#!/bin/bash --
#  _               _                                       _
# | |__   __ _ ___| |__    _ __  _ __ ___  _ __ ___  _ __ | |_
# | '_ \ / _` / __| '_ \  | '_ \| '__/ _ \| '_ ` _ \| '_ \| __|
# | |_) | (_| \__ \ | | | | |_) | | | (_) | | | | | | |_) | |_
# |_.__/ \__,_|___/_| |_| | .__/|_|  \___/|_| |_| |_| .__/ \__|
#                         |_|                       |_|

term_red=$(    tput setaf 1) \
term_green=$(  tput setaf 2) \
term_yellow=$( tput setaf 3) \
term_blue=$(   tput setaf 4) \
term_magenta=$(tput setaf 5) \
term_cyan=$(   tput setaf 6) \
term_reset=$(  tput sgr0   ) \
term_bold=$(   tput bold   ) \
term_reverse=$(tput rev    ) \
prompt_time_color= prompt_time_text= \
prompt_path= \
|| : # in case the last tput(1) command fails and errexit is on

function updateprompt {
    local d MAPFILE old_rematch path_parts 'IFS=/'

    if [[ ${prompt_timer+is_set} ]]; then
        prompt_time_text=$((
            (10#0${EPOCHREALTIME//[!0123456789]} - prompt_timer) / 1000
        ))
    else
        prompt_time_text=0
    fi

    if   (( prompt_time_text <=  20 )); then
        prompt_time_color=$term_green
    elif (( prompt_time_text <= 100 )); then
        prompt_time_color=$term_yellow
    elif (( prompt_time_text <= 250 )); then
        prompt_time_color=$term_cyan
    elif (( prompt_time_text <= 500 )); then
        prompt_time_color=$term_blue
    elif (( prompt_time_text <= 999 )); then
        prompt_time_color=$term_magenta
    else
        prompt_time_color=$term_red \
        prompt_time_text=$(( (prompt_time_text / 1000) % 1000 ))
    fi

    printf -v prompt_time_text %03d "$prompt_time_text"

    # using \w@P to make the prompt respect PROMPT_DIRTRIM
    prompt_path='\w' prompt_path=${prompt_path@P}
    case $prompt_path in
        \~) ;;
        /)  prompt_path=/   ;;
        *)  mapfile -td/ <<< "$prompt_path"
            MAPFILE[-1]=${MAPFILE[-1]%$'\n'} \
            path_parts=() \
            old_rematch=${BASH_REMATCH[*]@A}
            if [[ $old_rematch ]]; then
                if [[ ${BASH_REMATCH@a} ]]
                    then old_rematch=${old_rematch/-/-g}
                    else old_rematch='declare -g '$old_rematch
                fi
            elif declare -p BASH_REMATCH > /dev/null 2>&1
                then old_rematch='declare -g BASH_REMATCH'
            fi
            for d in "${MAPFILE[@]}"; do
                if [[
                    $d =~ [[:alnum:]] || $d =~ [[:print:]] || -z $d
                ]]; then
                    path_parts+=( "${BASH_REMATCH[0]}" )
                else
                    d=${d:0:1} prompt_path+=( "${d@Q}" )
                fi
            done
            unset -v BASH_REMATCH
            eval " $old_rematch"
            prompt_path=${path_parts[*]}
    esac
}

# using [^...] instead of [!...] because ! is expanded in POSIX mode.
PS0='${PS0:prompt_timer = 10#0${EPOCHREALTIME//[^0123456789]}:0}'

PROMPT_COMMAND+=( updateprompt 'unset -v prompt_timer' )

PS1=\
'\[$prompt_time_color\]$prompt_time_text\[$term_reset\] '\
'($BASHPID) $prompt_path \[$term_red\]\$\[$term_reset\] '