/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

package com.epam.dlab.billing.azure;

import com.epam.dlab.billing.BillingCalculationUtils;
import com.epam.dlab.billing.azure.config.BillingConfigurationAzure;
import com.epam.dlab.billing.azure.model.AzureDailyResourceInvoice;
import com.epam.dlab.billing.azure.model.AzureDlabBillableResource;
import com.epam.dlab.billing.azure.rate.AzureRateCardClient;
import com.epam.dlab.billing.azure.rate.Meter;
import com.epam.dlab.billing.azure.rate.RateCardResponse;
import com.epam.dlab.billing.azure.usage.AzureUsageAggregateClient;
import com.epam.dlab.billing.azure.usage.UsageAggregateRecord;
import com.epam.dlab.billing.azure.usage.UsageAggregateResponse;
import com.epam.dlab.exceptions.DlabException;
import com.microsoft.azure.AzureEnvironment;
import com.microsoft.azure.credentials.ApplicationTokenCredentials;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * Filters billing data and calculate prices for each
 * resource using combination of Microsoft Azure RateCard API and Usage API
 */
@Slf4j
public class AzureInvoiceCalculationService {

	/**
	 * According to Microsoft Azure documentation
	 * https://docs.microsoft.com/en-us/azure/active-directory/active-directory-configurable-token-lifetimes
	 * min TTL time of token 10 minutes
	 */
	private static final long MAX_AUTH_TOKEN_TTL_MILLIS = 9L * 60L * 1000L;

	private BillingConfigurationAzure billingConfigurationAzure;
	private Map<String, AzureDlabBillableResource> billableResources;

	/**
	 * Constructs service class
	 *
	 * @param billingConfigurationAzure contains <code>billing-azure</code> module configuration
	 */
	public AzureInvoiceCalculationService(BillingConfigurationAzure billingConfigurationAzure) {
		this.billingConfigurationAzure = billingConfigurationAzure;
	}

	/**
	 * Prepares invoice records aggregated by day
	 *
	 * @param from start usage period
	 * @param to   end usage period
	 * @return list of invoice records for each meter category aggregated by day
	 */
	public List<AzureDailyResourceInvoice> generateInvoiceData(String from, String to) {

		long refreshTokenTime = System.currentTimeMillis() + MAX_AUTH_TOKEN_TTL_MILLIS;

		String authenticationToken = getNewToken();
		AzureRateCardClient azureRateCardClient = new AzureRateCardClient(billingConfigurationAzure,
                authenticationToken);
		AzureUsageAggregateClient azureUsageAggregateClient = new AzureUsageAggregateClient(billingConfigurationAzure,
                authenticationToken);

		List<AzureDailyResourceInvoice> invoiceData = new ArrayList<>();

		try {

			UsageAggregateResponse usageAggregateResponse = null;
			Map<String, Meter> rates = transformRates(azureRateCardClient.getRateCard());

			do {

				if (usageAggregateResponse != null && StringUtils.isNotEmpty(usageAggregateResponse.getNextLink())) {
					log.info("Get usage of resources using link {}", usageAggregateResponse.getNextLink());
					usageAggregateResponse = azureUsageAggregateClient.getUsageAggregateResponse
                            (usageAggregateResponse.getNextLink());
					log.info("Received usage of resources. Items {} ", usageAggregateResponse.getValue() != null ?
							usageAggregateResponse.getValue().size() : 0);
					log.info("Next link is {}", usageAggregateResponse.getNextLink());
				} else if (usageAggregateResponse == null) {
					log.info("Get usage of resources from {} to {}", from, to);
					usageAggregateResponse = azureUsageAggregateClient.getUsageAggregateResponse(from, to);
					log.info("Received usage of resources. Items {} ", usageAggregateResponse.getValue() != null ?
							usageAggregateResponse.getValue().size() : 0);
					log.info("Next link is {}", usageAggregateResponse.getNextLink());
				}

				invoiceData.addAll(generateBillingInfo(rates, usageAggregateResponse));

				if (System.currentTimeMillis() > refreshTokenTime) {
					authenticationToken = getNewToken();
					azureUsageAggregateClient.setAuthToken(authenticationToken);
				}

			} while (StringUtils.isNotEmpty(usageAggregateResponse.getNextLink()));

		} catch (IOException | RuntimeException | URISyntaxException e) {
			log.error("Cannot calculate billing information", e);
			throw new DlabException("Cannot prepare invoice data", e);
		}

		return invoiceData;
	}

	private List<AzureDailyResourceInvoice> generateBillingInfo(Map<String, Meter> rates, UsageAggregateResponse
            usageAggregateResponse) {
		List<UsageAggregateRecord> usageAggregateRecordList = usageAggregateResponse.getValue();
		List<AzureDailyResourceInvoice> invoices = new ArrayList<>();

		if (usageAggregateRecordList != null && !usageAggregateRecordList.isEmpty()) {
			log.info("Processing {} usage records", usageAggregateRecordList.size());
			usageAggregateRecordList = usageAggregateRecordList.stream().filter(e ->
					matchProperStructure(e) && isBillableDlabResource(e))
					.collect(Collectors.toList());

			log.info("Applicable records number is {}", usageAggregateRecordList.size());

			for (UsageAggregateRecord record : usageAggregateRecordList) {
				invoices.add(calculateInvoice(rates, record, record.getProperties().getParsedInstanceData()
						.getMicrosoftResources().getTags().get("Name")));
			}
		} else {
			log.error("No usage records in response.");
		}

		return invoices;
	}

	private Map<String, Meter> transformRates(RateCardResponse rateCardResponse) {
		Map<String, Meter> rates = new HashMap<>();
		for (Meter meter : rateCardResponse.getMeters()) {
			rates.put(meter.getMeterId(), meter);
		}

		return rates;
	}

	private boolean matchProperStructure(UsageAggregateRecord record) {
		if (record.getProperties() == null) {
			return false;
		}

		if (record.getProperties().getMeterId() == null || record.getProperties().getMeterId().isEmpty()) {
			return false;
		}

		return !(record.getProperties().getParsedInstanceData() == null
				|| record.getProperties().getParsedInstanceData().getMicrosoftResources() == null
				|| record.getProperties().getParsedInstanceData().getMicrosoftResources().getTags() == null
				|| record.getProperties().getParsedInstanceData().getMicrosoftResources().getTags().isEmpty());
	}

	private boolean isBillableDlabResource(UsageAggregateRecord record) {
		String dlabId = record.getProperties().getParsedInstanceData().getMicrosoftResources().getTags().get("Name");
		return dlabId != null && !dlabId.isEmpty() && dlabId.startsWith(billingConfigurationAzure.getSbn());
	}

	private AzureDailyResourceInvoice calculateInvoice(Map<String, Meter> rates, UsageAggregateRecord record, String dlabId) {
		String meterId = record.getProperties().getMeterId();
		Meter rateCard = rates.get(meterId);

		if (rateCard != null) {
			Map<String, Double> meterRates = rateCard.getMeterRates();
			if (meterRates != null) {
				Double rate = meterRates.get(AzureRateCardClient.MAIN_RATE_KEY);
				if (rate != null) {
					return AzureDailyResourceInvoice.builder()
							.dlabId(dlabId)
							.usageStartDate(getDay(record.getProperties().getUsageStartTime()))
							.usageEndDate(getDay(record.getProperties().getUsageEndTime()))
							.meterCategory(record.getProperties().getMeterCategory())
							.cost(BillingCalculationUtils.round(rate * record.getProperties().getQuantity(), 3))
							.day(getDay(record.getProperties().getUsageStartTime()))
							.currencyCode(billingConfigurationAzure.getCurrency())
							.build();
				} else {
					log.error("Rate Card {} has no rate for meter id {} and rate id {}. Skip record {}.",
							rateCard, meterId, AzureRateCardClient.MAIN_RATE_KEY, record);
				}
			} else {
				log.error("Rate Card {} has no meter rates fro meter id {}. Skip record {}",
						rateCard, meterId, record);
			}
		} else {
			log.error("Meter rate {} form usage aggregate is not found in rate card. Skip record {}.", meterId, record);
		}

		return null;
	}

	private String getNewToken() {
		try {
			log.info("Requesting authentication token ... ");
			ApplicationTokenCredentials applicationTokenCredentials = new ApplicationTokenCredentials(
					billingConfigurationAzure.getClientId(),
					billingConfigurationAzure.getTenantId(),
					billingConfigurationAzure.getClientSecret(),
					AzureEnvironment.AZURE);

			return applicationTokenCredentials.getToken(AzureEnvironment.AZURE.resourceManagerEndpoint());
		} catch (IOException e) {
			log.error("Cannot retrieve authentication token due to", e);
			throw new DlabException("Cannot retrieve authentication token", e);
		}
	}

	private String getDay(String dateTime) {
		if (dateTime != null) {
			String[] parts = dateTime.split("T");
			if (parts.length == 2) {
				return parts[0];
			}
		}

		log.error("Wrong usage date format {} ", dateTime);
		return null;
	}

}