import os

# default callbacks
def none(window):
    return None

def last_buffer(window):
    bl = window.application.bufferlist
    return bl.hidden_buffers[0].name()

def current_buffer(window):
    return window.buffer.name()

def last_replace_before(window):
    return None #XYZ
    if window.application.last_replace_before:
        return window.application.last_replace_before
    else:
        return None

def last_replace_after(window):
    return None #XYZ
    if window.application.last_replace_after:
        return window.application.last_replace_after
    else:
        return None

def current_working_dir(window):
    home = os.getenv('HOME')
    cwd = os.getcwd()
    if cwd.startswith(home):
        cwd = cwd.replace(home, '~', 1)
    if not cwd.endswith('/'):
        cwd += '/'
    return cwd

def path_dirname(window):
    if hasattr(window.buffer, 'path'):
        return os.path.dirname(window.buffer.path) + '/'

# default callback builders
def build_constant(c):
    return lambda w: c

def build_mode_var(name):
    return lambda w: hasattr(w.mode, name) and getattr(w.mode, name) or ''