bash-powerline.sh

#!/usr/bin/env bash

__powerline() {

    readonly DISABLE_GIT_STATUS=${DISABLE_GIT_STATUS:-''}

    # Max length of full path
    readonly MAX_PATH_LENGTH=${MAX_PATH_LENGTH:-30}

    # Unicode symbols
    readonly PS_SYMBOL_DARWIN=''
    readonly PS_SYMBOL_LINUX='$'
    readonly PS_SYMBOL_OTHER='%'
    readonly GIT_BRANCH_SYMBOL='⑂ '
    readonly GIT_BRANCH_CHANGED_SYMBOL='+'
    readonly GIT_NEED_PUSH_SYMBOL='⇡'
    readonly GIT_NEED_PULL_SYMBOL='⇣'

    # Solarized colorscheme
    readonly FG_BASE03="\[$(tput setaf 8)\]"
    readonly FG_BASE02="\[$(tput setaf 0)\]"
    readonly FG_BASE01="\[$(tput setaf 10)\]"
    readonly FG_BASE00="\[$(tput setaf 11)\]"
    readonly FG_BASE0="\[$(tput setaf 12)\]"
    readonly FG_BASE1="\[$(tput setaf 14)\]"
    readonly FG_BASE2="\[$(tput setaf 7)\]"
    readonly FG_BASE3="\[$(tput setaf 15)\]"

    readonly BG_BASE03="\[$(tput setab 8)\]"
    readonly BG_BASE02="\[$(tput setab 0)\]"
    readonly BG_BASE01="\[$(tput setab 10)\]"
    readonly BG_BASE00="\[$(tput setab 11)\]"
    readonly BG_BASE0="\[$(tput setab 12)\]"
    readonly BG_BASE1="\[$(tput setab 14)\]"
    readonly BG_BASE2="\[$(tput setab 7)\]"
    readonly BG_BASE3="\[$(tput setab 15)\]"

    readonly FG_YELLOW="\[$(tput setaf 3)\]"
    readonly FG_ORANGE="\[$(tput setaf 9)\]"
    readonly FG_RED="\[$(tput setaf 1)\]"
    readonly FG_MAGENTA="\[$(tput setaf 5)\]"
    readonly FG_VIOLET="\[$(tput setaf 13)\]"
    readonly FG_BLUE="\[$(tput setaf 4)\]"
    readonly FG_CYAN="\[$(tput setaf 6)\]"
    readonly FG_GREEN="\[$(tput setaf 2)\]"

    readonly BG_YELLOW="\[$(tput setab 3)\]"
    readonly BG_ORANGE="\[$(tput setab 9)\]"
    readonly BG_RED="\[$(tput setab 1)\]"
    readonly BG_MAGENTA="\[$(tput setab 5)\]"
    readonly BG_VIOLET="\[$(tput setab 13)\]"
    readonly BG_BLUE="\[$(tput setab 4)\]"
    readonly BG_CYAN="\[$(tput setab 6)\]"
    readonly BG_GREEN="\[$(tput setab 2)\]"

    readonly DIM="\[$(tput dim)\]"
    readonly REVERSE="\[$(tput rev)\]"
    readonly RESET="\[$(tput sgr0)\]"
    readonly BOLD="\[$(tput bold)\]"

    # what OS?
    case "$(uname)" in
        Darwin)
            readonly PS_SYMBOL=$PS_SYMBOL_DARWIN
            ;;
        Linux)
            readonly PS_SYMBOL=$PS_SYMBOL_LINUX
            ;;
        *)
            readonly PS_SYMBOL=$PS_SYMBOL_OTHER
    esac

    __git_info() {
        [ -x "$(which git)" ] || return    # git not found

        local git_eng="env LANG=C git"   # force git output in English to make our work easier
        # get current branch name or short SHA1 hash for detached head
        local branch="$($git_eng symbolic-ref -q --short HEAD 2>/dev/null || $git_eng rev-list --abbrev-commit --max-count=1 HEAD 2>/dev/null)"
        [ -n "$branch" ] || return  # git branch not found

        local marks

        if [ -z "$DISABLE_GIT_STATUS" ]; then
            # branch is modified?
            [ -n "$($git_eng status --porcelain 2>/dev/null)" ] && marks+=" $GIT_BRANCH_CHANGED_SYMBOL"

            # how many commits local branch is ahead/behind of remote?
            local stat="$($git_eng status --porcelain --branch 2>/dev/null | grep '^##' | grep -o '\[.\+\]$')"
            local aheadN="$(echo $stat | grep -o 'ahead [[:digit:]]\+' | grep -o '[[:digit:]]\+')"
            local behindN="$(echo $stat | grep -o 'behind [[:digit:]]\+' | grep -o '[[:digit:]]\+')"
            [ -n "$aheadN" ] && marks+=" $GIT_NEED_PUSH_SYMBOL$aheadN"
            [ -n "$behindN" ] && marks+=" $GIT_NEED_PULL_SYMBOL$behindN"
        fi

        # print the git branch segment without a trailing newline
        printf " $GIT_BRANCH_SYMBOL$branch$marks "
    }

    __virtualenv() {
        # Copied from Python virtualenv's activate.sh script.
        # https://github.com/pypa/virtualenv/blob/a9b4e673559a5beb24bac1a8fb81446dd84ec6ed/virtualenv_embedded/activate.sh#L62
        # License: MIT
        if [ "x${VIRTUAL_ENV-}" != "x" ]; then
            if [ "`basename \"$VIRTUAL_ENV\"`" == "__" ]; then
                # special case for Aspen magic directories
                # see http://www.zetadev.com/software/aspen/
                printf "[`basename \`dirname \"$VIRTUAL_ENV\"\``]"
            else
                printf "(`basename \"$VIRTUAL_ENV\"`)"
            fi
        fi
    }

    __pwd() {
        # Use ~ to represent $HOME prefix
        local pwd=$(pwd | sed -e "s|^$HOME|~|")
        if [[ ( $pwd = ~\/*\/* || $pwd = \/*\/*/* ) && ${#pwd} -gt $MAX_PATH_LENGTH ]]; then
            local IFS='/'
            read -ra split <<< "$pwd"
            if [[ $pwd = ~* ]]; then
                pwd="~/.../${split[-1]}"
            else
                pwd="/${split[1]}/.../${split[-1]}"
            fi
        fi
        printf "$pwd"
    }

    ps1() {
        # Check the exit code of the previous command and display different
        # colors in the prompt accordingly.
        if [ $? -eq 0 ]; then
            local BG_EXIT="$BG_GREEN"
        else
            local BG_EXIT="$BG_RED"
        fi

        # Bash by default expands the content of PS1 unless promptvars is disabled.
        # We must use another layer of reference to prevent expanding any user
        # provided strings, which would cause security issues.
        # POC: https://github.com/njhartwell/pw3nage
        # Related fix in git-bash: https://github.com/git/git/blob/9d77b0405ce6b471cb5ce3a904368fc25e55643d/contrib/completion/git-prompt.sh#L324
        __powerline_virtualenv="$(__virtualenv)"
        __powerline_pwd="$(__pwd)"
        __powerline_git_info="$(__git_info)"
        PS1=""
        if shopt -q promptvars; then
            PS1+="$BG_BASE0$FG_BASE3\${__powerline_virtualenv}$RESET"
            PS1+="$BG_BASE1$FG_BASE3 \${__powerline_pwd} $RESET"
            PS1+="$BG_BLUE$FG_BASE3\${__powerline_git_info}$RESET"
        else
            # promptvars is disabled. Directly print out and unset unnecessary vars.
            PS1+="$BG_BASE0$FG_BASE3${__powerline_virtualenv}$RESET"
            PS1+="$BG_BASE1$FG_BASE3 ${__powerline_pwd} $RESET"
            PS1+="$BG_BLUE$FG_BASE3${__powerline_git_info}$RESET"
            unset __powerline_virtualenv
            unset __powerline_pwd
            unset __powerline_git_info
        fi
        PS1+="$BG_EXIT$FG_BASE3 $PS_SYMBOL $RESET "
    }

    PROMPT_COMMAND=ps1
}

__powerline
unset __powerline