#!/bin/bash  -u
#console_codes(4) man page... vt100/2 et && EMCA-48 standard
# (c) la walsh (2013) -- free to use and modify for personal use.
#                     -- optionally licenced under Gnu v3 license.

# v0.0.3    - try to reduce tabcols to minimal set to reproduce.
# v0.0.2    - set tabs for full terminal width (try to get term width)

shopt -s expand_aliases extglob
alias int='declare -i'        sub='function'    array='declare -a'
alias intArray='declare -ia'  P=printf          string=declare

P -v clrallts  "\x1b[3g"
P -v sts       "\033H"
P -v cpr       "\x1b[6n"

sub getcols() {
  local sttyout="$(stty size </dev/tty)"
  int default_cols=80
  if [[ -n ${COLUMNS:-""} && $COLUMNS =~ ^[0-9]+$ ]]; then 
    default_cols=$COLUMNS; fi
  [[ -z ${sttyout:-""} ]] && { echo $default_cols; return 0; } 
  int cols="${sttyout#*\ }"
  echo -n $[cols<2?default_cols:cols]
  return 0
}

sub getpos () {
  string ans    wanted=${1:-xy}
  int attempt=0 max_attempt=1   # in case of rare failure case
                                # use 'attempt' value as additional
                                # time to wait for response
  while : ; do  
    ( ( P "\x1b[6n" >/dev/tty) & 2>/dev/null )  
    read  -sd R -r -t $[2 + attempt] ans </dev/tty; 
    ans=${ans:2}; 
    int x=0-1 y=0-1
    if ! x="${ans#*;}" y="${ans%;*}" 2>/dev/null  || 
      ((x==-1||y==-1)); then
      ((attempt+=1 < max_attempt)) && continue
    fi  
  break; done
  string out=""
  [[ $wanted =~ x ]] && out="$x"
  [[ $wanted =~ y ]] && out="${out:+$x }$y"
  [[ $out ]] && echo -n "$out"
}

declare -iga tabs

sub get_tabs () {
  P "\r"
  tabs=()
  int pos=0 oldpos=0-1
  while ((oldpos!=pos));do
    ((pos)) && tabs+=($pos)
    oldpos=pos
    P "\t"
    pos=$(getpos x)
  done
  P "\r"
  return 0
}

# Note: this sub uses ability to _read_ tabstops as _proxy_ for setting them
# (i.e. it makes no sense to be able to read them if you can't set them)

sub test_tabset_ability () {
  string prompt="tty_tab:"
  int newcol=${#prompt}+1
  P "\r$prompt"
  int mycol=$(getpos x)
  ((mycol && mycol==newcol)) && return 0    ## return OK  
  
  { P " Term tabset ability not detected mycol=${mycol:-''},"
    P " promptlen=$newcol)\n"; } >&2
  exit -1 
}

sub do_help_n_display_curtabs () {  
  P " <n>   - set tab stop to N\r"
  intArray diffs;
  int last=1  cur i
  string eol=""
  get_tabs && {
    for ((i=0; i<${#tabs[@]}; ++i)); do
      cur=${tabs[i]}
      diffs[i]=cur-last
      last=cur
    done  
    intArray reverse_tabs_set=()
    int prevtab=0-1
    for ((i=${#diffs[@]}-2; i>0; --i)); do
      int thistab=${diffs[i]}
      if ((thistab!= prevtab)) ;then 
        reverse_tabs_set+=($thistab)
        prevtab=thistab
      fi
    done
    P "current value: tty_tab "
      for ((i=${#reverse_tabs_set[@]}-1; i>=0; --i)); do
        P "%d " "${reverse_tabs_set[i]}"; done
    P "\r";
  }
  get_tabs  && {
    P "(from 1, tabs skip to column: "
    P "%s " "${tabs[@]}"
    P "\r\n"
  }
}

sub set_tabs () {
  int max_col=${1:-80}    tabstop=${2:-"need a param for tabstop"}
  int tab=$tabstop        pos=0
  string str=""
  P $clrallts               ## reset old tabs
  while ((++pos<cols)) ;do  ## move across screen setting tabs
    str+=" "
    ((pos%tab)) || str+="$sts"
  done
  P "\r$str\r"
}


int cols=$(getcols)

test_tabset_ability         ## exits if no ability


if (($#==0)) ; then
  do_help_n_display_curtabs
  exit 1
else
  set_tabs "$cols" "$@"
fi

# vim: ts=2 sw=2