preview-tui

#!/usr/bin/env bash

# Description: Terminal based file previewer
#
# Note: This plugin needs a "NNN_FIFO" to work. See man.
#
# Dependencies:
#   - Supports 6 independent methods to preview with:
#       - tmux (>=3.0), or
#       - kitty with allow_remote_control and listen_on set in kitty.conf, or
#       - wezterm (https://wezfurlong.org/wezterm), or
#       - QuickLook on WSL (https://github.com/QL-Win/QuickLook), or
#       - Windows Terminal (https://github.com/Microsoft/Terminal | https://aka.ms/terminal) with WSL, or
#       - $NNN_TERMINAL set to a terminal (it's xterm by default).
#   - less or $NNN_PAGER
#   - tree or exa/eza or (GNU) ls
#   - mediainfo or file
#   - mktemp
#   - unzip
#   - tar
#   - man
#   - optional: bsdtar or atool for additional archive preview
#   - optional: bat for code syntax highlighting
#   - optional: ueberzug, kitty terminal, wezterm terminal, img2sixel, viu, catimg, timg or chafa for images
#   - optional: convert(ImageMagick) for playing gif preview (mandatory for kitty image previews)
#   - optional: mpv for gif and video
#       Also requires a terminal supporting the sixel (https://www.arewesixelyet.com/)
#       or kitty (https://sw.kovidgoyal.net/kitty/graphics-protocol) video_output backends.
#       Requires tmux compiled with `./configure --enable-sixel` if used.
#   - optional: ffmpegthumbnailer for video thumbnails (https://github.com/dirkvdb/ffmpegthumbnailer)
#   - optional: ffmpeg for audio thumbnails
#   - optional: libreoffce for opendocument/officedocument preview
#   - optional: pdftoppm(poppler) for pdf thumbnails
#   - optional: gnome-epub-thumbnailer for epub thumbnails (https://gitlab.gnome.org/GNOME/gnome-epub-thumbnailer)
#   - optional: fontpreview for font preview (https://github.com/sdushantha/fontpreview)
#   - optional: djvulibre for djvu
#   - optional: glow or lowdown for markdown
#   - optional: w3m or lynx or elinks for html
#   - optional: set/export NNN_ICONLOOKUP as 1 to enable file icons in front of directory previews with .iconlookup
#       Icons and colors are configurable in .iconlookup
#   - optional: scope.sh file viewer from ranger.
#       1. drop scope.sh executable in $PATH
#       2. set/export $NNN_SCOPE as 1
#   - optional: pistol file viewer (https://github.com/doronbehar/pistol).
#       1. install pistol
#       2. set/export $NNN_PISTOL as 1
#   - optional: librsvg for rsvg-convert
#
# Usage:
#   You need to set a NNN_FIFO path and a key for the plugin with NNN_PLUG,
#   then start `nnn`:
#
#     $ nnn -a
#
#   or
#
#     $ NNN_FIFO=/tmp/nnn.fifo nnn
#
#   Then launch the `preview-tui` plugin in `nnn`.
#
#   If you provide the same NNN_FIFO to all nnn instances, there will be a
#   single common preview window. If you provide different FIFO path (e.g.
#   with -a), they will be independent.
#
#   The previews will be shown in a tmux split. If that isn't possible, it
#   will try to use a kitty terminal split. And as a final fallback, a
#   different terminal window will be used ($NNN_TERMINAL).
#
#   Kitty users need something similar to the following in their kitty.conf:
#   - `allow_remote_control yes`
#   - `listen_on unix:$TMPDIR/kitty`
#   - `enabled_layouts splits` (optional)
#   With ImageMagick installed, this terminal can use the icat kitten to display images.
#   Refer to kitty documentation for further details.
#
#   Users with both tmux and kitty can leverage image previews inside tmux with kitty's icat kitten
#   - setup kitty as stated above
#   - tmux >= v3.3a required
#   - add the following to your tmux.conf:
#     - `set -g allow-passthrough on`
#
#   Wezterm should work out of the box. If `NNN_PREVIEWIMGPROG` is not specified it will use
#   built in iTerm2 image protocol.
#
#   Note that GNU ls is used for its `--group-directories-first` flag.
#   On MacOS this may be installed with `brew install coreutils`, or the flag can be removed.
#   iTerm2 users are recommended to use viu to view images without getting pixelated.
#
#   Windows Terminal users can set "Profile termination behavior" under "Profile > Advanced" settings
#   to automatically close pane on quit when exit code is 0.
#
#   When specifying a different terminal, additional arguments are supported. In particular, you can
#   append a specific title to the terminal and set it to "nofocus" in your WM config.
#   E.g for alacritty and i3, you can set $NNN_TERMINAL to 'alacritty --title preview-tui' and add
#   'no_focus [title="preview-tui"]' to your i3 config file.
#
# Shell: Bash (for environment manipulation through arrays)
# Authors: Todd Yamakawa, Léo Villeveygoux, @Recidiviste, Mario Ortiz Manero, Luuk van Baal, @WanderLanz, @flipflop133

# Configurable environment variables:
NNN_SPLIT=${NNN_SPLIT:-}                                   # permanent split direction
NNN_TERMINAL=${NNN_TERMINAL:-}                             # external terminal to be used
NNN_SPLITSIZE=${NNN_SPLITSIZE:-50}                         # previewer split size percentage
TMPDIR=${TMPDIR:-/tmp}                                     # location of temporary files
ENVVARS=(
  "NNN_SCOPE=${NNN_SCOPE:-0}"                              # use scope
  "NNN_PISTOL=${NNN_PISTOL:-0}"                            # use pistol
  "NNN_ICONLOOKUP=${NNN_ICONLOOKUP:-0}"                    # use .iconlookup
  "NNN_PAGER=${NNN_PAGER:-less -P?n -R -C}"                # pager options
  "NNN_BATTHEME=${NNN_BATTHEME:-ansi}"                     # bat theme
  "NNN_BATSTYLE=${NNN_BATSTYLE:-numbers}"                  # bat style
  "NNN_PREVIEWWIDTH=${NNN_PREVIEWWIDTH:-1920}"             # width of generated preview images
  "NNN_PREVIEWHEIGHT=${NNN_PREVIEWHEIGHT:-1080}"           # height of generated preview images
  "NNN_PREVIEWDIR=${NNN_PREVIEWDIR:-$TMPDIR/nnn/previews}" # location of generated preview images
  "NNN_PREVIEWIMGPROG=${NNN_PREVIEWIMGPROG:-}"             # command used to preview images
  "NNN_PREVIEWVIDEO=${NNN_PREVIEWVIDEO:-}"                 # mpv backend used to preview video
)
# Non-configurable environment variables
NNN_PARENT=${NNN_FIFO#*.}
[ "$NNN_PARENT" -eq "$NNN_PARENT" ] 2>/dev/null || NNN_PARENT="" # Make empty if non-numeric
ENVVARS+=(
  "PWD=$PWD"
  "PATH=$PATH"
  "NNN_FIFO=$NNN_FIFO"
  "FIFOPID=$TMPDIR/nnn-preview-tui-fifopid.$NNN_PARENT"
  "FIFOPATH=$TMPDIR/nnn-preview-tui-fifo.$NNN_PARENT"
  "PREVIEWPID=$TMPDIR/nnn-preview-tui-previewpid.$NNN_PARENT"
  "CURSEL=$TMPDIR/nnn-preview-tui-selection.$NNN_PARENT"
  "FIFO_UEBERZUG=$TMPDIR/nnn-preview-tui-ueberzug-fifo.$NNN_PARENT"
  "POSOFFSET=$TMPDIR/nnn-preview-tui-posoffset"
)

trap '' PIPE
exists() { type "$1" >/dev/null 2>&1 ;}
pkill() { command pkill "$@" >/dev/null 2>&1 ;}
prompt() { clear; printf "%b" "$@"; cfg=$(stty -g); stty raw -echo; head -c 1; stty "$cfg" ;}
pidkill() {
    if [ -f "$1" ]; then
        PID="$(cat "$1" 2>/dev/null)" || return 1
        kill "$PID" >/dev/null 2>&1
        RET=$?
        wait "$PID" 2>/dev/null
        return $RET
    fi
    return 1
}

start_preview() {
    if [ -e "${TMUX%%,*}" ] && tmux -V | grep -q '[ -][3456789]\.'; then
        NNN_TERMINAL=tmux
        exists mpv && tmux display -p '#{client_termfeatures}' | grep -q 'sixel' && ENVVARS+=("NNN_PREVIEWVIDEO=sixel")
    elif [ -n "$KITTY_LISTEN_ON" ]; then
        NNN_TERMINAL=kitty
        exists mpv && ENVVARS+=("NNN_PREVIEWVIDEO=kitty")
    elif [ -n "$WEZTERM_PANE" ]; then
        NNN_TERMINAL=wezterm
        exists mpv && ENVVARS+=("NNN_PREVIEWVIDEO=kitty")
    elif [ -z "$NNN_TERMINAL" ] && [ "$TERM_PROGRAM" = "iTerm.app" ]; then
        NNN_TERMINAL=iterm
        exists mpv && ENVVARS+=("NNN_PREVIEWVIDEO=sixel")
    elif [ -n "$WT_SESSION" ]; then
        NNN_TERMINAL=winterm
    else
        NNN_TERMINAL="${NNN_TERMINAL:-xterm}"
    fi

    if [ -z "$NNN_SPLIT" ] && [ $(($(tput lines) * 2)) -gt "$(tput cols)" ]; then
        NNN_SPLIT='h'
    elif [ "$NNN_SPLIT" != 'h' ]; then
        NNN_SPLIT='v'
    fi

    ENVVARS+=("NNN_TERMINAL=$NNN_TERMINAL" "NNN_SPLIT=$NNN_SPLIT" "QLPATH=$2" "PREVIEW_MODE=1")
    case "$NNN_TERMINAL" in
        iterm|winterm) # has to run in separate shell command: escape
            ENVVARS=("${ENVVARS[@]/#/\\\"}")
            ENVVARS=("${ENVVARS[@]/%/\\\"}")
            command="$SHELL -c 'env ${ENVVARS[*]} \\\"$0\\\" \\\"$1\\\"'" ;;
    esac

    case "$NNN_TERMINAL" in
        tmux) # tmux splits are inverted
            ENVVARS=("${ENVVARS[@]/#/-e}")
            if [ "$NNN_SPLIT" = "v" ]; then split="h"; else split="v"; fi
            tmux split-window -l"$NNN_SPLITSIZE"% "${ENVVARS[@]}" -d"$split" -p"$NNN_SPLITSIZE" "$0" "$1" ;;
        kitty) # Setting the layout for the new window. It will be restored after the script ends.
            ENVVARS=("${ENVVARS[@]/#/--env=}")
            kitty @ goto-layout splits
            # Trying to use kitty's integrated window management as the split window.
            kitty @ launch --no-response --title "preview-tui" --keep-focus \
                --cwd "$PWD" "${ENVVARS[@]}" --location "${NNN_SPLIT}split" "$0" "$1" ;;
        wezterm)
            export "${ENVVARS[@]}"
            if [ "$NNN_SPLIT" = "v" ]; then split="--horizontal"; else split="--bottom"; fi
            wezterm cli split-pane --cwd "$PWD" $split --percent "$NNN_SPLITSIZE" "$0" "$1" >/dev/null
            wezterm cli activate-pane-direction Prev ;;
        iterm)
            if [ "$NNN_SPLIT" = "h" ]; then split="horizontally"; else split="vertically"; fi
            osascript <<-EOF
            tell application "iTerm"
                tell current session of current window
                    split $split with default profile command "$command"
                end tell
            end tell
EOF
            ;;
        winterm)
            if [ "$NNN_SPLIT" = "h" ]; then split="H"; else split="V"; fi
            wt -w 0 sp -$split -s"0.$NNN_SPLITSIZE" "$command" \; -w 0 mf previous 2>/dev/null ;;
        *)  if [ -n "$2" ]; then
                env "${ENVVARS[@]}" QUICKLOOK=1 "$0" "$1" &
            else
                # shellcheck disable=SC2086 # (allow arguments)
                env "${ENVVARS[@]}" $NNN_TERMINAL -e "$0" "$1" &
            fi ;;
    esac
}

toggle_preview() {
    export "${ENVVARS[@]}"
    if exists QuickLook.exe; then
        QLPATH="QuickLook.exe"
    elif exists Bridge.exe; then
        QLPATH="Bridge.exe"
    fi
    if pidkill "$FIFOPID"; then
        [ -p "$NNN_PPIPE" ] && printf "0" > "$NNN_PPIPE"
        pidkill "$PREVIEWPID"
        pkill -f "tail --follow $FIFO_UEBERZUG"
        if [ -n "$QLPATH" ] && stat "$1"; then
            f="$(wslpath -w "$1")" && "$QLPATH" "$f" &
        fi
    else
        [ -p "$NNN_PPIPE" ] && printf "1" > "$NNN_PPIPE"
        start_preview "$1" "$QLPATH"
    fi
}

fifo_pager() {
    cmd="$1"
    shift

    # We use a FIFO to access $NNN_PAGER PID in jobs control
    mkfifo "$FIFOPATH" || return

    $NNN_PAGER < "$FIFOPATH" &
    printf "%s" "$!" > "$PREVIEWPID"

    (
        exec > "$FIFOPATH"
        if [ "$cmd" = "pager" ]; then
            if exists bat; then
                bat --terminal-width="$cols" --decorations=always --color=always \
                    --paging=never --style="$NNN_BATSTYLE" --theme="$NNN_BATTHEME" "$@" &
            else
                $NNN_PAGER "$@" &
            fi
        else
            "$cmd" "$@" &
        fi
    )

    rm -- "$FIFOPATH"
}

# Binary file: show file info inside the pager
print_bin_info() {
    printf -- "-------- \033[1;31mBinary file\033[0m --------\n"
    if exists mediainfo; then
        mediainfo "$1"
    else
        file -b "$1"
    fi
}

handle_mime() {
    case "$2" in
        image/jpeg) image_preview "$cols" "$lines" "$1" ;;
        image/gif) generate_preview "$cols" "$lines" "$1" "gif" ;;
        image/vnd.djvu) generate_preview "$cols" "$lines" "$1" "djvu" ;;
        image/*) generate_preview "$cols" "$lines" "$1" "image" ;;
        video/*) generate_preview "$cols" "$lines" "$1" "video" ;;
        audio/*) generate_preview "$cols" "$lines" "$1" "audio" ;;
        application/font*|application/*opentype|font/*) generate_preview "$cols" "$lines" "$1" "font" ;;
        */*office*|*/*document*|*/*msword|*/*ms-excel) generate_preview "$cols" "$lines" "$1" "office" ;;
        application/zip) fifo_pager unzip -l "$1" ;;
        text/troff)
            if exists man; then
                fifo_pager man -Pcat -l "$1"
            else
                fifo_pager pager "$1"
            fi ;;
        *) handle_ext "$1" "$3" "$4" ;;
    esac
}

handle_ext() {
    case "$2" in
        epub) generate_preview "$cols" "$lines" "$1" "epub" ;;
        pdf) generate_preview "$cols" "$lines" "$1" "pdf" ;;
        gz|bz2) fifo_pager tar -tvf "$1" ;;
        md) if exists glow; then
                fifo_pager glow -s dark "$1"
            elif exists lowdown; then
                fifo_pager lowdown -Tterm "$1"
            else
                fifo_pager pager "$1"
            fi ;;
        htm|html|xhtml)
            if exists w3m; then
                fifo_pager w3m "$1"
            elif exists lynx; then
                fifo_pager lynx "$1"
            elif exists elinks; then
                fifo_pager elinks "$1"
            else
                fifo_pager pager "$1"
            fi ;;
        7z|a|ace|alz|arc|arj|bz|cab|cpio|deb|jar|lha|lz|lzh|lzma|lzo\
        |rar|rpm|rz|t7z|tar|tbz|tbz2|tgz|tlz|txz|tZ|tzo|war|xpi|xz|Z)
            if exists atool; then
                fifo_pager atool -l "$1"
            elif exists bsdtar; then
                fifo_pager bsdtar -tvf "$1"
            fi ;;
        *) if [ "$3" = "bin" ]; then
               fifo_pager print_bin_info "$1"
           else
               fifo_pager pager "$1"
           fi ;;
    esac
}

preview_file() {
    clear
    # Trying to use pistol if it's available.
    if [ "$NNN_PISTOL" -ne 0 ] && exists pistol; then
        fifo_pager pistol "$1"
        return
    fi

    # Trying to use scope.sh if it's available.
    if [ "$NNN_SCOPE" -ne 0 ] && exists scope.sh; then
        fifo_pager scope.sh "$1" "$cols" "$lines" "$(mktemp -d)" "True"
        return
    fi

    # Use QuickLook if it's available.
    if [ -n "$QUICKLOOK" ]; then
        stat "$1" && f="$(wslpath -w "$1")" && "$QLPATH" "$f" &
        return
    fi

    # Detecting the exact type of the file: the encoding, mime type, and extension in lowercase.
    encoding="$(file -bL --mime-encoding -- "$1")"
    mimetype="$(file -bL --mime-type -- "$1")"
    ext="${1##*.}"
    [ -n "$ext" ] && ext="$(printf "%s" "${ext}" | tr '[:upper:]' '[:lower:]')"
    lines=$(tput lines)
    cols=$(tput cols)

    # Otherwise, falling back to the defaults.
    if [ -d "$1" ]; then
        cd "$1" || return
        if [ "$NNN_ICONLOOKUP" -ne 0 ] && [ -f "$(dirname "$0")"/.iconlookup ]; then
            [ "$NNN_SPLIT" = v ] && BSTR="\n"
            # shellcheck disable=SC2012
            ls -F --group-directories-first | head -n "$((lines - 3))" | "$(dirname "$0")"/.iconlookup -l "$cols" -B "$BSTR" -b " "
        elif exists tree; then
            fifo_pager tree --filelimit "$(find . -maxdepth 1 | wc -l)" -L 3 -C -F --dirsfirst --noreport
        elif exists exa; then
            fifo_pager exa -T --group-directories-first --colour=always -L 3
        elif exists eza; then # eza is a community fork of exa (exa is unmaintained)
            fifo_pager eza -T --group-directories-first --colour=always -L 3
        else
            fifo_pager ls -F --group-directories-first --color=always
        fi
        cd ..
    elif [ "${encoding#*)}" = "binary" ]; then
        handle_mime "$1" "$mimetype" "$ext" "bin"
    else
        handle_mime "$1" "$mimetype" "$ext"
    fi
}

generate_preview() {
  if [ -n "$QLPATH" ] && stat "$3"; then
        f="$(wslpath -w "$3")" && "$QLPATH" "$f" &
  elif [ -n "$NNN_PREVIEWVIDEO" ] && [[ "$4" == +(gif|video) ]]; then
    [ "$4" = "video" ] && args=(--start=10% --length=4) || args=()
    video_preview "$1" "$2" "$3" "${args[@]}" && return
  elif [ ! -f "$NNN_PREVIEWDIR/$3.jpg" ] || [ -n "$(find -L "$3" -newer "$NNN_PREVIEWDIR/$3.jpg")" ]; then
        mkdir -p "$NNN_PREVIEWDIR/${3%/*}"
        case $4 in
            audio) ffmpeg -i "$3" -filter_complex "scale=iw*min(1\,min($NNN_PREVIEWWIDTH/iw\,ih)):-1" "$NNN_PREVIEWDIR/$3.jpg" -y ;;
            epub) gnome-epub-thumbnailer "$3" "$NNN_PREVIEWDIR/$3.jpg" ;;
            font) fontpreview -i "$3" -o "$NNN_PREVIEWDIR/$3.jpg" ;;
            gif) if [ -p "$FIFO_UEBERZUG" ] && exists convert; then
                    frameprefix="$NNN_PREVIEWDIR/$3/${3##*/}"
                    if [ ! -d "$NNN_PREVIEWDIR/$3" ]; then
                        mkdir -p "$NNN_PREVIEWDIR/$3"
                        convert -coalesce -resize "$NNN_PREVIEWWIDTH"x"$NNN_PREVIEWHEIGHT"\> "$3" "$frameprefix.jpg" ||
                        MAGICK_TMPDIR="/tmp" convert -coalesce -resize "$NNN_PREVIEWWIDTH"x"$NNN_PREVIEWHEIGHT"\> "$3" "$frameprefix.jpg"
                    fi
                    frames=$(($(find "$NNN_PREVIEWDIR/$3" | wc -l) - 2))
                    [ $frames -lt 0 ] && return
                    while true; do
                        for i in $(seq 0 $frames); do
                            image_preview "$1" "$2" "$frameprefix-$i.jpg"
                            sleep 0.1
                        done
                    done &
                    printf "%s" "$!" > "$PREVIEWPID"
                    return
                 elif [ -n "$NNN_PREVIEWVIDEO" ]; then
                    video_preview "$1" "$2" "$3" && return
                 else
                    image_preview "$1" "$2" "$3" && return
                 fi ;;
            image) if exists rsvg-convert && [[ "${3##*.}" == "svg" ]]; then
                       rsvg-convert -a -w "$NNN_PREVIEWWIDTH" -h "$NNN_PREVIEWHEIGHT" -f png -o "$NNN_PREVIEWDIR/$3.png" "$3"
                   elif exists convert; then
                       convert "$3" -flatten -resize "$NNN_PREVIEWWIDTH"x"$NNN_PREVIEWHEIGHT"\> "$NNN_PREVIEWDIR/$3.jpg"
                   else
                       image_preview "$1" "$2" "$3" && return
                   fi ;;
            office) libreoffice --convert-to jpg "$3" --outdir "$NNN_PREVIEWDIR/${3%/*}"
                    filename="$(printf "%s" "${3##*/}" | cut -d. -f1)"
                    mv -- "$NNN_PREVIEWDIR/${3%/*}/$filename.jpg" "$NNN_PREVIEWDIR/$3.jpg" ;;
            pdf) pdftoppm -jpeg -f 1 -singlefile "$3" "$NNN_PREVIEWDIR/$3" ;;
            djvu) ddjvu -format=ppm -page=1 "$3" "$NNN_PREVIEWDIR/$3.jpg" ;;
            video) video_preview "$1" "$2" "$3" && return ;;
        esac
    fi
    if [ -f "$NNN_PREVIEWDIR/$3.jpg" ]; then
        image_preview "$1" "$2" "$NNN_PREVIEWDIR/$3.jpg"
    elif [[ "${3##*.}" == "svg" ]] && [ -f "$NNN_PREVIEWDIR/$3.png" ]; then
        image_preview "$1" "$2" "$NNN_PREVIEWDIR/$3.png"
    else
        fifo_pager print_bin_info "$3"
    fi
} >/dev/null 2>&1

image_preview() {
    clear
    exec >/dev/tty
    if [ "$NNN_TERMINAL" = "kitty" ] && [[ "$NNN_PREVIEWIMGPROG" == +(|icat) ]]; then
        kitty +kitten icat --silent --scale-up --place "$1"x"$2"@0x0 --transfer-mode=stream --stdin=no "$3" &
    elif [ "$NNN_TERMINAL" = "tmux" ] && [[ -n "$KITTY_LISTEN_ON" ]] && [[ "$NNN_PREVIEWIMGPROG" == +(|icat) ]]; then
        kitty +kitten icat --silent --scale-up --place "$(($1 - 1))x$(($2 - 1))"@0x0 --transfer-mode=memory --stdin=no "$3" &
    elif [ "$NNN_TERMINAL" = "wezterm" ] && [[ "$NNN_PREVIEWIMGPROG" == +(|imgcat) ]]; then
        wezterm imgcat "$3" &
    elif exists ueberzug && [[ "$NNN_PREVIEWIMGPROG" == +(|ueberzug) ]]; then
        ueberzug_layer "$1" "$2" "$3" && return
    elif exists "${NNN_PREVIEWIMGPROG%% *}"; then # can include command flags; only check first word
        "$NNN_PREVIEWIMGPROG" "$3" &
    else
        fifo_pager print_bin_info "$3" && return
    fi
    printf "%s" "$!" > "$PREVIEWPID"
}

video_preview() {
    clear
    exec >/dev/tty
    if [ -n "$NNN_PREVIEWVIDEO" ]; then
        mpv --no-config --really-quiet --vo="$NNN_PREVIEWVIDEO" --profile=sw-fast --loop-file --no-audio "$4" "$3" &
    else
        ffmpegthumbnailer -m -s0 -i "$3" -o "$NNN_PREVIEWDIR/$3.jpg" || rm -- "$NNN_PREVIEWDIR/$3.jpg" &
    fi
    printf "%s" "$!" > "$PREVIEWPID"
}

ueberzug_layer() {
    [ -f "$POSOFFSET" ] && read -r x y < "$POSOFFSET"
    printf '{"action": "add", "identifier": "nnn_ueberzug", "x": %d, "y": %d, "width": "%d", "height": "%d", "scaler": "fit_contain", "path": "%s"}\n'\
        "${x:-0}" "${y:-0}" "$1" "$2" "$3" > "$FIFO_UEBERZUG"
}

ueberzug_remove() {
    printf '{"action": "remove", "identifier": "nnn_ueberzug"}\n' > "$FIFO_UEBERZUG"
}

winch_handler() {
    clear
    pidkill "$PREVIEWPID"
    if [ -p "$FIFO_UEBERZUG" ]; then
        pkill -f "tail --follow $FIFO_UEBERZUG"
        tail --follow "$FIFO_UEBERZUG" | ueberzug layer --silent --parser json &
    fi
    preview_file "$(cat "$CURSEL")"
}

preview_fifo() {
    while read -r selection; do
        if [ -n "$selection" ]; then
            pidkill "$PREVIEWPID"
            [ -p "$FIFO_UEBERZUG" ] && ueberzug_remove
            [ "$selection" = "close" ] && break
            preview_file "$selection"
            printf "%s" "$selection" > "$CURSEL"
        fi
    done < "$NNN_FIFO"
    sleep 0.1 # make sure potential preview by winch_handler is killed
    pkill -P "$$"
}

if [ "$PREVIEW_MODE" -eq 1 ] 2>/dev/null; then
    if exists ueberzug && [ "$NNN_TERMINAL" != "kitty" ] && [[ "$NNN_PREVIEWIMGPROG" == +(|ueberzug) ]]; then
        mkfifo "$FIFO_UEBERZUG"
        tail --follow "$FIFO_UEBERZUG" | ueberzug layer --silent --parser json &
    fi

    preview_file "$PWD/$1"
    preview_fifo & WAITPID=$!
    printf "%s" "$!" > "$FIFOPID"
    printf "%s" "$PWD/$1" > "$CURSEL"
    trap 'winch_handler' WINCH
    trap 'rm -- "$PREVIEWPID" "$CURSEL" "$FIFO_UEBERZUG" "$FIFOPID" "$POSOFFSET" 2>/dev/null' INT HUP EXIT
    while kill -s 0 $WAITPID; do
      wait $WAITPID 2>/dev/null
    done
    exit 0
else
    if [ ! -r "$NNN_FIFO" ]; then
        prompt "No FIFO available! (\$NNN_FIFO='$NNN_FIFO')\nPlease read Usage in '$0'."
    elif [ "$KITTY_WINDOW_ID" ] && [ -z "$TMUX" ] && [ -z "$KITTY_LISTEN_ON" ]; then
        prompt "\$KITTY_LISTEN_ON not set!\nPlease read Usage in '$0'."
    else
        toggle_preview "$1" &
    fi
fi