import datetime
import json
import logging

metrics_logger = logging.getLogger('metrics')


class Metrics:
    def __init__(self, category: str, context: dict = None):
        self.context = context or {}
        self.metrics = {}
        self.category = category

    def add_metric(self, key, value):
        self.metrics[key] = value

    def send(self):
        self.send_metrics_to_log()
        self.send_metrics_to_stdout()

    def send_metrics_to_stdout(self):
        print(self.serialize_json())

    def send_metrics_to_log(self):
        data = f'{self.category}: {self.serialize_json()}'
        metrics_logger.info(data)

    def serialize_json(self):
        result = {'metrics_category': self.category, **self.metrics, **self.context}
        return json.dumps(result)

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.send()
        return False


class DurationMetrics(Metrics):
    def __init__(self, category: str, context: dict = None):
        super().__init__(category, context)
        self.started_at = None
        self.completed_at = None
        self.duration = None

    def start(self):
        self.started_at = datetime.datetime.now()
        self.add_metric('started', self.started_at.replace(microsecond=0).isoformat())

    def finish(self):
        self.completed_at = datetime.datetime.now()
        self.add_metric('completed', self.completed_at.replace(microsecond=0).isoformat())
        self.duration = self.completed_at - self.started_at
        self.add_metric('duration_sec', round(self.duration.total_seconds()))

    def __enter__(self):
        self.start()
        return super().__enter__()

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.finish()
        return super().__exit__(exc_type, exc_val, exc_tb)