// 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.

#ifndef SRC_TINT_FUZZERS_TINT_SPIRV_TOOLS_FUZZER_MUTATOR_H_
#define SRC_TINT_FUZZERS_TINT_SPIRV_TOOLS_FUZZER_MUTATOR_H_

#include <cassert>
#include <cstdint>
#include <string>
#include <vector>

namespace tint::fuzzers::spvtools_fuzzer {

/// This is an interface that is used to define custom mutators based on the
/// SPIR-V tools.
class Mutator {
 public:
  /// The status of the mutation.
  enum class Status {
    /// Binary is valid, the limit is not reached - can mutate further.
    kComplete,

    /// The binary is valid, the limit of mutations has been reached -
    /// can't mutate further.
    kLimitReached,

    /// The binary is valid, the limit is not reached but the mutator has spent
    /// too much time without mutating anything - better to restart to make sure
    /// we can make any progress.
    kStuck,

    /// The binary is invalid - this is likely a bug in the mutator - must
    /// abort.
    kInvalid
  };

  /// Represents the result of the mutation. The following states are possible:
  /// - if `IsChanged() == false`, then `GetStatus()` can be either
  ///   `kLimitReached` or `kStuck`.
  /// - otherwise, any value of `Status` is possible.
  class Result {
   public:
    /// Constructor.
    /// @param status - the status of the mutation.
    /// @param is_changed - whether the module was changed during mutation.
    Result(Status status, bool is_changed);

    /// @return the status of the mutation.
    Status GetStatus() const { return status_; }

    /// @return whether the module was changed during mutation.
    bool IsChanged() const { return is_changed_; }

   private:
    Status status_;
    bool is_changed_;
  };

  /// Virtual destructor.
  virtual ~Mutator();

  /// Causes the mutator to apply a mutation. This method can be called
  /// multiple times as long as the previous call didn't return
  /// `Status::kInvalid`.
  ///
  /// @return the status of the mutation (e.g. success, error etc) and whether
  ///     the binary was changed during mutation.
  virtual Result Mutate() = 0;

  /// Returns the mutated binary. The returned binary is guaranteed to be valid
  /// iff the previous call to the `Mutate` method returned didn't return
  /// `Status::kInvalid`.
  ///
  /// @return the mutated SPIR-V binary. It might be identical to the original
  ///     binary if `Result::IsChanged` returns `false`.
  virtual std::vector<uint32_t> GetBinary() const = 0;

  /// Returns errors, produced by the mutator.
  ///
  /// @param path - the directory to which the errors are printed to. No files
  ///     are created if the `path` is nullptr.
  /// @param count - the number of the error. Files for this error will be
  ///     prefixed with `count`.
  virtual void LogErrors(const std::string* path, uint32_t count) const = 0;

  /// @return errors encountered during the mutation. The returned string is
  ///     if there were no errors during mutation.
  virtual std::string GetErrors() const = 0;
};

}  // namespace tint::fuzzers::spvtools_fuzzer

#endif  // SRC_TINT_FUZZERS_TINT_SPIRV_TOOLS_FUZZER_MUTATOR_H_