slackmoji-string

#!/usr/bin/env bash
set -euo pipefail

usage() {
  cat <<'EOF'
Usage:
  alphabet-emoji [-w|-y|-m|-a] "text to spell"

Options:
  -w  white (default)
  -y  yellow
  -m  mixed: alternate color every emitted token (letters + supported specials)
  -a  alternate color every word (word1 white, word2 yellow, ...)

Supported:
  - A-Z letters (case-insensitive)
  - Special characters: @ # ! ?

Spacing:
  - Each space in input becomes TWO spaces in output.
  - No other spaces are inserted.
EOF
}

mode="w"
while getopts ":wymah" opt; do
  case "$opt" in
    w) mode="w" ;;
    y) mode="y" ;;
    m) mode="m" ;;
    a) mode="a" ;;
    h) usage; exit 0 ;;
    \?) echo "Unknown option: -$OPTARG" >&2; usage; exit 2 ;;
  esac
done
shift $((OPTIND - 1))

if [[ $# -lt 1 ]]; then
  echo "Error: missing text string." >&2
  usage
  exit 2
fi

input="$*"

emit_token() {
  local color="$1" token="$2"
  printf ':alphabet-%s-%s:' "$color" "$token"
}

# Echo token name + return 0 if supported, else return 1.
char_to_token() {
  local c="$1" lc="${c,,}"

  if [[ "$lc" =~ ^[a-z]$ ]]; then
    printf '%s' "$lc"
    return 0
  fi

  case "$c" in
    '@') printf 'at'; return 0 ;;
    '#') printf 'hash'; return 0 ;;
    '!') printf 'exclamation'; return 0 ;;
    '?') printf 'question'; return 0 ;;
  esac

  return 1
}

# Alternation state
mix_toggle=0  # for -m: 0 => white, 1 => yellow
word_toggle=0 # for -a: 0 => white, 1 => yellow (first word white)
in_word=0     # for -a: 0 => not in word, 1 => in word

for ((i=0; i<${#input}; i++)); do
  c="${input:i:1}"

  if [[ "$c" == " " ]]; then
    # Interpret a single space as a double space
    printf '  '
    in_word=0
    continue
  fi

  if token="$(char_to_token "$c")"; then
    # Decide color (and update alternation state) WITHOUT subshells
    case "$mode" in
      w) color="white" ;;
      y) color="yellow" ;;
      m)
        if (( mix_toggle == 0 )); then color="white"; else color="yellow"; fi
        mix_toggle=$((1 - mix_toggle))
        ;;
      a)
        if (( in_word == 0 )); then
          # new word: flip color except for the very first word
          if (( i != 0 )); then
            word_toggle=$((1 - word_toggle))
          fi
          in_word=1
        fi
        if (( word_toggle == 0 )); then color="white"; else color="yellow"; fi
        ;;
    esac

    emit_token "$color" "$token"
  else
    # Unhandled characters pass through unchanged
    printf '%s' "$c"
    # Keep punctuation inside the word for -a (so hello-world counts as one word)
    if [[ "$mode" == "a" ]]; then
      in_word=1
    fi
  fi
done

printf '\n'