#!/bin/bash

# Day/night theme switcher + wallpaper/color applier.
# Two wallpapers: day.jpg (9:00-18:00) and night.jpg (18:00-9:00).
#
# Usage:
#   ./theme-switcher.sh            one-shot: apply based on current time, then exit
#   ./theme-switcher.sh day|light  force light theme, then exit
#   ./theme-switcher.sh night|dark force dark theme, then exit
#   ./theme-switcher.sh --daemon   continuous time-based loop (used at login)

WALLPAPERS="$HOME/Pictures/wallpapers"
STATE_FILE="/tmp/current_theme_state"
WALLPAPER_STATE_FILE="/tmp/current_wallpaper_state"
BACKDROP_STATE_FILE="/tmp/current_backdrop_state"
PID_FILE="/tmp/theme-switcher.daemon.pid"
LOG="/tmp/theme-switcher.log"
SCRIPT_DIR="$(cd "$(dirname "$(realpath "$0")")" && pwd)"
SET_BACKDROP="$SCRIPT_DIR/set-backdrop.sh"

log() {
  printf '%s %s\n' "$(date '+%Y-%m-%d %H:%M:%S')" "$*" >>"$LOG"
}

# Resolve TARGET_STATE / MODE / WALLPAPER. Optional $1 forces day|night.
resolve_target() {
  local force="${1:-}"
  if [ "$force" = "day" ] || [ "$force" = "light" ]; then
    TARGET_STATE="light"
    MODE="light"
    WALLPAPER="$WALLPAPERS/day.jpg"
  elif [ "$force" = "night" ] || [ "$force" = "dark" ]; then
    TARGET_STATE="dark"
    MODE="dark"
    WALLPAPER="$WALLPAPERS/night.jpg"
  else
    local HOUR
    HOUR=$(date +%H)
    HOUR=$((10#$HOUR))
    if [ "$HOUR" -ge 9 ] && [ "$HOUR" -lt 18 ]; then
      TARGET_STATE="light"
      MODE="light"
      WALLPAPER="$WALLPAPERS/day.jpg"
    else
      TARGET_STATE="dark"
      MODE="dark"
      WALLPAPER="$WALLPAPERS/night.jpg"
    fi
  fi
}

# Apply the resolved target once. Returns 0 on success.
apply_target() {
  if [ ! -f "$WALLPAPER" ]; then
    log "wallpaper missing: $WALLPAPER"
    return 1
  fi

  local CURRENT_THEME CURRENT_WALLPAPER EXPECTED_BACKDROP ACTUAL_BACKDROP

  CURRENT_THEME=$(cat "$STATE_FILE" 2>/dev/null || true)
  # Already in the correct theme: don't re-run wallust/matugen every loop tick.
  # Still self-heal a drifted backdrop below, then bail out.
  if [ "$CURRENT_THEME" = "$TARGET_STATE" ]; then
    EXPECTED_BACKDROP=$(cat "$BACKDROP_STATE_FILE" 2>/dev/null || true)
    ACTUAL_BACKDROP=$(awww query -n backdrop -j 2>/dev/null | jq -r '.["backdrop"][0].displaying.image // empty')
    if [ -n "$EXPECTED_BACKDROP" ] && [ "$ACTUAL_BACKDROP" != "$EXPECTED_BACKDROP" ]; then
      "$SET_BACKDROP" "$WALLPAPER"
    fi
    return 0
  fi
  CURRENT_WALLPAPER=$(cat "$WALLPAPER_STATE_FILE" 2>/dev/null || true)

  # Self-heal the Overview backdrop if it drifted from the expected image.
  EXPECTED_BACKDROP=$(cat "$BACKDROP_STATE_FILE" 2>/dev/null || true)
  ACTUAL_BACKDROP=$(awww query -n backdrop -j 2>/dev/null | jq -r '.["backdrop"][0].displaying.image // empty')
  if [ -n "$EXPECTED_BACKDROP" ] && [ "$ACTUAL_BACKDROP" != "$EXPECTED_BACKDROP" ]; then
    "$SET_BACKDROP" "$WALLPAPER"
  fi

  log "switching to $TARGET_STATE ($WALLPAPER)"
  if sh "$SCRIPT_DIR/apply-colors.sh" "$WALLPAPER" "$MODE"; then
    if [ "$CURRENT_THEME" != "$TARGET_STATE" ]; then
      darkman set "$TARGET_STATE"
    fi

    ln -sf \
      "theme-${TARGET_STATE}.css" \
      "$HOME/dotfiles-gentoo/waybar/.config/waybar/theme.css"

    ln -sf \
      "settings-${TARGET_STATE}.ini" \
      "$HOME/dotfiles-gentoo/gtk/.config/gtk-3.0/settings.ini"

    echo "$TARGET_STATE" >"$STATE_FILE"
    echo "$WALLPAPER" >"$WALLPAPER_STATE_FILE"
    log "switched to $TARGET_STATE ($WALLPAPER)"
    return 0
  else
    log "FAILED to apply $TARGET_STATE ($WALLPAPER)"
    return 1
  fi
}

daemon_loop() {
  # Refuse to run a second daemon instance (e.g. manual run while one is alive).
  if [ -f "$PID_FILE" ] && kill -0 "$(cat "$PID_FILE" 2>/dev/null)" 2>/dev/null; then
    log "daemon already running (pid $(cat "$PID_FILE")), exiting"
    exit 0
  fi
  echo $$ >"$PID_FILE"

  while true; do
    resolve_target
    apply_target || true # failure is retried on the next loop, state is left untouched
    sleep 60
  done
}

case "${1:-}" in
--daemon | -d) daemon_loop ;;
"" | day | light | night | dark)
  resolve_target "${1:-}"
  apply_target
  exit $?
  ;;
-h | --help)
  echo "usage: $0 [day|night|--daemon]" >&2
  exit 0
  ;;
*)
  echo "usage: $0 [day|night|--daemon]" >&2
  exit 1
  ;;
esac