// 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;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Maps;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
import com.google.devtools.build.lib.cmdline.ResolvedTargets;
import com.google.devtools.build.lib.cmdline.TargetParsingException;
import com.google.devtools.build.lib.events.EventHandler;
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.NoSuchThingException;
import com.google.devtools.build.lib.packages.OutputFile;
import com.google.devtools.build.lib.packages.Package;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.pkgcache.PackageProvider;
import com.google.devtools.build.lib.pkgcache.TargetEdgeObserver;
import com.google.devtools.build.lib.pkgcache.TargetPatternEvaluator;
import com.google.devtools.build.lib.pkgcache.TargetProvider;
import com.google.devtools.build.lib.pkgcache.TransitivePackageLoader;
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.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.QueryExpressionEvalListener;
import com.google.devtools.build.lib.query2.engine.QueryUtil.AbstractUniquifier;
import com.google.devtools.build.lib.query2.engine.QueryUtil.AggregateAllCallback;
import com.google.devtools.build.lib.query2.engine.SkyframeRestartQueryException;
import com.google.devtools.build.lib.query2.engine.Uniquifier;
import com.google.devtools.build.lib.query2.engine.VariableContext;
import com.google.devtools.build.lib.util.Preconditions;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * The environment of a Blaze query. Not thread-safe.
 */
public class BlazeQueryEnvironment extends AbstractBlazeQueryEnvironment<Target> {

  private static final int MAX_DEPTH_FULL_SCAN_LIMIT = 20;
  private final Map<String, Set<Target>> resolvedTargetPatterns = new HashMap<>();
  private final TargetPatternEvaluator targetPatternEvaluator;
  private final TransitivePackageLoader transitivePackageLoader;
  private final TargetProvider targetProvider;
  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);

  /**
   * 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
   */
  BlazeQueryEnvironment(TransitivePackageLoader transitivePackageLoader,
      PackageProvider packageProvider,
      TargetPatternEvaluator targetPatternEvaluator,
      boolean keepGoing,
      boolean strictScope,
      int loadingPhaseThreads,
      Predicate<Label> labelFilter,
      EventHandler eventHandler,
      Set<Setting> settings,
      Iterable<QueryFunction> extraFunctions,
      QueryExpressionEvalListener<Target> evalListener) {
    super(
        keepGoing, strictScope, labelFilter, eventHandler, settings, extraFunctions, evalListener);
    this.targetPatternEvaluator = targetPatternEvaluator;
    this.transitivePackageLoader = transitivePackageLoader;
    this.targetProvider = packageProvider;
    this.errorObserver = new ErrorPrintingTargetEdgeErrorObserver(this.eventHandler);
    this.loadingPhaseThreads = loadingPhaseThreads;
    this.labelVisitor = new LabelVisitor(packageProvider, dependencyFilter);
  }

  /**
   * Calling close is optional because {@link BlazeQueryEnvironment} has no resources that need
   * manual management.
   */
  @Override
  public void close() {}

  @Override
  public DigraphQueryEvalResult<Target> evaluateQuery(QueryExpression expr,
      final Callback<Target> callback) throws QueryException, InterruptedException {
    // Some errors are reported as QueryExceptions and others as ERROR events (if --keep_going). The
    // result is set to have an error iff there were errors emitted during the query, so we reset
    // errors here.
    eventHandler.resetErrors();
    final AtomicBoolean empty = new AtomicBoolean(true);
    resolvedTargetPatterns.clear();
    QueryEvalResult queryEvalResult = super.evaluateQuery(expr, new Callback<Target>() {
      @Override
      public void process(Iterable<Target> partialResult)
          throws QueryException, InterruptedException {
        empty.compareAndSet(true, Iterables.isEmpty(partialResult));
        callback.process(partialResult);
      }
    });
    return new DigraphQueryEvalResult<>(queryEvalResult.getSuccess(), empty.get(), graph);
  }

  @Override
  public void getTargetsMatchingPattern(
      QueryExpression caller, 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.

    Set<Target> targets = new LinkedHashSet<>(resolvedTargetPatterns.get(pattern));

    // Sets.filter would be more convenient here, but can't deal with exceptions.
    Iterator<Target> targetIterator = targets.iterator();
    while (targetIterator.hasNext()) {
      Target target = targetIterator.next();
      if (!validateScope(target.getLabel(), strictScope)) {
        targetIterator.remove();
      }
    }

    Set<PathFragment> packages = new HashSet<>();
    for (Target target : targets) {
      packages.add(target.getLabel().getPackageFragment());
    }

    Set<Target> result = new LinkedHashSet<>();
    for (Target target : targets) {
      result.add(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.getLabels(dependencyFilter)) {
          if (!packages.contains(label.getPackageFragment())) {
            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(result);
  }

  @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);
    }
  }

  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) {
    Set<Target> result = new HashSet<>();
    for (Target target : targets) {
      result.addAll(getTargetsFromNodes(getNode(target).getSuccessors()));
    }
    return result;
  }

  @Override
  public Collection<Target> getReverseDeps(Iterable<Target> targets) {
    Set<Target> result = new HashSet<>();
    for (Target target : targets) {
      result.addAll(getTargetsFromNodes(getNode(target).getPredecessors()));
    }
    return result;
  }

  @Override
  public Set<Target> getTransitiveClosure(Set<Target> targetNodes) {
    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,
                                     Set<Target> targetNodes,
                                     int maxDepth) throws QueryException, InterruptedException {
    Set<Target> targets = targetNodes;
    preloadTransitiveClosure(targets, maxDepth);
    labelVisitor.syncWithVisitor(eventHandler, targets, keepGoing,
        loadingPhaseThreads, maxDepth, errorObserver, new GraphBuildingObserver());

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

  @Override
  public Set<Target> getNodesOnPath(Target from, Target to) {
    return getTargetsFromNodes(graph.getShortestPath(getNode(from), getNode(to)));
  }

  @Override
  public void eval(QueryExpression expr, VariableContext<Target> context, Callback<Target> callback)
      throws QueryException, InterruptedException {
    AggregateAllCallback<Target> aggregator = new AggregateAllCallback<>();
    expr.eval(this, context, aggregator);
    callback.process(aggregator.getResult());
  }

  @Override
  public Uniquifier<Target> createUniquifier() {
    return new AbstractUniquifier<Target, Label>() {
      @Override
      protected Label extractKey(Target target) {
        return target.getLabel();
      }
    };
  }

  private void preloadTransitiveClosure(Set<Target> targets, int maxDepth)
      throws QueryException, InterruptedException {
    if (maxDepth >= MAX_DEPTH_FULL_SCAN_LIMIT && transitivePackageLoader != 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.
      transitivePackageLoader.sync(
          eventHandler, targets, ImmutableSet.<Label>of(), keepGoing, loadingPhaseThreads, -1);
    }
  }

  /**
   * 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 synchronized void edge(Target from, Attribute attribute, Target to) {
      Preconditions.checkState(attribute == null ||
          dependencyFilter.apply(((Rule) from), attribute),
          "Disallowed edge from LabelVisitor: %s --> %s", from, to);
      makeEdge(from, to);
    }

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

    @Override
    public void missingEdge(Target target, Label to, NoSuchThingException e) {
      // No - op.
    }
  }

  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;
  }

  // TODO(bazel-team): rename this to getDependentFiles when all implementations
  // of QueryEnvironment is fixed.
  @Override
  public Set<Target> getBuildFiles(
      final QueryExpression caller,
      Set<Target> nodes,
      boolean buildFiles,
      boolean subincludes,
      boolean loads)
      throws QueryException {
    Set<Target> dependentFiles = new LinkedHashSet<>();
    Set<Package> seenPackages = new HashSet<>();
    // Keep track of seen labels, to avoid adding a fake subinclude label that also exists as a
    // real target.
    Set<Label> seenLabels = new HashSet<>();

    // Adds all the package definition files (BUILD files and build
    // extensions) for package "pkg", to "buildfiles".
    for (Target x : nodes) {
      Package pkg = x.getPackage();
      if (seenPackages.add(pkg)) {
        if (buildFiles) {
          addIfUniqueLabel(getNode(pkg.getBuildFile()), seenLabels, dependentFiles);
        }

        List<Label> extensions = new ArrayList<>();
        if (subincludes) {
          extensions.addAll(pkg.getSubincludeLabels());
        }
        if (loads) {
          extensions.addAll(pkg.getSkylarkFileDependencies());
        }

        for (Label subinclude : extensions) {
          addIfUniqueLabel(getSubincludeTarget(subinclude, pkg), seenLabels, dependentFiles);

          // Also add the BUILD file of the subinclude.
          if (buildFiles) {
            try {
              addIfUniqueLabel(
                  getSubincludeTarget(subinclude.getLocalTargetLabel("BUILD"), pkg),
                  seenLabels,
                  dependentFiles);

            } catch (LabelSyntaxException e) {
              throw new AssertionError("BUILD should always parse as a target name", e);
            }
          }
        }
      }
    }
    return dependentFiles;
  }

  private static final Function<ResolvedTargets<Target>, Set<Target>> RESOLVED_TARGETS_TO_TARGETS =
      new Function<ResolvedTargets<Target>, Set<Target>>() {
        @Override
        public Set<Target> apply(ResolvedTargets<Target> resolvedTargets) {
          return resolvedTargets.getTargets();
        }
      };

  @Override
  protected void preloadOrThrow(QueryExpression caller, Collection<String> patterns)
      throws TargetParsingException, InterruptedException {
    if (!resolvedTargetPatterns.keySet().containsAll(patterns)) {
      // Note that this may throw a RuntimeException if deps are missing in Skyframe and this is
      // being called from within a SkyFunction.
      resolvedTargetPatterns.putAll(
          Maps.transformValues(
              targetPatternEvaluator.preloadTargetPatterns(eventHandler, patterns, keepGoing),
              RESOLVED_TARGETS_TO_TARGETS));
    }
  }

  private static void addIfUniqueLabel(Node<Target> node, Set<Label> labels, Set<Target> nodes) {
    if (labels.add(node.getLabel().getLabel())) {
      nodes.add(node.getLabel());
    }
  }

  private Node<Target> getSubincludeTarget(final Label label, Package pkg) {
    return getNode(new FakeSubincludeTarget(label, pkg));
  }

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

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