Host<->User Mutual Providers

What Mutual-Config Mean

Mutual Configs means that not only a User contributes configuration to a Host, but also that a Host contributes configurations to a User.

Default, unidirectional OS configuration

Den framework is built around context pipeline transformations. In order to create a full OS configuration, everything starts with a host definition:

den.hostx.x86_64-linux.igloo.users.tux = {}

We need to build the nixos Nix module that will later be used by lib.nixosSystem. To do so, Den invokes the den.ctx.host pipeline like this:

Tip: Zoom diagrams using your mouse wheel or drag to move.

sequenceDiagram
   participant Den
   participant host as den.ctx.host
   participant user as den.ctx.user
   participant igloo as den.aspects.igloo
   participant tux as den.aspects.tux

   Den  ->>  host  :  {host = igloo}

   host ->> igloo : request nixos class
   igloo -->> igloo : each .includes takes { host }
   igloo -->> host : { nixos = ... } owned and parametric results

   host ->> user : fan-outs for each user: { host, user }

   user ->> tux : request nixos class
   tux -->> tux : home classes forwarded as nixos class
   tux -->> tux : each .includes takes { host, user }
   tux -->> user : { nixos = ... } owned and parametric results

   user -->> host : { nixos = ... } all user contributions

   host -->> Den : complete nixos module for lib.nixosSystem

This is the normal den.ctx.host pipeline. All OS contributions come from the host itself and from each of its user.

`den.provides.mutual-provider`

The den.provides.mutual-provider battery allows you to define mutual configurations by letting you to define named aspects under .provides. to create explicit relationship between users and hosts.

# mutual-provider is activated at a `{host,user}` context
# either per-user or for all of them.
den.ctx.user.includes = [ den._.mutual-provider ];

# user aspect provides to specific host or to all where it lives
den.aspects.tux = {
  provides.igloo.nixos.programs.emacs.enable = true;
  provides.to-hosts = { host, ... }: {
    nixos.programs.nh.enable = host.name == "igloo";
  };
};

# host aspect provides to specific user or to all its users
den.aspects.igloo = {
  provides.alice.homeManager.programs.vim.enable = true;
  provides.to-users = { user, ... }: {
    homeManager.programs.helix.enable = user.name == "alice";
  };
};

Tip: Zoom diagrams using your mouse wheel or drag to move.

sequenceDiagram
   participant Den
   participant host as den.ctx.host
   participant user as den.ctx.user
   participant igloo as den.aspects.igloo
   participant igloo-users as den.aspects.igloo.provides.to-users
   participant igloo-tux as den.aspects.igloo.provides.tux
   participant tux as den.aspects.tux
   participant tux-hosts as den.aspects.tux.provides.to-hosts
   participant tux-igloo as den.aspects.tux.provides.igloo

   Den  ->>  host  :  {host = igloo}

   host ->> igloo : request nixos class
   igloo -->> igloo : each .includes takes { host }
   igloo -->> host : { nixos = ... } owned and parametric results

   host ->> user : fan-outs for each user: { host, user }

   user ->> tux : request nixos class
   tux -->> tux : home classes forwarded as nixos class
   tux -->> tux : each .includes takes { host, user }
   tux -->> user : { nixos = ... } owned and parametric results

   user ->> igloo-users : host configs its users: { host, user }
   igloo-users -->> igloo-users : home classes forwarded as nixos class
   igloo-users -->> igloo-users : each .includes takes { host, user }
   igloo-users -->> user : { nixos = ... }

   user ->> igloo-tux : host configs tux: { host, user }
   igloo-tux -->> igloo-tux : home classes forwarded as nixos class
   igloo-tux -->> igloo-tux : each .includes takes { host, user }
   igloo-tux -->> user : { nixos = ... }

   user ->> tux-hosts : user configs its hosts: { host, user }
   tux-hosts -->> tux-hosts : home classes forwarded as nixos class
   tux-hosts -->> tux-hosts : each .includes takes { host, user }
   tux-hosts -->> user : { nixos = ... }

   user ->> tux-igloo : user configs igloo: { host, user }
   tux-igloo -->> tux-igloo : home classes forwarded as nixos class
   tux-igloo -->> tux-igloo : each .includes takes { host, user }
   tux-igloo -->> user : { nixos = ... }


   user -->> host : { nixos = ... } all user contributions

   host -->> Den : complete nixos module for lib.nixosSystem

User Peers Configuration

A user alice can provide configurations for other users in the same system, either by name or for all of them (exluding alice itself).

den.ctx.user.includes = [ den._.mutual-provider ];

den.aspects.alice = {
  provides.bob = { homeManager.programs.vim.enable = true; };
  provides.to-users = { user, ... }: {
    homeManager.programs.tmux.enable = lib.elem user.userName [ "carl" "david" ];
  };
};

Standalone HomeManager - Host Specific Configuration

If you have two standalone homes sharing same user aspect, you can provide host specific configuration even if the Host is not a NixOS system managed by you.

den.ctx.home.includes = [ den._.mutual-provider ];

den.homes.x86_64-linux."tux@igloo" = {};
den.homes.x86_64-linux."tux@iceberg" = {};

den.aspects.tux = {
  homeManager.programs.vim.enable = true; # tux on ALL homes and hosts.

  provides.igloo = {
    homeManager.programs.helix.enable = true; # ONLY at igloo
  };

  provides.iceberg = {
    homeManager.programs.emacs.enable = true; # ONLY at iceberg
  };
};

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