#!/usr/bin/env python

# Copyright 2021 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: fbravo@whitestack.com
##

import os
import pymongo
import yaml
import aiohttp
import asyncio
import copy
import json
import time
from bson.json_util import dumps
from bson import ObjectId

# Env variables
mongodb_url = os.environ["MONGODB_URL"]
target_database = os.environ["TARGET_DATABASE"]
prometheus_config_file = os.environ["PROMETHEUS_CONFIG_FILE"]
prometheus_url = os.environ["PROMETHEUS_URL"]


def get_jobs(client):
    return json.loads(dumps(client[target_database].prometheus_jobs.find({})))


def save_successful_jobs(client, jobs):
    for job in jobs:
        client[target_database].prometheus_jobs.update_one(
            {"_id": ObjectId(job["_id"]["$oid"])},
            {"$set": {"is_active": True}}
        )


def clean_up_job(prometheus_job):
    cleaned_prometheus_job = copy.deepcopy(prometheus_job)
    # take out _id and internal keys
    cleaned_prometheus_job.pop("_id", None)
    cleaned_prometheus_job.pop("is_active", None)
    cleaned_prometheus_job.pop("vnfr_id", None)
    cleaned_prometheus_job.pop("nsr_id", None)
    return cleaned_prometheus_job


def generate_prometheus_config(prometheus_jobs, config_file_path):
    config_file = open(config_file_path, encoding="utf-8", mode="r")
    config_file_contents = config_file.read()
    config_file.close()

    config_file_yaml = yaml.load(config_file_contents, yaml.FullLoader)
    if config_file_yaml is None:
        config_file_yaml = {}

    if len(prometheus_jobs) == 0:
        config_file_yaml["scrape_configs"] = []
        return config_file_yaml

    config_file_yaml["scrape_configs"] = []

    for prometheus_job in prometheus_jobs:
        cleaned_up_job = clean_up_job(prometheus_job)
        config_file_yaml["scrape_configs"].append(cleaned_up_job)

    return config_file_yaml


async def reload_prometheus_config(prom_url):
    async with aiohttp.ClientSession() as session:
        async with session.post(prom_url + "/-/reload") as resp:
            if resp.status > 204:
                print(f"Error while updating prometheus config: {resp.text()}")
                return False
        await asyncio.sleep(5)
        return True


def check_configuration_equal(a_config, b_config):
    if a_config is None and b_config is None:
        return True
    if a_config is None or b_config is None:
        return False
    if "scrape_configs" not in a_config and "scrape_configs" not in b_config:
        return True
    if "scrape_configs" not in a_config or "scrape_configs" not in b_config:
        return False
    a_jobs = [j["job_name"] for j in a_config["scrape_configs"]]
    b_jobs = [j["job_name"] for j in b_config["scrape_configs"]]

    return a_jobs == b_jobs


async def validate_configuration(prom_url, new_config):
    async with aiohttp.ClientSession() as session:
        # Gets the configuration from prometheus
        # and compares with the inserted one
        # If prometheus does not admit this configuration,
        # the old one will remain
        async with session.get(prom_url + "/api/v1/status/config") as resp:
            if resp.status > 204:
                print(f"Error while updating prometheus config: {resp.text()}")
                return False
            current_config = await resp.json()
            return check_configuration_equal(
                yaml.safe_load(current_config["data"]["yaml"]), new_config
            )


async def main_task(client):
    stored_jobs = get_jobs(client)
    print(f"Jobs detected : {len(stored_jobs):d}")
    generated_prometheus_config = generate_prometheus_config(
        stored_jobs, prometheus_config_file
    )
    print(f"Writing new config file to {prometheus_config_file}")
    config_file = open(prometheus_config_file, "w")
    config_file.truncate(0)
    config_file.write(yaml.dump(generated_prometheus_config))
    config_file.close()
    print("New config written, updating prometheus")
    update_resp = await reload_prometheus_config(prometheus_url)
    is_valid = await validate_configuration(
        prometheus_url, generated_prometheus_config
    )
    if update_resp and is_valid:
        print("Prometheus config update successful")
        save_successful_jobs(client, stored_jobs)
    else:
        print(
            "Error while updating prometheus config: "
            "current config doesn't match with updated values"
        )


async def main():
    client = pymongo.MongoClient(mongodb_url)
    print("Connected to MongoDB!")

    try:
        print("Refreshing prometheus config file for first time")
        await main_task(client)
    except Exception as error:
        print("Error in first configuration attempt!")
        print(error)

    while True:
        try:
            # Needs mongodb in replica mode as this feature relies in OpLog
            change_stream = client[target_database].prometheus_jobs.watch(
                [
                    {
                        "$match": {
                            # If you want to modify a particular job,
                            # delete and insert it again
                            "operationType": {"$in": ["insert", "delete"]}
                        }
                    }
                ]
            )

            # Single thread, no race conditions and ops are queued up in order
            print("Listening to changes in prometheus jobs collection")
            for change in change_stream:
                print("Change detected, updating prometheus config")
                await main_task(client)
                print()
        except Exception as error:
            print(error)
        print(
            "Detected failure while listening to prometheus jobs collection, "
            "retrying..."
        )
        time.sleep(5)


asyncio.run(main())