.bash_prompt_command

# Define colors
RESET='\[\033[00m\]'
FGBK='\[\033[0;30m\]' # foreground black
FGRD='\[\033[0;31m\]' # foreground red
FGGN='\[\033[0;32m\]' # foreground green
FGYL='\[\033[0;33m\]' # foreground yellow
FGBL='\[\033[0;34m\]' # foreground blue
FGMG='\[\033[0;35m\]' # foreground magenta
FGCY='\[\033[0;36m\]' # foreground cyan
FGWT='\[\033[0;37m\]' # foreground white
FGBKBT='\[\033[1;30m\]' # foreground black bright
FGRDBT='\[\033[1;31m\]' # foreground red bright
FGGNBT='\[\033[1;32m\]' # foreground green bright
FGYLBT='\[\033[1;33m\]' # foreground yellow bright
FGBLBT='\[\033[1;34m\]' # foreground blue bright
FGMGBT='\[\033[1;35m\]' # foreground magenta bright
FGCYBT='\[\033[1;36m\]' # foreground cyan bright
FGWTBT='\[\033[1;37m\]' # foreground white bright
BGBK='\[\033[40m\]' # background black
BGRD='\[\033[41m\]' # background red
BGGN='\[\033[42m\]' # background green
BGYL='\[\033[43m\]' # background yellow
BGBL='\[\033[44m\]' # background blue
BGMG='\[\033[45m\]' # background magenta
BGCY='\[\033[46m\]' # background cyan
BGWT='\[\033[47m\]' # background white

# Give the hostname an emphasized color
HOSTCOLOR="$FGRD"

# Date Format
DATEFORMAT='%a %b %d %T'


# set the prompt symbol character differently for root
function set_prompt_character () {
  if [[ ${EUID} == 0 ]]; then
    PROMPT_CHARACTER='#'
  else
    PROMPT_CHARACTER='$'
  fi
}


# Return the prompt symbol to use, colorized based on the return value of the
# previous command.
function set_prompt_symbol () {
  if [[ ${1} -eq 0 ]]; then
    PROMPT_SYMBOL="${PROMPT_CHARACTER}"
  else
    PROMPT_SYMBOL="${FGRD}${PROMPT_CHARACTER}${RESET}"
  fi
}


# Change the color of the username if root
function prompt_set_user_color () {
  if [[ ${EUID} == 0 ]]; then
    USER_COLOR="${FGWT}${BGRD}"
  else
    USER_COLOR="${FGBL}"
  fi
}


# Detect whether the current directory is a git repository.
function is_git_repository {
  git branch > /dev/null 2>&1
}


# Determine the branch/state information for this git repository.
function set_git_branch {
  # Capture the output of the "git status" command.
  git_status="$(git status 2> /dev/null)"

  # Set color based on clean/staged/dirty.
  if [[ ${git_status} =~ "working tree clean" ]]; then    # clean
    state=$FGGN
  elif [[ ${git_status} =~ "Changes to be committed" ]]; then  # staged
    state=$FGYL
  elif [[ ${git_status} =~ "Changes not staged" ]]; then       # unstaged
    state=$FGYL
  elif [[ ${git_status} =~ "Untracked files" ]]; then          # untracked
    state=$FGYL
  else    # unknown
    state=$FGRD
  fi

  # Set arrow icon based on status against remote.
  remote=""
  remote_pattern="Your branch is ([[:graph:]]+)"
  diverge_pattern="Your branch and (.*) have diverged"
  if [[ ${git_status} =~ ${remote_pattern} ]]; then
    if [[ ${BASH_REMATCH[1]} == "ahead" ]]; then
      remote="↑"
    elif [[ ${BASH_REMATCH[1]} == "behind" ]]; then
      remote="↓"
    fi
  elif [[ ${git_status} =~ ${diverge_pattern} ]]; then
    remote="↕"
  fi

  # Get the name of the branch.
  branch_pattern="On branch ([^${IFS}]*)"
  detached_pattern="HEAD detached at ([^${IFS}]*)"
  if [[ ${git_status} =~ ${branch_pattern} ]]; then
    branch=${BASH_REMATCH[1]}
  elif [[ ${git_status} =~ ${detached_pattern} ]]; then
    branch=${BASH_REMATCH[1]}
  else
    branch="<???>"
  fi

  # Set the final branch string.
  BRANCH_COLOR="${state}[${branch}]${remote}$RESET"
  BRANCH_PLAIN="[${branch}]${remote}"
}


# Set the full bash prompt.
function set_bash_prompt () {
  # Set the BRANCH variable.
  if is_git_repository ; then
    set_git_branch
  else
    BRANCH_COLOR=''
    BRANCH_PLAIN=''
  fi

  # Set USER_COLOR
  prompt_set_user_color

  ps1_username=$(whoami)
  ps1_username="${ps1_username:0:10}"
  ps1_hostname=$(hostname -s)
  ps1_hostname="${ps1_hostname:0:20}"
  ps1_pwd=$(pwd | sed "s|^$HOME|~|")
  ps1_datetime=$(date "+${DATEFORMAT}")

  user_at_host="${ps1_username}@${ps1_hostname}"
  lefthalf="${user_at_host} ${ps1_pwd} ${BRANCH_PLAIN}"
  righthalf="${ps1_datetime}"

  # Fill spaces between the left and right halves
  termwidth=${COLUMNS:-$(tput cols 2>&-||echo 80)}
  let fillsize=${termwidth}-${#lefthalf}-${#righthalf}

  if [[ $fillsize -gt 1 ]]; then
    fill=$(printf ' %.0s' {1..300}) # 300 spaces
    fill=${fill:0:$fillsize}
  else
    ps1_pwd="${ps1_pwd:0:20}..${ps1_pwd:(23+${#lefthalf}+${#righthalf}-${termwidth})}"
    fill=' '
  fi

  # Set the bash prompt variable.
  PS1="\n${USER_COLOR}${ps1_username}${FGCY}@${HOSTCOLOR}${ps1_hostname}${RESET} ${FGWT}${ps1_pwd}${RESET} ${BRANCH_COLOR}${fill}${FGBL}${ps1_datetime}${RESET}\n${PROMPT_SYMBOL} "
}

# Set PROMPT_CHARACTER
set_prompt_character

# Set PROMPT_SYMBOL -- caller must pass ${?} to properly set result code
set_prompt_symbol "${1}"

# Set PS1
set_bash_prompt

# Output PS1
echo "${PS1}"