// Copyright (c) 2019 Google LLC
//
// 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.

#include "source/fuzz/fuzzer.h"

#include <cassert>
#include <memory>
#include <sstream>

#include "source/fuzz/fact_manager.h"
#include "source/fuzz/fuzzer_context.h"
#include "source/fuzz/fuzzer_pass_add_dead_breaks.h"
#include "source/fuzz/fuzzer_pass_add_dead_continues.h"
#include "source/fuzz/fuzzer_pass_add_useful_constructs.h"
#include "source/fuzz/fuzzer_pass_adjust_selection_controls.h"
#include "source/fuzz/fuzzer_pass_apply_id_synonyms.h"
#include "source/fuzz/fuzzer_pass_construct_composites.h"
#include "source/fuzz/fuzzer_pass_copy_objects.h"
#include "source/fuzz/fuzzer_pass_obfuscate_constants.h"
#include "source/fuzz/fuzzer_pass_permute_blocks.h"
#include "source/fuzz/fuzzer_pass_split_blocks.h"
#include "source/fuzz/protobufs/spirvfuzz_protobufs.h"
#include "source/fuzz/pseudo_random_generator.h"
#include "source/opt/build_module.h"
#include "source/spirv_fuzzer_options.h"
#include "source/util/make_unique.h"

namespace spvtools {
namespace fuzz {

namespace {
const uint32_t kIdBoundGap = 100;

const uint32_t kTransformationLimit = 500;

const uint32_t kChanceOfApplyingAnotherPass = 85;

template <typename T>
void MaybeAddPass(
    std::vector<std::unique_ptr<FuzzerPass>>* passes,
    opt::IRContext* ir_context, FactManager* fact_manager,
    FuzzerContext* fuzzer_context,
    protobufs::TransformationSequence* transformation_sequence_out) {
  if (fuzzer_context->ChooseEven()) {
    passes->push_back(MakeUnique<T>(ir_context, fact_manager, fuzzer_context,
                                    transformation_sequence_out));
  }
}

}  // namespace

struct Fuzzer::Impl {
  explicit Impl(spv_target_env env) : target_env(env) {}

  const spv_target_env target_env;  // Target environment.
  MessageConsumer consumer;         // Message consumer.
};

Fuzzer::Fuzzer(spv_target_env env) : impl_(MakeUnique<Impl>(env)) {}

Fuzzer::~Fuzzer() = default;

void Fuzzer::SetMessageConsumer(MessageConsumer c) {
  impl_->consumer = std::move(c);
}

Fuzzer::FuzzerResultStatus Fuzzer::Run(
    const std::vector<uint32_t>& binary_in,
    const protobufs::FactSequence& initial_facts,
    spv_const_fuzzer_options options, std::vector<uint32_t>* binary_out,
    protobufs::TransformationSequence* transformation_sequence_out) const {
  // Check compatibility between the library version being linked with and the
  // header files being used.
  GOOGLE_PROTOBUF_VERIFY_VERSION;

  spvtools::SpirvTools tools(impl_->target_env);
  tools.SetMessageConsumer(impl_->consumer);
  if (!tools.IsValid()) {
    impl_->consumer(SPV_MSG_ERROR, nullptr, {},
                    "Failed to create SPIRV-Tools interface; stopping.");
    return Fuzzer::FuzzerResultStatus::kFailedToCreateSpirvToolsInterface;
  }

  // Initial binary should be valid.
  if (!tools.Validate(&binary_in[0], binary_in.size())) {
    impl_->consumer(SPV_MSG_ERROR, nullptr, {},
                    "Initial binary is invalid; stopping.");
    return Fuzzer::FuzzerResultStatus::kInitialBinaryInvalid;
  }

  // Build the module from the input binary.
  std::unique_ptr<opt::IRContext> ir_context = BuildModule(
      impl_->target_env, impl_->consumer, binary_in.data(), binary_in.size());
  assert(ir_context);

  // Make a PRNG, either from a given seed or from a random device.
  PseudoRandomGenerator random_generator(
      options->has_random_seed ? options->random_seed
                               : static_cast<uint32_t>(std::random_device()()));

  // The fuzzer will introduce new ids into the module.  The module's id bound
  // gives the smallest id that can be used for this purpose.  We add an offset
  // to this so that there is a sizeable gap between the ids used in the
  // original module and the ids used for fuzzing, as a readability aid.
  //
  // TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2541) consider the
  //  case where the maximum id bound is reached.
  auto minimum_fresh_id = ir_context->module()->id_bound() + kIdBoundGap;
  FuzzerContext fuzzer_context(&random_generator, minimum_fresh_id);

  FactManager fact_manager;
  fact_manager.AddFacts(impl_->consumer, initial_facts, ir_context.get());

  // Add some essential ingredients to the module if they are not already
  // present, such as boolean constants.
  FuzzerPassAddUsefulConstructs(ir_context.get(), &fact_manager,
                                &fuzzer_context, transformation_sequence_out)
      .Apply();

  // Apply some semantics-preserving passes.
  std::vector<std::unique_ptr<FuzzerPass>> passes;
  while (passes.empty()) {
    MaybeAddPass<FuzzerPassAddDeadBreaks>(&passes, ir_context.get(),
                                          &fact_manager, &fuzzer_context,
                                          transformation_sequence_out);
    MaybeAddPass<FuzzerPassAddDeadContinues>(&passes, ir_context.get(),
                                             &fact_manager, &fuzzer_context,
                                             transformation_sequence_out);
    MaybeAddPass<FuzzerPassApplyIdSynonyms>(&passes, ir_context.get(),
                                            &fact_manager, &fuzzer_context,
                                            transformation_sequence_out);
    MaybeAddPass<FuzzerPassConstructComposites>(&passes, ir_context.get(),
                                                &fact_manager, &fuzzer_context,
                                                transformation_sequence_out);
    MaybeAddPass<FuzzerPassCopyObjects>(&passes, ir_context.get(),
                                        &fact_manager, &fuzzer_context,
                                        transformation_sequence_out);
    MaybeAddPass<FuzzerPassObfuscateConstants>(&passes, ir_context.get(),
                                               &fact_manager, &fuzzer_context,
                                               transformation_sequence_out);
    MaybeAddPass<FuzzerPassPermuteBlocks>(&passes, ir_context.get(),
                                          &fact_manager, &fuzzer_context,
                                          transformation_sequence_out);
    MaybeAddPass<FuzzerPassSplitBlocks>(&passes, ir_context.get(),
                                        &fact_manager, &fuzzer_context,
                                        transformation_sequence_out);
  }

  bool is_first = true;
  while (static_cast<uint32_t>(
             transformation_sequence_out->transformation_size()) <
             kTransformationLimit &&
         (is_first ||
          fuzzer_context.ChoosePercentage(kChanceOfApplyingAnotherPass))) {
    is_first = false;
    passes[fuzzer_context.RandomIndex(passes)]->Apply();
  }

  // Now apply some passes that it does not make sense to apply repeatedly,
  // as they do not unlock other passes.
  if (fuzzer_context.ChooseEven()) {
    FuzzerPassAdjustSelectionControls(ir_context.get(), &fact_manager,
                                      &fuzzer_context,
                                      transformation_sequence_out)
        .Apply();
  }

  // Encode the module as a binary.
  ir_context->module()->ToBinary(binary_out, false);

  return Fuzzer::FuzzerResultStatus::kComplete;
}

}  // namespace fuzz
}  // namespace spvtools