split waybar into multiple files

modules/desktop/waybar/cal.nix

@@ -0,0 +1,93 @@
+{
+  pkgs,
+  config,
+  lib,
+  ...
+}:
+with lib;
+let
+  calwatcher =
+    (pkgs.writeShellApplication {
+      name = "calwatcher";
+      runtimeInputs = [
+        pkgs.inotify-tools
+        pkgs.khal
+        pkgs.jq
+      ];
+      text = ''
+         # in parts ripped from https://git.sr.ht/~whynothugo/dotfiles/tree/3768ec57/item/home/.local/lib/waybar-khal
+         render() {
+          # Find events starting in two minutes.
+          # So if my current event ends in two minutes and another one starts, the
+          # widget is already updated with what's upcoming.
+          SINCE="$(date -d 'now +2 min' '+%FT%H:%M:%S')"
+          UNTIL="1d"
+
+          EVENT="$(
+            khal list "$SINCE" "$UNTIL" \
+              --day-format 'SKIPME' \
+              --format "{start-end-time-style} {title:.31}{repeat-symbol}" |
+              grep -v SKIPME |  # filter out headers
+              grep -v -P '↦|↔ |⇥' |  # filter out continuing all day events
+              grep -v '^ ' |  # exclude full-day events
+              head -n 1  # show just the first
+          )"
+
+          if [ -z "$EVENT" ]; then
+            TEXT="  (nothing upcoming)"
+            CLASS="no-event"
+          else
+            TEXT="  $EVENT"
+            CLASS="event"
+          fi
+
+          jq --compact-output \
+            --null-input \
+            --arg text "$TEXT" \
+            --arg class "$CLASS" \
+            --arg tooltip "$(khal list today 7d --day-format '<span color="#ffead3"><b>{name} {date-long}</b></span>')" \
+            '{"text": $text, "class": $class, "tooltip": $tooltip}'
+        }
+
+        render # Render once for initial state.
+
+        # In order to make sure events are updated as time passes, this re-renderes
+        # every two minutes. That aside, whenever a calendar event changes, we alreays
+        # re-render immediately.
+        #
+        # It would be ideal to determine _when_ the current event ends, and set the
+        # timeout accordinly. That would require parsing khal's output a bit more.
+        while true; do
+          (inotifywait \
+            --event modify \
+            --event create \
+            --event delete \
+            --event close_write \
+            --event moved_to \
+            --event move \
+            --monitor \
+            --timeout 120 \
+            --recursive \
+            "$HOME/.calendars" 2> /dev/null) || true | \
+            while read -r _; do
+              render
+              timeout 3 cat || true # debounce for 3s, https://stackoverflow.com/a/69945839
+            done
+        done
+      '';
+
+    })
+    + "/bin/calwatcher";
+in
+lib.mkIf (config.xyno.user-services.khal.enable) {
+  xyno.desktop.waybar.config = {
+    "custom/cal" = {
+      exec = calwatcher;
+      restart-interval = 5;
+      return-type = "json";
+      "on-click" = "${pkgs.foot}/bin/footclient --app-id floating-alacritty ${pkgs.khal}/bin/ikhal";
+    };
+    modules-right = mkOrder 1999 [ "custom/cal" ]; # left of clock, right of everything else
+  };
+
+}