#!/usr/bin/env bash
set -e

# Cycles through the background images available for the current theme.
# Declarative + Hybrid (instant swww) for Nomarchy NixOS.

STATE_DIR="$HOME/.config/nomarchy"
STATE_FILE="$STATE_DIR/state.json"
mkdir -p "$STATE_DIR"
[[ ! -f $STATE_FILE ]] && echo "{}" > "$STATE_FILE"

THEME_NAME=$(jq -r '.theme // "nord"' "$STATE_FILE")

# Resolve themes directory (Built-in from Nix store via Home Manager, or user extra)
if [ -d "$HOME/.config/nomarchy/themes/$THEME_NAME" ]; then
  THEMES_DIR="$HOME/.config/nomarchy/themes"
else
  THEMES_DIR="$HOME/.local/share/nomarchy/themes"
fi

BG_DIR="$THEMES_DIR/$THEME_NAME/backgrounds"

if [ ! -d "$BG_DIR" ]; then
    notify-send "No background directory found for theme $THEME_NAME"
    exit 1
fi

mapfile -t BACKGROUNDS < <(ls "$BG_DIR" | sort)
TOTAL=${#BACKGROUNDS[@]}

if (( TOTAL == 0 )); then
    notify-send "No backgrounds found in $BG_DIR"
    exit 1
fi

CURRENT_BG=$(jq -r '.wallpaper' "$STATE_FILE")
INDEX=-1
for i in "${!BACKGROUNDS[@]}"; do
    if [[ "$BG_DIR/${BACKGROUNDS[$i]}" == "$CURRENT_BG" ]]; then
        INDEX=$i
        break
    fi
done

NEXT_INDEX=$(((INDEX + 1) % TOTAL))
NEW_BG="$BG_DIR/${BACKGROUNDS[$NEXT_INDEX]}"

TMP_JSON=$(mktemp)
jq --arg wp "$NEW_BG" '.wallpaper = $wp' "$STATE_FILE" > "$TMP_JSON" && mv "$TMP_JSON" "$STATE_FILE"

# Instant feedback via swww
if pgrep -x swww-daemon >/dev/null; then
    swww img "$NEW_BG" --transition-type outer --transition-pos 0.85,0.97 --transition-step 90
else
    swww init && swww img "$NEW_BG"
fi

echo "Background set to $NEW_BG declaratively."