#!/usr/bin/env bash
# Author: Lu Xu <oliver_lew at outlook dot com>
# License: MIT
# References: https://specifications.freedesktop.org/desktop-entry-spec
#             https://specifications.freedesktop.org/icon-theme-spec

# XDG directories
XDG_DATA_HOME=${XDG_DATA_HOME:-$HOME/.local/share}
XDG_CACHE_HOME=${XDG_CACHE_HOME:-$HOME/.cache}
XDG_CONFIG_HOME=${XDG_CONFIG_HOME:-$HOME/.config}
XDG_DATA_DIRS=${XDG_DATA_DIRS:-/usr/share:/usr/local/share}

# Apply default configuration values
SHOW_ALL=${XDG_MENU_SHOW_ALL:-}
TERMINAL=${XDG_MENU_TERMINAL:-xterm}
SIZE=${XDG_MENU_ICON_SIZE:-24}
ICON_THEME=${XDG_MENU_ICON_THEME:-$(
    if command -v gtk-query-settings > /dev/null; then
        gtk-query-settings gtk-icon-theme-name | awk '{ print $2 }' | tr -d '"'
    else
        echo Adwaita
    fi
)}
FALLBACK_ICON=${XDG_MENU_FALLBACK_ICON:-application-x-executable}

# Read CLI arguments
while getopts "ab:fhi:ns:t:" arg; do
    case "$arg" in
        a) SHOW_ALL=1;;
        b) FALLBACK_ICON=$OPTARG;;
        f) force_cache=1;;
        i) ICON_THEME=$OPTARG;;
        n) not_cache=1;;
        s) SIZE=$OPTARG;;
        t) TERMINAL=$OPTARG;;
        h|*) echo "$0 [-a] [-b icon] [-f] [-i theme] [-n] [-s size] [-t term]" && exit ;;
    esac
done

# Directories
DATA_DIRS=$XDG_DATA_HOME:$XDG_DATA_DIRS
CACHE_DIR="$XDG_CACHE_HOME/xdg-xmenu"
CACHE_ICON_DIR="$CACHE_DIR/icons"
mkdir -p "$CACHE_ICON_DIR"

# Find directories in an icon theme matching the target size
valid_dirs() {
    theme_dir=$1
    [ -f "$theme_dir/index.theme" ] || return
    while IFS='=' read -r key value; do
        # parse the index.theme file
        case "$key" in
        \[*\])
            # FIXME: scaled icons are ignored for now, sorry HiDPI
            # deal with last subdirectory, only Size is mandatory
            if [ "${Scale-1}" = 1 ] && [ -n "$Size" ]; then
                # defaults if they are not specified
                Type=${Type:-Threshold}
                MaxSize=${MaxSize:-Size}
                MinSize=${MinSize:-Size}
                Threshold=${Threshold:-2}

                # match subdirectory sizes based on 'Type'
                # 1. fixed size, has to be exact
                { [ "$Type" = Fixed ] &&
                    [ "$SIZE" = "$Size" ]; } ||
                # 2. threshold size, within Threshold times
                { [ "$Type" = Threshold ] &&
                    [ "$SIZE" -ge "$((Size / Threshold))" ] &&
                    [ "$SIZE" -le "$((Size * Threshold))" ]; } ||
                # 3. scalable size, Min/MaxSize as lower/upper limits
                { [ "$Type" = Scalable ] &&
                    [ "$SIZE" -ge "$MinSize" ] &&
                    [ "$SIZE" -le "$MaxSize" ]; } &&
                # found it
                echo "$theme_dir/$subdir"
            fi

            # clean up variables for the new subdirectory
            unset MaxSize MinSize Scale Size Threshold Type subdir
            subdir=${key#[}
            subdir=${subdir%]}
            ;;
        *)
            # read each key-value pair into shell variables
            [ -n "$value" ] && eval "$key=\"$value\""
            ;;
        esac
    done < "$theme_dir/index.theme"
}

# Find all directories matching the size and containing icons directly
find_all_dirs() {
    IFS=':'
    for datadir in $DATA_DIRS; do unset IFS
        for theme in "$ICON_THEME" "hicolor"; do
            valid_dirs "$datadir/icons/$theme"
        done
    done
    echo "/usr/share/pixmaps"
}

all_dirs=$(find_all_dirs)

# Search for an icon based on its name
find_icon() {
    icon=$1
    # find any png, svg or xpm icon in available directories
    for dir in $all_dirs; do
        for ext in png svg xpm; do
            if [ -f "$dir/$icon.$ext" ]; then
                echo "$dir/$icon.$ext"
                return
            fi
        done
    done
    # when the fallback icon is not found, return none instead
    [ "$icon" = "$FALLBACK_ICON" ] && echo "" || echo "$FALLBACK_ICON"
}

# xmenu does not support svg, so convert svg to png
cache_icon() {
    icon=$1

    # icon is a existing png/xpm file
    [ -f "$icon" ] && [ ${icon##*.} != 'svg' ] && echo "$icon" && return

    # cache path in $CACHE_ICON_DIR with the flattened name
    [ -f "$icon" ] && basename=$(echo $icon | tr '/' '_') || basename=${icon##*/}
    cache_path=$CACHE_ICON_DIR/$basename.png

    # already cached, skip unless forced to cache again
    if [ -f "$cache_path" ] && [ -z "$force_cache" ]; then
        echo "$cache_path" && return
    fi

    # find the icon in icon themes if the name is not a path
    [ -f "$icon" ] && icon_path=$icon || icon_path=$(find_icon "$icon")

    # convert svg -> png
    if [ "${icon_path##*.}" = "svg" ]; then
        # first try the fasted, then the slower ones
        if [ -n "$not_cache" ]; then
            : # not doing caching in dry run mode
        elif command -v rsvg-convert > /dev/null; then
            rsvg-convert -w "$SIZE" -h "$SIZE" "$icon_path" -o "$cache_path"
        elif command -v convert > /dev/null; then
            convert -background none -size "${SIZE}x${SIZE}" "$icon_path" "$cache_path"
        elif command -v inkscape > /dev/null; then
            inkscape -w "$SIZE" -h "$SIZE" "$icon_path" -o "$cache_path"
        else
            echo >&2 "[Error]: Convert svg icons failed."
            echo >&2 "Please install one of the following programs:"
            echo >&2 "rsvg-convert(librsvg), convert(imagemagick), inkscape"
            exit 1
        fi
        echo "$cache_path"
    else
        # use png and xpm icons in-place
        # this could be empty if no fallback icon is found, and it will work
        echo "$icon_path"
    fi
}

FALLBACK_ICON=$(cache_icon "$FALLBACK_ICON")

# parse the desktop entries and categorize them
IFS=:
for datadir in $DATA_DIRS; do unset IFS
    appdir="$datadir/applications"
    [ ! -d "$appdir" ] && continue
    for app in "$appdir"/*.desktop; do
        unset icon name genname cmd category nodisplay useterm added
        while IFS="=" read -r key value; do
            case "$key" in
            Categories) [ -z "$category" ] && category=$value ;;
            Icon)       [ -z "$icon" ]     && icon=$(cache_icon "$value") ;;
            Name)       [ -z "$name" ]     && name="$value" ;;
            GenericName)[ -z "$genname" ]  && genname=$value ;;
            Exec)       [ -z "$cmd" ]      && cmd=$value &&
                        # remove %* place holders
                        [ "${cmd#*%}" != "$cmd" ] && cmd=$(
                            echo "$cmd" | sed 's/ %[fFuUick]//g' | sed 's/%%/$/g'
                        ) ;;
            NoDisplay)  [ "$value" != "false" ] && nodisplay=1 ;;
            Terminal)   [ "$value" != "false" ] && useterm=1 ;;
            # FIXME: show_all not working as it should
            OnlyShowIn)     [ -z "$SHOW_ALL" ] && nodisplay=1 ;;
            esac
        done < "$app"

        [ -n "$nodisplay" ] && continue
        [ -n "$useterm" ]   && cmd="$TERMINAL -e $cmd"
        [ -n "$genname" ]   && name="$name ($genname)"
        icon="${icon-$FALLBACK_ICON}"
        icon="${icon:+\tIMG:$icon}"
        item="$icon\t$name\t$cmd"

        IFS=\;
        for c in $category; do unset IFS
            case "$c" in
            Audio*|*Video) added=1; Multimedia="$Multimedia$item\n"   ;;
            Development)   added=1; Development="$Development$item\n" ;;
            Education)     added=1; Education="$Education$item\n"     ;;
            Game)          added=1; Games="$Games$item\n"             ;;
            Graphics)      added=1; Graphics="$Graphics$item\n"       ;;
            Network)       added=1; Internet="$Internet$item\n"       ;;
            Office)        added=1; Office="$Office$item\n"           ;;
            Science)       added=1; Science="$Science$item\n"         ;;
            Settings)      added=1; Settings="$Settings$item\n"       ;;
            System)        added=1; System="$System$item\n"           ;;
            Utility)       added=1; Accessories="$Accessories$item\n" ;;
            esac
        done
        [ -z "$added" ] && Others="$Others$item\n"
    done
done

category_sort() {
    category_icon=$1
    category_name=$2
    category_apps=$3
    icon=$(cache_icon "$category_icon")
    # create top level folder
    printf "${icon:+IMG:$icon\t}%s\n" "$category_name"
    # sort the applications by their names
    # FIXME: when icon is missing, name is in first column
    printf "$category_apps%s" | sort -f -k 2 | uniq
}

category_sort applications-accessories Accessories "$Accessories"
category_sort applications-development Development "$Development"
category_sort applications-education   Education   "$Education"
category_sort applications-games       Games       "$Games"
category_sort applications-graphics    Graphics    "$Graphics"
category_sort applications-internet    Internet    "$Internet"
category_sort applications-multimedia  Multimedia  "$Multimedia"
category_sort applications-office      Office      "$Office"
category_sort applications-science     Science     "$Science"
category_sort preferences-desktop      Settings    "$Settings"
category_sort applications-system      System      "$System"
category_sort applications-other       Others      "$Others"