towerops/flake.nix

{
  description = "Towerops - Phoenix LiveView SNMP monitoring platform";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

    flake-parts = {
      url = "github:hercules-ci/flake-parts";
      inputs.nixpkgs-lib.follows = "nixpkgs";
    };

    systems.url = "github:nix-systems/default";

    pre-commit-hooks = {
      url = "github:cachix/pre-commit-hooks.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = inputs @ { self, nixpkgs, flake-parts, systems, pre-commit-hooks }:
    flake-parts.lib.mkFlake { inherit inputs; } {
      systems = import systems;

      perSystem = { config, self', inputs', pkgs, system, ... }: {
        _module.args.pkgs = import nixpkgs {
          inherit system;
          config = {
            allowUnfree = false;
          };
          overlays = [
            # Pin specific Elixir and Erlang versions to match .tool-versions
            # Elixir 1.19.5-otp-28, Erlang 28.3
            (final: prev: {
              # Use Erlang 28 (OTP 28.3)
              erlang = prev.erlang_28;

              # Use Elixir 1.19 with Erlang 28 (1.19.5-otp-28)
              elixir = prev.beam.packages.erlang_28.elixir_1_19;

              # Ensure beam packages use our pinned versions
              # This affects mixRelease and all BEAM-related builds
              beamPackages = prev.beam.packages.erlang_28;
            })
          ];
        };

        packages = {
          # C NIF shared library (cached separately from Elixir code)
          towerops-nif = pkgs.callPackage ./nix/c-nif.nix { };

          # Main Elixir release
          towerops = pkgs.callPackage ./nix/build.nix {
            inherit (self'.packages) towerops-nif;
          };

          # Docker OCI image (pure Nix, no Dockerfile)
          dockerImage = pkgs.callPackage ./nix/docker.nix {
            towerops = self'.packages.towerops;
          };

          # Default package
          default = self'.packages.towerops;
        };

        # Development shell with PostgreSQL, Redis, LSPs, formatters
        devShells.default = pkgs.callPackage ./nix/shell.nix {
          pre-commit-hooks = inputs.pre-commit-hooks.lib.${system};
        };

        # Nix formatter for flake files
        formatter = pkgs.nixfmt;
      };

      flake = {
        # Cachix binary cache configuration
        # Setup instructions:
        #   1. Create cache: cachix create towerops
        #   2. Generate keypair: cachix generate-keypair towerops
        #   3. Get public key: cachix get towerops
        #   4. Add CACHIX_AUTH_TOKEN to GitLab CI/CD variables
        #   5. Update public key below after cache creation
        nixConfig = {
          extra-substituters = [
            "https://cache.nixos.org"
            "https://towerops.cachix.org"
          ];
          extra-trusted-public-keys = [
            "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
            # Replace with your Cachix public key after setup:
            # "towerops.cachix.org-1:YOUR_PUBLIC_KEY_HERE"
          ];
        };
      };
    };
}