feat(night-shift): default Night Shift to always on

home-manager/programs/gh/default.nix

@@ -2,7 +2,10 @@
 {
   programs.gh = {
     enable = true;
-    extensions = with pkgs; [ gh-markdown-preview gh-stack ];
+    extensions = with pkgs; [
+      gh-markdown-preview
+      gh-stack
+    ];
     settings = {
       editor = "nvim";
       git_protocol = "https";

home-manager/services/default.nix

@@ -21,6 +21,7 @@ let
   keydApplicationMapper = ./keyd-application-mapper;
   makeUpdater = import ./make-updater { inherit pkgs; };
   neversslKeepalive = import ./neverssl-keepalive { inherit pkgs; };
+  nightShift = import ./night-shift { inherit pkgs; };
   obsidian = import ./obsidian { inherit config pkgs inputs; };
   ollama = ./ollama;
   qmd = ./qmd;
@@ -46,6 +47,7 @@ in
   keydApplicationMapper
   makeUpdater
   neversslKeepalive
+  nightShift
   obsidian
   ollama
   qmd

home-manager/services/night-shift/apply-night-shift.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+nightlight_bin="@nightlightBin@"
+temperature=@temperature@
+
+# A sunset-to-sunrise schedule turns Night Shift back off at sunrise, so the
+# schedule has to be cleared before `on` can mean "stays on".
+"$nightlight_bin" schedule stop
+"$nightlight_bin" temp "$temperature"
+"$nightlight_bin" on

home-manager/services/night-shift/default.nix

@@ -0,0 +1,30 @@
+{ pkgs }:
+let
+  # 0 = least warm, 100 = warmest.
+  temperature = 100;
+
+  applyNightShiftScript = pkgs.replaceVars ./apply-night-shift.sh {
+    nightlightBin = "${pkgs.nightlight}/bin/nightlight";
+    inherit temperature;
+  };
+in
+{
+  # Night Shift state lives in the per-user CoreBrightness session and is not
+  # exposed through any plist `system.defaults` can write, so the only way to
+  # express "on by default" is to talk to that session on login.
+  #
+  # RunAtLoad without a StartInterval deliberately makes this a default rather
+  # than an enforcement: a manual toggle sticks until the next login.
+  launchd.agents.night-shift = pkgs.lib.mkIf pkgs.stdenv.isDarwin {
+    enable = true;
+    config = {
+      ProgramArguments = [
+        "${pkgs.bash}/bin/bash"
+        "${applyNightShiftScript}"
+      ];
+      RunAtLoad = true;
+      StandardOutPath = "/tmp/night-shift.log";
+      StandardErrorPath = "/tmp/night-shift.error.log";
+    };
+  };
+}

spec/night_shift_spec.sh

@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# shellcheck disable=SC2329
+
+Describe 'home-manager/services/night-shift/apply-night-shift.sh'
+SCRIPT="$PWD/home-manager/services/night-shift/apply-night-shift.sh"
+
+Describe 'script properties'
+It 'uses bash shebang'
+When run bash -c "head -1 '$SCRIPT'"
+The output should include '#!/usr/bin/env bash'
+End
+
+It 'uses strict mode'
+When run bash -c "head -5 '$SCRIPT'"
+The output should include 'set -euo pipefail'
+End
+
+It 'passes bash syntax check after replacing placeholders'
+When run bash -c "sed -e 's|@nightlightBin@|/usr/bin/true|g' -e 's|@temperature@|100|g' '$SCRIPT' | bash -n"
+The status should be success
+End
+End
+
+setup_night_shift_script() {
+  TEST_DIR=$(mktemp -d)
+  NIGHTLIGHT_LOG="$TEST_DIR/nightlight.log"
+  NIGHTLIGHT_BIN="$TEST_DIR/nightlight"
+  PREPROCESSED_SCRIPT="$TEST_DIR/apply-night-shift.sh"
+  : >"$NIGHTLIGHT_LOG"
+
+  cat >"$NIGHTLIGHT_BIN" <<'EOF'
+#!/usr/bin/env bash
+set -eu
+printf '%s\n' "$*" >>"$NIGHTLIGHT_LOG"
+EOF
+  chmod +x "$NIGHTLIGHT_BIN"
+
+  sed \
+    -e "s|@nightlightBin@|$NIGHTLIGHT_BIN|g" \
+    -e 's|@temperature@|100|g' \
+    "$SCRIPT" >"$PREPROCESSED_SCRIPT"
+  chmod +x "$PREPROCESSED_SCRIPT"
+}
+
+cleanup_night_shift_script() {
+  rm -rf "$TEST_DIR"
+}
+
+Describe 'applying the Night Shift default'
+Before 'setup_night_shift_script'
+After 'cleanup_night_shift_script'
+
+It 'clears the schedule before turning Night Shift on'
+When run bash -c ': >"'"$NIGHTLIGHT_LOG"'"; NIGHTLIGHT_LOG="'"$NIGHTLIGHT_LOG"'" "'"$PREPROCESSED_SCRIPT"'" >/dev/null && cat "'"$NIGHTLIGHT_LOG"'"'
+The status should be success
+The line 1 of output should eq 'schedule stop'
+The line 2 of output should eq 'temp 100'
+The line 3 of output should eq 'on'
+End
+End
+
+End