#!/usr/bin/env sh

# Description: Terminal based file previewer
#
# Note: This plugin needs a "NNN_FIFO" to work. See man.
# For a more extended version of this script with additional optional dependencies, see preview-tui-ext.
#
# Dependencies:
#   - Supports 4 independent methods to preview with:
#       - tmux (>=3.0), or
#       - kitty with allow_remote_control and listen_on set in kitty.conf, or
#       - QuickLook on WSL (https://github.com/QL-Win/QuickLook)
#       - $TERMINAL set to a terminal (it's xterm by default).
#   - less or $PAGER
#   - tree or exa or ls
#   - mediainfo or file
#   - mktemp
#   - unzip
#   - tar
#   - man
#   - optional: bat for code syntax highlighting
#   - optional: ueberzug, kitty terminal, viu or catimg for images.
#   - optional: scope.sh file viewer from ranger.
#       1. drop scope.sh executable in $PATH
#       2. set/export $USE_SCOPE as 1
#   - optional: pistol file viewer (https://github.com/doronbehar/pistol).
#       1. install pistol
#       2. set/export $USE_PISTOL as 1
#
# 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 ($TERMINAL).
#
#   Tmux and kitty users can configure $SPLIT to either "h" or "v" to set a
#   'h'orizontal split or a 'v'ertical split (as in, the line that splits the
#   windows will be horizontal or vertical).
#
#   Kitty users need `allow_remote_control` set to `yes`, and `listen_on` set
#   to e.g. "$TMPDIR/kitty". To customize the window split, `enabled_layouts`
#   has to be set to `all` or `splits` (the former is the default value).
#   This terminal is also able to show images without extra dependencies.
#
# Shell: POSIX compliant
# Authors: Todd Yamakawa, Léo Villeveygoux, @Recidiviste, Mario Ortiz Manero, Luuk van Baal

#SPLIT="$SPLIT"  # you can set a permanent split here
#TERMINAL="$TERMINAL"  # same goes for the terminal
USE_SCOPE="${USE_SCOPE:-0}"
USE_PISTOL="${USE_PISTOL:-0}"
PAGER="${PAGER:-less -P?n -R}"
TMPDIR="${TMPDIR:-/tmp}"
BAT_STYLE="${BAT_STYLE:-numbers}"
NNN_PARENT="${NNN_FIFO#*.}"
FIFOPID="$TMPDIR/nnn-preview-tui-fifopid.$NNN_PARENT"
PAGERPID="$TMPDIR/nnn-preview-tui-pagerpid.$NNN_PARENT"
IMGPID="$TMPDIR/nnn-preview-tui-imgpid.$NNN_PARENT"
CURSEL="$TMPDIR/nnn-preview-tui-selection.$NNN_PARENT"
FIFO_UEBERZUG="$TMPDIR/nnn-preview-tui-ueberzug-fifo.$NNN_PARENT"

start_preview() {
    [ "$PAGER" = "most" ] && PAGER="less -R"

    if [ -e "${TMUX%%,*}" ] && tmux -V | grep -q '[ -][3456789]\.'; then
        TERMINAL=tmux
    elif [ -n "$KITTY_LISTEN_ON" ]; then
        TERMINAL=kitty
    else
        TERMINAL="${TERMINAL:-xterm}"
    fi

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

    case "$TERMINAL" in
        tmux) # tmux splits are inverted
            if [ "$SPLIT" = "v" ]; then DSPLIT="h"; else DSPLIT="v"; fi
            tmux split-window -e "NNN_FIFO=$NNN_FIFO" -e "PREVIEW_MODE=1" -e "PAGER=$PAGER" \
                -e "USE_SCOPE=$USE_SCOPE" -e "SPLIT=$SPLIT" -e "USE_PISTOL=$USE_PISTOL" \
                -e "BAT_STYLE=$BAT_STYLE" -e "PAGERPID=$PAGERPID" -e "FIFOPID=$FIFOPID" \
                -e "IMGPID=$IMGPID" -e "CURSEL=$CURSEL" -e "TMPDIR=$TMPDIR" \
                -e "FIFO_UEBERZUG=$FIFO_UEBERZUG" -e "QLPATH=$QLPATH" -d"$DSPLIT" "$0" "$1" ;;
        kitty) # Setting the layout for the new window. It will be restored after the script ends.
            kitty @ goto-layout splits
            # Trying to use kitty's integrated window management as the split window. All
            # environmental variables that will be used in the new window must be explicitly passed.
            kitty @ launch --no-response --title "nnn preview" --keep-focus \
                --cwd "$PWD" --env "PATH=$PATH" --env "NNN_FIFO=$NNN_FIFO" --env "FIFOPID=$FIFOPID" \
                --env "PREVIEW_MODE=1" --env "PAGER=$PAGER" --env "TMPDIR=$TMPDIR" \
                --env "USE_SCOPE=$USE_SCOPE" --env "SPLIT=$SPLIT" --env "TERMINAL=$TERMINAL"\
                --env "USE_PISTOL=$USE_PISTOL" --env "BAT_STYLE=${BAT_STYLE:-numbers}" \
                --env "PAGERPID=$PAGERPID" --env "IMGPID=$IMGPID" --env "FIFO_UEBERZUG=$FIFO_UEBERZUG" \
                --env "CURSEL=$CURSEL" --location "${SPLIT}split" "$0" "$1" ;;
        *)  if [ -n "$2" ]; then
                QUICKLOOK=1 QLPATH="$2" PREVIEW_MODE=1 "$0" "$1" &
            else
                PAGERPID="$PAGERPID" IMGPID="$IMGPID" CURSEL="$CURSEL" PREVIEW_MODE=1 \
                     FIFOPID="$FIFOPID" FIFO_UEBERZUG="$FIFO_UEBERZUG" $TERMINAL -e "$0" "$1" &
            fi ;;
    esac
} >/dev/null 2>&1

toggle_preview() {
    if exists QuickLook.exe; then
        QLPATH="QuickLook.exe"
    elif exists Bridge.exe; then
        QLPATH="Bridge.exe"
    fi
    if pkill -P "$(cat "$FIFOPID")"; then
        if [ -n "$QLPATH" ] && stat "$1"; then
            f="$(wslpath -w "$1")" && "$QLPATH" "$f" &
        fi
    else
        start_preview "$1" "$QLPATH"
    fi
} >/dev/null 2>&1

exists() {
    type "$1" >/dev/null
}

fifo_pager() {
    cmd="$1"
    shift

    # We use a FIFO to access $PAGER PID in jobs control
    tmpfifopath="$TMPDIR/nnn-preview-tui-fifo.$$"
    mkfifo "$tmpfifopath" || return

    $PAGER < "$tmpfifopath" &
    printf "%s" "$!" > "$PAGERPID"

    (
        exec > "$tmpfifopath"
        if [ "$cmd" = "pager" ]; then
            if exists bat; then
                bat --terminal-width="$(tput cols)" --decorations=always --color=always \
                    --paging=never --style="$BAT_STYLE" "$@" &
            else
                $PAGER "$@" &
            fi
        else
            "$cmd" "$@" &
        fi
    )

    rm "$tmpfifopath"
} 2>/dev/null

# 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
} 2>/dev/null

handle_mime() {
    case "$2" in
        image/*) image_preview "$cols" "$lines" "$1" ;;
        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
        gz|bz2) fifo_pager tar -tvf "$1" ;;
        *) 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 [ "$USE_PISTOL" -ne 0 ] && exists pistol; then
        fifo_pager pistol "$1"
        return
    fi

    # Trying to use scope.sh if it's available.
    if [ "$USE_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 "$1" || return
        if exists tree; then
            fifo_pager tree --filelimit "$(find . -maxdepth 1 | wc -l)" -L 3 -C -F --dirsfirst --noreport
        elif exists exa; then
            exa -G --group-directories-first --colour=always
        else
            fifo_pager ls -F --group-directories-first --color=always
        fi
    elif [ "${encoding#*)}" = "binary" ]; then
        handle_mime "$1" "$mimetype" "$ext" "bin"
    else
        handle_mime "$1" "$mimetype" "$ext"
    fi
} 2>/dev/null

image_preview() {
    if [ "$TERMINAL" = "kitty" ]; then
        # Kitty terminal users can use the native image preview method
        kitty +kitten icat --silent --place "$1"x"$2"@0x0 --transfer-mode=stream --stdin=no "$3" &
    elif [ -n "$QLPATH" ] && stat "$3"; then
        f="$(wslpath -w "$3")" && "$QLPATH" "$f" && return
    elif exists ueberzug; then
        ueberzug_layer "$1" "$2" "$3" && return
    elif exists catimg; then
        catimg "$3" &
    elif exists viu; then
        viu -t "$3" &
    else
        fifo_pager print_bin_info "$3" && return
    fi
    printf "%s" "$!" > "$IMGPID"
} 2>/dev/null

ueberzug_layer() {
    printf '{"action": "add", "identifier": "nnn_ueberzug", "x": 0, "y": 0, "width": "%d", "height": "%d", "scaler": "fit_contain", "path": "%s"}\n' "$1" "$2" "$3" > "$FIFO_UEBERZUG"
}

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

winch_handler() {
    clear
    kill "$(cat "$IMGPID")" "$(cat "$PAGERPID")"
    pkill -P "$$"
    if [ -p "$FIFO_UEBERZUG" ]; then tail --follow "$FIFO_UEBERZUG" | ueberzug layer --silent --parser json & fi
    cat "$CURSEL" > "$NNN_FIFO"
    preview_file "$(cat "$CURSEL")"
    preview_fifo &
    wait "$!"
} 2>/dev/null

preview_fifo() {
    printf "%s" "$$" > "$FIFOPID"
    while read -r selection; do
        kill "$(cat "$IMGPID")" "$(cat "$PAGERPID")"
        [ -p "$FIFO_UEBERZUG" ] && ueberzug_remove
        preview_file "$selection"
        printf "%s" "$selection" > "$CURSEL"
    done < "$NNN_FIFO"
} 2>/dev/null

if [ "$PREVIEW_MODE" ]; then
    if [ "$TERMINAL" != "kitty" ] && exists ueberzug; then
        mkfifo "$FIFO_UEBERZUG"
        tail --follow "$FIFO_UEBERZUG" | ueberzug layer --silent --parser json &
    fi

    printf "%s" "$PWD/$1" > "$CURSEL"
    preview_file "$PWD/$1"
    preview_fifo &
    trap 'winch_handler' WINCH
    trap 'rm "$PAGERPID" "$IMGPID" "$CURSEL" "$FIFO_UEBERZUG" "$FIFOPID" 2>/dev/null' INT HUP EXIT
    wait "$!" 2>/dev/null
else
    if [ ! -r "$NNN_FIFO" ]; then
        clear
        printf "No FIFO available! (\$NNN_FIFO='%s')\nPlease read Usage in preview-tui." "$NNN_FIFO"
        cfg=$(stty -g); stty raw -echo; head -c 1; stty "$cfg"
    elif [ "$KITTY_WINDOW_ID" ] && [ -z "$KITTY_LISTEN_ON" ]; then
        clear
        printf "\$KITTY_LISTEN_ON not set!\nPlease read Usage in preview-tui."
        cfg=$(stty -g); stty raw -echo; head -c 1; stty "$cfg"
    else
        toggle_preview "$1" &
    fi
fi