/*
 * Copyright 2010-2013 Ning, Inc.
 * Copyright 2014-2016 Groupon, Inc
 * Copyright 2014-2016 The Billing Project, LLC
 *
 * The Billing Project 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 org.killbill.billing.junction.plumbing.billing;

import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
import java.util.UUID;

import javax.annotation.Nullable;

import org.killbill.billing.ObjectType;
import org.killbill.billing.account.api.AccountApiException;
import org.killbill.billing.account.api.AccountInternalApi;
import org.killbill.billing.account.api.ImmutableAccountData;
import org.killbill.billing.callcontext.InternalCallContext;
import org.killbill.billing.catalog.api.CatalogApiException;
import org.killbill.billing.catalog.api.CatalogService;
import org.killbill.billing.catalog.api.StaticCatalog;
import org.killbill.billing.entitlement.api.Entitlement.EntitlementState;
import org.killbill.billing.entitlement.api.SubscriptionEventType;
import org.killbill.billing.events.EffectiveSubscriptionInternalEvent;
import org.killbill.billing.invoice.api.DryRunArguments;
import org.killbill.billing.junction.BillingEvent;
import org.killbill.billing.junction.BillingEventSet;
import org.killbill.billing.junction.BillingInternalApi;
import org.killbill.billing.subscription.api.SubscriptionBase;
import org.killbill.billing.subscription.api.SubscriptionBaseInternalApi;
import org.killbill.billing.subscription.api.SubscriptionBaseTransitionType;
import org.killbill.billing.subscription.api.user.SubscriptionBaseApiException;
import org.killbill.billing.subscription.api.user.SubscriptionBaseBundle;
import org.killbill.billing.tag.TagInternalApi;
import org.killbill.billing.util.UUIDs;
import org.killbill.billing.util.tag.ControlTagType;
import org.killbill.billing.util.tag.Tag;
import org.killbill.clock.Clock;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Function;
import com.google.common.collect.Collections2;
import com.google.inject.Inject;

public class DefaultInternalBillingApi implements BillingInternalApi {

    private static final Logger log = LoggerFactory.getLogger(DefaultInternalBillingApi.class);
    private final AccountInternalApi accountApi;
    private final BillCycleDayCalculator bcdCalculator;
    private final SubscriptionBaseInternalApi subscriptionApi;
    private final CatalogService catalogService;
    private final BlockingCalculator blockCalculator;
    private final TagInternalApi tagApi;
    private final Clock clock;

    @Inject
    public DefaultInternalBillingApi(final AccountInternalApi accountApi,
                                     final BillCycleDayCalculator bcdCalculator,
                                     final SubscriptionBaseInternalApi subscriptionApi,
                                     final BlockingCalculator blockCalculator,
                                     final CatalogService catalogService,
                                     final TagInternalApi tagApi,
                                     final Clock clock) {
        this.accountApi = accountApi;
        this.bcdCalculator = bcdCalculator;
        this.subscriptionApi = subscriptionApi;
        this.catalogService = catalogService;
        this.blockCalculator = blockCalculator;
        this.tagApi = tagApi;
        this.clock = clock;
    }

    @Override
    public BillingEventSet getBillingEventsForAccountAndUpdateAccountBCD(final UUID accountId, final DryRunArguments dryRunArguments, final InternalCallContext context) throws CatalogApiException, AccountApiException {
        final List<SubscriptionBaseBundle> bundles = subscriptionApi.getBundlesForAccount(accountId, context);
        final StaticCatalog currentCatalog = catalogService.getCurrentCatalog(context);

        final ImmutableAccountData account = accountApi.getImmutableAccountDataById(accountId, context);
        final DefaultBillingEventSet result = new DefaultBillingEventSet(false, currentCatalog.getRecurringBillingMode());



        final Set<UUID> skippedSubscriptions = new HashSet<UUID>();
        try {
            // Check to see if billing is off for the account
            final List<Tag> accountTags = tagApi.getTags(accountId, ObjectType.ACCOUNT, context);
            final boolean found_AUTO_INVOICING_OFF = is_AUTO_INVOICING_OFF(accountTags);
            if (found_AUTO_INVOICING_OFF) {
                return new DefaultBillingEventSet(true, currentCatalog.getRecurringBillingMode()); // billing is off, we are done
            }

            addBillingEventsForBundles(bundles, account, dryRunArguments, context, result, skippedSubscriptions);
        } catch (SubscriptionBaseApiException e) {
            log.warn("Failed while getting BillingEvent", e);
        }

        // Pretty-print the events, before and after the blocking calculator does its magic
        final StringBuilder logStringBuilder = new StringBuilder("Computed billing events for accountId='").append(accountId).append("'");
        eventsToString(logStringBuilder, result, "\nBilling Events Raw");
        blockCalculator.insertBlockingEvents(result, skippedSubscriptions, context);
        eventsToString(logStringBuilder, result, "\nBilling Events After Blocking");
        log.info(logStringBuilder.toString());

        return result;
    }

    private void eventsToString(final StringBuilder stringBuilder, final SortedSet<BillingEvent> events, final String title) {
        stringBuilder.append(title);
        for (final BillingEvent event : events) {
            stringBuilder.append("\n").append(event.toString());
        }
    }

    private void addBillingEventsForBundles(final List<SubscriptionBaseBundle> bundles, final ImmutableAccountData account, final DryRunArguments dryRunArguments, final InternalCallContext context,
                                            final DefaultBillingEventSet result, final Set<UUID> skipSubscriptionsSet) throws SubscriptionBaseApiException, AccountApiException {

        final boolean dryRunMode = dryRunArguments != null;

        // In dryRun mode, when we care about invoice generated for new BASE subscription, no such bundle exists yet; we still
        // want to tap into subscriptionBase logic, so we make up a bundleId
        if (dryRunArguments != null &&
            dryRunArguments.getAction() == SubscriptionEventType.START_BILLING &&
            dryRunArguments.getBundleId() == null) {
            final UUID fakeBundleId = UUIDs.randomUUID();
            final List<SubscriptionBase> subscriptions = subscriptionApi.getSubscriptionsForBundle(fakeBundleId, dryRunArguments, context);

            addBillingEventsForSubscription(account, subscriptions, fakeBundleId, dryRunMode, context, result, skipSubscriptionsSet);

        }

        for (final SubscriptionBaseBundle bundle : bundles) {
            final DryRunArguments dryRunArgumentsForBundle = (dryRunArguments != null &&
                                                              dryRunArguments.getBundleId() != null &&
                                                              dryRunArguments.getBundleId().equals(bundle.getId())) ?
                                                             dryRunArguments : null;
            final List<SubscriptionBase> subscriptions = subscriptionApi.getSubscriptionsForBundle(bundle.getId(), dryRunArgumentsForBundle, context);

            //Check if billing is off for the bundle
            final List<Tag> bundleTags = tagApi.getTags(bundle.getId(), ObjectType.BUNDLE, context);
            boolean found_AUTO_INVOICING_OFF = is_AUTO_INVOICING_OFF(bundleTags);
            if (found_AUTO_INVOICING_OFF) {
                for (final SubscriptionBase subscription : subscriptions) { // billing is off so list sub ids in set to be excluded
                    result.getSubscriptionIdsWithAutoInvoiceOff().add(subscription.getId());
                }
            } else { // billing is not off
                addBillingEventsForSubscription(account, subscriptions, bundle.getId(), dryRunMode, context, result, skipSubscriptionsSet);
            }
        }
    }


    private void addBillingEventsForSubscription(final ImmutableAccountData account,
                                                 final List<SubscriptionBase> subscriptions,
                                                 final UUID bundleId,
                                                 final boolean dryRunMode,
                                                 final InternalCallContext context,
                                                 final DefaultBillingEventSet result,
                                                 final Set<UUID> skipSubscriptionsSet) throws AccountApiException {

        // If dryRun is specified, we don't want to to update the account BCD value, so we initialize the flag updatedAccountBCD to true
        boolean updatedAccountBCD = dryRunMode;


        int currentAccountBCD = accountApi.getBCD(account.getId(), context);
        for (final SubscriptionBase subscription : subscriptions) {

            // The subscription did not even start, so there is nothing to do yet, we can skip and avoid some NPE down the line when calculating the BCD
            if (subscription.getState() == EntitlementState.PENDING) {
                continue;
            }

            final List<EffectiveSubscriptionInternalEvent> billingTransitions = subscriptionApi.getBillingTransitions(subscription, context);
            if (billingTransitions.isEmpty() ||
                (billingTransitions.get(0).getTransitionType() != SubscriptionBaseTransitionType.CREATE &&
                 billingTransitions.get(0).getTransitionType() != SubscriptionBaseTransitionType.TRANSFER)) {
                log.warn("Skipping billing events for subscription " + subscription.getId() + ": Does not start with a valid CREATE transition");
                skipSubscriptionsSet.add(subscription.getId());
                return;
            }


            Integer overridenBCD = null;
            for (final EffectiveSubscriptionInternalEvent transition : billingTransitions) {
                try {
                    //
                    // A BCD_CHANGE transition defines a new billCycleDayLocal for the subscription and this overrides whatever computation
                    // occurs below (which is based on billing alignment policy). Also multiple of those BCD_CHANGE transitions could occur,
                    // to define different intervals with different billing cycle days.
                    //
                    overridenBCD = transition.getNextBillCycleDayLocal() != null ? transition.getNextBillCycleDayLocal() : overridenBCD;
                    final int bcdLocal = overridenBCD != null ?
                                         overridenBCD :
                                         bcdCalculator.calculateBcd(account, currentAccountBCD, bundleId, subscription, transition, context);

                    if (currentAccountBCD == 0 && !updatedAccountBCD) {
                        accountApi.updateBCD(account.getExternalKey(), bcdLocal, context);
                        updatedAccountBCD = true;
                    }

                    final BillingEvent event = new DefaultBillingEvent(account, transition, subscription, bcdLocal, account.getCurrency(), catalogService.getFullCatalog(context));
                    result.add(event);
                } catch (CatalogApiException e) {
                    log.error("Failing to identify catalog components while creating BillingEvent from transition: " +
                              transition.getId().toString(), e);
                } catch (AccountApiException e) {
                    // This is unexpected  (failed to update BCD) but if this happens we don't want to ignore..
                    throw e;
                } catch (Exception e) {
                    log.warn("Failed while getting BillingEvent", e);
                }
            }
        }
    }

    private final boolean is_AUTO_INVOICING_OFF(final List<Tag> tags) {
        return ControlTagType.isAutoInvoicingOff(Collections2.transform(tags, new Function<Tag, UUID>() {
            @Nullable
            @Override
            public UUID apply(@Nullable final Tag tag) {
                return tag.getTagDefinitionId();
            }
        }));
    }
}
