// Copyright 2016 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.analysis.actions;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.actions.ActionAnalysisMetadata;
import com.google.devtools.build.lib.actions.ActionInputHelper;
import com.google.devtools.build.lib.actions.ActionOwner;
import com.google.devtools.build.lib.actions.Actions;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
import com.google.devtools.build.lib.actions.ArtifactOwner;
import com.google.devtools.build.lib.actions.ArtifactPrefixConflictException;
import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
import com.google.devtools.build.lib.analysis.FilesToRunProvider;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
import com.google.devtools.build.lib.util.Preconditions;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.util.Map;

/**
 * A placeholder action that, at execution time, expands into a list of {@link SpawnAction}s that
 * will be executed.
 *
 * <p>SpawnActionTemplate is for users who want to dynamically register SpawnActions operating on
 * individual {@link TreeFileArtifact} inside input and output TreeArtifacts at execution time.
 *
 * <p>It takes in one TreeArtifact and generates one TreeArtifact. The following happens at
 * execution time for SpawnActionTemplate:
 * <ol>
 *   <li>Input TreeArtifact is resolved.
 *   <li>For each individual {@link TreeFileArtifact} inside input TreeArtifact, generate an output
 *       {@link TreeFileArtifact} inside output TreeArtifact at the parent-relative path provided by
 *       {@link OutputPathMapper}.
 *   <li>For each pair of input and output {@link TreeFileArtifact}s, generate an associated
 *       {@link SpawnAction}.
 *   <li>All expanded {@link SpawnAction}s are executed and their output {@link TreeFileArtifact}s
 *       collected.
 *   <li>Output TreeArtifact is resolved.
 * </ol>
 */
public final class SpawnActionTemplate implements ActionAnalysisMetadata {
  private final Artifact inputTreeArtifact;
  private final Artifact outputTreeArtifact;
  private final NestedSet<Artifact> commonInputs;
  private final NestedSet<Artifact> allInputs;
  private final NestedSet<Artifact> commonTools;
  private final ActionOwner actionOwner;
  private final String mnemonic;
  private final OutputPathMapper outputPathMapper;
  private final SpawnAction.Builder spawnActionBuilder;
  private final CustomCommandLine commandLineTemplate;

  /**
   * Interface providing mapping between expanded input files under the input TreeArtifact and
   * parent-relative paths of their associated output file under the output TreeArtifact.
   *
   * <p>Users of SpawnActionTemplate must provide a mapper object implementing this interface.
   * SpawnActionTemplate uses the mapper to query for the path of output artifact associated with
   * each input {@link TreeFileArtifact} resolved at execution time.
   */
  public interface OutputPathMapper {
   /**
    * Given the input {@link TreeFileArtifact}, returns the parent-relative path of the associated
    * output {@link TreeFileArtifact}.
    *
    * @param input the input {@link TreeFileArtifact}
    */
    PathFragment parentRelativeOutputPath(TreeFileArtifact input);
  }

  private SpawnActionTemplate(
      ActionOwner actionOwner,
      Artifact inputTreeArtifact,
      Artifact outputTreeArtifact,
      NestedSet<Artifact> commonInputs,
      NestedSet<Artifact> commonTools,
      OutputPathMapper outputPathMapper,
      CustomCommandLine commandLineTemplate,
      String mnemonic,
      SpawnAction.Builder spawnActionBuilder) {
    this.inputTreeArtifact = inputTreeArtifact;
    this.outputTreeArtifact = outputTreeArtifact;
    this.commonTools = commonTools;
    this.commonInputs = NestedSetBuilder.<Artifact>stableOrder()
        .addTransitive(commonInputs)
        .addTransitive(commonTools)
        .build();
    this.allInputs = NestedSetBuilder.<Artifact>stableOrder()
        .add(inputTreeArtifact)
        .addTransitive(this.commonInputs)
        .build();
    this.outputPathMapper = outputPathMapper;
    this.actionOwner = actionOwner;
    this.mnemonic = mnemonic;
    this.spawnActionBuilder = spawnActionBuilder;
    this.commandLineTemplate = commandLineTemplate;
  }

  /**
   * Given a list of input TreeFileArtifacts resolved at execution time, returns a list of expanded
   * SpawnActions to be executed.
   *
   * @param inputTreeFileArtifacts the list of {@link TreeFileArtifact}s inside input TreeArtifact
   *     resolved at execution time
   * @param artifactOwner the {@link ArtifactOwner} of the generated output
   *     {@link TreeFileArtifact}s
   * @return a list of expanded {@link SpawnAction}s to execute, one for each input
   *     {@link TreeFileArtifact}
   * @throws ActionConflictException if the expanded actions have duplicated outputs
   * @throws ArtifactPrefixConflictException if there is prefix conflict among the outputs of
   *     expanded actions
   */
  public Iterable<SpawnAction> generateActionForInputArtifacts(
      Iterable<TreeFileArtifact> inputTreeFileArtifacts, ArtifactOwner artifactOwner)
      throws ActionConflictException,  ArtifactPrefixConflictException {
    ImmutableList.Builder<SpawnAction> expandedActions = new ImmutableList.Builder<>();
    for (TreeFileArtifact inputTreeFileArtifact : inputTreeFileArtifacts) {
      PathFragment parentRelativeOutputPath =
          outputPathMapper.parentRelativeOutputPath(inputTreeFileArtifact);

      TreeFileArtifact outputTreeFileArtifact = createTreeFileArtifact(
          outputTreeArtifact,
          checkOutputParentRelativePath(parentRelativeOutputPath),
          artifactOwner);

      expandedActions.add(createAction(inputTreeFileArtifact, outputTreeFileArtifact));
    }

    Iterable<SpawnAction> actions = expandedActions.build();
    checkActionAndArtifactConflicts(ImmutableList.<ActionAnalysisMetadata>copyOf(actions));
    return actions;
  }

  /**
   * Returns a SpawnAction that takes inputTreeFileArtifact as input and generates
   * outputTreeFileArtifact.
   */
  private SpawnAction createAction(
      TreeFileArtifact inputTreeFileArtifact, TreeFileArtifact outputTreeFileArtifact) {
    SpawnAction.Builder actionBuilder = new SpawnAction.Builder(spawnActionBuilder);
    actionBuilder.addInput(inputTreeFileArtifact);
    actionBuilder.addOutput(outputTreeFileArtifact);

    CommandLine commandLine = commandLineTemplate.evaluateTreeFileArtifacts(
        ImmutableList.of(inputTreeFileArtifact, outputTreeFileArtifact));
    actionBuilder.setCommandLine(commandLine);

    // Note that we pass in nulls below because SpawnActionTemplate does not support param file, and
    // it does not use any default value for executable or shell environment. They must be set
    // explicitly via builder method #setExecutable and #setEnvironment.
    return actionBuilder.buildSpawnAction(
        getOwner(),
        /*defaultShellEnvironment=*/ null,
        /*variableShellEnvironment=*/ null,
        /*defaultShellExecutable=*/ null,
        /*paramsFile=*/ null,
        /*paramFileWriteAction=*/ null);
  }

  private static void checkActionAndArtifactConflicts(Iterable<ActionAnalysisMetadata> actions)
      throws ActionConflictException,  ArtifactPrefixConflictException {
    Map<Artifact, ActionAnalysisMetadata> generatingActions =
        Actions.findAndThrowActionConflict(actions);
    Map<ActionAnalysisMetadata, ArtifactPrefixConflictException> artifactPrefixConflictMap =
        Actions.findArtifactPrefixConflicts(generatingActions);

    if (!artifactPrefixConflictMap.isEmpty()) {
      throw artifactPrefixConflictMap.values().iterator().next();
    }

    return;
  }

  private static PathFragment checkOutputParentRelativePath(PathFragment parentRelativeOutputPath) {
    Preconditions.checkArgument(
        parentRelativeOutputPath.isNormalized() && !parentRelativeOutputPath.isAbsolute(),
        "%s is not a proper relative path",
        parentRelativeOutputPath);
    return parentRelativeOutputPath;
  }

  private static TreeFileArtifact createTreeFileArtifact(Artifact parentTreeArtifact,
      PathFragment parentRelativeOutputPath, ArtifactOwner artifactOwner) {
    return ActionInputHelper.treeFileArtifact(
        parentTreeArtifact,
        parentRelativeOutputPath,
        artifactOwner);
  }


  /**
   * Returns the input TreeArtifact.
   *
   * <p>This method is called by Skyframe to expand the input TreeArtifact into child
   * TreeFileArtifacts. Skyframe then expands this SpawnActionTemplate with the TreeFileArtifacts
   * through {@link #generateActionForInputArtifacts}.
   */
  public Artifact getInputTreeArtifact() {
    return inputTreeArtifact;
  }

  /** Returns the output TreeArtifact. */
  public Artifact getOutputTreeArtifact() {
    return outputTreeArtifact;
  }

  @Override
  public ActionOwner getOwner() {
    return actionOwner;
  }


  @Override
  public final String getMnemonic() {
    return mnemonic;
  }

  @Override
  public Iterable<Artifact> getTools() {
    return commonTools;
  }

  @Override
  public Iterable<Artifact> getInputs() {
    return allInputs;
  }

  @Override
  public ImmutableSet<Artifact> getOutputs() {
    return ImmutableSet.of(outputTreeArtifact);
  }

  @Override
  public Iterable<Artifact> getMandatoryInputs() {
    return getInputs();
  }

  @Override
  public ImmutableSet<Artifact> getMandatoryOutputs() {
    return ImmutableSet.of();
  }

  @Override
  public Artifact getPrimaryInput() {
    return inputTreeArtifact;
  }

  @Override
  public Artifact getPrimaryOutput() {
    return outputTreeArtifact;
  }

  @Override
  public Iterable<String> getClientEnvironmentVariables() {
    return spawnActionBuilder
        .buildSpawnAction(getOwner(), null, null, null, null, null)
        .getClientEnvironmentVariables();
  }

  @Override
  public boolean shouldReportPathPrefixConflict(ActionAnalysisMetadata action) {
    return this != action;
  }

  @Override
  public MiddlemanType getActionType() {
    return MiddlemanType.NORMAL;
  }

  @Override
  public String prettyPrint() {
    return String.format("action template with output TreeArtifact %s",
        outputTreeArtifact.prettyPrint());
  }

  /** Builder class to construct {@link SpawnActionTemplate} instances. */
  public static class Builder {
    private String actionTemplateMnemonic = "Unknown";
    private OutputPathMapper outputPathMapper;
    private CustomCommandLine commandLineTemplate;
    private PathFragment executable;

    private final Artifact inputTreeArtifact;
    private final Artifact outputTreeArtifact;
    private final NestedSetBuilder<Artifact> inputsBuilder = NestedSetBuilder.stableOrder();
    private final NestedSetBuilder<Artifact> toolsBuilder = NestedSetBuilder.stableOrder();
    private final SpawnAction.Builder spawnActionBuilder;

    /**
     * Creates a {@link SpawnActionTemplate} builder.
     * 
     * @param inputTreeArtifact the required input TreeArtifact.
     * @param outputTreeArtifact the required output TreeArtifact.
     */
    public Builder(Artifact inputTreeArtifact, Artifact outputTreeArtifact) {
      Preconditions.checkState(
          inputTreeArtifact.isTreeArtifact() && outputTreeArtifact.isTreeArtifact(),
          "Either %s or %s is not a TreeArtifact",
          inputTreeArtifact,
          outputTreeArtifact);
      this.inputTreeArtifact = inputTreeArtifact;
      this.outputTreeArtifact = outputTreeArtifact;
      this.spawnActionBuilder = new SpawnAction.Builder();
    }


    /**
     * Sets the mnemonics for both the {@link SpawnActionTemplate} and expanded {@link SpawnAction}.
     */
    public Builder setMnemonics(String actionTemplateMnemonic, String expandedActionMnemonic) {
      this.actionTemplateMnemonic = actionTemplateMnemonic;
      spawnActionBuilder.setMnemonic(expandedActionMnemonic);
      return this;
    }

    /**
     * Adds common tool artifacts. All common tool artifacts will be added as tool artifacts for
     * expanded actions.
     */
    public Builder addCommonTools(Iterable<Artifact> artifacts) {
      toolsBuilder.addAll(artifacts);
      spawnActionBuilder.addTools(artifacts);
      return this;
    }

    /**
     * Adds common tool artifacts. All common tool artifacts will be added as input tool artifacts
     * for expanded actions.
     */
    public Builder addCommonTool(FilesToRunProvider tool) {
      toolsBuilder.addAll(tool.getFilesToRun());
      spawnActionBuilder.addTool(tool);
      return this;
    }

    /**
     * Adds common input artifacts. All common input artifacts will be added as input artifacts for
     * expanded actions.
     */
    public Builder addCommonInputs(Iterable<Artifact> artifacts) {
      inputsBuilder.addAll(artifacts);
      spawnActionBuilder.addInputs(artifacts);
      return this;
    }

    /**
     * Adds transitive common input artifacts. All common input artifacts will be added as input
     * artifacts for expanded actions.
     */
    public Builder addCommonTransitiveInputs(NestedSet<Artifact> artifacts) {
      inputsBuilder.addTransitive(artifacts);
      spawnActionBuilder.addTransitiveInputs(artifacts);
      return this;
    }

    /** Sets the map of environment variables for expanded actions. */
    public Builder setEnvironment(Map<String, String> environment) {
      spawnActionBuilder.setEnvironment(environment);
      return this;
    }

    /**
     * Sets the map of execution info for expanded actions.
     */
    public Builder setExecutionInfo(Map<String, String> executionInfo) {
      spawnActionBuilder.setExecutionInfo(executionInfo);
      return this;
    }

    /**
     * Sets the executable used by expanded actions as a configured target. Automatically adds the
     * files to run to the tools and uses the executable of the target as the executable.
     *
     * <p>Calling this method overrides any previous values set via calls to
     * {@link #setExecutable(Artifact)} and {@link #setExecutable(PathFragment)}.
     */
    public Builder setExecutable(FilesToRunProvider executableProvider) {
      Preconditions.checkArgument(
          executableProvider.getExecutable() != null, "The target does not have an executable");
      spawnActionBuilder.setExecutable(executableProvider);
      addCommonTool(executableProvider);
      this.executable = executableProvider.getExecutable().getExecPath();
      return this;
    }

    /**
     * Sets the executable path used by expanded actions. The path is interpreted relative to the
     * execution root.
     *
     * <p>Calling this method overrides any previous values set via calls to
     * {@link #setExecutable(Artifact)} and {@link #setExecutable(FilesToRunProvider)}.
     */
    public Builder setExecutable(PathFragment executable) {
      spawnActionBuilder.setExecutable(executable);
      this.executable = executable;
      return this;
    }

    /**
     * Sets the executable artifact used by expanded actions. The path is interpreted relative to
     * the execution root.
     *
     * <p>Calling this method overrides any previous values set via calls to
     * {@link #setExecutable(FilesToRunProvider)} and {@link #setExecutable(PathFragment)}.
     */
    public Builder setExecutable(Artifact artifact) {
      spawnActionBuilder.setExecutable(artifact);
      addCommonTools(ImmutableList.of(artifact));
      this.executable = artifact.getExecPath();
      return this;
    }

    /**
     * Sets the command line template used to expand actions.
     */
    public Builder setCommandLineTemplate(CustomCommandLine commandLineTemplate) {
      this.commandLineTemplate = commandLineTemplate;
      return this;
    }

    /**
     * Sets the {@link OutputPathMapper} object used to get the parent-relative paths of output
     * {@link TreeFileArtifact}.
     */
    public Builder setOutputPathMapper(OutputPathMapper outputPathMapper) {
      this.outputPathMapper = outputPathMapper;
      return this;
    }

    /**
     * Builds and returns the {@link SpawnActionTemplate} using the accumulated builder information.
     *
     * @param actionOwner the action owner of the SpawnActionTemplate to be built.
     */
    public SpawnActionTemplate build(ActionOwner actionOwner) {
      Preconditions.checkNotNull(executable);

      return new SpawnActionTemplate(
          actionOwner,
          Preconditions.checkNotNull(inputTreeArtifact),
          Preconditions.checkNotNull(outputTreeArtifact),
          inputsBuilder.build(),
          toolsBuilder.build(),
          Preconditions.checkNotNull(outputPathMapper),
          Preconditions.checkNotNull(commandLineTemplate),
          actionTemplateMnemonic,
          spawnActionBuilder);
    }
  }
}