# utils/modules/set-nix-channel.nix
{ config, pkgs, ... }:

{
  systemd.services.set-nix-channel = {
    description = "Set nix-channel from /var/bento/channel";
    after = [ "network.target" ]; # Ensure network is up
    wantedBy = [ "multi-user.target" ]; # Start on boot

    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = true; # Consider the service "active" after successful run
      User = "root";
      ExecStart = pkgs.writeShellScript "set-nix-channel-script" ''
        set -e # Exit immediately if a command exits with a non-zero status.
        CHANNEL_FILE="/var/bento/channel"
        CHANNEL_NAME="nixos"

        if [ ! -f "$CHANNEL_FILE" ]; then
          echo "Error: Channel file $CHANNEL_FILE not found." >&2
          exit 1
        fi

        CHANNEL_URL=$(cat "$CHANNEL_FILE")

        if [ -z "$CHANNEL_URL" ]; then
          echo "Error: Channel file $CHANNEL_FILE is empty." >&2
          exit 1
        fi

        # Attempt to remove existing channel to ensure clean state, ignore error if it doesn't exist
        ${pkgs.nix}/bin/nix-channel --remove "$CHANNEL_NAME" || true
        ${pkgs.nix}/bin/nix-channel --add "$CHANNEL_URL" "$CHANNEL_NAME"
        ${pkgs.nix}/bin/nix-channel --update "$CHANNEL_NAME"

        echo "Successfully set and updated channel '$CHANNEL_NAME' from $CHANNEL_FILE."
      '';
    };
  };
}