// Copyright 2021 The Tint Authors.
//
// 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 "fuzzers/tint_spirv_tools_fuzzer/spirv_reduce_mutator.h"

#include <fstream>

#include "fuzzers/tint_spirv_tools_fuzzer/util.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/opt/build_module.h"
#include "source/reduce/conditional_branch_to_simple_conditional_branch_opportunity_finder.h"
#include "source/reduce/merge_blocks_reduction_opportunity_finder.h"
#include "source/reduce/operand_to_const_reduction_opportunity_finder.h"
#include "source/reduce/operand_to_dominating_id_reduction_opportunity_finder.h"
#include "source/reduce/operand_to_undef_reduction_opportunity_finder.h"
#include "source/reduce/remove_block_reduction_opportunity_finder.h"
#include "source/reduce/remove_function_reduction_opportunity_finder.h"
#include "source/reduce/remove_selection_reduction_opportunity_finder.h"
#include "source/reduce/remove_unused_instruction_reduction_opportunity_finder.h"
#include "source/reduce/remove_unused_struct_member_reduction_opportunity_finder.h"
#include "source/reduce/simple_conditional_branch_to_branch_opportunity_finder.h"
#include "source/reduce/structured_loop_to_selection_reduction_opportunity_finder.h"

namespace tint {
namespace fuzzers {
namespace spvtools_fuzzer {

SpirvReduceMutator::SpirvReduceMutator(spv_target_env target_env,
                                       std::vector<uint32_t> binary,
                                       uint32_t seed,
                                       uint32_t reductions_batch_size,
                                       bool enable_all_reductions,
                                       bool validate_after_each_reduction)
    : ir_context_(nullptr),
      finders_(),
      generator_(seed),
      errors_(),
      is_valid_(true),
      reductions_batch_size_(reductions_batch_size),
      total_applied_reductions_(0),
      enable_all_reductions_(enable_all_reductions),
      validate_after_each_reduction_(validate_after_each_reduction),
      original_binary_(std::move(binary)),
      seed_(seed) {
  ir_context_ = spvtools::BuildModule(
      target_env, spvtools::fuzz::fuzzerutil::kSilentMessageConsumer,
      original_binary_.data(), original_binary_.size());
  assert(ir_context_ && "|binary| is invalid");

  do {
    MaybeAddFinder<
        spvtools::reduce::
            ConditionalBranchToSimpleConditionalBranchOpportunityFinder>();
    MaybeAddFinder<spvtools::reduce::MergeBlocksReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::OperandToConstReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::OperandToDominatingIdReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::OperandToUndefReductionOpportunityFinder>();
    MaybeAddFinder<spvtools::reduce::RemoveBlockReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::RemoveFunctionReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::RemoveSelectionReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::RemoveUnusedInstructionReductionOpportunityFinder>(
        true);
    MaybeAddFinder<
        spvtools::reduce::RemoveUnusedStructMemberReductionOpportunityFinder>();
    MaybeAddFinder<
        spvtools::reduce::SimpleConditionalBranchToBranchOpportunityFinder>();
    MaybeAddFinder<spvtools::reduce::
                       StructuredLoopToSelectionReductionOpportunityFinder>();
  } while (finders_.empty());
}

Mutator::Result SpirvReduceMutator::Mutate() {
  assert(is_valid_ && "Can't mutate invalid module");

  // The upper limit on the number of applied reduction passes.
  const uint32_t kMaxAppliedReductions = 500;
  const auto old_applied_reductions = total_applied_reductions_;

  // The upper limit on the number of failed attempts to apply reductions (i.e.
  // when no reduction was returned by the reduction finder).
  const uint32_t kMaxConsecutiveFailures = 10;
  uint32_t num_consecutive_failures = 0;

  // Iterate while we haven't exceeded the limit on the total number of applied
  // reductions, the limit on the number of reductions applied at once and limit
  // on the number of consecutive failed attempts.
  while (total_applied_reductions_ < kMaxAppliedReductions &&
         (reductions_batch_size_ == 0 ||
          total_applied_reductions_ - old_applied_reductions <
              reductions_batch_size_) &&
         num_consecutive_failures < kMaxConsecutiveFailures) {
    // Select an opportunity finder and get some reduction opportunities from
    // it.
    auto finder = GetRandomElement(&finders_);
    auto reduction_opportunities =
        finder->GetAvailableOpportunities(ir_context_.get(), 0);

    if (reduction_opportunities.empty()) {
      // There is nothing to reduce. We increase the counter to make sure we
      // don't stuck in this situation.
      num_consecutive_failures++;
    } else {
      // Apply a random reduction opportunity. The latter should be applicable.
      auto opportunity = GetRandomElement(&reduction_opportunities);
      assert(opportunity->PreconditionHolds() && "Preconditions should hold");
      total_applied_reductions_++;
      num_consecutive_failures = 0;
      if (!ApplyReduction(opportunity)) {
        // The module became invalid as a result of the applied reduction.
        is_valid_ = false;
        return {Mutator::Status::kInvalid,
                total_applied_reductions_ != old_applied_reductions};
      }
    }
  }

  auto is_changed = total_applied_reductions_ != old_applied_reductions;
  if (total_applied_reductions_ == kMaxAppliedReductions) {
    return {Mutator::Status::kLimitReached, is_changed};
  }

  if (num_consecutive_failures == kMaxConsecutiveFailures) {
    return {Mutator::Status::kStuck, is_changed};
  }

  assert(is_changed && "This is the only way left to break the loop");
  return {Mutator::Status::kComplete, is_changed};
}

bool SpirvReduceMutator::ApplyReduction(
    spvtools::reduce::ReductionOpportunity* reduction_opportunity) {
  reduction_opportunity->TryToApply();
  return !validate_after_each_reduction_ ||
         spvtools::fuzz::fuzzerutil::IsValidAndWellFormed(
             ir_context_.get(), spvtools::ValidatorOptions(),
             util::GetBufferMessageConsumer(&errors_));
}

std::vector<uint32_t> SpirvReduceMutator::GetBinary() const {
  std::vector<uint32_t> result;
  ir_context_->module()->ToBinary(&result, true);
  return result;
}

std::string SpirvReduceMutator::GetErrors() const {
  return errors_.str();
}

void SpirvReduceMutator::LogErrors(const std::string* path,
                                   uint32_t count) const {
  auto message = GetErrors();
  std::cout << count << " | SpirvReduceMutator (seed: " << seed_ << ")"
            << std::endl;
  std::cout << message << std::endl;

  if (path) {
    auto prefix = *path + std::to_string(count);

    // Write errors to file.
    std::ofstream(prefix + ".reducer.log") << "seed: " << seed_ << std::endl
                                           << message << std::endl;

    // Write the invalid SPIR-V binary.
    util::WriteBinary(prefix + ".reducer.invalid.spv", GetBinary());

    // Write the original SPIR-V binary.
    util::WriteBinary(prefix + ".reducer.original.spv", original_binary_);
  }
}

}  // namespace spvtools_fuzzer
}  // namespace fuzzers
}  // namespace tint