// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

package com.android.tools.r8.ir.analysis.proto.schema;

import static com.android.tools.r8.graph.DexProgramClass.asProgramClassOrNull;

import com.android.tools.r8.graph.AppInfoWithClassHierarchy;
import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexField;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.FieldResolutionResult;
import com.android.tools.r8.graph.ProgramDefinition;
import com.android.tools.r8.graph.ProgramField;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.graph.analysis.EnqueuerAnalysis;
import com.android.tools.r8.ir.analysis.proto.GeneratedMessageLiteShrinker;
import com.android.tools.r8.ir.analysis.proto.ProtoEnqueuerUseRegistry;
import com.android.tools.r8.ir.analysis.proto.ProtoReferences;
import com.android.tools.r8.ir.analysis.proto.ProtoShrinker;
import com.android.tools.r8.ir.analysis.proto.RawMessageInfoDecoder;
import com.android.tools.r8.ir.analysis.type.TypeElement;
import com.android.tools.r8.ir.code.BasicBlock;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.IRCodeUtils;
import com.android.tools.r8.ir.code.Instruction;
import com.android.tools.r8.ir.code.InvokeMethod;
import com.android.tools.r8.ir.code.StaticGet;
import com.android.tools.r8.ir.code.StaticPut;
import com.android.tools.r8.ir.code.Value;
import com.android.tools.r8.ir.optimize.info.FieldOptimizationInfo;
import com.android.tools.r8.shaking.Enqueuer;
import com.android.tools.r8.shaking.EnqueuerWorklist;
import com.android.tools.r8.shaking.InstantiationReason;
import com.android.tools.r8.shaking.KeepReason;
import com.android.tools.r8.utils.BitUtils;
import com.android.tools.r8.utils.OptionalBool;
import com.android.tools.r8.utils.Timing;
import com.android.tools.r8.utils.collections.ProgramMethodSet;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Predicate;

// TODO(b/112437944): Handle cycles in the graph + add a test that fails with the current
//  implementation. The current caching mechanism is unsafe, because we may mark a message as not
//  containing a map/required field in presence of cycles, although it does.

// TODO(b/112437944): Handle incomplete information about extensions + add a test that fails with
//  the current implementation. If there are some extensions that cannot be resolved, then we should
//  keep fields that could reach extensions to be conservative.
public class ProtoEnqueuerExtension extends EnqueuerAnalysis {

  private final AppView<? extends AppInfoWithClassHierarchy> appView;
  private final RawMessageInfoDecoder decoder;
  private final ProtoFieldTypeFactory factory;
  private final ProtoReferences references;

  // Mapping for the set of proto message that have already become live.
  private final Map<DexType, ProtoMessageInfo> liveProtos = new IdentityHashMap<>();

  // Mapping for additional proto messages that have not yet become live. If there is a proto that
  // has become live, then its schema may refer to another proto message that has not yet become
  // live. In that case, we still need to decode the schema of the not-yet-live proto message,
  // because we need to check if it has a required/map field.
  private final Map<DexType, ProtoMessageInfo> seenButNotLiveProtos = new IdentityHashMap<>();

  // To cache whether a proto message contains a map/required field directly or indirectly.
  private final Map<ProtoMessageInfo, OptionalBool> reachesMapOrRequiredFieldFromMessageCache =
      new IdentityHashMap<>();

  // Keeps track of the set of dynamicMethod() methods for which we have traced const-class and
  // static-get instructions.
  private final Set<DexEncodedMethod> dynamicMethodsWithTracedProtoObjects =
      Sets.newIdentityHashSet();

  // The findLiteExtensionByNumber() methods that have become live since the last fixpoint.
  private final ProgramMethodSet findLiteExtensionByNumberMethods = ProgramMethodSet.create();

  // Mapping from extension container types to the extensions for that type.
  private final Map<DexType, Set<DexType>> extensionGraph = new IdentityHashMap<>();

  public ProtoEnqueuerExtension(AppView<? extends AppInfoWithClassHierarchy> appView) {
    ProtoShrinker protoShrinker = appView.protoShrinker();
    this.appView = appView;
    this.decoder = protoShrinker.decoder;
    this.factory = protoShrinker.factory;
    this.references = protoShrinker.references;
  }

  @Override
  public void processNewlyLiveClass(DexProgramClass clazz, EnqueuerWorklist worklist) {
    assert appView.appInfo().hasClassHierarchy();
    AppInfoWithClassHierarchy appInfo = appView.appInfo().withClassHierarchy();
    if (appInfo.isStrictSubtypeOf(clazz.type, references.generatedMessageLiteType)) {
      markGeneratedMessageLiteSubtypeAsInstantiated(clazz, worklist);
    }
  }

  private void markGeneratedMessageLiteSubtypeAsInstantiated(
      DexProgramClass clazz, EnqueuerWorklist worklist) {
    if (clazz.isAbstract()) {
      assert clazz.type == references.extendableMessageType;
      return;
    }
    ProgramMethod dynamicMethod = clazz.lookupProgramMethod(references.dynamicMethod);
    if (dynamicMethod != null) {
      worklist.enqueueMarkInstantiatedAction(
          clazz,
          dynamicMethod,
          InstantiationReason.REFLECTION,
          KeepReason.reflectiveUseIn(dynamicMethod));
    } else {
      assert false
          : "Expected class `" + clazz.type.toSourceString() + "` to declare a dynamicMethod()";
    }
  }

  /**
   * When a dynamicMethod() of a proto message becomes live, then build the corresponding {@link
   * ProtoMessageInfo} object, and create a mapping from the holder to it.
   */
  @Override
  public void processNewlyLiveMethod(ProgramMethod method, ProgramDefinition context) {
    if (references.isFindLiteExtensionByNumberMethod(method.getReference())) {
      findLiteExtensionByNumberMethods.add(method);
      return;
    }

    if (!references.isDynamicMethod(method)) {
      return;
    }

    DexType holderType = method.getHolderType();
    if (seenButNotLiveProtos.containsKey(holderType)) {
      // The proto is now live instead of dead.
      liveProtos.put(holderType, seenButNotLiveProtos.remove(holderType));
      return;
    }

    // Since this dynamicMethod() only becomes live once, and it has just become live, it must be
    // the case that the proto is not already live.
    assert !liveProtos.containsKey(holderType);
    createProtoMessageInfoFromDynamicMethod(method, liveProtos);
  }

  private void createProtoMessageInfoFromDynamicMethod(
      ProgramMethod dynamicMethod, Map<DexType, ProtoMessageInfo> protos) {
    DexType holder = dynamicMethod.getHolderType();
    assert !protos.containsKey(holder);

    IRCode code = dynamicMethod.buildIR(appView);
    InvokeMethod newMessageInfoInvoke =
        GeneratedMessageLiteShrinker.getNewMessageInfoInvoke(code, references);
    ProtoMessageInfo protoMessageInfo =
        newMessageInfoInvoke != null ? decoder.run(dynamicMethod, newMessageInfoInvoke) : null;
    protos.put(holder, protoMessageInfo);
  }

  @Override
  public void notifyFixpoint(Enqueuer enqueuer, EnqueuerWorklist worklist, Timing timing) {
    timing.begin("[Proto] Extend fixpoint");
    populateExtensionGraph(enqueuer);

    markMapOrRequiredFieldsAsReachable(enqueuer, worklist);

    // The ProtoEnqueuerUseRegistry does not trace the const-class instructions in dynamicMethod().
    // Therefore, we manually trace the const-class instructions in each dynamicMethod() here,
    // ***but only those that will remain after the proto schema has been optimized***.
    if (enqueuer.getUseRegistryFactory() == ProtoEnqueuerUseRegistry.getFactory()) {
      // We only use the ProtoEnqueuerUseRegistry in the second round of tree shaking. This means
      // that the initial round of tree shaking will be less precise, but likely faster.
      assert enqueuer.getMode().isFinalTreeShaking();
      if (worklist.isEmpty()) {
        tracePendingInstructionsInDynamicMethods(enqueuer, worklist);
      }
    }
    timing.end();
  }

  /**
   * For each extension field referenced from any of the methods in {@link
   * #findLiteExtensionByNumberMethods}, this method finds the definition of the field, and then
   * adds an edge to the proto extension graph {@link #extensionGraph} based on the definition of
   * the field.
   *
   * <p>Example: If the field is defined as below, then an edge is added from the container type
   * MyProtoMessage (argument #0) to the extension type MyProtoMessage$Ext (argument #2).
   *
   * <pre>
   *   GeneratedMessageLite.newSingularGeneratedExtension(
   *       MyProtoMessage.getDefaultInstance(),
   *       MyProtoMessage.Ext.getDefaultInstance(),
   *       MyProtoMessage.Ext.getDefaultInstance(),
   *       null,
   *       10,
   *       WireFormat.FieldType.MESSAGE,
   *       MyProtoMessage.Ext.class);
   * </pre>
   *
   * In addition to {@code newSingularGeneratedExtension()} we also model {@code
   * newRepeatedGeneratedExtension()}. Both of these methods forward to {@code
   * GeneratedExtension.<init>()}, hence we also model this constructor for robustness against
   * inlining.
   */
  private void populateExtensionGraph(Enqueuer enqueuer) {
    collectExtensionFields()
        .forEach(
            (clazz, extensionFields) -> {
              ProgramMethod clinit = clazz.getProgramClassInitializer();
              if (clinit == null) {
                assert false; // Should generally not happen.
                return;
              }

              IRCode code = clinit.buildIR(appView);
              Map<DexEncodedField, StaticPut> uniqueStaticPuts =
                  IRCodeUtils.findUniqueStaticPuts(appView, code, extensionFields);
              for (DexEncodedField extensionField : extensionFields) {
                StaticPut staticPut = uniqueStaticPuts.get(extensionField);
                if (staticPut == null) {
                  // Could happen after we have optimized the code.
                  assert enqueuer.getMode().isFinalTreeShaking();
                  continue;
                }
                populateExtensionGraphWithExtensionFieldDefinition(staticPut);
              }
            });

    // Clear the set of methods such that we don't re-analyze these methods upon the next fixpoint.
    findLiteExtensionByNumberMethods.clear();
  }

  /**
   * Finds the extension fields referenced in the methods in {@link
   * #findLiteExtensionByNumberMethods}.
   */
  private Map<DexProgramClass, Set<DexEncodedField>> collectExtensionFields() {
    Map<DexProgramClass, Set<DexEncodedField>> extensionFieldsByClass = new IdentityHashMap<>();
    for (ProgramMethod findLiteExtensionByNumberMethod : findLiteExtensionByNumberMethods) {
      IRCode code = findLiteExtensionByNumberMethod.buildIR(appView);
      for (BasicBlock block : code.blocks(BasicBlock::isReturnBlock)) {
        Value returnValue = block.exit().asReturn().returnValue().getAliasedValue();
        if (returnValue.isPhi()) {
          assert false;
          continue;
        }

        if (returnValue.isZero()) {
          continue; // OK.
        }

        Instruction definition = returnValue.definition;
        if (definition.isStaticGet()) {
          StaticGet staticGet = definition.asStaticGet();
          DexEncodedField field =
              appView.appInfo().resolveField(staticGet.getField()).getResolvedField();
          if (field == null) {
            assert false;
            continue;
          }

          DexProgramClass holder =
              asProgramClassOrNull(appView.definitionFor(field.getHolderType()));
          if (holder == null) {
            assert false;
            continue;
          }

          extensionFieldsByClass
              .computeIfAbsent(holder, ignore -> Sets.newIdentityHashSet())
              .add(field);
          continue;
        }

        assert definition.isInvokeMethodWithReceiver()
            && references.isFindLiteExtensionByNumberMethod(
                definition.asInvokeMethodWithReceiver().getInvokedMethod());
      }
    }
    return extensionFieldsByClass;
  }

  /**
   * Updates {@link #extensionGraph} based on the definition of {@param staticPut}.
   *
   * <p>See also {@link #populateExtensionGraph}.
   */
  private void populateExtensionGraphWithExtensionFieldDefinition(StaticPut staticPut) {
    Value value = staticPut.value().getAliasedValue();
    if (value.isPhi()) {
      return;
    }

    Instruction extensionFactory = value.definition;
    if (extensionFactory.isNewInstance()) {
      extensionFactory =
          extensionFactory.asNewInstance().getUniqueConstructorInvoke(appView.dexItemFactory());
      if (extensionFactory == null) {
        assert false;
        return;
      }
    }

    if (extensionFactory.isInvokeDirect() || extensionFactory.isInvokeStatic()) {
      InvokeMethod invoke = extensionFactory.asInvokeMethod();
      DexMethod invokedMethod = invoke.getInvokedMethod();

      TypeElement containerType, extensionType;
      if (invokedMethod == references.generatedMessageLiteMethods.newRepeatedGeneratedExtension) {
        containerType = invoke.arguments().get(0).getType();
        extensionType = invoke.arguments().get(1).getType();
      } else if (invokedMethod
          == references.generatedMessageLiteMethods.newSingularGeneratedExtension) {
        containerType = invoke.arguments().get(0).getType();
        extensionType = invoke.arguments().get(2).getType();
      } else if (references.generatedExtensionMethods.isConstructor(invokedMethod)) {
        containerType = invoke.arguments().get(1).getType();
        extensionType = invoke.arguments().get(3).getType();
      } else {
        return;
      }

      if (extensionType.isNullType()) {
        return; // Extension is a primitive type.
      }

      if (!containerType.isClassType() || !extensionType.isClassType()) {
        assert false; // Should generally not happen.
        return;
      }

      extensionGraph
          .computeIfAbsent(
              containerType.asClassType().getClassType(), ignore -> Sets.newIdentityHashSet())
          .add(extensionType.asClassType().getClassType());
    }
  }

  private void markMapOrRequiredFieldsAsReachable(Enqueuer enqueuer, EnqueuerWorklist worklist) {
    // TODO(b/112437944): We only need to check if a given field can reach a map/required field
    //  once. Maybe maintain a map `newlyLiveProtos` that store the set of proto messages that have
    //  become live since the last intermediate fixpoint.

    // TODO(b/112437944): We only need to visit the subset of protos in `liveProtos` that has at
    //  least one field that is not yet live. Maybe split `liveProtos` into `partiallyLiveProtos`
    //  and `fullyLiveProtos`.
    for (ProtoMessageInfo protoMessageInfo : liveProtos.values()) {
      if (protoMessageInfo == null || !protoMessageInfo.hasFields()) {
        continue;
      }

      ProgramMethod dynamicMethod = protoMessageInfo.getDynamicMethod();
      for (ProtoFieldInfo protoFieldInfo : protoMessageInfo.getFields()) {
        ProgramField valueStorage = protoFieldInfo.getValueStorage(appView, protoMessageInfo);
        if (valueStorage == null) {
          continue;
        }

        boolean valueStorageIsLive;
        if (enqueuer.isFieldLive(valueStorage)) {
          if (enqueuer.isFieldRead(valueStorage)
              || enqueuer.isFieldWrittenOutsideDefaultConstructor(valueStorage)
              || reachesMapOrRequiredField(protoFieldInfo)) {
            // Mark that the field is both read and written by reflection such that we do not
            // (i) optimize field reads into loading the default value of the field or (ii) remove
            // field writes to proto fields that could be read using reflection by the proto
            // library.
            enqueuer.registerReflectiveFieldAccess(valueStorage.getReference(), dynamicMethod);
          }
          valueStorageIsLive = true;
        } else if (reachesMapOrRequiredField(protoFieldInfo)) {
          // Map/required fields cannot be removed. Therefore, we mark such fields as both read and
          // written such that we cannot optimize any field reads or writes.
          enqueuer.registerReflectiveFieldAccess(valueStorage.getReference(), dynamicMethod);
          worklist.enqueueMarkReachableFieldAction(
              valueStorage, dynamicMethod, KeepReason.reflectiveUseIn(dynamicMethod));
          valueStorageIsLive = true;
        } else {
          valueStorageIsLive = false;
        }

        ProgramField newlyLiveField = null;
        if (valueStorageIsLive) {
          // For one-of fields, mark the corresponding one-of-case field as live, and for proto2
          // singular fields, mark the corresponding hazzer-bit field as live.
          if (protoFieldInfo.getType().isOneOf()) {
            newlyLiveField = protoFieldInfo.getOneOfCaseField(appView, protoMessageInfo);
          } else if (protoFieldInfo.hasHazzerBitField(protoMessageInfo)) {
            newlyLiveField = protoFieldInfo.getHazzerBitField(appView, protoMessageInfo);
            enqueuer.registerReflectiveFieldAccess(valueStorage.getReference(), dynamicMethod);
          }
        } else {
          // For one-of fields, mark the one-of field as live if the one-of-case field is live, and
          // for proto2 singular fields, mark the field as live if the corresponding hazzer-bit
          // field is live.
          if (protoFieldInfo.getType().isOneOf()) {
            ProgramField oneOfCaseField =
                protoFieldInfo.getOneOfCaseField(appView, protoMessageInfo);
            if (oneOfCaseField != null && enqueuer.isFieldLive(oneOfCaseField)) {
              newlyLiveField = valueStorage;
            }
          } else if (protoFieldInfo.hasHazzerBitField(protoMessageInfo)) {
            ProgramField hazzerBitField =
                protoFieldInfo.getHazzerBitField(appView, protoMessageInfo);
            if (hazzerBitField == null || !enqueuer.isFieldLive(hazzerBitField)) {
              continue;
            }

            if (appView.options().enableFieldBitAccessAnalysis && appView.isAllCodeProcessed()) {
              FieldOptimizationInfo optimizationInfo =
                  hazzerBitField.getDefinition().getOptimizationInfo();
              int hazzerBitIndex = protoFieldInfo.getHazzerBitFieldIndex(protoMessageInfo);
              if (!BitUtils.isBitSet(optimizationInfo.getReadBits(), hazzerBitIndex)) {
                continue;
              }
            }

            newlyLiveField = valueStorage;
          }
        }

        if (newlyLiveField != null) {
          // Mark hazzer and one-of proto fields as read from dynamicMethod() if they are written in
          // the app. This is needed to ensure that field writes are not removed from the app.
          ProgramMethod defaultInitializer =
              dynamicMethod.getHolder().getProgramDefaultInitializer();
          assert defaultInitializer != null;
          Predicate<ProgramMethod> neitherDefaultConstructorNorDynamicMethod =
              writer ->
                  !writer.isStructurallyEqualTo(defaultInitializer)
                      && !writer.isStructurallyEqualTo(dynamicMethod);
          if (enqueuer.isFieldWrittenInMethodSatisfying(
              newlyLiveField, neitherDefaultConstructorNorDynamicMethod)) {
            enqueuer.registerReflectiveFieldRead(newlyLiveField.getReference(), dynamicMethod);
          }

          // Unconditionally register the hazzer and one-of proto fields as written from
          // dynamicMethod().
          if (enqueuer.registerReflectiveFieldWrite(newlyLiveField.getReference(), dynamicMethod)) {
            worklist.enqueueMarkReachableFieldAction(
                newlyLiveField, dynamicMethod, KeepReason.reflectiveUseIn(dynamicMethod));
          }
        }
      }

      registerWriteToOneOfObjectsWithLiveOneOfCaseObject(protoMessageInfo, enqueuer, worklist);
    }
  }

  private void tracePendingInstructionsInDynamicMethods(
      Enqueuer enqueuer, EnqueuerWorklist worklist) {
    for (ProtoMessageInfo protoMessageInfo : liveProtos.values()) {
      if (protoMessageInfo == null || !protoMessageInfo.hasFields()) {
        continue;
      }

      ProgramMethod dynamicMethod = protoMessageInfo.getDynamicMethod();
      if (!dynamicMethodsWithTracedProtoObjects.add(dynamicMethod.getDefinition())) {
        continue;
      }

      for (ProtoFieldInfo protoFieldInfo : protoMessageInfo.getFields()) {
        List<ProtoObject> objects = protoFieldInfo.getObjects();
        if (objects == null || objects.isEmpty()) {
          // Nothing to trace.
          continue;
        }

        // NOTE: If `valueStorage` is not a live field, then code for it will not be emitted in the
        // schema, and therefore we do need to trace the const-class instructions that will be
        // emitted for it.
        ProgramField valueStorage = protoFieldInfo.getValueStorage(appView, protoMessageInfo);
        if (valueStorage != null && enqueuer.isFieldLive(valueStorage)) {
          for (ProtoObject object : objects) {
            if (object.isProtoObjectFromStaticGet()) {
              worklist.enqueueTraceStaticFieldRead(
                  object.asProtoObjectFromStaticGet().getField(), dynamicMethod);
            } else if (object.isProtoTypeObject()) {
              worklist.enqueueTraceConstClassAction(
                  object.asProtoTypeObject().getType(), dynamicMethod);
            }
          }
        }
      }
    }
  }

  /** Marks each oneof field whose corresponding oneof-case field is live as being written. */
  private void registerWriteToOneOfObjectsWithLiveOneOfCaseObject(
      ProtoMessageInfo protoMessageInfo, Enqueuer enqueuer, EnqueuerWorklist worklist) {
    if (protoMessageInfo.numberOfOneOfObjects() == 0) {
      return;
    }

    for (ProtoOneOfObjectPair oneOfObjectPair : protoMessageInfo.getOneOfObjects()) {
      registerWriteToOneOfObjectIfOneOfCaseObjectIsLive(oneOfObjectPair, enqueuer, worklist);
    }
  }

  /** Marks the given oneof field as being written if the corresponding oneof-case field is live. */
  private void registerWriteToOneOfObjectIfOneOfCaseObjectIsLive(
      ProtoOneOfObjectPair oneOfObjectPair, Enqueuer enqueuer, EnqueuerWorklist worklist) {
    ProtoFieldObject oneOfCaseObject = oneOfObjectPair.getOneOfCaseObject();
    if (!oneOfCaseObject.isLiveProtoFieldObject()) {
      assert false;
      return;
    }

    DexField oneOfCaseFieldReference = oneOfCaseObject.asLiveProtoFieldObject().getField();
    FieldResolutionResult oneOfCaseFieldResolutionResult =
        appView.appInfo().resolveField(oneOfCaseFieldReference);
    if (oneOfCaseFieldResolutionResult.isFailedOrUnknownResolution()) {
      assert false;
      return;
    }

    ProgramField oneOfCaseField =
        oneOfCaseFieldResolutionResult
            .asSuccessfulResolution()
            .getResolutionPair()
            .asProgramField();
    if (oneOfCaseField == null) {
      assert false;
      return;
    }

    ProgramMethod dynamicMethod =
        oneOfCaseField.getHolder().lookupProgramMethod(references.dynamicMethod);
    if (dynamicMethod == null) {
      assert false;
      return;
    }

    if (!enqueuer.isFieldLive(oneOfCaseField)) {
      return;
    }

    ProtoFieldObject oneOfObject = oneOfObjectPair.getOneOfObject();
    if (!oneOfObject.isLiveProtoFieldObject()) {
      assert false;
      return;
    }

    DexField oneOfFieldReference = oneOfObject.asLiveProtoFieldObject().getField();
    FieldResolutionResult oneOfFieldResolutionResult =
        appView.appInfo().resolveField(oneOfFieldReference);
    if (oneOfFieldResolutionResult.isFailedOrUnknownResolution()) {
      assert false;
      return;
    }

    ProgramField oneOfField =
        oneOfFieldResolutionResult.asSuccessfulResolution().getResolutionPair().asProgramField();
    if (oneOfField == null || oneOfField.getHolder() != oneOfCaseField.getHolder()) {
      assert false;
      return;
    }

    if (enqueuer.registerReflectiveFieldWrite(oneOfField.getReference(), dynamicMethod)) {
      worklist.enqueueMarkReachableFieldAction(
          oneOfField, dynamicMethod, KeepReason.reflectiveUseIn(dynamicMethod));
    }
  }

  /**
   * Traverses the proto schema graph.
   *
   * @return true if this proto field contains a map/required field directly or indirectly.
   */
  private boolean reachesMapOrRequiredField(ProtoFieldInfo protoFieldInfo) {
    ProtoFieldType protoFieldType = protoFieldInfo.getType();

    // If it is a map/required field, return true.
    if (protoFieldType.isMap() || protoFieldType.isRequired()) {
      return true;
    }

    if (!appView.options().protoShrinking().traverseOneOfAndRepeatedProtoFields) {
      if (protoFieldType.isOneOf() || protoFieldType.isRepeated()) {
        return false;
      }
    }

    // Otherwise, check if the type of the field may contain a map/required field.
    DexType baseMessageType = protoFieldInfo.getBaseMessageType(factory);
    if (baseMessageType != null) {
      ProtoMessageInfo protoMessageInfo = getOrCreateProtoMessageInfo(baseMessageType);
      if (protoMessageInfo != null) {
        return reachesMapOrRequiredField(protoMessageInfo);
      }
      assert false : "Unable to find proto message info for `" + baseMessageType + "`";
    }
    return false;
  }

  /**
   * Traverses the proto schema graph.
   *
   * @return true if this proto message contains a map/required field directly or indirectly.
   */
  private boolean reachesMapOrRequiredField(ProtoMessageInfo protoMessageInfo) {
    if (!protoMessageInfo.hasFields() && !extensionGraph.containsKey(protoMessageInfo.getType())) {
      return false;
    }

    OptionalBool cache =
        reachesMapOrRequiredFieldFromMessageCache.getOrDefault(
            protoMessageInfo, OptionalBool.unknown());
    if (!cache.isUnknown()) {
      return cache.isTrue();
    }

    // To guard against infinite recursion, we set the cache for this message to false, although
    // we may later find out that this message actually contains a map/required field.
    reachesMapOrRequiredFieldFromMessageCache.put(protoMessageInfo, OptionalBool.of(false));

    // Check if any of the fields contains a map/required field.
    if (protoMessageInfo.hasFields()) {
      for (ProtoFieldInfo protoFieldInfo : protoMessageInfo.getFields()) {
        if (reachesMapOrRequiredField(protoFieldInfo)) {
          reachesMapOrRequiredFieldFromMessageCache.put(protoMessageInfo, OptionalBool.of(true));
          return true;
        }
      }
    }

    Iterable<DexType> extensionTypes =
        extensionGraph.getOrDefault(protoMessageInfo.getType(), ImmutableSet.of());
    for (DexType extensionType : extensionTypes) {
      ProtoMessageInfo protoExtensionMessageInfo = getOrCreateProtoMessageInfo(extensionType);
      assert protoExtensionMessageInfo != null;
      if (reachesMapOrRequiredField(protoExtensionMessageInfo)) {
        reachesMapOrRequiredFieldFromMessageCache.put(protoMessageInfo, OptionalBool.of(true));
        return true;
      }
    }

    return false;
  }

  private ProtoMessageInfo getOrCreateProtoMessageInfo(DexType type) {
    if (liveProtos.containsKey(type)) {
      return liveProtos.get(type);
    }

    if (seenButNotLiveProtos.containsKey(type)) {
      return seenButNotLiveProtos.get(type);
    }

    DexProgramClass clazz = asProgramClassOrNull(appView.definitionFor(type));
    if (clazz == null) {
      seenButNotLiveProtos.put(type, null);
      return null;
    }

    ProgramMethod dynamicMethod = clazz.lookupProgramMethod(references.dynamicMethod);
    if (dynamicMethod == null) {
      seenButNotLiveProtos.put(type, null);
      return null;
    }

    createProtoMessageInfoFromDynamicMethod(dynamicMethod, seenButNotLiveProtos);

    return seenButNotLiveProtos.get(type);
  }
}