# -*- coding: utf-8 -*-
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# to you under the Apache License, Version 2.0 (the
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#   http://www.apache.org/licenses/LICENSE-2.0
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"""
Utilities module for cli
"""
from __future__ import absolute_import

import functools
import getpass
import json
import socket
import sys
from argparse import Namespace
from datetime import datetime

from airflow.models import Log
from airflow.utils import cli_action_loggers


def action_logging(f):
    """
    Decorates function to execute function at the same time submitting action_logging
    but in CLI context. It will call action logger callbacks twice,
    one for pre-execution and the other one for post-execution.

    Action logger will be called with below keyword parameters:
        sub_command : name of sub-command
        start_datetime : start datetime instance by utc
        end_datetime : end datetime instance by utc
        full_command : full command line arguments
        user : current user
        log : airflow.models.log.Log ORM instance
        dag_id : dag id (optional)
        task_id : task_id (optional)
        execution_date : execution date (optional)
        error : exception instance if there's an exception

    :param f: function instance
    :return: wrapped function
    """
    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        """
        An wrapper for cli functions. It assumes to have Namespace instance
        at 1st positional argument

        :param args: Positional argument. It assumes to have Namespace instance
            at 1st positional argument
        :param kwargs: A passthrough keyword argument
        """
        assert args
        assert isinstance(args[0], Namespace), \
            "1st positional argument should be argparse.Namespace instance, " \
            "but {}".format(args[0])
        metrics = _build_metrics(f.__name__, args[0])
        cli_action_loggers.on_pre_execution(**metrics)
        try:
            return f(*args, **kwargs)
        except Exception as e:
            metrics['error'] = e
            raise
        finally:
            metrics['end_datetime'] = datetime.utcnow()
            cli_action_loggers.on_post_execution(**metrics)

    return wrapper


def _build_metrics(func_name, namespace):
    """
    Builds metrics dict from function args
    It assumes that function arguments is from airflow.bin.cli module's function
    and has Namespace instance where it optionally contains "dag_id", "task_id",
    and "execution_date".

    :param func_name: name of function
    :param namespace: Namespace instance from argparse
    :return: dict with metrics
    """

    metrics = {'sub_command': func_name, 'start_datetime': datetime.utcnow(),
               'full_command': '{}'.format(list(sys.argv)), 'user': getpass.getuser()}

    assert isinstance(namespace, Namespace)
    tmp_dic = vars(namespace)
    metrics['dag_id'] = tmp_dic.get('dag_id')
    metrics['task_id'] = tmp_dic.get('task_id')
    metrics['execution_date'] = tmp_dic.get('execution_date')
    metrics['host_name'] = socket.gethostname()

    extra = json.dumps(dict((k, metrics[k]) for k in ('host_name', 'full_command')))
    log = Log(
        event='cli_{}'.format(func_name),
        task_instance=None,
        owner=metrics['user'],
        extra=extra,
        task_id=metrics.get('task_id'),
        dag_id=metrics.get('dag_id'),
        execution_date=metrics.get('execution_date'))
    metrics['log'] = log
    return metrics
