autoload -U colors && colors

setopt promptsubst
setopt promptpercent

local time='%F{cyan}%B[%D{%H:%M}]%b%f'
local user='%F{yellow}%B%n%b%f'
local host='%F{blue}%B%M%b%f'
local dir='%F{yellow}%~%f'
local git='$(git_prompt_string)'
local nix='$(nix_shell_prompt_string)'
local error='%F{red}%B%?%b%f'

PROMPT="$time $user@$host $dir $git%# "
RPROMPT="%(?.$nix.$error)"

# Show Git branch/tag, or name-rev if on detached head
parse_git_branch() {
  (git symbolic-ref -q HEAD || git rev-parse --short HEAD) 2> /dev/null
}

# Show different symbols as appropriate for various Git repository states
parse_git_state() {

  # Compose this value via multiple conditional appends.
  local GIT_STATE=""

  local GIT_CHANGED="$(git diff --name-only --diff-filter=ACDMRT | wc -l | tr -d ' ')"
  local GIT_STAGED="$(git diff --staged --name-status --diff-filter=ACDMRT | wc -l | tr -d ' ')"
  local GIT_CONFLICTS="$(git diff --staged --name-status --diff-filter=U | wc -l | tr -d ' ')"
  local GIT_UNTRACKED="$(git ls-files --other --exclude-standard | wc -l | tr -d ' ')"

  if [ $GIT_STAGED -ne 0 ]; then
    GIT_STATE="$GIT_STATE%F{green}+$GIT_STAGED%f"
  fi

  if [ $GIT_CONFLICTS -ne 0 ]; then
    GIT_STATE="$GIT_STATE%F{red}x$GIT_CONFLICTS%f"
  fi

  if [ $GIT_CHANGED -ne 0 ]; then
    GIT_STATE="$GIT_STATE%F{red}*$GIT_CHANGED%f"
  fi

  if [ $GIT_UNTRACKED -ne 0 ]; then
    GIT_STATE="$GIT_STATE.."
  fi

  if [ $GIT_CHANGED -eq 0 -a $GIT_STAGED -eq 0 -a $GIT_CONFLICTS -eq 0 -a $GIT_UNTRACKED -eq 0 ]; then
    GIT_STATE="$GIT_STATE%B%F{green}ok%f%b"
  fi

  if [[ -n $GIT_STATE ]]; then
    echo $GIT_STATE
  fi

}

# If inside a Git repository, print its branch and state
git_prompt_string() {
  local git_where="$(parse_git_branch)"
  if [ -n "$git_where" ]; then
    git_where="%B%F{magenta}${git_where#(refs/heads/|tags/)}%f%b"

    local NUM_AHEAD="$(git log --oneline @{u}.. 2> /dev/null | wc -l | tr -d ' ')"
    if [ "$NUM_AHEAD" -gt 0 ]; then
      git_where="$git_where^$NUM_AHEAD"
    fi

    local NUM_BEHIND="$(git log --oneline ..@{u} 2> /dev/null | wc -l | tr -d ' ')"
    if [ "$NUM_BEHIND" -gt 0 ]; then
      git_where=$git_where"v$NUM_BEHIND"
    fi

    echo "($git_where|$(parse_git_state))"
  fi
}

nix_shell_prompt_string() {
  if [ -n "$IN_NIX_SHELL" ]; then
    echo "[%F{yellow}nix%f]"
  fi
}