#!/usr/bin/env bash
set -eu

minimum=4
words=$(diceware --no-caps --num 2 --delimiter " ")
first=${words%??? *}
second=${words#* ???}

[ ${#first} -lt $minimum ] && "$0" && exit
[ ${#second} -lt $minimum ] && "$0" && exit

vowels="a e i o u"
sounds="h r w y"
consonants="b c d f g j k l m n p q s t v x z"
suffix=${first: -1:1}
prefix=${second: 0:1}
digraph="$suffix$prefix"
compressed="${first: 0:-1}${second: 1}"

printf 'words:      %s\n'   "$words"
printf 'digraph:    %s\n'   "$digraph"
printf 'merge:      %s%s\n' "$first" "$second"
printf 'compressed: %s\n\n' "$compressed"

Grammar() {
  for left in $consonants; do
    [ "$suffix" = "$left" ] &&
      {
        for right in $consonants; do
          [ "$prefix" = "$right" ] &&
            printf '%s\n' "$compressed" &&
            exit
        done
      }
  done || printf '%s%s\n' "$first" "$second"
}

Grammar