initial liquidsoap service expression

nixos/modules/misc/ids.nix

···
       systemd-network = 152;
       systemd-resolve = 153;
       systemd-timesync = 154;
+      liquidsoap = 155;
 
       # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!
 
···
       systemd-network = 152;
       systemd-resolve = 153;
       systemd-timesync = 154;
+      liquidsoap = 155;
 
       # When adding a gid, make sure it doesn't match an existing uid. And don't use gids above 399!
 

nixos/modules/module-list.nix

···
   ./services/audio/alsa.nix
   # Disabled as fuppes it does no longer builds.
   # ./services/audio/fuppes.nix
+  ./services/audio/liquidsoap.nix
   ./services/audio/mpd.nix
   ./services/audio/mopidy.nix
   ./services/backup/almir.nix

nixos/modules/services/audio/liquidsoap.nix

···
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  streams = builtins.attrNames config.services.liquidsoap.streams;
+
+  streamService =
+    name:
+    let stream = builtins.getAttr name config.services.liquidsoap.streams; in
+    { inherit name;
+      value = {
+        after = [ "network-online.target" "sound.target" ];
+        description = "${name} liquidsoap stream";
+        wantedBy = [ "multi-user.target" ];
+        path = [ pkgs.wget ];
+        preStart =
+          ''
+            mkdir -p /var/log/liquidsoap
+            chown liquidsoap -R /var/log/liquidsoap
+          '';
+        serviceConfig = {
+          PermissionsStartOnly="true";
+          ExecStart = "${pkgs.liquidsoap}/bin/liquidsoap ${stream}";
+          User = "liquidsoap";
+        };
+      };
+    };
+in
+{
+
+  ##### interface
+
+  options = {
+
+    services.liquidsoap.streams = mkOption {
+
+      description =
+        ''
+          Set of Liquidsoap streams to start,
+          one systemd service per stream.
+        '';
+
+      default = {};
+
+      example = {
+        myStream1 = literalExample "\"/etc/liquidsoap/myStream1.liq\"";
+        myStream2 = literalExample "./myStream2.liq";
+        myStream3 = literalExample "\"out(playlist(\"/srv/music/\"))\"";
+      };
+
+      type = types.attrsOf (types.either types.path types.str);
+    };
+
+  };
+  ##### implementation
+
+  config = mkIf (builtins.length streams != 0) {
+
+    users.extraUsers.liquidsoap = {
+      uid = config.ids.uids.liquidsoap;
+      group = "liquidsoap";
+      extraGroups = [ "audio" ];
+      description = "Liquidsoap streaming user";
+      home = "/var/lib/liquidsoap";
+      createHome = true;
+    };
+
+    users.extraGroups.liquidsoap.gid = config.ids.gids.liquidsoap;
+
+    systemd.services = builtins.listToAttrs ( map streamService streams );
+  };
+
+}