Command menu (terminal,bash,fzf_reload,/tmp,only .bashrc/function)

#   Oct 28, 2022, 11:18:18  Command menu (terminal,bash,fzf_reload,/tmp,only .bashrc/function)
#
#
#   .bashrc :
#
#   Command menu with multiple pages (bash, fzf).
#
#   Usage :     menu file1.txt file2.txt file3.txt ...
#               menu <only .txt files with path>
#
#   Example :   menu ~/.bash_history
#               menu ~/.bash_history ~/.bashrc
#
#               To collate pages, use the alias command.
#
#               alias m='menu file1.txt file2.txt file3.txt'
#
#
#   Oct 28, 2022, 11:18:43 :    Return to the array variable (ps like pages) instead of copying.
#       Main motivation         Use mapfile command instead of head/tail command.
#
#   fake readline (up and delete line) source :
#   https://stackoverflow.com/questions/18362837/how-to-display-and-refresh-multiple-lines-in-bash
#   https://stackoverflow.com/questions/22322879/how-to-print-current-bash-prompt
#
#   fzf insert = edit source :
#   https://github.com/junegunn/fzf/wiki/examples#git (under fstash)
#
#   neccesary packages :
#   ncurses : tput
#
#   variables (using shared memory) :
#   /tmp/pm : page maximum
#   /tmp/pn : page number
#   /tmp/pd : page decrease
#   /tmp/pi : page increase
#   /tmp/ps : pages
#   https://stackoverflow.com/questions/13207292/bash-background-process-modify-global-variable
#   https://github.com/junegunn/fzf/issues/2976#issuecomment-1254529831


function menu {

if [ $# -eq 0 ]                         #   Empty command does nothing (quits).
then                                    #   (or print help/usage ?)
return
fi

if [ ! -s /tmp/pn ]                     #   Define page number, if neccesary.
then                                    #   (Page number test, if missing then 0.)
echo 0 >/tmp/pn
fi

echo "$@">/tmp/ps                       #   Define pages array.
ps=($@)
                                        #   page increase and page decrease commands copy to /tmp folder for fzf_reload

echo 'ps=($(</tmp/ps));i=$(</tmp/pn);((++i));[ $i -gt $(</tmp/pm) ]&&i=0||:;echo $i>/tmp/pn;cat ${ps[i]}'>/tmp/pi
echo 'ps=($(</tmp/ps));i=$(</tmp/pn);((--i));[ $i -lt 0 ]&&i=$(</tmp/pm)||:;echo $i>/tmp/pn;cat ${ps[i]}'>/tmp/pd

echo $(($#-1))>/tmp/pm                  #   Define page maximum.
#   echo $((${#ps[@]}-1))>/tmp/pm       #   Define page maximum. Another option.

if [ $(</tmp/pn) -gt $(</tmp/pm) ]      #   Page number adjustment, if neccesary.
then                                    #   (or zero ?)
echo $(</tmp/pm)>/tmp/pn
fi

tty=""                                  #   tty : --height=50% --border=vertical
if [ "$TERM" = linux ]
then
tty="--height=50% --border=vertical"
fi
                                        #   fzf engine

line=$(< ${ps[$(</tmp/pn)]} fzf --reverse --exact --no-color --no-info --expect=insert --cycle --bind "right:reload(. /tmp/pi),left:reload(. /tmp/pd)" $tty)

if [ "$line" = "" ]                     #   fzf escape, ctrl-c, empty string
then
tput cuu1 && tput el                    #   fake readline (up and delete line)
return
fi

mapfile -t line <<< "$line"             #   https://github.com/junegunn/fzf/wiki/examples#git
key="${line[0]}"                        #   under fstash
cmd="${line[1]}"

if [ "$key" = insert ]                  #   Just insert for editing.
then
tput cuu1 && tput el                    #   fake readline (up and delete line)
read -p "${PS1@P}" -eri "$cmd" cmd
fi

history -s $FUNCNAME $@
history -s $cmd

tput cuu1 && tput el                    #   fake readline (up and delete line)
echo "${PS1@P}"$cmd

eval $cmd

}


#   Example.

alias m='menu ~/.bash_history ~/.bashrc'

#   Personal examples.
#
#   alias m='menu ~/cmd.txt ~/pacman.txt ~/backup.txt ~/hdd.txt ~/swap.txt ~/install.txt'
#
#   Older one page settings (out of habit).
#
#   alias b='menu ~/backup.txt' s='menu ~/cmd.txt' pk='menu ~/pacman.txt' hdd='menu ~/hdd.txt'
#   alias swap='menu ~/swap.txt' i='menu ~/install.txt'