//===- MutagenDispatcher.h - Internal header for the mutagen ----*- C++ -* ===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// mutagen::MutationDispatcher
//===----------------------------------------------------------------------===//

#ifndef LLVM_FUZZER_MUTAGEN_DISPATCHER_H
#define LLVM_FUZZER_MUTAGEN_DISPATCHER_H

#include "FuzzerRandom.h"
#include "Mutagen.h"
#include "MutagenDictionary.h"
#include "MutagenSequence.h"
#include <cstddef>
#include <cstdint>
#include <string>

namespace mutagen {
namespace {

using fuzzer::Random;
using fuzzer::Unit;
using fuzzer::Vector;
using fuzzer::Word;

} // namespace

class MutationDispatcher final {
public:
  struct Mutator {
    size_t (MutationDispatcher::*Fn)(uint8_t *Data, size_t Size, size_t Max);
    const char *Name;
  };

  explicit MutationDispatcher(const LLVMMutagenConfiguration *Config);
  ~MutationDispatcher() = default;

  /// Indicate that we are about to start a new sequence of mutations.
  void StartMutationSequence();
  /// Returns the current sequence of mutations. May truncate the sequence
  /// unless Verbose is true. Sets |OutSize| to the length of the untrancated
  /// sequence, if provided.
  const Sequence<Mutator> &MutationSequence();
  /// Returns the current sequence of dictionary entries. May truncate the
  /// sequence unless Verbose is true. Sets |OutSize| to the length of the
  /// untrancated sequence, if provided.
  const Sequence<DictionaryEntry *> &DictionaryEntrySequence();
  /// Indicate that the current sequence of mutations was successful.
  void RecordSuccessfulMutationSequence();
  /// Mutates data by invoking user-provided mutator.
  size_t Mutate_Custom(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by invoking user-provided crossover.
  size_t Mutate_CustomCrossOver(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by shuffling bytes.
  size_t Mutate_ShuffleBytes(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by erasing bytes.
  size_t Mutate_EraseBytes(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by inserting a byte.
  size_t Mutate_InsertByte(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by inserting several repeated bytes.
  size_t Mutate_InsertRepeatedBytes(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by changing one byte.
  size_t Mutate_ChangeByte(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by changing one bit.
  size_t Mutate_ChangeBit(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Mutates data by copying/inserting a part of data into a different place.
  size_t Mutate_CopyPart(uint8_t *Data, size_t Size, size_t MaxSize);

  /// Mutates data by adding a word from the manual dictionary.
  size_t Mutate_AddWordFromManualDictionary(uint8_t *Data, size_t Size,
                                            size_t MaxSize);

  /// Mutates data by adding a word from the TORC.
  size_t Mutate_AddWordFromTORC(uint8_t *Data, size_t Size, size_t MaxSize);

  /// Mutates data by adding a word from the persistent automatic dictionary.
  size_t Mutate_AddWordFromPersistentAutoDictionary(uint8_t *Data, size_t Size,
                                                    size_t MaxSize);

  /// Tries to find an ASCII integer in Data, changes it to another ASCII int.
  size_t Mutate_ChangeASCIIInteger(uint8_t *Data, size_t Size, size_t MaxSize);
  /// Change a 1-, 2-, 4-, or 8-byte integer in interesting ways.
  size_t Mutate_ChangeBinaryInteger(uint8_t *Data, size_t Size, size_t MaxSize);

  /// CrossOver Data with CrossOverWith.
  size_t Mutate_CrossOver(uint8_t *Data, size_t Size, size_t MaxSize);

  size_t AddWordFromDictionary(Dictionary &D, uint8_t *Data, size_t Size,
                               size_t MaxSize);
  size_t MutateImpl(uint8_t *Data, size_t Size, size_t MaxSize,
                    Vector<Mutator> &Mutators);

  size_t InsertPartOf(const uint8_t *From, size_t FromSize, uint8_t *To,
                      size_t ToSize, size_t MaxToSize);
  size_t CopyPartOf(const uint8_t *From, size_t FromSize, uint8_t *To,
                    size_t ToSize);
  size_t ApplyDictionaryEntry(uint8_t *Data, size_t Size, size_t MaxSize,
                              DictionaryEntry &DE);

  template <class T>
  DictionaryEntry MakeDictionaryEntryFromCMP(T Arg1, T Arg2,
                                             const uint8_t *Data, size_t Size);
  DictionaryEntry MakeDictionaryEntryFromCMP(const Word &Arg1, const Word &Arg2,
                                             const uint8_t *Data, size_t Size);
  DictionaryEntry MakeDictionaryEntryFromCMP(const void *Arg1, const void *Arg2,
                                             const void *Arg1Mutation,
                                             const void *Arg2Mutation,
                                             size_t ArgSize,
                                             const uint8_t *Data, size_t Size);

  /// Applies one of the configured mutations.
  /// Returns the new size of data which could be up to MaxSize.
  size_t Mutate(uint8_t *Data, size_t Size, size_t MaxSize);

  /// Applies one of the configured mutations to the bytes of Data
  /// that have '1' in Mask.
  /// Mask.size() should be >= Size.
  size_t MutateWithMask(uint8_t *Data, size_t Size, size_t MaxSize,
                        const Vector<uint8_t> &Mask);

  /// Applies one of the default mutations. Provided as a service
  /// to mutation authors.
  size_t DefaultMutate(uint8_t *Data, size_t Size, size_t MaxSize);

  /// Creates a cross-over of two pieces of Data, returns its size.
  size_t CrossOver(const uint8_t *Data1, size_t Size1, const uint8_t *Data2,
                   size_t Size2, uint8_t *Out, size_t MaxOutSize);

  void AddWordToManualDictionary(const Word &W);

  // Creates a recommended dictionary and returns its number of entries. The
  // entries can be retrieved by subsequent calls to
  // |LLVMMutagenRecommendDictionaryEntry|.
  const Dictionary &RecommendDictionary();

  // Returns the ASCII representation of the next recommended dictionary entry,
  // and sets |OutUseCount| to its use count. The return pointer is valid until
  // the next call to this method.
  const char *RecommendDictionaryEntry(size_t *OutUseCount);

  void SetCrossOverWith(const Unit *U) { CrossOverWith = U; }

  Random &GetRand() { return Rand; }

private:
  // Imports and validates the disptacher's configuration.
  void SetConfig(const LLVMMutagenConfiguration *Config);

  Random Rand;
  LLVMMutagenConfiguration Config;

  // Dictionary provided by the user via -dict=DICT_FILE.
  Dictionary ManualDictionary;
  // Persistent dictionary modified by the fuzzer, consists of
  // entries that led to successful discoveries in the past mutations.
  Dictionary PersistentAutoDictionary;
  // Recommended dictionary buolt by |RecommendDictionary|.
  Dictionary RecommendedDictionary;
  size_t NextRecommendedDictionaryEntry = 0;
  std::string DictionaryEntryWord;

  Sequence<DictionaryEntry *> CurrentDictionaryEntrySequence;

  static const size_t kCmpDictionaryEntriesDequeSize = 16;
  DictionaryEntry CmpDictionaryEntriesDeque[kCmpDictionaryEntriesDequeSize];
  size_t CmpDictionaryEntriesDequeIdx = 0;

  const Unit *CrossOverWith = nullptr;
  Vector<uint8_t> MutateInPlaceHere;
  Vector<uint8_t> MutateWithMaskTemp;
  // CustomCrossOver needs its own buffer as a custom implementation may call
  // LLVMFuzzerMutate, which in turn may resize MutateInPlaceHere.
  Vector<uint8_t> CustomCrossOverInPlaceHere;

  Vector<Mutator> Mutators;
  Vector<Mutator> DefaultMutators;
  Sequence<Mutator> CurrentMutatorSequence;
};

// Returns a pointer to the MutationDispatcher is use by MutagenInterface.
// This should only be used for testing.
MutationDispatcher *GetMutationDispatcherForTest();

} // namespace mutagen

#endif // LLVM_FUZZER_MUTAGEN_DISPATCHER_H