// Copyright 2016 The Nomulus Authors. All Rights Reserved.
//
// 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.

package google.registry.batch;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.Sets.difference;
import static google.registry.mapreduce.MapreduceRunner.PARAM_DRY_RUN;
import static google.registry.mapreduce.inputs.EppResourceInputs.createChildEntityInput;
import static google.registry.model.common.Cursor.CursorType.RECURRING_BILLING;
import static google.registry.model.ofy.ObjectifyService.ofy;
import static google.registry.pricing.PricingEngineProxy.getDomainRenewCost;
import static google.registry.util.CollectionUtils.union;
import static google.registry.util.DateTimeUtils.START_OF_TIME;
import static google.registry.util.DateTimeUtils.earliestOf;
import static google.registry.util.DomainNameUtils.getTldFromDomainName;
import static google.registry.util.PipelineUtils.createJobPath;

import com.google.appengine.tools.mapreduce.Mapper;
import com.google.appengine.tools.mapreduce.Reducer;
import com.google.appengine.tools.mapreduce.ReducerInput;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Range;
import com.googlecode.objectify.Key;
import com.googlecode.objectify.VoidWork;
import com.googlecode.objectify.Work;
import google.registry.mapreduce.MapreduceRunner;
import google.registry.mapreduce.inputs.NullInput;
import google.registry.model.billing.BillingEvent;
import google.registry.model.billing.BillingEvent.Flag;
import google.registry.model.billing.BillingEvent.OneTime;
import google.registry.model.billing.BillingEvent.Recurring;
import google.registry.model.common.Cursor;
import google.registry.model.domain.DomainResource;
import google.registry.model.registry.Registry;
import google.registry.request.Action;
import google.registry.request.Parameter;
import google.registry.request.Response;
import google.registry.util.Clock;
import google.registry.util.FormattingLogger;
import java.util.Set;
import javax.inject.Inject;
import org.joda.money.Money;
import org.joda.time.DateTime;

/**
 * A mapreduce that expands {@link Recurring} billing events into synthetic {@link OneTime} events.
 *
 * <p>The cursor used throughout this mapreduce (overridden if necessary using the parameter
 * {@code cursorTime}) represents the inclusive lower bound on the range of billing times that will
 * be expanded as a result of the job (the exclusive upper bound being the execution time of the
 * job).
 */
@Action(path = "/_dr/task/expandRecurringBillingEvents")
public class ExpandRecurringBillingEventsAction implements Runnable {

  public static final String PARAM_CURSOR_TIME = "cursorTime";
  private static final String ERROR_COUNTER = "errors";
  private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();

  @Inject Clock clock;
  @Inject MapreduceRunner mrRunner;
  @Inject @Parameter(PARAM_DRY_RUN) boolean isDryRun;
  @Inject @Parameter(PARAM_CURSOR_TIME) Optional<DateTime> cursorTimeParam;
  @Inject Response response;
  @Inject ExpandRecurringBillingEventsAction() {}

  @Override
  public void run() {
    Cursor cursor = ofy().load().key(Cursor.createGlobalKey(RECURRING_BILLING)).now();
    DateTime executeTime = clock.nowUtc();
    DateTime persistedCursorTime = (cursor == null ? START_OF_TIME : cursor.getCursorTime());
    DateTime cursorTime = cursorTimeParam.or(persistedCursorTime);
    checkArgument(
        cursorTime.isBefore(executeTime),
        "Cursor time must be earlier than execution time.");
    logger.infofmt(
        "Running Recurring billing event expansion for billing time range [%s, %s).",
        cursorTime,
        executeTime);
    response.sendJavaScriptRedirect(createJobPath(mrRunner
        .setJobName("Expand Recurring billing events into synthetic OneTime events.")
        .setModuleName("backend")
        .runMapreduce(
            new ExpandRecurringBillingEventsMapper(isDryRun, cursorTime, clock.nowUtc()),
            new ExpandRecurringBillingEventsReducer(isDryRun, persistedCursorTime),
            // Add an extra shard that maps over a null recurring event (see the mapper for why).
            ImmutableList.of(
                new NullInput<Recurring>(),
                createChildEntityInput(
                    ImmutableSet.<Class<? extends DomainResource>>of(DomainResource.class),
                    ImmutableSet.<Class<? extends Recurring>>of(Recurring.class))))));
  }

  /** Mapper to expand {@link Recurring} billing events into synthetic {@link OneTime} events. */
  public static class ExpandRecurringBillingEventsMapper
      extends Mapper<Recurring, DateTime, DateTime> {

    private static final long serialVersionUID = 8376442755556228455L;

    private final boolean isDryRun;
    private final DateTime cursorTime;
    private final DateTime executeTime;

    public ExpandRecurringBillingEventsMapper(
        boolean isDryRun, DateTime cursorTime, DateTime executeTime) {
      this.isDryRun = isDryRun;
      this.cursorTime = cursorTime;
      this.executeTime = executeTime;
    }

    @Override
    public final void map(final Recurring recurring) {
      // This single emit forces the reducer to run at the end of the map job, so that a mapper
      // that runs without error will advance the cursor at the end of processing (unless this was
      // a dry run, in which case the cursor should not be advanced).
      if (recurring == null) {
        emit(cursorTime, executeTime);
        return;
      }
      getContext().incrementCounter("Recurring billing events encountered");
      // Ignore any recurring billing events that have yet to apply.
      if (recurring.getEventTime().isAfter(executeTime)
          // This second case occurs when a domain is transferred or deleted before first renewal.
          || recurring.getRecurrenceEndTime().isBefore(recurring.getEventTime())) {
        getContext().incrementCounter("Recurring billing events ignored");
        return;
      }
      int billingEventsSaved = 0;
      try {
        billingEventsSaved = ofy().transactNew(new Work<Integer>() {
          @Override
          public Integer run() {
            ImmutableSet.Builder<OneTime> syntheticOneTimesBuilder =
                new ImmutableSet.Builder<>();
            final Registry tld = Registry.get(getTldFromDomainName(recurring.getTargetId()));

            // Determine the complete set of times at which this recurring event should occur
            // (up to and including the runtime of the mapreduce).
            Iterable<DateTime> eventTimes =
                recurring.getRecurrenceTimeOfYear().getInstancesInRange(Range.closed(
                    recurring.getEventTime(),
                    earliestOf(recurring.getRecurrenceEndTime(), executeTime)));

            // Convert these event times to billing times
            final ImmutableSet<DateTime> billingTimes =
                getBillingTimesInScope(eventTimes, cursorTime, executeTime, tld);

            Iterable<OneTime> oneTimesForDomain = ofy().load()
                .type(OneTime.class)
                .ancestor(recurring.getParentKey().getParent());

            // Determine the billing times that already have OneTime events persisted.
            ImmutableSet<DateTime> existingBillingTimes =
                getExistingBillingTimes(oneTimesForDomain, recurring);

            // Create synthetic OneTime events for all billing times that do not yet have an event
            // persisted.
            for (DateTime billingTime : difference(billingTimes, existingBillingTimes)) {
              DateTime eventTime = billingTime.minus(tld.getAutoRenewGracePeriodLength());
              // Determine the cost for a one-year renewal.
              Money renewCost = getDomainRenewCost(recurring.getTargetId(), eventTime, 1);
              syntheticOneTimesBuilder.add(new BillingEvent.OneTime.Builder()
                  .setBillingTime(billingTime)
                  .setClientId(recurring.getClientId())
                  .setCost(renewCost)
                  .setEventTime(eventTime)
                  .setFlags(union(recurring.getFlags(), Flag.SYNTHETIC))
                  .setParent(recurring.getParentKey())
                  .setPeriodYears(1)
                  .setReason(recurring.getReason())
                  .setSyntheticCreationTime(executeTime)
                  .setCancellationMatchingBillingEvent(Key.create(recurring))
                  .setTargetId(recurring.getTargetId())
                  .build());
            }
            Set<OneTime> syntheticOneTimes = syntheticOneTimesBuilder.build();
            if (!isDryRun) {
              ofy().save().entities(syntheticOneTimes).now();
            }
            return syntheticOneTimes.size();
          }
        });
      } catch (Throwable t) {
        logger.severefmt(
            t, "Error while expanding Recurring billing events for %s", recurring.getId());
        getContext().incrementCounter("error: " + t.getClass().getSimpleName());
        getContext().incrementCounter(ERROR_COUNTER);
        throw t;
      }
      if (!isDryRun) {
        getContext().incrementCounter("Saved OneTime billing events", billingEventsSaved);
      } else {
        getContext().incrementCounter(
            "Generated OneTime billing events (dry run)", billingEventsSaved);
      }
    }

    /**
     * Filters a set of {@link DateTime}s down to event times that are in scope for a particular
     * mapreduce run, given the cursor time and the mapreduce execution time.
     */
    private ImmutableSet<DateTime> getBillingTimesInScope(
        Iterable<DateTime> eventTimes,
        DateTime cursorTime,
        DateTime executeTime,
        final Registry tld) {
      return FluentIterable.from(eventTimes)
          .transform(new Function<DateTime, DateTime>() {
            @Override
            public DateTime apply(DateTime eventTime) {
              return eventTime.plus(tld.getAutoRenewGracePeriodLength());
            }})
          .filter(Range.closedOpen(cursorTime, executeTime))
          .toSet();
    }

    /**
     * Determines an {@link ImmutableSet} of {@link DateTime}s that have already been persisted
     * for a given recurring billing event.
     */
    private ImmutableSet<DateTime> getExistingBillingTimes(
        Iterable<BillingEvent.OneTime> oneTimesForDomain,
        final BillingEvent.Recurring recurringEvent) {
      return FluentIterable.from(oneTimesForDomain)
          .filter(new Predicate<BillingEvent.OneTime>() {
            @Override
            public boolean apply(OneTime billingEvent) {
              return Key.create(recurringEvent)
                  .equals(billingEvent.getCancellationMatchingBillingEvent());
            }})
          .transform(new Function<OneTime, DateTime>() {
            @Override
            public DateTime apply(OneTime billingEvent) {
              return billingEvent.getBillingTime();
            }})
          .toSet();
    }
  }


  /**
   * "Reducer" to advance the cursor after all map jobs have been completed. The NullInput into the
   * mapper will cause the mapper to emit one timestamp pair (current cursor and execution time),
   * and the cursor will be advanced (and the timestamps logged) at the end of a successful
   * mapreduce.
   */
  public static class ExpandRecurringBillingEventsReducer
      extends Reducer<DateTime, DateTime, Void> {

    private final boolean isDryRun;
    private final DateTime expectedPersistedCursorTime;

    public ExpandRecurringBillingEventsReducer(
        boolean isDryRun, DateTime expectedPersistedCursorTime) {
      this.isDryRun = isDryRun;
      this.expectedPersistedCursorTime = expectedPersistedCursorTime;
    }

    @Override
    public void reduce(final DateTime cursorTime, final ReducerInput<DateTime> executionTimeInput) {
      if (getContext().getCounter(ERROR_COUNTER).getValue() > 0) {
        logger.severefmt("One or more errors logged during recurring event expansion. Cursor will"
            + " not be advanced.");
        return;
      }
      final DateTime executionTime = executionTimeInput.next();
      logger.infofmt(
          "Recurring event expansion %s complete for billing event range [%s, %s).",
          isDryRun ? "(dry run) " : "",
          cursorTime,
          executionTime);
      ofy().transact(new VoidWork() {
        @Override
        public void vrun() {
          Cursor cursor = ofy().load().key(Cursor.createGlobalKey(RECURRING_BILLING)).now();
          DateTime currentCursorTime = (cursor == null ? START_OF_TIME : cursor.getCursorTime());
          if (!currentCursorTime.equals(expectedPersistedCursorTime)) {
            logger.severefmt(
                "Current cursor position %s does not match expected cursor position %s.",
                currentCursorTime,
                expectedPersistedCursorTime);
            return;
          }
          if (!isDryRun) {
            ofy().save().entity(Cursor.createGlobal(RECURRING_BILLING, executionTime));
          }
        }
      });
    }
  }
}