import logging
import datetime

SESSION = None


def __gen_session_name__():
    now = datetime.datetime.utcnow()
    return "treeNLU-session-{}.org".format(
        now.strftime("%y_%m_%d %H:%M:%S_%f"))


def create_global_session(fname):
    global SESSION
    SESSION = OrgModeSession(fname)


def global_session():
    if SESSION is None:
        session_name = __gen_session_name__()
        logging.warn("Session not created, saved on {}".format(session_name))
        create_global_session(session_name)

    assert(SESSION is not None)
    return SESSION


class OrgModeSession:
    def __init__(self, fname):
        self.f = open(fname, 'wt')
        self.last_level = 0

    def annotate(self, annotation):
        self.f.write("{indentation} {data}\n".format(
            indentation=' ' * (self.last_level + 2 + 1),
            data=annotation))

    def log_step(self, string, level):
        self.f.write("{indentation} {data}\n".format(
            indentation='*' * (level + 1),
            data=string))
        self.last_level = level

    def close(self):
        self.f.close()