prompt.bash

declare -A _my_bash_prompt_sep_widths=(
    [prefix]=12
    [time]=$(( 23 + 3 ))
)
declare -A _my_bash_prompt_sep=(
    [prefix]="------------"
    [error_prefix]="!-"
    [with_time]="\D{%F %T %Z}---"
)
declare -A _my_bash_prompt_sigil=()

function _my_bash_prompt_terminal_width() { _my_terminal_width || print 60 ;}

function _my_bash_prompt_setup_widths()
{
    _my_bash_prompt_sep_widths[total]=$(_my_bash_prompt_terminal_width)
    _my_bash_prompt_sep_widths[stretch]=$((  _my_bash_prompt_sep_widths[total]
                                           - (  _my_bash_prompt_sep_widths[prefix]
                                              + _my_bash_prompt_sep_widths[time]) ))
    _my_bash_prompt_sep[stretch]=""
    local stretch=${_my_bash_prompt_sep_widths[stretch]}
    while (( stretch-- >= 1 )); do
        _my_bash_prompt_sep[stretch]+="${_my_bash_prompt_sep[char]}"
    done
}

function _my_bash_prompt_setup_chars()
{
    if _my_terminal_supports_unicode ; then
        local field char="${_my_bash_prompt_sep[char]}"
        for field in prefix error_prefix with_time ; do
            _my_bash_prompt_sep[$field]=${_my_bash_prompt_sep[$field]//"-"/"$char"}
        done
    fi
}

function _my_bash_prompt_setup()
{
    if _my_terminal_supports_colors; then
        local DO_COLORS=yes
    else
        local DO_COLORS=no
    fi

    # Preserve any preexisting PROMPT_COMMAND and execute it.  NixOS /etc/bashrc
    # sets it for showing info in VTE terminals' window title.  The preexisting
    # command must be executed after, so that _my_bash_prompt_command is
    # executed first, as needed to capture the PREV_EXIT_STATUS=$? of the user's
    # command.
    PROMPT_COMMAND="_my_bash_prompt_command $DO_COLORS ${PROMPT_COMMAND:+;} ${PROMPT_COMMAND:-}"

    if _my_terminal_supports_unicode ; then
        _my_bash_prompt_sep[char]="⏤"
        _my_bash_prompt_sigil[PS1]="▸"  # Alts: ▹‣❭❱⟩⟫〉
        _my_bash_prompt_sigil[root_PS1]="▪"  # Alts: •▫
        _my_bash_prompt_sigil[PS2]="⁝"
    else
        _my_bash_prompt_sep[char]="-"
        _my_bash_prompt_sigil[PS1]="\\$"
        _my_bash_prompt_sigil[root_PS1]="\\$"
        _my_bash_prompt_sigil[PS2]=":"
    fi
    _my_bash_prompt_setup_widths
    _my_bash_prompt_setup_chars
}

function _my_bash_prompt_command()
{
    local PREV_EXIT_STATUS=$?
    local - ; set +o xtrace +o verbose  # When user has these enabled, don't want for prompt.
    local DO_COLORS="$1"

    if [ "$(_my_bash_prompt_terminal_width)" -ne "${_my_bash_prompt_sep_widths[total]}" ]; then
        _my_bash_prompt_setup_widths
    fi

    # shellcheck disable=SC2034  # Unused variables left for readability.
    if [ "$DO_COLORS" = yes ]; then
        local RED="\e[01;31m"
        local GREEN="\e[01;32m"
        local YELLOW="\e[01;33m"
        local BLUE="\e[01;34m"
        local WHITE="\e[01;37m"
        local GREY="\e[00;37m"
        local MAGENTA="\e[01;35m"
        local NO_COLOR="\e[00m"
    else
        local RED=""
        local GREEN=""
        local YELLOW=""
        local BLUE=""
        local WHITE=""
        local GREY=""
        local MAGENTA=""
        local NO_COLOR=""
    fi

    if ((PREV_EXIT_STATUS == 0)); then
        local STATUS_PREFIX="\[${GREY}\]${_my_bash_prompt_sep[prefix]}"
    else
        local PAD=""
        local PAD_WIDTH=${#_my_bash_prompt_sep[prefix]}
        (( PAD_WIDTH -= (${#_my_bash_prompt_sep[error_prefix]} + ${#PREV_EXIT_STATUS}) ))
        while (( PAD_WIDTH-- >= 1 )); do
            PAD+="${_my_bash_prompt_sep[char]}"
        done
        local STATUS_PREFIX="\[${RED}\]${_my_bash_prompt_sep[error_prefix]}"
        local STATUS_PREFIX+="${PREV_EXIT_STATUS}${PAD}"
    fi

    if [ $EUID -eq 0 ]; then
        local USER_HOST_COLOR="\[${MAGENTA}\]"
        local CWD_COLOR="\[${BLUE}\]"
        local SIGIL_COLOR="\[${RED}\]"
        local SIGIL="${_my_bash_prompt_sigil[root_PS1]}"
    else
        local USER_HOST_COLOR="\[${GREEN}\]"
        local CWD_COLOR="\[${BLUE}\]"
        local SIGIL_COLOR="\[${YELLOW}\]"
        local SIGIL="${_my_bash_prompt_sigil[PS1]}"
    fi

    PS1="${STATUS_PREFIX}${_my_bash_prompt_sep[stretch]}${_my_bash_prompt_sep[with_time]}\n"
    PS1+="${USER_HOST_COLOR}\u@\h ${CWD_COLOR}\w\n"
    PS1+="${SIGIL_COLOR}${SIGIL}\[${NO_COLOR}\] "

    # Set the title to: user@host dir
    case "$TERM" in
        xterm*|rxvt*|screen|vt100)
            PS1="\[\e]0;\u@\h: \w\a\]$PS1"
            ;;
        *)
            ;;
    esac

    PS2="${SIGIL_COLOR}${_my_bash_prompt_sigil[PS2]}\[${NO_COLOR}\] "

    # (Must not have '\[' & '\]' in PS0.)
    PS0="${GREY}${_my_bash_prompt_sep[prefix]}${_my_bash_prompt_sep[stretch]}"
    PS0+="${_my_bash_prompt_sep[with_time]}${NO_COLOR}\n"
}

_my_bash_prompt_setup

# unset -f _my_bash_prompt_setup