// Copyright (C) 2012 The Android Open Source Project
//
// 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 com.google.gerrit.server.project;

import com.google.common.collect.Streams;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.data.SubmitRecord;
import com.google.gerrit.common.data.SubmitTypeRecord;
import com.google.gerrit.entities.Change;
import com.google.gerrit.exceptions.StorageException;
import com.google.gerrit.metrics.Description;
import com.google.gerrit.metrics.Description.Units;
import com.google.gerrit.metrics.MetricMaker;
import com.google.gerrit.metrics.Timer0;
import com.google.gerrit.server.index.OnlineReindexMode;
import com.google.gerrit.server.plugincontext.PluginSetContext;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.rules.PrologRule;
import com.google.gerrit.server.rules.SubmitRule;
import com.google.inject.Inject;
import com.google.inject.assistedinject.Assisted;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

/**
 * Evaluates a submit-like Prolog rule found in the rules.pl file of the current project and filters
 * the results through rules found in the parent projects, all the way up to All-Projects.
 */
public class SubmitRuleEvaluator {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();

  private static final String DEFAULT_MSG = "Error evaluating project rules, check server log";

  private final ProjectCache projectCache;
  private final PrologRule prologRule;
  private final PluginSetContext<SubmitRule> submitRules;
  private final Timer0 submitRuleEvaluationLatency;
  private final Timer0 submitTypeEvaluationLatency;
  private final SubmitRuleOptions opts;

  public interface Factory {
    /** Returns a new {@link SubmitRuleEvaluator} with the specified options */
    SubmitRuleEvaluator create(SubmitRuleOptions options);
  }

  @Inject
  private SubmitRuleEvaluator(
      ProjectCache projectCache,
      PrologRule prologRule,
      PluginSetContext<SubmitRule> submitRules,
      MetricMaker metricMaker,
      @Assisted SubmitRuleOptions options) {
    this.projectCache = projectCache;
    this.prologRule = prologRule;
    this.submitRules = submitRules;
    this.submitRuleEvaluationLatency =
        metricMaker.newTimer(
            "change/submit_rule_evaluation",
            new Description("Latency for evaluating submit rules on a change.")
                .setCumulative()
                .setUnit(Units.MILLISECONDS));
    this.submitTypeEvaluationLatency =
        metricMaker.newTimer(
            "change/submit_type_evaluation",
            new Description("Latency for evaluating the submit type on a change.")
                .setCumulative()
                .setUnit(Units.MILLISECONDS));

    this.opts = options;
  }

  public static SubmitRecord defaultRuleError() {
    return createRuleError(DEFAULT_MSG);
  }

  public static SubmitRecord createRuleError(String err) {
    SubmitRecord rec = new SubmitRecord();
    rec.status = SubmitRecord.Status.RULE_ERROR;
    rec.errorMessage = err;
    return rec;
  }

  public static SubmitTypeRecord defaultTypeError() {
    return SubmitTypeRecord.error(DEFAULT_MSG);
  }

  /**
   * Evaluate the submit rules.
   *
   * @return List of {@link SubmitRecord} objects returned from the evaluated rules, including any
   *     errors.
   * @param cd ChangeData to evaluate
   */
  public List<SubmitRecord> evaluate(ChangeData cd) {
    try (Timer0.Context ignored = submitRuleEvaluationLatency.start()) {
      Change change;
      ProjectState projectState;
      try {
        change = cd.change();
        if (change == null) {
          throw new StorageException("Change not found");
        }

        projectState = projectCache.get(cd.project());
        if (projectState == null) {
          throw new NoSuchProjectException(cd.project());
        }
      } catch (StorageException | NoSuchProjectException e) {
        return Collections.singletonList(ruleError("Error looking up change " + cd.getId(), e));
      }

      if ((!opts.allowClosed() || OnlineReindexMode.isActive()) && change.isClosed()) {
        SubmitRecord rec = new SubmitRecord();
        rec.status = SubmitRecord.Status.CLOSED;
        return Collections.singletonList(rec);
      }

      // We evaluate all the plugin-defined evaluators,
      // and then we collect the results in one list.
      return Streams.stream(submitRules)
          .map(c -> c.call(s -> s.evaluate(cd)))
          .filter(Optional::isPresent)
          .map(Optional::get)
          .collect(Collectors.toList());
    }
  }

  private SubmitRecord ruleError(String err, Exception e) {
    logger.atSevere().withCause(e).log(err);
    return defaultRuleError();
  }

  /**
   * Evaluate the submit type rules to get the submit type.
   *
   * @return record from the evaluated rules.
   * @param cd
   */
  public SubmitTypeRecord getSubmitType(ChangeData cd) {
    try (Timer0.Context ignored = submitTypeEvaluationLatency.start()) {
      ProjectState projectState;
      try {
        projectState = projectCache.get(cd.project());
        if (projectState == null) {
          throw new NoSuchProjectException(cd.project());
        }
      } catch (NoSuchProjectException e) {
        return typeError("Error looking up change " + cd.getId(), e);
      }

      return prologRule.getSubmitType(cd);
    }
  }

  private SubmitTypeRecord typeError(String err, Exception e) {
    logger.atSevere().withCause(e).log(err);
    return defaultTypeError();
  }
}