#!/bin/bash

# Manual theme switcher + wallpaper/color applier.
# No time-based switching: you pick the wallpaper and mode explicitly.
#
# Usage:
#   ./theme-switcher.sh <image> <day|night>   apply <image> in light/dark mode, remember it
#   ./theme-switcher.sh --last                 apply the last manually-set wallpaper+mode
#   ./theme-switcher.sh -h | --help            show this help

WALLPAPERS="$HOME/Pictures/wallpapers"
STATE_FILE="/tmp/current_theme_state"
WALLPAPER_STATE_FILE="/tmp/current_wallpaper_state"
BACKDROP_STATE_FILE="/tmp/current_backdrop_state"
LAST_FILE="${XDG_STATE_HOME:-$HOME/.local/state}/theme-switcher/last"
LOG="/tmp/theme-switcher.log"
SCRIPT_DIR="$(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"
}

# Persist the last manually-chosen wallpaper + mode so --last survives reboots.
save_last() {
  mkdir -p "$(dirname "$LAST_FILE")"
  printf '%s\n%s\n' "$WALLPAPER" "$MODE" >"$LAST_FILE"
}

# Load the last chosen wallpaper + mode. Falls back to the old default so a
# fresh boot (nothing saved yet) never lands on a blank wallpaper.
load_last() {
  if [ -f "$LAST_FILE" ]; then
    WALLPAPER=$(sed -n '1p' "$LAST_FILE")
    MODE=$(sed -n '2p' "$LAST_FILE")
    case "$MODE" in
      light) TARGET_STATE="light" ;;
      *) TARGET_STATE="dark"; MODE="dark" ;;
    esac
  else
    WALLPAPER="$WALLPAPERS/night.jpg"
    TARGET_STATE="dark"
    MODE="dark"
  fi
}

# Resolve TARGET_STATE / MODE from an explicit mode argument.
resolve_explicit() {
  local mode="$1"
  case "$mode" in
    day | light) TARGET_STATE="light"; MODE="light" ;;
    night | dark) TARGET_STATE="dark"; MODE="dark" ;;
    *)
      echo "mode must be day|night (got: $mode)" >&2
      exit 1
      ;;
  esac
}

# 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)
  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

  # Already in this exact theme AND wallpaper: skip the heavy color work.
  if [ "$CURRENT_THEME" = "$TARGET_STATE" ] && [ "$CURRENT_WALLPAPER" = "$WALLPAPER" ]; then
    return 0
  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/.config/waybar/theme.css"

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

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

usage() {
  cat >&2 <<EOF
usage: $0 <image> <day|night> | --last
  <image> <day|night>   apply <image> in light/dark mode and remember it
  --last                apply the last manually-set wallpaper + mode
EOF
}

case "${1:-}" in
  --last)
    load_last
    apply_target
    exit $?
    ;;
  -h | --help)
    usage
    exit 0
    ;;
  "")
    usage
    exit 1
    ;;
  *)
    WALLPAPER="${1:-}"
    MODEARG="${2:-}"
    if [ -z "$MODEARG" ]; then
      echo "missing mode (day|night)" >&2
      usage
      exit 1
    fi
    resolve_explicit "$MODEARG"
    apply_target
    exit $?
    ;;
esac