pulls in the python-based compose
  ];

  # 2) Enable the Docker daemon:
  services.docker.enable = true;

  # 3) Create a directory for your Compose file and copy it from the flake:
  #    If your flake repo has a sibling file `docker-compose.yml`, this will drop
  #    it into /etc/docker-compose-app/docker-compose.yml on the VM.
  environment.etc."docker-compose-app/docker-compose.yml".text = builtins.readFile ./docker-compose.yml;

  # 4) Make sure that directory exists with the right permissions:
  systemd.tmpfiles.rules = [
    # D     = create directory if missing, mode 0755, owner root:root
    "D! /etc/docker-compose-app 0755 root root - -"
  ];

  # 5) Define a systemd service to run `docker-compose up`:
  systemd.services.dockerComposeApp = {
    description = "docker-compose stack for my application";
    after = [ "network-online.target" "docker.service" ];
    wants = [ "network-online.target" "docker.service" ];

    serviceConfig = {
      # Run in foreground but let systemd restart if it crashes
      ExecStart = "${pkgs.docker-compose}/bin/docker-compose -f ${composeDir}/docker-compose.yml up";
      ExecStop  = "${pkgs.docker-compose}/bin/docker-compose -f ${composeDir}/docker-compose.yml down";
      WorkingDirectory = composeDir;
      Restart = "always";
      RestartSec = 10;
    };

    # Make sure the directory exists before this service starts:
    preStart = ''
      mkdir -p ${composeDir}
      chown root:root ${composeDir}
    '';

    wantedBy = [ "multi-user.target" ];
  };

  # 6) (Optional) If any volumes need to exist, define them here, for example:
  #    environment.etc."docker-compose-app/data".source = "/path/to/local/data";
}