refactor: move zellij to shared module

nixosModules/zellij/default.nix

@@ -0,0 +1,39 @@
+{
+  lib,
+  pkgs,
+  config,
+}:
+{
+  options.local.zellij = lib.mkEnableOption "zellij" // {
+    default = true;
+  };
+
+  config = lib.mkIf config.local.zellij {
+    local.packages = {
+      inherit (pkgs) zellij;
+    };
+
+    programs.zsh.interactiveShellInit =
+      let
+        monitorScript = pkgs.replaceVarsWith {
+          src = ./monitor.ps;
+          replacements = builtins.mapAttrs (_: lib.getExe) {
+            inherit (pkgs) perl xdotool;
+          };
+          isExecutable = true;
+        };
+      in
+      ''
+        if [[ -z "$ZELLIJ" ]]; then
+          if [[ -n "$SSH_TTY" ]]; then
+            zellij attach -c "SSH@$USER"
+          else
+            MONITOR="$(${monitorScript} || true)"
+            zellij attach -c "''${MONITOR:+"$MONITOR@"}$USER"
+          fi
+          exit
+        fi
+      '';
+
+  };
+}

nixosModules/zellij/monitor.ps

@@ -0,0 +1,45 @@
+#!@perl@
+
+use strict;
+
+my %M;    # hash to hold keys from 'xdotool getmouselocation --shell'
+my $pipe; # file handle for the pipes we're going to open
+
+# get the current cursor location into $M{X} and $M{Y}
+open($pipe, "-|", qw(@xdotool@ getmouselocation --shell)) ||
+    die "couldn't open pipe from xdotool: $!\n";
+
+while(<$pipe>) {
+  chomp;
+  my($key, $val) = split /=/;
+  $M{$key} = $val;
+};
+close($pipe);
+
+# compare mouse location to monitor co-ordinates
+open($pipe, "-|", "xrandr") ||
+    die "couldn't open pipe from xrandr: $!\n";
+
+while(<$pipe>) {
+  my ($display, $width, $height, $x_offset, $y_offset);
+
+  next unless m/ connected /;
+  my @F = split;
+  $display = $F[0];
+
+  # co-ordinates are on fourth field (F[3]) on the primary display
+  # or on third field (F[2]) on non-primary displays. Perl arrays
+  # start from zero, not one (same as in bash).
+  if ($F[2] eq "primary") {
+    ($width, $height, $x_offset, $y_offset) = split /[x+]/, $F[3];
+  } else {
+    ($width, $height, $x_offset, $y_offset) = split /[x+]/, $F[2];
+  };
+
+  if ($M{X} >= $x_offset && $M{X} <= $width + $x_offset &&
+      $M{Y} >= $y_offset && $M{Y} <= $height + $y_offset) {
+    print "$display\n";
+    last;
+  };
+};
+close($pipe);