#!/usr/bin/env bash
# /home/krosh/Documents/Github/nixos-config/home-manager/modules/zsh/next_wallpaper.sh
# Pick next or random wallpaper from ~/Pictures/Wallpapers and update symlink ~/Pictures/wallpaper.png
# Then call: swww img "$WALLPAPER"

set -euo pipefail

RANDOM_MODE=0
while getopts "r" opt; do
    case "$opt" in
        r) RANDOM_MODE=1 ;;
        *) echo "Usage: $0 [-r]" >&2; exit 2 ;;
    esac
done

WALLPAPERS_DIR="$HOME/Pictures/Wallpapers"
SYMLINK="$HOME/Pictures/wallpaper.png"

if [ ! -d "$WALLPAPERS_DIR" ]; then
    echo "Wallpapers directory not found: $WALLPAPERS_DIR" >&2
    exit 1
fi

# Resolve current wallpaper (target of symlink). If not a symlink or missing, CUR will be empty.
CUR="$(readlink -f "$SYMLINK" 2>/dev/null || true)"

# Collect png files; sort by timestamp ascending (oldest first) using ls -tr.
# If there are spaces in names, ls handles them, but filenames with newlines are unsupported.
mapfile -t FILES < <(find "$WALLPAPERS_DIR" -maxdepth 1 -type f -iname '*.png' -print0 | xargs -0 ls -1tr 2>/dev/null || true)

if [ "${#FILES[@]}" -eq 0 ]; then
    echo "No png wallpapers found in $WALLPAPERS_DIR" >&2
    exit 1
fi

choose_random() {
    # pick random file different from CUR if possible
    candidates=()
    for f in "${FILES[@]}"; do
        [ "$(readlink -f "$f")" = "$CUR" ] && continue
        candidates+=("$f")
    done
    if [ "${#candidates[@]}" -eq 0 ]; then
        # only current exists
        echo "No other wallpaper to choose (only current exists)." >&2
        exit 1
    fi
    idx=$((RANDOM % ${#candidates[@]}))
    echo "${candidates[$idx]}"
}

choose_next() {
    # find current in sorted list and pick next (wrap). If current not found, choose first.
    n=${#FILES[@]}
    if [ "$n" -eq 1 ]; then
        # only one file
        if [ "$(readlink -f "${FILES[0]}")" = "$CUR" ]; then
            echo "No other wallpaper to choose (only current exists)." >&2
            exit 1
        else
            echo "${FILES[0]}"
            return
        fi
    fi

    # find index of current
    idx=-1
    for i in "${!FILES[@]}"; do
        if [ "$(readlink -f "${FILES[i]}")" = "$CUR" ]; then
            idx="$i"
            break
        fi
    done

    if [ "$idx" -eq -1 ]; then
        # current not in list: choose first
        echo "${FILES[0]}"
        return
    fi

    # next index with wrap
    next=$(( (idx + 1) % n ))
    # if next equals current (possible if only one), error handled above
    echo "${FILES[$next]}"
}

if [ "$RANDOM_MODE" -eq 1 ]; then
    NEW="$(choose_random)"
else
    NEW="$(choose_next)"
fi

# Ensure absolute path
NEW="$(readlink -f "$NEW")"

# Create symlink (atomic-ish): create temporary symlink and move
TMP_SYMLINK="$(mktemp -u "${SYMLINK}.tmp.XXXX")"
ln -sfn -- "$NEW" "$TMP_SYMLINK"
mv -f "$TMP_SYMLINK" "$SYMLINK"

# Export for hyprctl command (and run it)
WALLPAPER="$NEW"

swww img "$WALLPAPER" --transition-type fade
hyprpanel -q ; hyprpanel & disown
wal -c
wal -n -i "$WALLPAPER"

exit 0