#! /usr/bin/env sh
# Taken in verbatim from: https://unix.stackexchange.com/a/113450, and somewhat changed

LE_print_debug() {
    LE_debug="$1"
    LE_debug_msg="$2"
    [ -n "$LE_debug" ] && printf "\nDBG: (%s)\n" "$LE_debug_msg" > outfile.debug
}

LE() {
  # Shell Line Editor. Extremely slow and stupid code. However it
  # should work on ansi/vt100/linux derived terminals on POSIX
  # systems.
  # Understands some emacs key bindings: CTRL-(A,B,D,E,F,H,K,L)
  # plus the CTRL-W and CTRL-U normal killword and kill.
  # no Meta-X key, but handling of <Left>, <Right>, <Home>, <End>
  # <Suppr>.
  #
  # Args:
  #  [1]: prompt (\x sequences recognized, defaults to "")
  #  [2]: max input length (unlimited if < 0, (default))
  #  [3]: fill character when erasing (defaults to space)
  #  [4]: initial value.
  #  [5]: whether to output debugfiles (outfile.debug and outfile.raw.debug)
  # Returns:
  #  0: OK
  #  1: od(d) error or CTRL-C hit

  LE_prompt="$1"
  LE_max=${2--1}
  LE_fill=${3-" "}
  LE_debug="$5"

  LE_backward() {
    LE_substract="$1"
    while [ -n "$LE_substract" ]; do
      printf '\b%s' "$2"
      LE_substract=${LE_substract%?}
    done
  }

  LE_fill() {
    LE_substract="$1"
    while [ -n "$LE_substract" ]; do
      printf '%s' "$LE_fill"
      LE_substract=${LE_substract%?}
    done
  }

  # Used but not right now
  # shellcheck disable=2016
  LE_restore='stty "$LE_tty"
              LC_COLLATE='${LC_COLLATE-"; unset LC_COLLATE"}

  # LE_tty is used in the restore above
  # shellcheck disable=2034
  LE_ret=1 LE_tty=$(stty -g) LC_COLLATE=C

  # text on the right of the cursor
  LE_left=$4
  # text on the left of the cursor
  LE_right=''

  # Tell the terminal to show us every char inputted
  stty -icanon -echo -isig min 3 time 1 -istrip
  printf '%b%s' "$LE_prompt" "$LE_left"

  # clear the output
  [ -n "$LE_debug" ] && printf "" > outfile.debug
  [ -n "$LE_debug" ] && printf "" > outfile.raw.debug

  # The value needs to be split for it to work (and it's either way just numbers)
  # shellcheck disable=2046
  while set -- $(dd bs=3 count=1 2> /dev/null | od -vAn -to1); do
    while [ "$#" -gt 0 ]; do
      [ -n "$LE_debug" ] && printf "%b" "\0$1" >> outfile.debug
      [ -n "$LE_debug" ] && printf "%s " "$1" >> outfile.raw.debug
      LE_current_key=$1
      shift

      # 033 is ^[ (`printf "\\$1\n" | cat -v`)
      if [ "$LE_current_key" = 033 ]; then
        case "$1$2$3" in
          # [ C | O C -> ^F forward
          133103*|117103*) shift 2; LE_current_key=006;;
          # [ D | O D -> ^B backward
          133104*|117104*) shift 2; LE_current_key=002;;
          # [ H | O H -> ^A beginning of line
          133110*|117110*) shift 2; LE_current_key=001;;
          # [ P | O P -> ^D del char
          133120*|117120*) shift 2; LE_current_key=004;;
          # [ F | O F -> ^E end of line
          133106*|117106*) shift 2; LE_current_key=005;;
          # [ 1 ~ -> ^A beginning of line
          133061176) shift 3; LE_current_key=001;;
          # [ 4 ~ -> ^E end of line
          133064176) shift 3; LE_current_key=005;;
          # [ 3 ~ -> ^D del char
          133063176) shift 3; LE_current_key=004;;
          # [ | O
          133*|117*)
            shift
            # Is $1 in ge 0 AND le 9 OR eq ';'?
            # These are control sequences for things like colors; Ignore them
            while [ "0$1" -ge 060 ] && [ "0$1" -le 071 ] ||
                  [ "0$1" -eq 073 ]; do
              shift
            done;;
        esac
      fi

      case "$LE_current_key" in
        001) # ^A beginning of line
          LE_backward "$LE_left"
          LE_right="$LE_left$LE_right"
          LE_left=;;
        002) # ^B backward
          if [ "$LE_left" = "" ]; then
            # bell
            printf '\a'
            LE_print_debug "$LE_debug" "backward with empty left"
          else
            printf '\b'
            LE_tmp="${LE_left%?}"
            LE_right="${LE_left#"$LE_tmp"}$LE_right"
            LE_left="$LE_tmp"
          fi;;
        003) # CTRL-C
          break 2;;
        004) # ^D del char
          if [ "$LE_right" = "" ]; then
            # bell (tell the user that the line is empty)
            printf '\a'
            LE_print_debug "$LE_debug" "delete with empty right"
          else
            LE_right="${LE_right#?}"
            printf '%s\b' "$LE_right$LE_fill"
            LE_backward "$LE_right"
          fi;;
        012|015) # NL or CR
          LE_ret=0
          break 2;;
        005) # ^E end of line
          printf '%s' "$LE_right"
          LE_left="$LE_left$LE_right"
          LE_right=;;
        006) # ^F forward
          if [ "$LE_right" = "" ]; then
            # bell (tell the user that the line is empty)
            printf '\a'
            LE_print_debug "$LE_debug" "forward with empty right"
          else
            LE_tmp="${LE_right#?}"
            LE_left="$LE_left${LE_right%"$LE_tmp"}"
            printf %s "${LE_right%"$LE_tmp"}"
            LE_right="$LE_tmp"
          fi;;
        010|177) # backspace or del
          if [ "$LE_left" = "" ]; then
            # bell
            printf '\a'
            LE_print_debug "$LE_debug" "backspace with empty left"
          else
            printf '\b%s\b' "$LE_right$LE_fill"
            LE_backward "$LE_right"
            LE_left="${LE_left%?}"
          fi;;
        013) # ^K kill to end of line
          LE_fill "$LE_right"
          LE_backward "$LE_right"
          LE_right=""
          ;;
        014) # ^L redraw
          printf '\r%b%s' "$LE_prompt" "$LE_left$LE_right"
          LE_backward "$LE_right";;
        025) # ^U kill line
          LE_backward "$LE_left"
          LE_fill "$LE_left$LE_right"
          LE_backward "$LE_left$LE_right"
          LE_left=""
          LE_right=""
          ;;
        027) # ^W kill word
          if [ "$LE_left" = "" ]; then
            # bell
            printf '\a'
          else
            LE_tmp="${LE_left% *}"
            LE_backward "${LE_left#"$LE_tmp"}"
            LE_fill "${LE_left#"$LE_tmp"}"
            LE_backward "${LE_left#"$LE_tmp"}"
            LE_left="$LE_tmp"
          fi;;
        # Print the received key, as it did not match a special key
        [02][4-7]?|[13]??) # 040 -> 177, 240 -> 377
                           # was assuming iso8859-x at the time
          if [ "$LE_max" -gt 0 ] && LE_tmp="$LE_left$LE_right" \
             && [ "${#LE_tmp}" -eq "$LE_max" ]; then
            # bell, when the user is trying to cross the line limit
            printf '\a'
            LE_print_debug "$LE_debug" "max output reached"
          else
            LE_left="$LE_left$(printf '%b' "\0$LE_current_key")"
            printf '%b%s' "\0$LE_current_key" "$LE_right"
            LE_backward "$LE_right"
          fi;;
        *)
          LE_print_debug "$LE_debug" "key not recognized: $(printf "%b" "\0$LE_current_key")"
          printf '\a';;
      esac
    done
  done
  eval "$LE_restore"
  REPLY=$LE_left$LE_right
  echo
  return "$LE_ret"
}