simple powerline for xonsh

prompt.xsh

import os
from collections import namedtuple

Section = namedtuple('Section', ['line', 'fg', 'bg'])

PARTS = 3

def cwd_sec():
    cwd = $PWD
    if cwd.startswith($HOME):
        cwd = '~' + cwd[len($HOME):]

    ps = cwd.strip('/').split(os.sep)

    if len(ps) > PARTS:
        new_ps = [ps[0]]
        new_ps.append('…')
        new_ps += ps[-(PARTS-1):]
        ps = new_ps


    return Section(' '+'  '.join(ps) + ' ', 'WHITE', '#333')

def branch_sec():
    if $FORMATTER_DICT['curr_branch']():
        return Section(' {curr_branch} ', '#333', $FORMATTER_DICT['branch_bg_color']()[1+len('background_'):-1])

def virtualenv_sec():
    try:
        venv = os.path.basename($VIRTUAL_ENV)
    except KeyError:
        return
    return Section(' ('+ venv +') ', 'INTENSE_CYAN', 'BLUE')

def end_sec():
    bg = 'INTENSE_CYAN'
    try:
        if __xonsh_history__.rtns[-1] != 0:
            bg = 'RED'
    except IndexError:
        pass
    return Section(' {prompt_end} ', '#333', bg)

pre_sections = [
    cwd_sec,
    branch_sec,
    virtualenv_sec,
    end_sec,
]


def prompt():
    p = []
    sections = []
    for s in pre_sections:
        if isinstance(s, Section):
            sections.append(s)
        else:
            r = s()
            if r is not None:
                sections.append(r)

    size = len(sections)
    for i, sec in enumerate(sections):
        last = (i == size-1)
        first = (i == 0)
        p.append('{'+sec.fg+'}')

        if first:
            p.append('{BACKGROUND_'+sec.bg+'}')
        p.append(sec[0])
        if last:
            p.append('{NO_COLOR}')
            p.append('{'+sec.bg+'}')
            p.append(' ')
            p.append('{NO_COLOR}')
        else:
            p.append('{'+sec.bg+'}')
            p.append('{BACKGROUND_'+sections[i+1].bg+'}')
            p.append('')

    return ''.join(p)

$PROMPT = prompt
$MULTILINE_PROMPT = '—'