// Copyright 2014 The Bazel 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 com.google.devtools.build.lib.query2.query;

import static com.google.common.collect.ImmutableSet.toImmutableSet;

import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.PackageIdentifier;
import com.google.devtools.build.lib.cmdline.TargetParsingException;
import com.google.devtools.build.lib.cmdline.TargetPattern;
import com.google.devtools.build.lib.cmdline.TargetPattern.Parser;
import com.google.devtools.build.lib.collect.compacthashset.CompactHashSet;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.events.ExtendedEventHandler;
import com.google.devtools.build.lib.graph.Digraph;
import com.google.devtools.build.lib.graph.Node;
import com.google.devtools.build.lib.packages.Attribute;
import com.google.devtools.build.lib.packages.CachingPackageLocator;
import com.google.devtools.build.lib.packages.LabelPrinter;
import com.google.devtools.build.lib.packages.NoSuchThingException;
import com.google.devtools.build.lib.packages.OutputFile;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.pkgcache.TargetEdgeObserver;
import com.google.devtools.build.lib.pkgcache.TargetPatternPreloader;
import com.google.devtools.build.lib.pkgcache.TargetProvider;
import com.google.devtools.build.lib.profiler.Profiler;
import com.google.devtools.build.lib.profiler.SilentCloseable;
import com.google.devtools.build.lib.query2.common.AbstractBlazeQueryEnvironment;
import com.google.devtools.build.lib.query2.common.QueryTransitivePackagePreloader;
import com.google.devtools.build.lib.query2.compat.FakeLoadTarget;
import com.google.devtools.build.lib.query2.engine.Callback;
import com.google.devtools.build.lib.query2.engine.DigraphQueryEvalResult;
import com.google.devtools.build.lib.query2.engine.MinDepthUniquifier;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment;
import com.google.devtools.build.lib.query2.engine.QueryEvalResult;
import com.google.devtools.build.lib.query2.engine.QueryException;
import com.google.devtools.build.lib.query2.engine.QueryExpression;
import com.google.devtools.build.lib.query2.engine.QueryExpressionContext;
import com.google.devtools.build.lib.query2.engine.QueryUtil.MinDepthUniquifierImpl;
import com.google.devtools.build.lib.query2.engine.QueryUtil.ThreadSafeMutableKeyExtractorBackedSetImpl;
import com.google.devtools.build.lib.query2.engine.QueryUtil.UniquifierImpl;
import com.google.devtools.build.lib.query2.engine.SkyframeRestartQueryException;
import com.google.devtools.build.lib.query2.engine.ThreadSafeOutputFormatterCallback;
import com.google.devtools.build.lib.query2.engine.Uniquifier;
import java.io.IOException;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.OptionalInt;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * The environment of a Blaze query. Not thread-safe.
 *
 * <p>This environment is valid only for a single query, called via {@link #evaluateQuery}. Call
 * only once!
 */
public class BlazeQueryEnvironment extends AbstractBlazeQueryEnvironment<Target> {
  private static final int MAX_DEPTH_FULL_SCAN_LIMIT = 20;
  private final Map<String, Collection<Target>> resolvedTargetPatterns = new HashMap<>();
  private final TargetPatternPreloader targetPatternPreloader;
  private final TargetPattern.Parser mainRepoTargetParser;
  @Nullable private final QueryTransitivePackagePreloader queryTransitivePackagePreloader;
  private final TargetProvider targetProvider;
  private final CachingPackageLocator cachingPackageLocator;
  private final Digraph<Target> graph = new Digraph<>();
  private final ErrorPrintingTargetEdgeErrorObserver errorObserver;
  private final LabelVisitor labelVisitor;
  protected final int loadingPhaseThreads;

  private final BlazeTargetAccessor accessor = new BlazeTargetAccessor(this);

  private boolean doneQuery;

  /**
   * Note that the correct operation of this class critically depends on the Reporter being a
   * singleton object, shared by all cooperating classes contributing to Query.
   *
   * @param strictScope if true, fail the whole query if a label goes out of scope.
   * @param loadingPhaseThreads the number of threads to use during loading the packages for the
   *     query.
   * @param labelFilter a predicate that determines if a specific label is allowed to be visited
   *     during query execution. If it returns false, the query execution is stopped with an error
   *     message.
   * @param settings a set of enabled settings
   */
  public BlazeQueryEnvironment(
      @Nullable QueryTransitivePackagePreloader queryTransitivePackagePreloader,
      TargetProvider targetProvider,
      CachingPackageLocator cachingPackageLocator,
      TargetPatternPreloader targetPatternPreloader,
      Parser mainRepoTargetParser,
      boolean keepGoing,
      boolean strictScope,
      int loadingPhaseThreads,
      Predicate<Label> labelFilter,
      ExtendedEventHandler eventHandler,
      Set<Setting> settings,
      Iterable<QueryFunction> extraFunctions,
      LabelPrinter labelPrinter) {
    super(
        keepGoing, strictScope, labelFilter, eventHandler, settings, extraFunctions, labelPrinter);
    this.targetPatternPreloader = targetPatternPreloader;
    this.mainRepoTargetParser = mainRepoTargetParser;
    this.queryTransitivePackagePreloader = queryTransitivePackagePreloader;
    this.targetProvider = targetProvider;
    this.cachingPackageLocator = cachingPackageLocator;
    this.errorObserver = new ErrorPrintingTargetEdgeErrorObserver(this.eventHandler);
    this.loadingPhaseThreads = loadingPhaseThreads;
    this.labelVisitor = new LabelVisitor(targetProvider, dependencyFilter);
  }

  @Override
  public void close() {
    // BlazeQueryEnvironment has no resources that need to be cleaned up.
  }

  @Override
  public DigraphQueryEvalResult<Target> evaluateQuery(
      QueryExpression expr, ThreadSafeOutputFormatterCallback<Target> callback)
      throws QueryException, InterruptedException, IOException {
    Preconditions.checkState(!doneQuery, "Can only use environment for one query: %s", expr);
    doneQuery = true;
    QueryEvalResult queryEvalResult = evaluateQueryInternal(expr, callback);
    return new DigraphQueryEvalResult<>(
        queryEvalResult.getSuccess(),
        queryEvalResult.isEmpty(),
        queryEvalResult.getDetailedExitCode(),
        graph);
  }

  @Override
  public Collection<Target> getSiblingTargetsInPackage(Target target) {
    Collection<Target> siblings = target.getPackage().getTargets().values();
    // Ensure that the sibling targets are in the graph being built-up.
    siblings.forEach(this::getNode);
    return siblings;
  }

  @Override
  public QueryTaskFuture<Void> getTargetsMatchingPattern(
      QueryExpression owner, String pattern, Callback<Target> callback) {
    try {
      getTargetsMatchingPatternImpl(pattern, callback);
      return immediateSuccessfulFuture(null);
    } catch (QueryException e) {
      return immediateFailedFuture(e);
    } catch (InterruptedException e) {
      return immediateCancelledFuture();
    }
  }

  private void getTargetsMatchingPatternImpl(String pattern, Callback<Target> callback)
      throws QueryException, InterruptedException {
    // We can safely ignore the boolean error flag. The evaluateQuery() method above wraps the
    // entire query computation in an error sensor.

    // This must be a collections class with a fast contains() implementation, or the code below
    // becomes quadratic in runtime.
    Set<Target> targets = new LinkedHashSet<>(resolvedTargetPatterns.get(pattern));

    validateScopeOfTargets(targets);

    Set<PackageIdentifier> packages = CompactHashSet.create();
    for (Target target : targets) {
      packages.add(target.getLabel().getPackageIdentifier());
    }

    for (Target target : targets) {
      // This triggers node creation in the Digraph; getOrCreate(X) returns X.
      getOrCreate(target);

      // Preservation of graph order: it is important that targets obtained via
      // a wildcard such as p:* are correctly ordered w.r.t. each other, so to
      // ensure this, we add edges between any pair of directly connected
      // targets in this set.
      if (target instanceof OutputFile) {
        OutputFile outputFile = (OutputFile) target;
        if (targets.contains(outputFile.getGeneratingRule())) {
          makeEdge(outputFile, outputFile.getGeneratingRule());
        }
      } else if (target instanceof Rule) {
        Rule rule = (Rule) target;
        for (Label label : rule.getSortedLabels(dependencyFilter)) {
          if (!packages.contains(label.getPackageIdentifier())) {
            continue; // don't cause additional package loading
          }
          try {
            if (!validateScope(label, strictScope)) {
              continue; // Don't create edges to targets which are out of scope.
            }
            Target to = getTargetOrThrow(label);
            if (targets.contains(to)) {
              makeEdge(rule, to);
            }
          } catch (NoSuchThingException e) {
            /* ignore */
          }
        }
      }
    }
    callback.process(targets);
  }

  @Override
  public Target getTarget(Label label)
      throws TargetNotFoundException, QueryException, InterruptedException {
    // Can't use strictScope here because we are expecting a target back.
    validateScope(label, true);
    try {
      return getNode(getTargetOrThrow(label)).getLabel();
    } catch (NoSuchThingException e) {
      throw new TargetNotFoundException(e, e.getDetailedExitCode());
    }
  }

  private Node<Target> getNode(Target target) {
    return graph.createNode(target);
  }

  private Collection<Node<Target>> getNodes(Iterable<Target> target) {
    Set<Node<Target>> result = new LinkedHashSet<>();
    for (Target t : target) {
      result.add(getNode(t));
    }
    return result;
  }

  @Override
  public Target getOrCreate(Target target) {
    return getNode(target).getLabel();
  }

  @Override
  public Collection<Target> getFwdDeps(
      Iterable<Target> targets, QueryExpressionContext<Target> context) {
    ThreadSafeMutableSet<Target> result = createThreadSafeMutableSet();
    for (Target target : targets) {
      result.addAll(getTargetsFromNodes(getNode(target).getSuccessors()));
    }
    return result;
  }

  @Override
  public Collection<Target> getReverseDeps(
      Iterable<Target> targets, QueryExpressionContext<Target> context) {
    ThreadSafeMutableSet<Target> result = createThreadSafeMutableSet();
    for (Target target : targets) {
      result.addAll(getTargetsFromNodes(getNode(target).getPredecessors()));
    }
    return result;
  }

  @Override
  public ThreadSafeMutableSet<Target> getTransitiveClosure(
      ThreadSafeMutableSet<Target> targetNodes, QueryExpressionContext<Target> context) {
    for (Target node : targetNodes) {
      checkBuilt(node);
    }
    return getTargetsFromNodes(graph.getFwdReachable(getNodes(targetNodes)));
  }

  /**
   * Checks that the graph rooted at 'targetNode' has been completely built; fails if not. Callers
   * of {@link #getTransitiveClosure} must ensure that {@link #buildTransitiveClosure} has been
   * called before.
   *
   * <p>It would be inefficient and failure-prone to make getTransitiveClosure call
   * buildTransitiveClosure directly. Also, it would cause nondeterministic behavior of the
   * operators, since the set of packages loaded (and hence errors reported) would depend on the
   * ordering details of the query operators' implementations.
   */
  private void checkBuilt(Target targetNode) {
    Preconditions.checkState(
        labelVisitor.hasVisited(targetNode.getLabel()),
        "getTransitiveClosure(%s) called without prior call to buildTransitiveClosure()",
        targetNode);
  }

  @Override
  public void buildTransitiveClosure(
      QueryExpression caller, ThreadSafeMutableSet<Target> targetNodes, OptionalInt maxDepth)
      throws QueryException, InterruptedException {
    try (SilentCloseable closeable = Profiler.instance().profile("preloadTransitiveClosure")) {
      preloadTransitiveClosure(targetNodes, maxDepth, caller);
    }
    try (SilentCloseable closeable = Profiler.instance().profile("syncWithVisitor")) {
      labelVisitor.syncWithVisitor(
          eventHandler,
          targetNodes,
          keepGoing,
          loadingPhaseThreads,
          maxDepth,
          new GraphBuildingObserver());
    }

    if (errorObserver.hasErrors()) {
      handleError(
          caller,
          "errors were encountered while computing transitive closure",
          errorObserver.getDetailedExitCode());
    }
  }

  @Override
  public Iterable<Target> getNodesOnPath(
      Target from, Target to, QueryExpressionContext<Target> context) {
    ImmutableList.Builder<Target> builder = ImmutableList.builder();
    for (Node<Target> node : graph.getShortestPath(getNode(from), getNode(to))) {
      builder.add(node.getLabel());
    }
    return builder.build();
  }

  @ThreadSafe
  @Override
  public ThreadSafeMutableSet<Target> createThreadSafeMutableSet() {
    return new ThreadSafeMutableKeyExtractorBackedSetImpl<>(
        TargetKeyExtractor.INSTANCE, Target.class);
  }

  @Override
  public Uniquifier<Target> createUniquifier() {
    return new UniquifierImpl<>(TargetKeyExtractor.INSTANCE);
  }

  @Override
  public MinDepthUniquifier<Target> createMinDepthUniquifier() {
    return new MinDepthUniquifierImpl<>(TargetKeyExtractor.INSTANCE, /*concurrencyLevel=*/ 1);
  }

  @Override
  public TransitiveLoadFilesHelper<Target> getTransitiveLoadFilesHelper() {
    return new TransitiveLoadFilesHelperForTargets() {
      @Override
      public Target getLoadFileTarget(Target originalTarget, Label bzlLabel) {
        return getNode(new FakeLoadTarget(bzlLabel, originalTarget.getPackage())).getLabel();
      }

      @Nullable
      @Override
      public Target maybeGetBuildFileTargetForLoadFileTarget(
          Target originalTarget, Label bzlLabel) {
        PackageIdentifier pkgIdOfBzlLabel = bzlLabel.getPackageIdentifier();
        String baseName = cachingPackageLocator.getBaseNameForLoadedPackage(pkgIdOfBzlLabel);
        if (baseName == null) {
          return null;
        }
        return getNode(
                new FakeLoadTarget(
                    Label.createUnvalidated(pkgIdOfBzlLabel, baseName),
                    originalTarget.getPackage()))
            .getLabel();
      }
    };
  }

  private void preloadTransitiveClosure(
      ThreadSafeMutableSet<Target> targets, OptionalInt maxDepth, QueryExpression callerForError)
      throws InterruptedException, QueryException {
    if (QueryEnvironment.shouldVisit(maxDepth, MAX_DEPTH_FULL_SCAN_LIMIT)
        && queryTransitivePackagePreloader != null) {
      // Only do the full visitation if "maxDepth" is large enough. Otherwise, the benefits of
      // preloading will be outweighed by the cost of doing more work than necessary.
      Set<Label> labels = targets.stream().map(Target::getLabel).collect(toImmutableSet());
      queryTransitivePackagePreloader.preloadTransitiveTargets(
          eventHandler,
          labels,
          keepGoing,
          loadingPhaseThreads,
          // Don't throw an error if in keep-going mode or if the depth was limited: it's possible
          // that an encountered error was deeper than the depth bound.
          keepGoing || maxDepth.isPresent() ? null : callerForError);
    }
  }

  /**
   * It suffices to synchronize the modifications of this.graph from within the
   * GraphBuildingObserver, because that's the only concurrent part. Concurrency is always
   * encapsulated within the evaluation of a single query operator (e.g. deps(), somepath(), etc).
   */
  private class GraphBuildingObserver implements TargetEdgeObserver {

    @Override
    public void edge(Target from, Attribute attribute, Target to) {
      Preconditions.checkState(
          attribute == null || dependencyFilter.test((Rule) from, attribute),
          "Disallowed edge from LabelVisitor: %s --> %s",
          from,
          to);
      makeEdge(from, to);
      errorObserver.edge(from, attribute, to);
    }

    @Override
    public void node(Target node) {
      graph.createNode(node);
      errorObserver.node(node);
    }

    @Override
    public void missingEdge(Target target, Label to, NoSuchThingException e) {
      errorObserver.missingEdge(target, to, e);
    }
  }

  private void makeEdge(Target from, Target to) {
    graph.addEdge(from, to);
  }

  private Target getTargetOrThrow(Label label)
      throws NoSuchThingException, SkyframeRestartQueryException, InterruptedException {
    Target target = targetProvider.getTarget(eventHandler, label);
    if (target == null) {
      throw new SkyframeRestartQueryException();
    }
    return target;
  }


  @Override
  protected void preloadOrThrow(QueryExpression caller, Collection<String> patterns)
      throws TargetParsingException, InterruptedException {
    Preconditions.checkState(
        resolvedTargetPatterns.isEmpty(),
        "Already resolved patterns: %s %s",
        patterns,
        resolvedTargetPatterns);
    // Note that this may throw a RuntimeException if deps are missing in Skyframe and this is
    // being called from within a SkyFunction.
    resolvedTargetPatterns.putAll(
        targetPatternPreloader.preloadTargetPatterns(
            eventHandler, mainRepoTargetParser, patterns, keepGoing));
  }

  @Override
  public TargetAccessor<Target> getAccessor() {
    return accessor;
  }

  /** Given a set of target nodes, returns the targets. */
  private ThreadSafeMutableSet<Target> getTargetsFromNodes(Iterable<Node<Target>> input) {
    ThreadSafeMutableSet<Target> result = createThreadSafeMutableSet();
    for (Node<Target> node : input) {
      result.add(node.getLabel());
    }
    return result;
  }
}