nixos/flake.nix

{

  description = "Deployment for skynet";

  inputs = {
    # gonna start off with a fairly modern base
    nixpkgs.url = "nixpkgs/nixos-22.11";

    # utility stuff
    flake-utils.url = "github:numtide/flake-utils";
    agenix.url = "github:ryantm/agenix";
    deploy-rs.url = "github:serokell/deploy-rs";

  };

  outputs = { self, nixpkgs, deploy-rs, ... }: let

    # can centralise the config for each machiene here
    machine_config = [
      # each system one line
      {
        # each machiene must have a name
        name = "test01";

        # core info about it
        system = "x86_64-linux";
        modules = [
          ./machines/base.nix
        ];

        # for the deployment
        hostname = "test01.home.brendan.ie";
        sshUser = "root";
      }
    ];

    # the best part, nix is functional, so lets have some functions

    # map applies this function to every item in an array
    create_nixosConfigurations = map (
      # converts it into {name_of_machiene = {system = '..'; modules = '..'}}
      config: {
        # need to extract teh name of the machiene
        ${config.name} = (
          # nixpkgs.lib.nixosSystem is a fucntion that is used to turn a attribute set into the config for a machiene
          nixpkgs.lib.nixosSystem {
            system = config.system;
            modules = config.modules;
          }
        );
      }
    );

    # this takes the config attributes and turns it into something useful for the nodes
    create_nodes = map (
      # this is fairly simple, just plug in teh values
      config: {
        ${config.name} = {
           hostname = config.hostname;
           profiles.system = {
             path = deploy-rs.lib."${config.system}".activate.nixos self.nixosConfigurations."${config.name}";
             sshUser = config.sshUser;
           };
         };
      }
    );

    # this merges together an array of atributes into just one set
    merge = nixpkgs.lib.lists.foldl (a: b: a // b) {};

  in {
    # values created using the data and functions above
    nixosConfigurations = merge (create_nixosConfigurations machine_config);
    deploy.nodes = merge (create_nodes machine_config);

    # This is highly advised, and will prevent many possible mistakes
    checks = builtins.mapAttrs (system: deployLib: deployLib.deployChecks self.deploy) deploy-rs.lib;
  };

}