.bash_prompt

#!/usr/bin/env bash

###############################################################################
# See top of .bashrc for usage instructions and overview. 
# 
# This uses the ANSI colors set by your terminal.
# See this post for an overview: https://chrisyeh96.github.io/2020/03/28/terminal-colors.html
# I recommend using the Nord.itermcolors theme with iTerm in my dotfiles repo. 
# Set it in iTerm's Preferences -> Profiles -> Colors -> Color Presets.
# 
# The git prompts are mostly copied from: https://github.com/alrra/dotfiles
# Some bits and pieces from: https://github.com/mathiasbynens/dotfiles 

############################################################################### 

enable_color_support() {
    if [[ $COLORTERM == gnome-* && $TERM == xterm ]] \
        && infocmp gnome-256color &> /dev/null; then
        export TERM="gnome-256color"
    fi
}

# Command line in git repos show helpful info
get_git_repository_details() {
    local branchName=""
    local tmp=""

    # Check if the current directory is in a Git repository.
    git rev-parse &>/dev/null || return

    # Check if in `.git/` directory (some of the following
    # checks don't make sense/won't work in the `.git` directory).
    [ "$(git rev-parse --is-inside-git-dir)" == "false" ] || return

    # Check for what branch we’re on.
    # Get the short symbolic ref. If HEAD isn’t a symbolic ref, get a
    # tracking remote branch or tag. Otherwise, get the
    # short SHA for the latest commit, or give up.
    branchName="$(git symbolic-ref --quiet --short HEAD 2> /dev/null || \
	    git describe --all --exact-match HEAD 2> /dev/null || \
	    git rev-parse --short HEAD 2> /dev/null || \
	    echo '(unknown)')"

    # Check for uncommitted changes in the index.
    if ! git diff --quiet --ignore-submodules --cached; then
        tmp+="+"
    fi

    # Check for unstaged changes.
    if ! git diff-files --quiet --ignore-submodules --; then
	tmp+="!"
    fi

    # Check for untracked files.
    if [ -n "$(git ls-files --others --exclude-standard)" ]; then
	tmp+="?"
    fi

    # Check for stashed files.
    if git rev-parse --verify refs/stash &>/dev/null; then
	tmp+="$"
    fi

    # Prepend a space if tmp has non-zero length
    [ -n "$tmp" ] && tmp=" [$tmp]"

    echo -e "${1}${branchName}${2}${tmp}"
}

set_prompts() {
    # ASCI escape codes for terminal graphics: the escape literal (in Bash, \e)
    # followed by some numbers, and punctuated with "m" forms a Select Graphic
    # Rendition (SGR) control sequence.
    local reset="\e[0m"
    local bold="\e[1m"

    local black="\e[30m" # Unused
    local red="\e[31m"
    local green="\e[32m"
    local yellow="\e[33m"
    local blue="\e[34m"
    local magenta="\e[35m"
    local cyan="\e[36m" # Unused 
    local white="\e[37m"

    # Highlight the user name when logged in as root.
    if [[ "${USER}" == "root" ]]; then
        local userStyle=${bold}${red}
    else
        local userStyle=${bold}${yellow}
    fi

    # Highlight the hostname when connected via SSH.
    if [[ "${SSH_TTY}" ]]; then
        local hostStyle=${bold}${red}
    else
        local hostStyle=${yellow}
    fi

    # Prompt Statement variables. See: http://ss64.com/bash/syntax-prompt.html
    # PS1 is the default interactive prompt and the one we see the most often. 
    # PS2, PS3, and PS4 also exist, but I haven't customized these; I just 
    # copied from: https://github.com/alrra/dotfiles

    # | PS1 - Default interactive prompt
    PS1="\[\033]0;\W\007\]" # Terminal title and prompt 
    PS1+="$reset\n"    # Newline
    PS1+="$userStyle\u"     # Username
    PS1+="$white in "
    PS1+="$green\w"         # Working directory full path 
    PS1+="\$(get_git_repository_details \"$white on $magenta\" \"$blue\")"
    PS1+="\n"
    PS1+="\[$reset\]\[$white\]\$ \[$reset\]"
    export PS1

    # | PS2 - Continuation interactive prompt
    PS2="⚡ "
    export PS2

    # | PS4 - Debug prompt
    # e.g:
    #
    # The GNU `date` command has the `%N` interpreted sequence while
    # other implementations don't (on macOS `gdate` can be used instead
    # of the native `date` if the `coreutils` package has been installed).
    #
    # local dateCmd=""
    #
    # if [ "$(date +%N)" != "N" ] || \
    #    [ ! -x "$(command -v "gdate")" ]; then
    #    dateCmd="date +%s.%N"
    # else
    #    dateCmd="gdate +%s.%N"
    # fi
    #
    # PS4="+$( tput cr && tput cuf 6 &&
    #          printf "$yellow %s $green%6s $reset" "$($dateCmd)" "[$LINENO]" )"
    #
    # PS4 output:
    #
    #   ++    1357074705.875970000  [123] '[' 1 == 0 ']'
    #   └──┬─┘└────┬───┘ └───┬───┘ └──┬─┘ └──────┬─────┘
    #      │       │         │        │          │
    #      │       │         │        │          └─ command
    #      │       │         │        └─ line number
    #      │       │         └─ nanoseconds
    #      │       └─ seconds since 1970-01-01 00:00:00 UTC
    #      └─ depth-level of the subshell
    PS4="+$( tput cr 2> /dev/null;
             tput cuf 6 2> /dev/null;
             printf "%s" "$reset" )"
    export PS4
}

main() {
    enable_color_support
    set_prompts
}

main

###############################################################################
# Cleanup.

unset -f enable_color_support
unset -f main
unset -f set_prompts