# AGENTS.md - NixOS Configuration Repository

This document provides guidelines for AI agents working on this NixOS flake configuration.

## Repository Overview

Multi-host NixOS flake managing servers and workstations with home-manager integration.
- **Hosts**: m3-aether, m3-ares, m3-atlas, m3-helios, m3-kratos
- **User**: m3tam3re
- **Key inputs**: nixpkgs (unstable), home-manager, agenix, disko, nix-colors

## Build/Rebuild Commands

```bash
# NixOS system rebuild
sudo nixos-rebuild switch --flake .#<hostname>
sudo nixos-rebuild switch --flake .#m3-atlas

# Home-manager rebuild
home-manager --flake . switch
home-manager --flake .#m3tam3re@m3-daedalus switch

# Flake operations
nix flake check                    # Validate flake
nix flake update                   # Update all inputs
nix flake lock --update-input <name>  # Update single input

# Development shell
nix develop .#infraShell           # OpenTofu + nixos-anywhere

# Format Nix files
alejandra .                        # Format all .nix files
alejandra <file.nix>               # Format single file
```

## Testing

No formal test suite. Verification is done via:
```bash
nix flake check                    # Syntax and evaluation check
nix build .#nixosConfigurations.<host>.config.system.build.toplevel --dry-run
```

## Directory Structure

```
.
├── flake.nix              # Flake definition with all hosts
├── secrets.nix            # Agenix public key mappings
├── home/
│   ├── common/            # Shared home-manager config (overlays, nix settings)
│   ├── features/          # Modular features
│   │   ├── cli/           # Shell tools (fish, nushell, starship, zellij)
│   │   ├── coding/        # Development tools
│   │   └── desktop/       # GUI apps, Hyprland, theming
│   └── m3tam3re/          # Per-host user configs
├── hosts/
│   ├── common/            # Shared NixOS config
│   │   ├── extraServices/ # Toggle-able services (ollama, podman, flatpak)
│   │   ├── users/         # User definitions
│   │   └── ports.nix      # Port allocations
│   └── m3-*/              # Host-specific configs
│       ├── default.nix    # Entry point (imports common + host modules)
│       ├── configuration.nix  # Core system config
│       ├── hardware-configuration.nix
│       ├── programs.nix   # Host-specific programs
│       ├── secrets.nix    # Agenix secret declarations
│       └── services/      # Service configurations
│           └── containers/ # OCI container definitions
├── modules/               # Custom NixOS/home-manager modules
├── overlays/              # Nixpkgs overlays (stable, locked, pinned, master)
├── pkgs/                  # Custom package definitions
└── secrets/               # Encrypted .age files
```

## Code Style Guidelines

### Module Pattern

Standard Nix module structure:
```nix
{
  config,
  lib,
  pkgs,
  ...
}: {
  imports = [
    ./submodule.nix
  ];

  # Configuration here
}
```

### Formatting

- **Formatter**: Use `alejandra` (included in CLI packages)
- **Indentation**: 2 spaces
- **Line length**: No strict limit, but keep readable
- **Trailing commas**: Required in lists and attrsets
- **Semicolons**: Required after each attribute

### Naming Conventions

| Type | Convention | Example |
|------|------------|---------|
| Files | lowercase, hyphenated | `hardware-configuration.nix` |
| Hosts | `m3-<name>` | `m3-atlas`, `m3-kratos` |
| Options | camelCase path | `extraServices.ollama.enable` |
| Feature flags | `features.<category>.<name>.enable` | `features.cli.nushell.enable` |
| Secrets | `<service>-env.age` or descriptive | `n8n-env.age`, `wg-DE.age` |

### Option Definitions

Use lib functions for custom options:
```nix
{
  config,
  lib,
  pkgs,
  ...
}:
with lib; let
  cfg = config.features.cli.myFeature;
in {
  options.features.cli.myFeature.enable = mkEnableOption "enable myFeature";

  config = mkIf cfg.enable {
    # Configuration when enabled
  };
}
```

### Imports

- Import order: inputs/modules first, then local files
- Use relative paths: `./subdir` or `../common`
- Group related imports together

### Package Lists

```nix
home.packages = with pkgs; [
  package1
  package2
  # Commented packages for reference
  # disabled-package
];
```

## Secrets Management

Uses **agenix** for encrypted secrets.

### Adding a New Secret

1. Create the secret file:
   ```bash
   agenix -e secrets/my-secret.age
   ```

2. Register in `secrets.nix`:
   ```nix
   "secrets/my-secret.age".publicKeys = systems ++ users;
   ```

3. Declare in host's `secrets.nix`:
   ```nix
   age.secrets.my-secret = {
     file = ../../secrets/my-secret.age;
     owner = "service-user";  # Optional
     mode = "644";            # Optional
   };
   ```

4. Reference in config:
   ```nix
   environmentFiles = [config.age.secrets.my-secret.path];
   ```

## Container Services Pattern

OCI containers via podman:
```nix
{config, ...}: {
  virtualisation.oci-containers.containers."service-name" = {
    image = "registry/image:tag";
    environmentFiles = [config.age.secrets.service-env.path];
    ports = ["127.0.0.1:8080:8080"];
    volumes = ["service_data:/data"];
    extraOptions = ["--network=web"];
  };

  # Traefik routing
  services.traefik.dynamicConfigOptions.http = {
    services.service-name.loadBalancer.servers = [
      { url = "http://localhost:8080/"; }
    ];
    routers.service-name = {
      rule = "Host(`service.domain.com`)";
      tls.certResolver = "godaddy";
      service = "service-name";
      entrypoints = "websecure";
    };
  };
}
```

## Theming

Uses **nix-colors** with Dracula scheme:
```nix
colorScheme = inputs.nix-colors.colorSchemes.dracula;

# Reference colors
"#${config.colorScheme.palette.base00}"  # Background
"#${config.colorScheme.palette.base05}"  # Foreground
```

## Overlays

Custom overlays in `overlays/default.nix`:
- `stable-packages`: nixpkgs-stable as `pkgs.stable.*`
- `locked-packages`: Pinned nixpkgs as `pkgs.locked.*`
- `master-packages`: nixpkgs-master as `pkgs.master.*`

Use when you need a specific package version:
```nix
home.packages = [ pkgs.stable.somePackage ];
```

## Common Pitfalls

1. **Missing imports**: Ensure new files are imported in parent `default.nix`
2. **Secret paths**: Use `config.age.secrets.<name>.path`, not hardcoded paths
3. **Rebuild required**: Changes need `nixos-rebuild` or `home-manager switch`
4. **Overlay scope**: Overlays must be added to both `home/common` and `hosts/common`
5. **Port conflicts**: Check `hosts/common/ports.nix` before allocating new ports

## Commit Style

Short, descriptive messages:
- `flake update` - Dependency updates
- `+package` - Adding new package
- `service-name: description` - Service changes
- `host: description` - Host-specific changes