// Copyright 2010-2021 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 <stdlib.h>

#include <cstdint>

#include "absl/types/span.h"
#include "ortools/base/logging.h"
#include "ortools/sat/cp_model.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/sat/cp_model_solver.h"
#include "ortools/sat/model.h"
#include "ortools/util/sorted_interval_list.h"

namespace operations_research {
namespace sat {

void NoOverlapSampleSat() {
  CpModelBuilder cp_model;
  const int64_t kHorizon = 21;  // 3 weeks.

  const Domain horizon(0, kHorizon);
  // Task 0, duration 2.
  const IntVar start_0 = cp_model.NewIntVar(horizon);
  const int64_t duration_0 = 2;
  const IntVar end_0 = cp_model.NewIntVar(horizon);
  const IntervalVar task_0 =
      cp_model.NewIntervalVar(start_0, duration_0, end_0);

  // Task 1, duration 4.
  const IntVar start_1 = cp_model.NewIntVar(horizon);
  const int64_t duration_1 = 4;
  const IntVar end_1 = cp_model.NewIntVar(horizon);
  const IntervalVar task_1 =
      cp_model.NewIntervalVar(start_1, duration_1, end_1);

  // Task 2, duration 3.
  const IntVar start_2 = cp_model.NewIntVar(horizon);
  const int64_t duration_2 = 3;
  const IntVar end_2 = cp_model.NewIntVar(horizon);
  const IntervalVar task_2 =
      cp_model.NewIntervalVar(start_2, duration_2, end_2);

  // Week ends.
  const IntervalVar weekend_0 = cp_model.NewIntervalVar(5, 2, 7);
  const IntervalVar weekend_1 = cp_model.NewIntervalVar(12, 2, 14);
  const IntervalVar weekend_2 = cp_model.NewIntervalVar(19, 2, 21);

  // No Overlap constraint.
  cp_model.AddNoOverlap(
      {task_0, task_1, task_2, weekend_0, weekend_1, weekend_2});

  // Makespan.
  IntVar makespan = cp_model.NewIntVar(horizon);
  cp_model.AddLessOrEqual(end_0, makespan);
  cp_model.AddLessOrEqual(end_1, makespan);
  cp_model.AddLessOrEqual(end_2, makespan);

  cp_model.Minimize(makespan);

  // Solving part.
  Model model;
  const CpSolverResponse response = SolveCpModel(cp_model.Build(), &model);
  LOG(INFO) << CpSolverResponseStats(response);

  if (response.status() == CpSolverStatus::OPTIMAL) {
    LOG(INFO) << "Optimal Schedule Length: " << response.objective_value();
    LOG(INFO) << "Task 0 starts at " << SolutionIntegerValue(response, start_0);
    LOG(INFO) << "Task 1 starts at " << SolutionIntegerValue(response, start_1);
    LOG(INFO) << "Task 2 starts at " << SolutionIntegerValue(response, start_2);
  }
}

}  // namespace sat
}  // namespace operations_research

int main() {
  operations_research::sat::NoOverlapSampleSat();

  return EXIT_SUCCESS;
}
