prompt_fmt='%%k%%f[ %s %s:%s %s]\n> '
prompt_fmtn='%%k%%f[ %%{\e[2;3m%s\e[0m%%} ]> '
prompt_user='%F{%(!.red.blue)}%n%f'
prompt_host='%m'
prompt_cwd='%F{green}%d%f'
prompt_git_fmt='\ue0a0 %s %s%%f '
prompt_state_file=/tmp/zsh_gitstatus_$$.tmp

printf -v PROMPT $prompt_fmt $prompt_user $prompt_host $prompt_cwd ''
printf -v PROMPT2 $prompt_fmtn '%_'
printf -v PROMPT3 $prompt_fmtn '?#'
printf -v PROMPT4 $prompt_fmtn '+%N:%i'
precmd.is_git_repo() {
    read -r git_dir < <(git rev-parse --git-dir 2>/dev/null) || return 1
    [[ ! -e $git_dir/nozsh ]]
}
precmd.git() {
    typeset raw_status
    raw_status=$(flock -n $prompt_state_file git --no-optional-locks status --porcelain -bu 2>/dev/null)
    (($?)) && return 0

    typeset branch_status git_status IFS=
    typeset staged_count=0 unstaged_count=0 untracked_count=0 unmerged_count=0

    while read line; do
        if [[ $line[1,2] == '##' ]]; then
            branch_status=${line[4,-1]%%...*}
            [[ $line =~ behind    ]] && branch_status+=?
            [[ $line =~ ahead     ]] && branch_status+=!
        fi
        [[ $line[1,2] == '??'     ]] && (( untracked_count++ ))
        [[ $line[1,2] =~ .[MD]    ]] && (( unstaged_count++  ))
        [[ $line[1,2] =~ [MDARC]. ]] && (( staged_count++    ))
        [[ $line[1,2] =~ [ADU]{2} ]] && (( unmerged_count++  ))
    done <<< $raw_status

    (( unstaged_count  )) && git_status+=%F{yellow}~$unstaged_count
    (( staged_count    )) && git_status+=%F{blue}+$staged_count
    (( untracked_count )) && git_status+=%F{red}-$untracked_count
    (( unmerged_count  )) && git_status+=%F{cyan}*$unmerged_count
    [[ -z $git_status  ]] && git_status=%F{green}ok

    printf $prompt_git_fmt $branch_status $git_status > $prompt_state_file
}
precmd.prompt() {
    printf -v PROMPT $prompt_fmt $prompt_user $prompt_host $prompt_cwd $1
}
precmd.git_update() {
    precmd.git
    kill -s USR1 $$
}
precmd() {
    if precmd.is_git_repo; then
        precmd.prompt $'\ue0a0 ... '
        precmd.git_update &!
    else
        precmd.prompt ''
    fi
}
TRAPUSR1() {
    precmd.prompt "$(<$prompt_state_file)"
    zle && zle reset-prompt
}
TRAPEXIT() {
    [[ -f $prompt_state_file ]] && rm $prompt_state_file
}