AndroidTerminal shell menu script

menu.sh

#!/system/xbin/bash

# AndroidTerminal shell menu script
#
# Displays a fullscreen menu in the terminal that adapts to terminal size and supports pagination.
# The menu can be navigated with the <w> and <s> keys (to reflect the wasd movement style), or with <u> and <d> (up and down).
# By pressing <return>, the menu item selectection can be confirmed, and the corresponding script will be executed.
#
# Usage: bash menu.sh <menu folder>
#
# <menu folder>: relative or absolute path to folder containing menu and entry files
#   example folder hierarchy:
#     menu folder:
#       - ./menu
#       - ./01.entry
#       - ./02.entry
#       - ./99.entry
#
# Menu and entry file format:
#   multiple lines of <key>: <value>
#   example file contents:
#     ./menu contents:
#       title: Example Menu
#       termtitle: Example
#     ./01.entry contents:
#       title: Exit
#       termtitle: Exit
#       command: echo exiting...; exit
#
# Legal keys for menu and entry files:
#   ./menu
#     title: name listed at top of menu
#     termtitle: name set to the terminal title while in menu
#   ./*.entry
#     title: name listed in menu, can contain terminal escape sequences
#            the content of this line is passed to printf
#     termtitle: name set to the terminal title during execution of entry
#     command: bash command to execute when selection confirmed
#              the value of this key passed to the builtin "eval"
#     checkcolor: escape sequence to determine the color and style of the "x" mark when menu item is selected

menu="$1"

gopos() {
    # move the terminal cursor to row $1 and column $2
    printf "\033[${1};${2}H"
}

get() {
    # return the value of key $2 (unquoted RegExp) in file $1
    grep "^$2: " "$1" | sed "s/^[^:]*: //"
}

getmenu() {
    # return the value of key $1 in the menu file associated with this menu
    get "$menu/menu" $1
}

getentry() {
    # return the value of key $2 in the $1-th entry file
    # behaviour for $1 > $entries is undefined
    get ${entry[$1]} $2
}

default() {
    # return $1 if it is non-empty, else $2
    if [ "$1" == "" ]; then
        printf -- "$2"
    else
        printf -- "$1"
    fi
}

init() {
    # initialize menu state
    # check if menu exists
    if [ ! -f "$menu/menu" ]; then
        echo "Couldn't find menu"
        exit 1
    fi
    # get list of entries, allow list of 0 entries (inescapable menu if ^C is not used)
    # it is advised to create an "exit" menu entry to make gracefully exiting the menu possible
    shopt -s nullglob
        entry=($menu/*.entry)
    shopt -u nullglob
    # set number of entries to $entries to avoid ugly array-length syntax
    entries=${#entry[@]}
    # select the first entry
    selected=0
}

reflow() {
    # check size of terminal and recalculate pagination if needed
    # get terminal size
    size=($(stty size 2>/dev/null))
    # AndroidTerm hack: in early terminal initialization, "stty size" returns errors
    if [ -z ${size[0]} ]; then
        # wait until terminal initialized correctly
        usleep 100000
        # re-call self
        reflow
    # if previous terminal height is not equal to current terminal height
    elif [ "${size[0]}" != "$lines" ]; then
        # update terminal height variable
        lines=${size[0]}
        # the first and last line per page are left free for pagination and terminal title
        # including 1 empty line below the title and above the pagination
        # total: height - 4 lines
        entries_per_page=$(($lines - 4))
        # pages is ceil(entries / entries_per_page)
        # bash doesn't have ceil()
        # so pages is floor(entries / entries_per_page) (+ 1 if entries % entries_per_page is not 0)
        pages=$(($entries / $entries_per_page))
        rest=$(($entries % $entries_per_page))
        if [ $rest -ne 0 ]; then
            pages=$(($pages + 1))
        fi
        # call redraw because pagination has changed
        redraw
    fi
}

page_of() {
    # calculate page of the $1-th entry
    cur=$(($1 / $entries_per_page))
    printf -- "$cur"
}

redraw() {
    # redraw the menu
    # this includes the menu title, termtitle, titles of entries, and unfilled "[ ]" for the selection mark
    cur_page=$(page_of $selected)
    # calculate number of entries on this page
    on_page=(${entry[@]:$(($entries_per_page * $cur_page)):$entries_per_page})
    # output termtitle and menu title
    out="\033]2;$(default "$(getmenu termtitle)" "Menu") \007$(default "$(getmenu title)" "Menu:")"
    # iterate over entries on this page
    for i in $(seq 0 $((${#on_page[@]} - 1))); do
        # output unfilled "[ ]" and entry title
        out+="$(gopos $(($i + 3)) 0)[ ] $(getentry $(($cur_page * $entries_per_page + $i)) title)"
    done
    # output pagination
    out+="$(gopos $(($lines)) 0)Page $(($cur_page + 1)) of $pages"
    # move cursor to not obscure pagination (to second-to-last line)
    out+="$(gopos $(($lines - 1)) 0)"
    # clear the screen
    clear
    # draw the screen
    printf -- "$out"
    # draw selection mark
    check
}

check() {
    # draw selection mark
    out=""
    cur_page=$(page_of $selected)
    # calculate number of entries on this page
    on_page=(${entry[@]:$(($entries_per_page * $cur_page)):$entries_per_page})
    # iterate over entries on this page
    for i in $(seq 0 $((${#on_page[@]} - 1))); do
        # output space (to overwrite the previous mark) if the item is not selected
        # else output the checkcolor for this entry and the selction mark "x"
        mark=" "
        if [ $(($entries_per_page * $cur_page + $i)) -eq $selected ]; then
            mark="$(default $(getentry $(($cur_page * $entries_per_page + $i)) checkcolor) "\e[93m")x\e[39m"
        fi
        out+="$(gopos $(($i + 3)) 2)$mark"
    done
    # move cursor to not obscure pagination (to second-to-last line)
    out+="$(gopos $(($lines - 1)) 0)"
    # draw selection mark, and clear old mark
    printf -- "$out"
}

prompt() {
    # check for a key press within the next second
    if read -sN1 -t1 key; then
        # call act if a keypress happened
        act "$key"
    fi
}

act() {
    # check input from prompt
    cur_page=$(page_of $selected)
    case "$1" in
        s|d) # if <s> or <d> (down)
            # if not last entry
            if [ $selected -lt $(($entries - 1)) ]; then
                # select next entry
                selected=$(($selected + 1))
            fi
            ;;
        w|u) # if <w> or <u> (up)
            # if not first entry
            if [ $selected -gt 0 ]; then
                # select previous entry
                selected=$(($selected - 1))
            fi
            ;;
        '') # if <return> (confirm)
            # print termtitle of entry
            printf "\033]2;$(default "$(getentry $selected termtitle)" "Command") \007"
            # clear the screen
            clear
            # run command
            eval "$(getentry $selected command)"
            # redraw the menu after command
            redraw
            ;;
    esac
    # if cursor went off the page
    if [ $cur_page -ne $(page_of $selected) ]; then
        # redraw menu, which switches to the next/previous page to display the correct menu entries
        # redraw calls check, to redraw the selection mark
        redraw
    else
        # redraw selection mark
        check
    fi
}

# initialize the menu
init
while true; do
    # check if terminal size changed
    reflow
    # check for user input
    prompt
done