#!/bin/bash
# sddm-theme-sync — regenerate the SDDM "caelestia" theme's colours and
# background from the desktop's live caelestia scheme, so the login screen
# matches the current wallpaper/palette. Run as root (the installer runs it
# once; re-run any time after changing wallpaper):
#   sudo sddm-theme-sync
set -euo pipefail

THEME=/usr/share/sddm/themes/caelestia

if [[ $EUID -ne 0 ]]; then
  echo "Error: run as root (sudo sddm-theme-sync)" >&2
  exit 1
fi
command -v jq >/dev/null 2>&1 || { echo "Error: jq is required" >&2; exit 1; }
[[ -d "$THEME" ]] || { echo "Error: theme not installed at $THEME" >&2; exit 1; }

# The desktop user whose scheme/wallpaper to mirror.
U="${SUDO_USER:-}"
if [[ -z "$U" || "$U" == "root" ]]; then
  U=$(loginctl list-sessions --no-legend 2>/dev/null | awk '$3 != "root" && $3 != "sddm" && $3 != "" { print $3; exit }')
fi
[[ -n "$U" ]] || { echo "Error: cannot determine the desktop user" >&2; exit 1; }
H=$(getent passwd "$U" | cut -d: -f6)

SCHEME="$H/.local/state/caelestia/scheme.json"
WALLPATH="$H/.local/state/caelestia/wallpaper/path.txt"
[[ -f "$SCHEME" ]] || { echo "Error: $SCHEME not found (no caelestia scheme yet)" >&2; exit 1; }

c() { jq -r ".colours.$1 // empty" "$SCHEME"; }
BASE=$(c background); SC=$(c surfaceContainer); SCH=$(c surfaceContainerHigh)
TEXT=$(c onSurface); SUB=$(c onSurfaceVariant); OUT=$(c outlineVariant)
PRI=$(c primary); ONPRI=$(c onPrimary); ERR=$(c error)
[[ -n "$BASE" && -n "$PRI" && -n "$TEXT" ]] || { echo "Error: scheme.json missing expected colours" >&2; exit 1; }

# Background: copy the current wallpaper into the theme (greeter runs as the
# sddm user and cannot read the user's home).
BG_LINE="background=backgrounds/wallpaper.png"
if [[ -f "$WALLPATH" ]]; then
  WALL=$(cat "$WALLPATH")
  if [[ -f "$WALL" ]]; then
    EXT="${WALL##*.}"
    install -d -m 0755 "$THEME/backgrounds"
    rm -f "$THEME"/backgrounds/wallpaper.*
    install -m 0644 "$WALL" "$THEME/backgrounds/wallpaper.$EXT"
    BG_LINE="background=backgrounds/wallpaper.$EXT"
  fi
fi

cat > "$THEME/theme.conf" << EOF
# Generated by sddm-theme-sync from $SCHEME — do not edit by hand.
[General]
$BG_LINE
base=#$BASE
surfaceContainer=#$SC
surfaceContainerHigh=#$SCH
text=#$TEXT
subtext=#$SUB
outline=#$OUT
primary=#$PRI
onPrimary=#$ONPRI
error=#$ERR
fontFile=/etc/xdg/quickshell/caelestia/assets/google-sans-flex/GoogleSansFlex-VariableFont_GRAD,ROND,opsz,slnt,wdth,wght.ttf
fontFallback=Rubik
EOF

echo ":: SDDM theme synced to $U's scheme (takes effect at the next greeter)"