# Finds a Python virtual environment in the current
# directory or any of its parents and enters it, or
# exits an virtual environment if we're in one
# but the current directory does not contain a virtualenv
function find_and_enter_virtualenv {
    # See if the current directory, or any of its
    # parents have a 'venv/bin/activate' script
    path=$(pwd)
    while [ ! -z $path ]; do
        if [ -f "$path/venv/bin/activate" ]; then
            path="$path/venv/bin/activate"
            break
        fi

        path="${path%/*}"
    done

    # No virtualenv found, try to de-activate
    # in case we're exiting one
    if [ -z $path ]; then
        deactivate &> /dev/null
        return
    fi

    # Enter the virtualenv
    source $path

    # Fix up the command prompt to make it
    # clear we're in a virtual env
    export PS1="\n$REDBOLD\u $CYAN(venv)$RESETCOLOR $PURPLE@ $GREEN\w $RESETCOLOR$CYAN → $RESETCOLOR"
}

# Override cd so we can intercept directory changes
function cd {
    builtin cd "$@"
    find_and_enter_virtualenv
}

# Suppose a bash prompt is opened and that directory
# is a virtual env, we'll activate it!
find_and_enter_virtualenv