# sound.${domain} -- Icecast + Liquidsoap internet radio, streaming MP3s
# dropped into /var/lib/radio/music (shuffled, watched for changes; no
# upload UI, files land there via scp/rsync). Modeled loosely on alfo's
# radiopi (Docker + Liquidsoap + HLS), but Nix-native and Icecast instead
# of HLS so the launcher frontend can be a plain <audio> tag.
#
# NOT using the upstream `services.icecast` module: it takes
# `admin.password` as a plain `str` option and interpolates it straight
# into a `pkgs.writeText` config file, i.e. a world-readable Nix store
# path -- exactly what secrets/README.md says not to do ("Secret-Werte
# niemals in Nix-Strings interpolieren"). Both units below instead render
# their config from a template at service start, substituting the
# password read live from the agenix runtime path, so it never touches
# the store.
{ config, pkgs, ... }:
let
  icecastPort = 8032;
  musicDir = "/var/lib/radio/music";

  # bind-address 0.0.0.0, not just the tailnet IP: Liquidsoap's source
  # connection below goes to 127.0.0.1 (same host), which a
  # tailnet-IP-only bind refuses ("Connection refused", confirmed by
  # testing) -- external reachability is still tailnet-only in practice,
  # gated by the firewall rule further down plus Traefik only proxying
  # from blunix over the tailnet.
  icecastConfigTemplate = pkgs.writeText "icecast.xml.template" ''
    <icecast>
      <hostname>sound.${config.domain}</hostname>
      <authentication>
        <source-password>@PASSWORD@</source-password>
        <admin-user>admin</admin-user>
        <admin-password>@PASSWORD@</admin-password>
      </authentication>
      <listen-socket>
        <port>${toString icecastPort}</port>
        <bind-address>0.0.0.0</bind-address>
      </listen-socket>
      <paths>
        <logdir>/var/log/icecast-radio</logdir>
        <webroot>${pkgs.icecast}/share/icecast/web</webroot>
        <adminroot>${pkgs.icecast}/share/icecast/admin</adminroot>
        <alias source="/" dest="/status.xsl"/>
      </paths>
      <security>
        <chroot>0</chroot>
      </security>
    </icecast>
  '';

  # Same shared secret authenticates both Icecast's source login (above)
  # and Liquidsoap's outgoing source connection (below) -- one password,
  # not a separate admin/source pair, to keep this minimal.
  liquidsoapScriptTemplate = pkgs.writeText "radio.liq.template" ''
    # mksafe(): output.icecast() requires an infallible source (one that's
    # type-guaranteed to always have a track ready), but playlist() is
    # fallible (e.g. between tracks, or if the directory is briefly
    # empty) -- mksafe() inserts silence on demand to bridge that,
    # confirmed necessary by testing without it: liquidsoap refused to
    # even start ("Error 7: Invalid value: That source is fallible").
    radio = mksafe(playlist(mode="randomize", reload_mode="watch", "${musicDir}"))
    output.icecast(
      %mp3(bitrate=128),
      host="127.0.0.1", port=${toString icecastPort},
      password="@PASSWORD@",
      mount="stream.mp3",
      radio
    )
  '';
in
{
  # Icecast segfaults instead of exiting cleanly if it detects it's
  # running as root without a <changeowner> configured (confirmed by
  # running it by hand: "ERROR: You should not run icecast2 as root" ->
  # signal 11). Simpler to never start as root at all than to lean on
  # icecast's own privilege-drop directive -- one shared system user for
  # both units, consistent with how the rest of this repo avoids running
  # services as root.
  users.groups.icecast-radio = { };
  users.users.icecast-radio = {
    isSystemUser = true;
    group = "icecast-radio";
  };

  systemd.tmpfiles.rules = [
    "d ${musicDir} 0755 drone users - -"
  ];

  systemd.services.icecast-radio = {
    description = "Icecast server for sound.${config.domain}";
    after = [ "network.target" ];
    wantedBy = [ "multi-user.target" ];
    restartTriggers = [ config.age.secrets.icecastPw.file ];
    serviceConfig = {
      Type = "simple";
      User = "icecast-radio";
      Group = "icecast-radio";
      LogsDirectory = "icecast-radio";
      RuntimeDirectory = "icecast-radio";
      ExecStartPre = pkgs.writeShellScript "icecast-radio-render-config" ''
        set -eu
        password="$(cat ${config.age.secrets.icecastPw.path})"
        sed "s/@PASSWORD@/$password/g" ${icecastConfigTemplate} > /run/icecast-radio/icecast.xml
      '';
      ExecStart = "${pkgs.icecast}/bin/icecast -c /run/icecast-radio/icecast.xml";
      Restart = "always";
      RestartSec = "5s";
    };
  };

  systemd.services.liquidsoap-radio = {
    description = "Liquidsoap source client for sound.${config.domain}";
    after = [ "icecast-radio.service" ];
    wants = [ "icecast-radio.service" ];
    wantedBy = [ "multi-user.target" ];
    restartTriggers = [ config.age.secrets.icecastPw.file ];
    serviceConfig = {
      Type = "simple";
      User = "icecast-radio";
      Group = "icecast-radio";
      RuntimeDirectory = "liquidsoap-radio";
      ExecStartPre = pkgs.writeShellScript "liquidsoap-radio-render-script" ''
        set -eu
        password="$(cat ${config.age.secrets.icecastPw.path})"
        sed "s/@PASSWORD@/$password/g" ${liquidsoapScriptTemplate} > /run/liquidsoap-radio/radio.liq
      '';
      ExecStart = "${pkgs.liquidsoap}/bin/liquidsoap /run/liquidsoap-radio/radio.liq";
      Restart = "always";
      RestartSec = "10s";
    };
  };

  networking.firewall.interfaces.tailscale0.allowedTCPPorts = [ icecastPort ];
}