// Copyright 2015 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.rules.objc;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.devtools.build.lib.rules.cpp.Link.LINK_LIBRARY_FILETYPES;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.DYNAMIC_FRAMEWORK_FILE;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.FORCE_LOAD_LIBRARY;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.IMPORTED_LIBRARY;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.LIBRARY;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.LINK_INPUTS;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.SDK_DYLIB;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.SDK_FRAMEWORK;
import static com.google.devtools.build.lib.rules.objc.ObjcProvider.STATIC_FRAMEWORK_FILE;
import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.COMPILABLE_SRCS_TYPE;
import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.HEADERS;
import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.NON_ARC_SRCS_TYPE;
import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.PRECOMPILED_SRCS_TYPE;
import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.SRCS_TYPE;
import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.STRIP;
import static java.nio.charset.StandardCharsets.ISO_8859_1;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import com.google.devtools.build.lib.actions.ActionAnalysisMetadata;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.CommandLine;
import com.google.devtools.build.lib.actions.ParamFileInfo;
import com.google.devtools.build.lib.actions.ParameterFile;
import com.google.devtools.build.lib.analysis.AnalysisEnvironment;
import com.google.devtools.build.lib.analysis.AnalysisUtils;
import com.google.devtools.build.lib.analysis.FilesToRunProvider;
import com.google.devtools.build.lib.analysis.PrerequisiteArtifacts;
import com.google.devtools.build.lib.analysis.RuleContext;
import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
import com.google.devtools.build.lib.analysis.actions.CustomCommandLine.VectorArg;
import com.google.devtools.build.lib.analysis.actions.ParameterFileWriteAction;
import com.google.devtools.build.lib.analysis.config.BuildConfigurationValue;
import com.google.devtools.build.lib.analysis.test.InstrumentedFilesCollector;
import com.google.devtools.build.lib.analysis.test.InstrumentedFilesCollector.InstrumentationSpec;
import com.google.devtools.build.lib.analysis.test.InstrumentedFilesCollector.LocalMetadataCollector;
import com.google.devtools.build.lib.analysis.test.InstrumentedFilesInfo;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
import com.google.devtools.build.lib.collect.nestedset.Order;
import com.google.devtools.build.lib.packages.BuildType;
import com.google.devtools.build.lib.packages.RuleClass.ConfiguredTargetFactory.RuleErrorException;
import com.google.devtools.build.lib.packages.TargetUtils;
import com.google.devtools.build.lib.rules.apple.AppleCommandLineOptions.AppleBitcodeMode;
import com.google.devtools.build.lib.rules.apple.AppleConfiguration;
import com.google.devtools.build.lib.rules.apple.XcodeConfigInfo;
import com.google.devtools.build.lib.rules.cpp.CcCommon;
import com.google.devtools.build.lib.rules.cpp.CcCompilationContext;
import com.google.devtools.build.lib.rules.cpp.CcCompilationOutputs;
import com.google.devtools.build.lib.rules.cpp.CcLinkingContext;
import com.google.devtools.build.lib.rules.cpp.CcLinkingHelper;
import com.google.devtools.build.lib.rules.cpp.CcToolchain;
import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.FeatureConfiguration;
import com.google.devtools.build.lib.rules.cpp.CcToolchainProvider;
import com.google.devtools.build.lib.rules.cpp.CppConfiguration;
import com.google.devtools.build.lib.rules.cpp.CppHelper;
import com.google.devtools.build.lib.rules.cpp.CppLinkAction;
import com.google.devtools.build.lib.rules.cpp.CppLinkActionBuilder;
import com.google.devtools.build.lib.rules.cpp.CppRuleClasses;
import com.google.devtools.build.lib.rules.cpp.CppSemantics;
import com.google.devtools.build.lib.rules.cpp.Link.LinkTargetType;
import com.google.devtools.build.lib.rules.cpp.Link.LinkingMode;
import com.google.devtools.build.lib.rules.objc.ObjcProvider.Flag;
import com.google.devtools.build.lib.rules.objc.ObjcVariablesExtension.VariableCategory;
import com.google.devtools.build.lib.util.FileTypeSet;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import net.starlark.java.annot.StarlarkMethod;
import net.starlark.java.eval.StarlarkValue;

/**
 * Support for rules that compile sources. Provides ways to determine files that should be output,
 * registering Xcode settings and generating the various actions that might be needed for
 * compilation.
 *
 * <p>A subclass should express a particular strategy for compile and link action registration.
 * Subclasses should implement the API without adding new visible methods - rule implementations
 * should be able to use a {@link CompilationSupport} instance to compile and link source without
 * knowing the subclass being used.
 *
 * <p>Methods on this class can be called in any order without impacting the result.
 */
public class CompilationSupport implements StarlarkValue {

  @VisibleForTesting static final String OBJC_MODULE_CACHE_DIR_NAME = "_objc_module_cache";

  @VisibleForTesting
  static final String ABSOLUTE_INCLUDES_PATH_FORMAT =
      "The path '%s' is absolute, but only relative paths are allowed.";

  // Flags for clang 6.1(xcode 6.4)
  @VisibleForTesting
  static final ImmutableList<String> CLANG_GCOV_COVERAGE_FLAGS =
      ImmutableList.of("-fprofile-arcs", "-ftest-coverage");

  @VisibleForTesting
  static final ImmutableList<String> CLANG_LLVM_COVERAGE_FLAGS =
      ImmutableList.of("-fprofile-instr-generate", "-fcoverage-mapping");

  // These are added by Xcode when building, because the simulator is built on OSX
  // frameworks so we aim compile to match the OSX objc runtime.
  @VisibleForTesting
  static final ImmutableList<String> SIMULATOR_COMPILE_FLAGS =
      ImmutableList.of(
          "-fexceptions", "-fasm-blocks", "-fobjc-abi-version=2", "-fobjc-legacy-dispatch");

  /**
   * Frameworks implicitly linked to iOS, watchOS, and tvOS binaries when using legacy compilation.
   */
  @VisibleForTesting
  static final NestedSet<String> AUTOMATIC_SDK_FRAMEWORKS =
      NestedSetBuilder.create(Order.STABLE_ORDER, "Foundation", "UIKit");

  /** Selects cc libraries that have alwayslink=1. */
  private static final Predicate<Artifact> ALWAYS_LINKED_CC_LIBRARY =
      input -> LINK_LIBRARY_FILETYPES.matches(input.getFilename());

  private static final String DEAD_STRIP_FEATURE_NAME = "dead_strip";

  private static final String GENERATE_LINKMAP_FEATURE_NAME = "generate_linkmap";

  private static final ImmutableList<String> OBJC_ACTIONS =
      ImmutableList.of(
          "objc-compile",
          "objc++-compile",
          "objc-archive",
          "objc-fully-link",
          "objc-executable",
          "objc++-executable");

  /** Returns the location of the xcrunwrapper tool. */
  public static final FilesToRunProvider xcrunwrapper(RuleContext ruleContext) {
    return ruleContext.getExecutablePrerequisite("$xcrunwrapper");
  }

  /**
   * Files which can be instrumented along with the attributes in which they may occur and the
   * attributes along which they are propagated from dependencies (via {@link
   * InstrumentedFilesInfo}).
   */
  private static final InstrumentationSpec INSTRUMENTATION_SPEC =
      new InstrumentationSpec(
              FileTypeSet.of(ObjcRuleClasses.NON_CPP_SOURCES, ObjcRuleClasses.CPP_SOURCES, HEADERS))
          .withSourceAttributes("srcs", "non_arc_srcs", "hdrs")
          .withDependencyAttributes("deps", "data", "binary", "xctest_app");

  private FeatureConfiguration getFeatureConfiguration(
      RuleContext ruleContext,
      CcToolchainProvider ccToolchain,
      BuildConfigurationValue configuration,
      CppSemantics cppSemantics) {
    ImmutableSet.Builder<String> activatedCrosstoolSelectables =
        ImmutableSet.<String>builder()
            .addAll(ruleContext.getFeatures())
            .addAll(OBJC_ACTIONS)
            .add(CppRuleClasses.LANG_OBJC);

    if (configuration.getFragment(ObjcConfiguration.class).shouldStripBinary()) {
      activatedCrosstoolSelectables.add(DEAD_STRIP_FEATURE_NAME);
    }
    if (configuration.getFragment(ObjcConfiguration.class).generateLinkmap()) {
      activatedCrosstoolSelectables.add(GENERATE_LINKMAP_FEATURE_NAME);
    }

    ImmutableSet.Builder<String> disabledFeatures =
        ImmutableSet.<String>builder().addAll(ruleContext.getDisabledFeatures());
    if (disableParseHeaders) {
      disabledFeatures.add(CppRuleClasses.PARSE_HEADERS);
    }
    if (disableLayeringCheck) {
      disabledFeatures.add(CppRuleClasses.LAYERING_CHECK);
    }

    return CcCommon.configureFeaturesOrReportRuleError(
        ruleContext,
        buildConfiguration,
        activatedCrosstoolSelectables.build(),
        disabledFeatures.build(),
        ccToolchain,
        cppSemantics);
  }

  /** Iterable wrapper providing strong type safety for arguments to binary linking. */
  static final class ExtraLinkArgs extends IterableWrapper<String> {
    ExtraLinkArgs(String... args) {
      super(args);
    }

    ExtraLinkArgs(Iterable<String> args) {
      super(args);
    }
  }

  /** Iterable wrapper providing strong type safety for extra compile flags. */
  static final class ExtraCompileArgs extends IterableWrapper<String> {
    static final ExtraCompileArgs NONE = new ExtraCompileArgs();

    ExtraCompileArgs(String... args) {
      super(args);
    }
  }

  @VisibleForTesting
  static final String FILE_IN_SRCS_AND_HDRS_WARNING_FORMAT = "File '%s' is in both srcs and hdrs.";

  @VisibleForTesting
  static final String FILE_IN_SRCS_AND_NON_ARC_SRCS_ERROR_FORMAT =
      "File '%s' is present in both srcs and non_arc_srcs which is forbidden.";

  @VisibleForTesting
  static final String BOTH_MODULE_NAME_AND_MODULE_MAP_SPECIFIED =
      "Specifying both module_name and module_map is invalid, please remove one of them.";

  static final ImmutableList<String> DEFAULT_COMPILER_FLAGS = ImmutableList.of("-DOS_IOS");

  /** Returns information about the given rule's compilation artifacts. */
  // TODO(bazel-team): Remove this information from ObjcCommon and move it internal to this class.
  static CompilationArtifacts compilationArtifacts(RuleContext ruleContext) {
    return compilationArtifacts(ruleContext, ObjcRuleClasses.intermediateArtifacts(ruleContext));
  }

  /**
   * Returns information about the given rule's compilation artifacts. Dependencies specified in the
   * current rule's attributes are obtained via {@code ruleContext}. Output locations are determined
   * using the given {@code intermediateArtifacts} object. The fact that these are distinct objects
   * allows the caller to generate compilation actions pertaining to a configuration separate from
   * the current rule's configuration.
   */
  static CompilationArtifacts compilationArtifacts(
      RuleContext ruleContext, IntermediateArtifacts intermediateArtifacts) {
    PrerequisiteArtifacts srcs =
        ruleContext.getPrerequisiteArtifacts("srcs").errorsForNonMatching(SRCS_TYPE);
    return new CompilationArtifacts.Builder()
        .addSrcs(srcs.filter(COMPILABLE_SRCS_TYPE).list())
        .addNonArcSrcs(
            ruleContext
                .getPrerequisiteArtifacts("non_arc_srcs")
                .errorsForNonMatching(NON_ARC_SRCS_TYPE)
                .list())
        .addPrivateHdrs(srcs.filter(HEADERS).list())
        .addPrecompiledSrcs(srcs.filter(PRECOMPILED_SRCS_TYPE).list())
        .setIntermediateArtifacts(intermediateArtifacts)
        .build();
  }

  /** Returns a list of framework library search paths. */
  static ImmutableList<String> frameworkLibrarySearchPaths(ObjcProvider provider) {
    ImmutableList.Builder<String> searchPaths = new ImmutableList.Builder<>();
    return searchPaths
        // Add library search paths corresponding to custom (non-SDK) frameworks. For each framework
        // foo/bar.framework, include "foo" as a search path.
        .addAll(provider.staticFrameworkPaths().toList())
        .addAll(provider.dynamicFrameworkPaths().toList())
        .build();
  }

  private final RuleContext ruleContext;
  private final BuildConfigurationValue buildConfiguration;
  private final ObjcConfiguration objcConfiguration;
  private final AppleConfiguration appleConfiguration;
  private final CppSemantics cppSemantics;
  private final CompilationAttributes attributes;
  private final IntermediateArtifacts intermediateArtifacts;
  private final CcToolchainProvider toolchain;
  private final boolean disableLayeringCheck;
  private final boolean disableParseHeaders;
  private Optional<CcCompilationContext> ccCompilationContext;

  @StarlarkMethod(name = "compilation_context", documented = false, structField = true)
  public CcCompilationContext getCcCompilationContext() {
    checkState(ccCompilationContext.isPresent());
    return ccCompilationContext.get();
  }

  /**
   * Creates a new compilation support for the given rule and build configuration.
   *
   * <p>All actions will be created under the given build configuration, which may be different than
   * the current rule context configuration.
   *
   * <p>The compilation and linking flags will be retrieved from the given compilation attributes.
   * The names of the generated artifacts will be retrieved from the given intermediate artifacts.
   *
   * <p>By instantiating multiple compilation supports for the same rule but with intermediate
   * artifacts with different output prefixes, multiple archives can be compiled for the same rule
   * context.
   */
  private CompilationSupport(
      RuleContext ruleContext,
      BuildConfigurationValue buildConfiguration,
      CppSemantics cppSemantics,
      IntermediateArtifacts intermediateArtifacts,
      CompilationAttributes compilationAttributes,
      CcToolchainProvider toolchain,
      boolean disableLayeringCheck,
      boolean disableParseHeaders)
      throws RuleErrorException {
    this.ruleContext = ruleContext;
    this.buildConfiguration = buildConfiguration;
    this.objcConfiguration = buildConfiguration.getFragment(ObjcConfiguration.class);
    this.appleConfiguration = buildConfiguration.getFragment(AppleConfiguration.class);
    this.cppSemantics = cppSemantics;
    this.attributes = compilationAttributes;
    this.intermediateArtifacts = intermediateArtifacts;
    this.ccCompilationContext = Optional.absent();
    this.disableLayeringCheck = disableLayeringCheck;
    this.disableParseHeaders = disableParseHeaders;
    if (toolchain == null
        && (ruleContext
                .attributes()
                .has(CcToolchain.CC_TOOLCHAIN_DEFAULT_ATTRIBUTE_NAME, BuildType.LABEL)
            || ruleContext
                .attributes()
                .has(
                    CcToolchain.CC_TOOLCHAIN_DEFAULT_ATTRIBUTE_NAME_FOR_STARLARK,
                    BuildType.LABEL))) {
      toolchain = CppHelper.getToolchainUsingDefaultCcToolchainAttribute(ruleContext);
    }

    this.toolchain = toolchain;
  }

  /** Builder for {@link CompilationSupport} */
  public static class Builder {
    private final RuleContext ruleContext;
    private final CppSemantics cppSemantics;
    private BuildConfigurationValue buildConfiguration;
    private IntermediateArtifacts intermediateArtifacts;
    private CompilationAttributes compilationAttributes;
    private CcToolchainProvider toolchain;
    private boolean disableLayeringCheck = false;
    private boolean disableParseHeaders = false;

    public Builder(RuleContext ruleContext, CppSemantics cppSemantics) {
      this.ruleContext = ruleContext;
      this.cppSemantics = cppSemantics;
    }

    /** Sets the {@link BuildConfigurationValue} for the calling target. */
    public Builder setConfig(BuildConfigurationValue buildConfiguration) {
      this.buildConfiguration = buildConfiguration;
      return this;
    }

    /** Sets {@link IntermediateArtifacts} for deriving artifact paths. */
    public Builder setIntermediateArtifacts(IntermediateArtifacts intermediateArtifacts) {
      this.intermediateArtifacts = intermediateArtifacts;
      return this;
    }

    /** Sets {@link CompilationAttributes} for the calling target. */
    public Builder setCompilationAttributes(CompilationAttributes compilationAttributes) {
      this.compilationAttributes = compilationAttributes;
      return this;
    }

    /** Sets that this {@link CompilationSupport} will disable layering check. */
    public Builder disableLayeringCheck() {
      this.disableLayeringCheck = true;
      return this;
    }

    /** Sets that this {@link CompilationSupport} will disable parse headers. */
    public Builder disableParseHeaders() {
      this.disableParseHeaders = true;
      return this;
    }

    /**
     * Sets {@link CcToolchainProvider} for the calling target.
     *
     * <p>This is needed if it can't correctly be inferred directly from the rule context. Setting
     * to null causes the default to be used as if this was never called.
     */
    public Builder setToolchainProvider(CcToolchainProvider toolchain) {
      this.toolchain = toolchain;
      return this;
    }

    /** Returns a {@link CompilationSupport} instance. */
    public CompilationSupport build() throws InterruptedException, RuleErrorException {
      if (buildConfiguration == null) {
        buildConfiguration = ruleContext.getConfiguration();
      }

      if (intermediateArtifacts == null) {
        intermediateArtifacts =
            ObjcRuleClasses.intermediateArtifacts(ruleContext, buildConfiguration);
      }

      if (compilationAttributes == null) {
        compilationAttributes = CompilationAttributes.Builder.fromRuleContext(ruleContext).build();
      }

      return new CompilationSupport(
          ruleContext,
          buildConfiguration,
          cppSemantics,
          intermediateArtifacts,
          compilationAttributes,
          toolchain,
          disableLayeringCheck,
          disableParseHeaders);
    }
  }

  /**
   * Returns a provider that collects this target's instrumented sources as well as those of its
   * dependencies.
   *
   * @param ruleContext the rule context of the target
   * @param toolchain the toolchain used by the target
   * @param buildConfiguration the build configuration of the target
   * @param objectFiles the object files generated by the target
   * @return an instrumented files provider
   */
  protected static InstrumentedFilesInfo getInstrumentedFilesProvider(
      RuleContext ruleContext,
      CcToolchainProvider toolchain,
      BuildConfigurationValue buildConfiguration,
      ImmutableList<Artifact> objectFiles)
      throws RuleErrorException {
    CppConfiguration cppConfiguration = buildConfiguration.getFragment(CppConfiguration.class);
    return InstrumentedFilesCollector.collect(
        ruleContext,
        INSTRUMENTATION_SPEC,
        OBJC_METADATA_COLLECTOR,
        objectFiles,
        CppHelper.getGcovFilesIfNeeded(ruleContext, toolchain),
        CppHelper.getCoverageEnvironmentIfNeeded(ruleContext, cppConfiguration, toolchain),
        /* withBaselineCoverage= */ true,
        /* reportedToActualSources= */ NestedSetBuilder.create(Order.STABLE_ORDER));
  }

  /**
   * Validates compilation-related attributes on this rule.
   *
   * @return this compilation support
   * @throws RuleErrorException if there are attribute errors
   */
  CompilationSupport validateAttributes() throws RuleErrorException {
    for (PathFragment absoluteInclude :
        Iterables.filter(attributes.includes().toList(), PathFragment::isAbsolute)) {
      ruleContext.attributeError(
          "includes", String.format(ABSOLUTE_INCLUDES_PATH_FORMAT, absoluteInclude));
    }

    if (ruleContext.attributes().has("srcs", BuildType.LABEL_LIST)) {
      ImmutableSet<Artifact> hdrsSet = attributes.hdrs().toSet();
      ImmutableSet<Artifact> srcsSet =
          ImmutableSet.copyOf(ruleContext.getPrerequisiteArtifacts("srcs").list());

      // Check for overlap between srcs and hdrs.
      for (Artifact header : Sets.intersection(hdrsSet, srcsSet)) {
        String path = header.getRootRelativePath().toString();
        ruleContext.attributeWarning(
            "srcs", String.format(FILE_IN_SRCS_AND_HDRS_WARNING_FORMAT, path));
      }

      // Check for overlap between srcs and non_arc_srcs.
      ImmutableSet<Artifact> nonArcSrcsSet =
          ImmutableSet.copyOf(ruleContext.getPrerequisiteArtifacts("non_arc_srcs").list());
      for (Artifact conflict : Sets.intersection(nonArcSrcsSet, srcsSet)) {
        String path = conflict.getRootRelativePath().toString();
        ruleContext.attributeError(
            "srcs", String.format(FILE_IN_SRCS_AND_NON_ARC_SRCS_ERROR_FORMAT, path));
      }
    }

    if (ruleContext.attributes().isAttributeValueExplicitlySpecified("module_name")
        && ruleContext.attributes().isAttributeValueExplicitlySpecified("module_map")) {
      ruleContext.attributeError("module_name", BOTH_MODULE_NAME_AND_MODULE_MAP_SPECIFIED);
    }

    ruleContext.assertNoErrors();
    return this;
  }

  private StrippingType getStrippingType(ExtraLinkArgs extraLinkArgs) {
    if (Iterables.contains(extraLinkArgs, "-dynamiclib")) {
      return StrippingType.DYNAMIC_LIB;
    }
    if (Iterables.contains(extraLinkArgs, "-bundle")) {
      return StrippingType.LOADABLE_BUNDLE;
    }
    if (Iterables.contains(extraLinkArgs, "-kext")) {
      return StrippingType.KERNEL_EXTENSION;
    }
    return StrippingType.DEFAULT;
  }

  /**
   * Registers any actions necessary to link this rule and its dependencies. Automatically infers
   * the toolchain from the configuration of this CompilationSupport.
   *
   * <p>Dsym bundle is generated if {@link ObjcConfiguration#generateDsym()} is set.
   *
   * <p>When Bazel flags {@code --compilation_mode=opt} and {@code --objc_enable_binary_stripping}
   * are specified, additional optimizations will be performed on the linked binary: all-symbol
   * stripping (using {@code /usr/bin/strip}) and dead-code stripping (using linker flags: {@code
   * -dead_strip}).
   *
   * @param objcProvider common information about this rule's attributes and its dependencies
   * @param ccLinkingContexts the linking contexts from this rule's dependencies
   * @param j2ObjcMappingFileProvider contains mapping files for j2objc transpilation
   * @param j2ObjcEntryClassProvider contains j2objc entry class information for dead code removal
   * @param extraLinkArgs any additional arguments to pass to the linker
   * @param extraLinkInputs any additional input artifacts to pass to the link action
   * @return this compilation support
   */
  CompilationSupport registerLinkActions(
      ObjcProvider objcProvider,
      Iterable<CcLinkingContext> ccLinkingContexts,
      J2ObjcMappingFileProvider j2ObjcMappingFileProvider,
      J2ObjcEntryClassProvider j2ObjcEntryClassProvider,
      ExtraLinkArgs extraLinkArgs,
      Iterable<Artifact> extraLinkInputs,
      boolean isStampingEnabled)
      throws InterruptedException, RuleErrorException {
    Iterable<Artifact> prunedJ2ObjcArchives =
        computeAndStripPrunedJ2ObjcArchives(
            j2ObjcEntryClassProvider, j2ObjcMappingFileProvider, objcProvider);
    ImmutableList<Artifact> bazelBuiltLibraries =
        Iterables.isEmpty(prunedJ2ObjcArchives)
            ? objcProvider.getObjcLibraries()
            : substituteJ2ObjcPrunedLibraries(objcProvider);

    // Passing large numbers of inputs on the command line triggers a bug in Apple's Clang
    // (b/29094356), so we'll create an input list manually and pass -filelist path/to/input/list.
    // We can't populate this list yet--it needs to contain any linkstamp objects, which we won't
    // know about until we actually create the CppLinkAction--but it needs to go into the
    // CppLinkAction too, so create it now.
    Artifact inputFileList = intermediateArtifacts.linkerObjList();

    ImmutableSet<Artifact> forceLinkArtifacts = getForceLoadArtifacts(objcProvider);

    // Clang loads archives specified in filelists and also specified as -force_load twice,
    // resulting in duplicate symbol errors unless they are deduped.
    ImmutableSet<Artifact> objFiles =
        ImmutableSet.copyOf(
            Iterables.filter(
                Iterables.concat(
                    bazelBuiltLibraries,
                    objcProvider.get(IMPORTED_LIBRARY).toList(),
                    objcProvider.getCcLibraries()),
                Predicates.not(Predicates.in(forceLinkArtifacts))));

    LinkTargetType linkType =
        objcProvider.is(Flag.USES_CPP)
            ? LinkTargetType.OBJCPP_EXECUTABLE
            : LinkTargetType.OBJC_EXECUTABLE;

    ObjcVariablesExtension.Builder extensionBuilder =
        new ObjcVariablesExtension.Builder()
            .setRuleContext(ruleContext)
            .setObjcProvider(objcProvider)
            .setConfiguration(buildConfiguration)
            .setIntermediateArtifacts(intermediateArtifacts)
            .setFrameworkNames(frameworkNames(objcProvider))
            .setFrameworkSearchPath(frameworkLibrarySearchPaths(objcProvider))
            .setLibraryNames(libraryNames(objcProvider))
            .setForceLoadArtifacts(getForceLoadArtifacts(objcProvider))
            .setAttributeLinkopts(attributes.linkopts())
            .addVariableCategory(VariableCategory.EXECUTABLE_LINKING_VARIABLES);

    Artifact binaryToLink = getBinaryToLink();
    FeatureConfiguration featureConfiguration =
        getFeatureConfiguration(ruleContext, toolchain, buildConfiguration, cppSemantics);

    Label binaryLabel = null;
    try {
      binaryLabel =
          Label.create(ruleContext.getLabel().getPackageIdentifier(), binaryToLink.getFilename());
    } catch (LabelSyntaxException e) {
      // Formed from existing label, just replacing name with artifact name.
    }

    CppConfiguration cppConfiguration = buildConfiguration.getFragment(CppConfiguration.class);
    CcLinkingHelper executableLinkingHelper =
        new CcLinkingHelper(
                ruleContext,
                binaryLabel,
                ruleContext,
                ruleContext,
                cppSemantics,
                featureConfiguration,
                toolchain,
                toolchain.getFdoContext(),
                buildConfiguration,
                cppConfiguration,
                ruleContext.getSymbolGenerator(),
                TargetUtils.getExecutionInfo(
                    ruleContext.getRule(), ruleContext.isAllowTagsPropagation()))
            .setGrepIncludes(CppHelper.getGrepIncludes(ruleContext))
            .setIsStampingEnabled(isStampingEnabled)
            .setTestOrTestOnlyTarget(ruleContext.isTestOnlyTarget() || ruleContext.isTestTarget())
            .addNonCodeLinkerInputs(bazelBuiltLibraries)
            .addNonCodeLinkerInputs(objcProvider.getCcLibraries())
            .addNonCodeLinkerInputs(ImmutableList.copyOf(extraLinkInputs))
            .addNonCodeLinkerInputs(ImmutableList.copyOf(attributes.linkInputs()))
            .addNonCodeLinkerInputs(ImmutableList.of(inputFileList))
            .addTransitiveAdditionalLinkerInputs(objcProvider.get(IMPORTED_LIBRARY))
            .addTransitiveAdditionalLinkerInputs(objcProvider.get(STATIC_FRAMEWORK_FILE))
            .addTransitiveAdditionalLinkerInputs(objcProvider.get(DYNAMIC_FRAMEWORK_FILE))
            .addTransitiveAdditionalLinkerInputs(objcProvider.get(LINK_INPUTS))
            .setShouldCreateStaticLibraries(false)
            .setDynamicLinkType(linkType)
            .setLinkingMode(LinkingMode.STATIC)
            .addLinkopts(ImmutableList.copyOf(extraLinkArgs));

    ImmutableList.Builder<Artifact> linkerOutputs = ImmutableList.builder();

    if (cppConfiguration.appleGenerateDsym()) {
      Artifact dsymSymbol =
          objcConfiguration.shouldStripBinary()
              ? intermediateArtifacts.dsymSymbolForUnstrippedBinary()
              : intermediateArtifacts.dsymSymbolForStrippedBinary();
      extensionBuilder
          .setDsymSymbol(dsymSymbol)
          .addVariableCategory(VariableCategory.DSYM_VARIABLES);
      linkerOutputs.add(dsymSymbol);
    }

    if (objcConfiguration.generateLinkmap()) {
      Artifact linkmap = intermediateArtifacts.linkmap();
      extensionBuilder.setLinkmap(linkmap).addVariableCategory(VariableCategory.LINKMAP_VARIABLES);
      linkerOutputs.add(linkmap);
    }

    if (cppConfiguration.getAppleBitcodeMode() == AppleBitcodeMode.EMBEDDED) {
      Artifact bitcodeSymbolMap = intermediateArtifacts.bitcodeSymbolMap();
      extensionBuilder
          .setBitcodeSymbolMap(bitcodeSymbolMap)
          .addVariableCategory(VariableCategory.BITCODE_VARIABLES);
      linkerOutputs.add(bitcodeSymbolMap);
    }

    executableLinkingHelper.addVariableExtension(extensionBuilder.build());

    executableLinkingHelper.addLinkerOutputs(linkerOutputs.build());

    CcLinkingContext.Builder linkstampsBuilder = CcLinkingContext.builder();
    for (CcLinkingContext context : ccLinkingContexts) {
      linkstampsBuilder.addLinkstamps(context.getLinkstamps().toList());
    }
    CcLinkingContext linkstamps = linkstampsBuilder.build();
    executableLinkingHelper.addCcLinkingContexts(ImmutableList.of(linkstamps));

    executableLinkingHelper.link(CcCompilationOutputs.EMPTY);

    ImmutableCollection<Artifact> linkstampValues =
        CppLinkActionBuilder.mapLinkstampsToOutputs(
                linkstamps.getLinkstamps().toSet(),
                ruleContext,
                ruleContext.getRepository(),
                buildConfiguration,
                binaryToLink,
                CppLinkAction.DEFAULT_ARTIFACT_FACTORY)
            .values();

    // Populate the input file list with both the compiled object files and any linkstamp object
    // files.
    registerObjFilelistAction(
        ImmutableSet.<Artifact>builder().addAll(objFiles).addAll(linkstampValues).build(),
        inputFileList);

    if (objcConfiguration.shouldStripBinary()) {
      registerBinaryStripAction(binaryToLink, getStrippingType(extraLinkArgs));
    }

    return this;
  }


  /**
   * Registers an action that writes given set of object files to the given objList. This objList is
   * suitable to signal symbols to archive in a libtool archiving invocation.
   */
  // TODO(ulfjack): Use NestedSet for objFiles.
  private CompilationSupport registerObjFilelistAction(
      ImmutableSet<Artifact> objFiles, Artifact objList) {
    CustomCommandLine.Builder objFilesToLinkParam = new CustomCommandLine.Builder();
    NestedSetBuilder<Artifact> treeObjFiles = NestedSetBuilder.stableOrder();

    for (Artifact objFile : objFiles) {
      // If the obj file is a tree artifact, we need to expand it into the contained individual
      // files properly.
      if (objFile.isTreeArtifact()) {
        treeObjFiles.add(objFile);
        objFilesToLinkParam.addExpandedTreeArtifactExecPaths(objFile);
      } else {
        objFilesToLinkParam.addPath(objFile.getExecPath());
      }
    }

    ruleContext.registerAction(
        new ParameterFileWriteAction(
            ruleContext.getActionOwner(),
            treeObjFiles.build(),
            objList,
            objFilesToLinkParam.build(),
            ParameterFile.ParameterFileType.UNQUOTED));
    return this;
  }

  /**
   * Registers an action to create an archive artifact by fully (statically) linking all transitive
   * dependencies of this rule.
   *
   * @param objcProvider provides all compiling and linking information to create this artifact
   * @param outputArchive the output artifact for this action
   * @return this {@link CompilationSupport} instance
   */
  CompilationSupport registerFullyLinkAction(ObjcProvider objcProvider, Artifact outputArchive)
      throws InterruptedException, RuleErrorException {
    checkNotNull(toolchain);
    checkNotNull(toolchain.getFdoContext());

    ObjcVariablesExtension extension =
        new ObjcVariablesExtension.Builder()
            .setRuleContext(ruleContext)
            .setObjcProvider(objcProvider)
            .setConfiguration(buildConfiguration)
            .setIntermediateArtifacts(intermediateArtifacts)
            .setFullyLinkArchive(outputArchive)
            .addVariableCategory(VariableCategory.FULLY_LINK_VARIABLES)
            .build();

    Label archiveLabel = null;
    try {
      archiveLabel =
          Label.create(
              ruleContext.getLabel().getPackageIdentifier(),
              FileSystemUtils.removeExtension(outputArchive.getFilename()));
    } catch (LabelSyntaxException e) {
      // Formed from existing label, just replacing name with artifact name.
    }

    new CcLinkingHelper(
            ruleContext,
            archiveLabel,
            ruleContext,
            ruleContext,
            cppSemantics,
            getFeatureConfiguration(ruleContext, toolchain, buildConfiguration, cppSemantics),
            toolchain,
            toolchain.getFdoContext(),
            buildConfiguration,
            buildConfiguration.getFragment(CppConfiguration.class),
            ruleContext.getSymbolGenerator(),
            TargetUtils.getExecutionInfo(
                ruleContext.getRule(), ruleContext.isAllowTagsPropagation()))
        .setGrepIncludes(CppHelper.getGrepIncludes(ruleContext))
        .setIsStampingEnabled(AnalysisUtils.isStampingEnabled(ruleContext))
        .setTestOrTestOnlyTarget(ruleContext.isTestOnlyTarget() || ruleContext.isTestTarget())
        .addNonCodeLinkerInputs(objcProvider.getObjcLibraries())
        .addNonCodeLinkerInputs(objcProvider.getCcLibraries())
        .addTransitiveAdditionalLinkerInputs(objcProvider.get(IMPORTED_LIBRARY))
        .setLinkingMode(LinkingMode.STATIC)
        .setStaticLinkType(LinkTargetType.OBJC_FULLY_LINKED_ARCHIVE)
        .setShouldCreateDynamicLibrary(false)
        .addVariableExtension(extension)
        .link(CcCompilationOutputs.EMPTY);

    return this;
  }

  /**
   * Returns all framework names to pass to the linker using {@code -framework} flags. For a
   * framework in the directory foo/bar.framework, the name is "bar". Each framework is found
   * without using the full path by means of the framework search paths. Search paths are added by
   * {@link#commonLinkAndCompileFlagsForClang(ObjcProvider, ObjcConfiguration, AppleConfiguration)})
   *
   * <p>It's awful that we can't pass the full path to the framework and avoid framework search
   * paths, but this is imposed on us by clang. clang does not support passing the full path to the
   * framework, so Bazel cannot do it either.
   */
  private Set<String> frameworkNames(ObjcProvider provider) {
    Set<String> names = new LinkedHashSet<>();
    names.addAll(provider.get(SDK_FRAMEWORK).toList());
    names.addAll(provider.staticFrameworkNames().toList());
    names.addAll(provider.dynamicFrameworkNames().toList());
    return names;
  }

  /** Returns libraries that should be passed to the linker. */
  private ImmutableList<String> libraryNames(ObjcProvider objcProvider) {
    ImmutableList.Builder<String> args = new ImmutableList.Builder<>();
    for (String dylib : objcProvider.get(SDK_DYLIB).toList()) {
      if (dylib.startsWith("lib")) {
        // remove lib prefix if it exists which is standard
        // for libraries (libxml.dylib -> -lxml).
        dylib = dylib.substring(3);
      }
      args.add(dylib);
    }
    return args.build();
  }

  /** Returns libraries that should be passed into the linker with {@code -force_load}. */
  private ImmutableSet<Artifact> getForceLoadArtifacts(ObjcProvider objcProvider) {
    List<Artifact> ccLibraries = objcProvider.getCcLibraries();
    Iterable<Artifact> ccLibrariesToForceLoad =
        Iterables.filter(ccLibraries, ALWAYS_LINKED_CC_LIBRARY);

    return ImmutableSet.<Artifact>builder()
        .addAll(objcProvider.get(FORCE_LOAD_LIBRARY).toList())
        .addAll(ccLibrariesToForceLoad)
        .build();
  }

  /** Returns pruned J2Objc archives for this target. */
  private ImmutableList<Artifact> j2objcPrunedLibraries(ObjcProvider objcProvider) {
    ImmutableList.Builder<Artifact> j2objcPrunedLibraryBuilder = ImmutableList.builder();
    for (Artifact j2objcLibrary : objcProvider.get(ObjcProvider.J2OBJC_LIBRARY).toList()) {
      j2objcPrunedLibraryBuilder.add(intermediateArtifacts.j2objcPrunedArchive(j2objcLibrary));
    }
    return j2objcPrunedLibraryBuilder.build();
  }

  /** Returns true if this build should strip J2Objc dead code. */
  private boolean stripJ2ObjcDeadCode(J2ObjcEntryClassProvider j2ObjcEntryClassProvider) {
    J2ObjcConfiguration j2objcConfiguration =
        buildConfiguration.getFragment(J2ObjcConfiguration.class);
    // Only perform J2ObjC dead code stripping if flag --j2objc_dead_code_removal is specified and
    // users have specified entry classes.
    return j2objcConfiguration.removeDeadCode()
        && !j2ObjcEntryClassProvider.getEntryClasses().isEmpty();
  }

  /** Registers actions to perform J2Objc dead code removal. */
  private void registerJ2ObjcDeadCodeRemovalActions(
      ObjcProvider objcProvider,
      J2ObjcMappingFileProvider j2ObjcMappingFileProvider,
      J2ObjcEntryClassProvider j2ObjcEntryClassProvider) {
    NestedSet<String> entryClasses = j2ObjcEntryClassProvider.getEntryClasses();
    NestedSet<Artifact> j2ObjcDependencyMappingFiles =
        j2ObjcMappingFileProvider.getDependencyMappingFiles();
    NestedSet<Artifact> j2ObjcHeaderMappingFiles =
        j2ObjcMappingFileProvider.getHeaderMappingFiles();
    NestedSet<Artifact> j2ObjcArchiveSourceMappingFiles =
        j2ObjcMappingFileProvider.getArchiveSourceMappingFiles();

    for (Artifact j2objcArchive : objcProvider.get(ObjcProvider.J2OBJC_LIBRARY).toList()) {
      Artifact prunedJ2ObjcArchive = intermediateArtifacts.j2objcPrunedArchive(j2objcArchive);
      Artifact dummyArchive =
          ruleContext
              .getPrerequisite("$dummy_lib", ObjcProvider.STARLARK_CONSTRUCTOR)
              .get(LIBRARY)
              .getSingleton();

      CustomCommandLine commandLine =
          CustomCommandLine.builder()
              .addExecPath("--input_archive", j2objcArchive)
              .addExecPath("--output_archive", prunedJ2ObjcArchive)
              .addExecPath("--dummy_archive", dummyArchive)
              .addExecPath("--xcrunwrapper", xcrunwrapper(ruleContext).getExecutable())
              .addExecPaths(
                  "--dependency_mapping_files",
                  VectorArg.join(",").each(j2ObjcDependencyMappingFiles))
              .addExecPaths(
                  "--header_mapping_files", VectorArg.join(",").each(j2ObjcHeaderMappingFiles))
              .addExecPaths(
                  "--archive_source_mapping_files",
                  VectorArg.join(",").each(j2ObjcArchiveSourceMappingFiles))
              .add("--entry_classes")
              .addAll(VectorArg.join(",").each(entryClasses))
              .build();

      ruleContext.registerAction(
          ObjcRuleClasses.spawnAppleEnvActionBuilder(
                  XcodeConfigInfo.fromRuleContext(ruleContext),
                  appleConfiguration.getSingleArchPlatform())
              .setMnemonic("DummyPruner")
              .setExecutable(ruleContext.getExecutablePrerequisite("$j2objc_dead_code_pruner"))
              .addInput(dummyArchive)
              .addInput(j2objcArchive)
              .addInput(xcrunwrapper(ruleContext).getExecutable())
              .addTransitiveInputs(j2ObjcDependencyMappingFiles)
              .addTransitiveInputs(j2ObjcHeaderMappingFiles)
              .addTransitiveInputs(j2ObjcArchiveSourceMappingFiles)
              .addCommandLine(
                  commandLine,
                  ParamFileInfo.builder(ParameterFile.ParameterFileType.UNQUOTED)
                      .setCharset(ISO_8859_1)
                      .setUseAlways(true)
                      .build())
              .addOutput(prunedJ2ObjcArchive)
              .build(ruleContext));
    }
  }

  /** Returns archives arising from j2objc transpilation after dead code removal. */
  private Iterable<Artifact> computeAndStripPrunedJ2ObjcArchives(
      J2ObjcEntryClassProvider j2ObjcEntryClassProvider,
      J2ObjcMappingFileProvider j2ObjcMappingFileProvider,
      ObjcProvider objcProvider) {
    Iterable<Artifact> prunedJ2ObjcArchives = ImmutableList.<Artifact>of();
    if (stripJ2ObjcDeadCode(j2ObjcEntryClassProvider)) {
      registerJ2ObjcDeadCodeRemovalActions(
          objcProvider, j2ObjcMappingFileProvider, j2ObjcEntryClassProvider);
      prunedJ2ObjcArchives = j2objcPrunedLibraries(objcProvider);
    }
    return prunedJ2ObjcArchives;
  }

  /**
   * Returns a nested set of Bazel-built ObjC libraries with all unpruned J2ObjC libraries
   * substituted with pruned ones.
   */
  private ImmutableList<Artifact> substituteJ2ObjcPrunedLibraries(ObjcProvider objcProvider) {
    ImmutableList.Builder<Artifact> libraries = new ImmutableList.Builder<>();

    Set<Artifact> unprunedJ2ObjcLibs = objcProvider.get(ObjcProvider.J2OBJC_LIBRARY).toSet();
    for (Artifact library : objcProvider.getObjcLibraries()) {
      // If we match an unpruned J2ObjC library, add the pruned version of the J2ObjC static library
      // instead.
      if (unprunedJ2ObjcLibs.contains(library)) {
        libraries.add(intermediateArtifacts.j2objcPrunedArchive(library));
      } else {
        libraries.add(library);
      }
    }
    return libraries.build();
  }

  /** Returns the artifact that should be the outcome of this build's link action */
  private Artifact getBinaryToLink() {

    // When compilation_mode=opt and objc_enable_binary_stripping are specified, the unstripped
    // binary containing debug symbols is generated by the linker, which also needs the debug
    // symbols for dead-code removal. The binary is also used to generate dSYM bundle if
    // --apple_generate_dsym is specified. A symbol strip action is later registered to strip
    // the symbol table from the unstripped binary.
    return objcConfiguration.shouldStripBinary()
        ? intermediateArtifacts.unstrippedSingleArchitectureBinary()
        : intermediateArtifacts.strippedSingleArchitectureBinary();
  }

  private static CommandLine symbolStripCommandLine(
      ImmutableList<String> extraFlags, Artifact unstrippedArtifact, Artifact strippedArtifact) {
    return CustomCommandLine.builder()
        .add(STRIP)
        .addAll(extraFlags)
        .addExecPath("-o", strippedArtifact)
        .addPath(unstrippedArtifact.getExecPath())
        .build();
  }

  /** Signals if stripping should include options for dynamic libraries. */
  private enum StrippingType {
    DEFAULT,
    DYNAMIC_LIB,
    LOADABLE_BUNDLE,
    KERNEL_EXTENSION
  }

  /**
   * Registers an action that uses the 'strip' tool to perform binary stripping on the given binary
   * subject to the given {@link StrippingType}.
   */
  private void registerBinaryStripAction(Artifact binaryToLink, StrippingType strippingType) {
    final ImmutableList<String> stripArgs;
    switch (strippingType) {
      case DYNAMIC_LIB:
      case LOADABLE_BUNDLE:
      case KERNEL_EXTENSION:
        // For dylibs, loadable bundles, and kexts, must strip only local symbols.
        stripArgs = ImmutableList.of("-x");
        break;
      case DEFAULT:
        stripArgs = ImmutableList.<String>of();
        break;
      default:
        throw new IllegalArgumentException("Unsupported stripping type " + strippingType);
    }

    Artifact strippedBinary = intermediateArtifacts.strippedSingleArchitectureBinary();

    ruleContext.registerAction(
        ObjcRuleClasses.spawnAppleEnvActionBuilder(
                XcodeConfigInfo.fromRuleContext(ruleContext),
                appleConfiguration.getSingleArchPlatform())
            .setMnemonic("ObjcBinarySymbolStrip")
            .setExecutable(xcrunwrapper(ruleContext))
            .addCommandLine(symbolStripCommandLine(stripArgs, binaryToLink, strippedBinary))
            .addOutput(strippedBinary)
            .addInput(binaryToLink)
            .build(ruleContext));
  }

  /**
   * Collector that, given a list of output artifacts, finds and registers coverage notes metadata
   * for any compilation action.
   */
  private static final LocalMetadataCollector OBJC_METADATA_COLLECTOR =
      new LocalMetadataCollector() {
        @Override
        public void collectMetadataArtifacts(
            Iterable<Artifact> artifacts,
            AnalysisEnvironment analysisEnvironment,
            NestedSetBuilder<Artifact> metadataFilesBuilder) {
          for (Artifact artifact : artifacts) {
            ActionAnalysisMetadata action = analysisEnvironment.getLocalGeneratingAction(artifact);
            if (action.getMnemonic().equals("ObjcCompile")
                || action.getMnemonic().equals("ObjcCompileHeader")) {
              addOutputs(metadataFilesBuilder, action, ObjcRuleClasses.COVERAGE_NOTES);
            }
          }
        }
      };

  public static Optional<Artifact> getCustomModuleMap(RuleContext ruleContext) {
    if (ruleContext.attributes().has("module_map", BuildType.LABEL)) {
      return Optional.fromNullable(ruleContext.getPrerequisiteArtifact("module_map"));
    }
    return Optional.absent();
  }
}