Zsh prompt wave

prompt-wave.zsh

function metronome() {
  local -rF tick_sec=0.3
  while true; do
    zselect -t $((int(ceil(tick_sec * 100))))
    print 2>/dev/null || break
  done
}

function update-prompt() {
  local -ri period=7
  typeset -gi phase
  (( phase = (phase + 1) % period ))
  local prompt=${(L)${(%)PS1}}
  local -i i
  for ((i = phase + 1; i <= $#prompt; i += period)); do
    prompt[i]=${(U)prompt[i]}
  done
  PS1=${prompt//\%/%%}
  zle .reset-prompt
  if (( ARGC == 2 )); then
    zle -F $1
  else
    local REPLY
    while read -t0 -u$1; do; done
  fi
}

() {
  local fd
  zmodload zsh/zselect zsh/mathfunc zsh/system &&
    exec {fd} < <(metronome)                   &&
    zle -F $fd update-prompt
}

PS1='%n@%m %~ %# '