bash_prompt.sh

#! /usr/bin/env bash

# Skip all of this if we don't have a TTY
tty -s || return 0

# Colors + \[...\] wrapping to ensure there's no odd wrapping on command line
C_OFF="\[$(tput sgr0)\]"
C_BOLD="\[$(tput bold)\]"
C_BLACK="\[$(tput setaf 0)\]"
C_RED="\[$(tput setaf 1)\]"
C_GREEN="\[$(tput setaf 2)\]"
C_YELLOW="\[$(tput setaf 3)\]"
C_BLUE="\[$(tput setaf 4)\]"
C_MAGENTA="\[$(tput setaf 5)\]"
C_CYAN="\[$(tput setaf 6)\]"
C_WHITE="\[$(tput setaf 7)\]"

C_MAIN="$C_CYAN"
C_ROOT="$C_WHITE"
C_FAIL="$C_RED"

p_prefix="["
p_suffix="]"
# p_prefix="┇"
# p_suffix="┆"
# p_prefix="「"
# p_suffix="」"

# Various variables for easier referencing
TIME24H="\t"
TIME12H="\T"
TIME12A="\@"
PATHSHORT="\w"
PATHFULL="\W"
HOSTNAMESHORT="\h"
HOSTNAMEFULL="\H"
NEWLINE="\n"
JOBS="\j"

# Command stack, use this to store last executed command
cmd_stack=()
trap 'cmd_stack=("${cmd_stack[@]}" "$BASH_COMMAND")' DEBUG

# Git information
__git_prompt() {
  local git_prompt
  local status
  local branch
  local ref
  local dirty
  local tracking

  status=$(git status 2> /dev/null)

  # Check dirty status
  [[ -z $(git status --porcelain 2> /dev/null) ]] \
    && dirty="${c_green}✓${c_off}" \
    || dirty="${c_red}✗${c_off}"

  # Get our branch or ref, depending if we're in detached HEAD or not.
  ref=$(git symbolic-ref HEAD 2>/dev/null) \
    && { ref=${ref#refs/heads/} ; branch="$ref" ; } \
    || ref=$(git reflog HEAD | awk 'NR==1 && /checkout:/ { print $NF }')

  # Check if we're ahead or behind upstream
  if [[ -n "$branch" ]] ; then
    local upstream_ref
    local ahead
    local behind

    upstream_ref=$(git for-each-ref --format='%(refname:short) %(upstream:short)' refs/heads | awk -v branch="$branch" '"/^$branch/" { print $NF }')

    if [[ -n "$upstream_ref" ]] ; then
      ahead=$(git rev-list --count --left-right "$upstream_ref"...HEAD | cut -f1)
      behind=$(git rev-list --count --left-right "$upstream_ref"...HEAD | cut -f2)

      [[ $ahead -gt 0 ]] && tracking+="${C_CYAN}<${ahead}${C_OFF}:"
      [[ $behind -gt 0 ]] && tracking+="${C_MAGENTA}<${behind}${C_OFF}:"
    fi
  fi

  # Put together our prompt string
  git_prompt+="["
  git_prompt+="${c_green}${ref}${c_off}:"
  git_prompt+="${tracking}"
  git_prompt+="${dirty}"
  git_prompt+="]"

  echo "$git_prompt"
}

prompt.git.dirty() {
  local status
  status=$(git status --porcelain 2> /dev/null) || return 1

  [[ -z $status ]] \
    && echo "${C_GREEN}✓${C_OFF}" \
    || echo "${C_RED}✗${C_OFF}"
}


prompt.git.updown() {
  local branch
  local tracking
  local upstream_ref
  local updown
  local git_ahead
  local git_behind

  branch="$(prompt.git.branch)"
  upstream_ref=$(git for-each-ref --format='%(refname:short)|%(upstream:short)' refs/heads \
    | grep "^$branch|" \
    | cut -d'|' -f2)

  if [[ "$upstream_ref" ]]; then
    updown=( $(git rev-list --count --left-right "$upstream_ref"...HEAD) )

    [[ ${updown[0]} -gt 0 ]] && tracking+="${C_CYAN}-${updown[0]}${C_OFF}:"    # Behind
    [[ ${updown[1]} -gt 0 ]] && tracking+="${C_MAGENTA}+${updown[1]}${C_OFF}:" # Ahead

    # git_ahead=$(git rev-list --count --left-right "$upstream_ref"...HEAD | cut -f1)
    # git_behind=$(git rev-list --count --left-right "$upstream_ref"...HEAD | cut -f2)
  fi

  echo "$tracking"
}

prompt.git.branch() {
  local branch
  branch="$(git symbolic-ref HEAD 2> /dev/null)"
  branch="${branch#refs/heads/}"

  # If we're in detached HEAD the above doesn't work, so use reflog instead
  [[ -z $branch ]] && branch="$(git reflog HEAD | grep 'checkout:' | head -n1 | grep -oE '[^ ]+$')"

  echo "$branch"
}

# Main prompt function
prompt() {
  local cmd_exit="$?" # Exit code of previous command
  local tformat="%T"
  # If last command was this function, reset cmd_exit
  [[ "${cmd_stack[@]}" == "prompt" ]] && cmd_exit=0

  # Reset stack
  cmd_stack=()

  # # Update the terminal title
  if [[ "$TERM" =~ xterm* ]] ; then
    echo -en "\033]0;${USER}@$(hostname -s):${PWD}\007"
  fi

  # Begin building up our prompt

  # Change the color if we're root :^D
  [[ $UID -eq 0 ]] && C_MAIN="$C_ROOT"

  # Show previous command exit code if non-zero
  PS1="${C_MAIN}${p_prefix}"
  if [[ $cmd_exit -eq 0 ]] ; then
    PS1+="$(date +$tformat)"
  else
    # Add some padding to look nice
    case "${#cmd_exit}" in
      1) PS1+="${C_FAIL}EXIT ${cmd_exit}  " ;;
      2) PS1+="${C_FAIL}EXIT ${cmd_exit} "  ;;
      3) PS1+="${C_FAIL}EXIT ${cmd_exit}"   ;;
    esac
    # PS1+="${C_RED}EXIT ${cmd_exit}"
  fi

  PS1+="${C_YELLOW}:\w${C_MAIN}${p_suffix}${C_OFF}"

  # Add Git information
  if [[ -d .git ]] || [[ $(git status 2> /dev/null) ]]; then
    PS1+="\n${C_GREEN}${p_prefix}"
    PS1+="$(prompt.git.branch):$(prompt.git.updown)$(prompt.git.dirty)"
    PS1+="${C_GREEN}${p_suffix}${C_OFF}"
  fi

  [[ -n $PL ]] \
    && PS1+="$(tput setab 4)$(tput setaf 7)$(tput bold) $PL $(tput sgr0)"

  # $ or # at the end of the prompt
  PS1+='\$ '

  # Export variables to the environment
  export PS1

  # Append last command to our history file
  history -a
}

export PROMPT_DIRTRIM=2
export PROMPT_COMMAND="prompt"