# -*- coding: utf-8 -*-

# Copyright 2018 Whitestack, LLC
# *************************************************************

# This file is part of OSM Monitoring module
# All Rights Reserved to Whitestack, LLC

# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at

#         http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
# For those usages not covered by the Apache License, Version 2.0 please
# contact: bdiaz@whitestack.com or glavado@whitestack.com
##
import base64
import logging
from typing import Dict

import requests

from osm_mon.core.config import Config
from osm_mon.evaluator.backends.base import BaseBackend

log = logging.getLogger(__name__)

OSM_METRIC_PREFIX = "osm_"


class PrometheusBackend(BaseBackend):
    def __init__(self, config: Config):
        super().__init__(config)
        self.conf = config

    def get_metric_value(self, metric_name: str, tags: dict):
        query = self._build_query(metric_name, tags)
        request_url = self._build_url(query)
        request_headers = self._build_headers()
        return self._query_metric(request_url, request_headers)

    def _query_metric(self, request_url: str, headers: Dict[str, str]):
        log.info("Querying Prometheus: %s", request_url)
        r = requests.get(
            request_url,
            timeout=int(self.conf.get("global", "request_timeout")),
            headers=headers,
        )
        if r.status_code == 200:
            json_response = r.json()
            if json_response["status"] == "success":
                return self._get_metric_value_from_response(json_response)
            else:
                log.warning(
                    "Prometheus response is not success. Got status %s",
                    json_response["status"],
                )
        else:
            log.warning(
                "Error contacting Prometheus. Got status code %s: %s",
                r.status_code,
                r.text,
            )
        return None

    def _build_query(self, metric_name: str, tags: dict) -> str:
        query_section_tags = []
        for k, v in tags.items():
            query_section_tags.append(k + '="' + v + '"')
        query_section = "query={0}{{{1}}}".format(
            OSM_METRIC_PREFIX + metric_name, ",".join(query_section_tags)
        )
        return query_section

    def _build_url(self, query: str):
        return self.conf.get("prometheus", "url") + "/api/v1/query?" + query

    def _build_headers(self) -> Dict[str, str]:
        headers = {}
        user = self.conf.get("prometheus", "user")
        password = self.conf.get("prometheus", "password")
        if user and password:
            _phrase = f"{user}:{password}".encode("utf-8")
            token = base64.b64encode(_phrase).decode("utf-8")
            headers["Authorization"] = f"Basic {token}"
        return headers

    def _get_metric_value_from_response(self, json_response):
        result = json_response["data"]["result"]
        if len(result):
            metric_value = float(result[0]["value"][1])
            log.info("Metric value: %s", metric_value)
            return metric_value
        else:
            return None
