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


def get_header():
    now = datetime.datetime.utcnow()
    return ("# Ran on {}\n".format(
        now.strftime("%y/%m/%d %H:%M:%S.%f")))

class LevelContext:
    def __init__(self, increaser, decreaser):
        self.increaser = increaser
        self.decreaser = decreaser

    def __enter__(self):
        self.increaser()

    def __exit__(self, _type, _value, _traceback):
        self.decreaser()


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

        self.f.write(get_header())

    def annotate(self, annotation):
        if self.dirty:
            self.f.write("{indentation} {data}\n".format(
                indentation='*' * (self.level + 1),
                data="---"))
            self.dirty = False

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

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

        return LevelContext(self.inc_level, self.dec_level)

    def inc_level(self):
        self.level += 1

    def dec_level(self):
        self.level -= 1
        self.dirty = True

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