// Copyright 2010-2025 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.

syntax = "proto3";

package operations_research;

// Information required to create a schedule for a school system.
message CourseSchedulingModel {
  // Schedule name, used only for logging purposes.
  string display_name = 1;

  // The number of days in a schedule rotation. If the school system uses a
  // block schedule, this value should be 1.
  int32 days_count = 2;

  // The number of time slots each day in a schedule rotation. If the school
  // system uses a block schedule, this value is the number of blocks.
  int32 daily_time_slot_count = 3;

  // List of courses that need to be scheduled.
  repeated Course courses = 4;

  // List of teachers.
  repeated Teacher teachers = 5;

  // List of students that need to be assigned to these courses.
  repeated Student students = 6;

  // List of rooms that the courses can be assigned to.
  repeated Room rooms = 7;
}

// Holds the solution to the course scheduling problem.
message CourseSchedulingResult {
  // Human readable message about the solver or given model.
  string message = 1;

  // Status of the solver.
  CourseSchedulingResultStatus solver_status = 2;

  // List of the time slot and room assignments for each section of a course.
  repeated ClassAssignment class_assignments = 3;

  // List of course and section assignments for each student.
  repeated StudentAssignment student_assignments = 4;
}

message ClassAssignment {
  // Index of the course in the CourseSchedulingModel.
  int32 course_index = 1;

  // Specific section of the course in the CourseSchedulingModel.
  int32 section_number = 2;

  // Time slots that this class has been assigned to in the
  // CourseSchedulingModel.
  repeated int32 time_slots = 3;

  // Indices of the rooms that the class is assigned to in the
  // CourseSchedulingModel. If this is not empty, then the number of indices
  // must match the number of time slots.
  repeated int32 room_indices = 4;
}

message StudentAssignment {
  // Index of the student in the CourseSchedulingModel.
  int32 student_index = 1;

  // Course indices in the CourseSchedulingModel that this student has been
  // assigned to. The number of indices must match the number of section
  // indices.
  repeated int32 course_indices = 2;

  // Section indices for each Course in the CourseSchedulingModel this this
  // student has been assigned to. The number of indices must match the number
  // of course indices.
  repeated int32 section_indices = 3;
}

message Course {
  // Course name, used only for logging purposes.
  string display_name = 1;

  // The number of times each section of this course needs to meet during a
  // schedule rotation. Each section of the course meets no more than once a
  // day. If the school system uses a block schedule, then this value should
  // be 1.
  int32 meetings_count = 2;

  // The maximum number of students for this course. This value can be equal to
  // +Infinity to encode a course has no maximum capacity.
  int32 max_capacity = 3;

  // The minimum number of students for this course.
  int32 min_capacity = 4;

  // The number of consecutive time slots that each section of this course needs
  // to be scheduled for. This value can only be 1 or 2. If the value is 2, then
  // 2 consecutive time slots in a day counts as 1 meeting time for the section.
  int32 consecutive_slots_count = 5;

  // List of indices for the teachers of this course. We are assuming that each
  // teacher teaches separately. Must have the same number of elements as the
  // number of sections list.
  repeated int32 teacher_indices = 6;

  // The number of sections each teacher teaches of this course. Must have the
  // same number of elements as the teacher index list.
  repeated int32 teacher_section_counts = 7;

  // List of the possible rooms that this course can be assigned to. This can
  // be empty.
  repeated int32 room_indices = 8;
}

message Teacher {
  // Teacher name, used only for logging purposes.
  string display_name = 1;

  // List of time slots that the teacher cannot be scheduled for. These time
  // slot values index to the accumulative number of time slots starting at 0.
  // For example, if a schedule rotation has 5 days and 8 time slots per day,
  // and a teacher cannot be scheduled for the last time slot of the fourth
  // day, the number here would be 31.
  repeated int32 restricted_time_slots = 2;
}

message Student {
  // Student name, used only for logging purposes.
  string display_name = 1;

  // List of course indices that the student needs to be enrolled in.
  repeated int32 course_indices = 2;
}

message Room {
  // Room name, used only for logging purposes.
  string display_name = 1;

  // Maximum number of students that can fit into this room.
  int32 capacity = 2;
}

// Status returned by the solver.
enum CourseSchedulingResultStatus {
  COURSE_SCHEDULING_RESULT_STATUS_UNSPECIFIED = 0;

  // The solver had enough time to find some solution that satisfies all
  // constraints, but it did not prove optimality (which means it may or may
  // not have reached the optimal).
  //
  // This can happen for large LP models (linear programming), and is a frequent
  // response for time-limited MIPs (mixed integer programming). This is also
  // what the CP (constraint programming) solver will return if there is no
  // objective specified.
  SOLVER_FEASIBLE = 1;

  // The solver found the proven optimal solution.
  SOLVER_OPTIMAL = 2;

  // The model does not have any solution, according to the solver (which
  // "proved" it, with the caveat that numerical proofs aren't actual proofs),
  // or based on trivial considerations (eg. a variable whose lower bound is
  // strictly greater than its upper bound).
  SOLVER_INFEASIBLE = 3;

  // Model errors. These are always deterministic and repeatable.
  // They should be accompanied with a string description of the error.
  SOLVER_MODEL_INVALID = 4;

  // The model has not been solved in the given time or the solver was not able
  // to solve the model given.
  SOLVER_NOT_SOLVED = 5;

  // An error (either numerical or from a bug in the code) occurred.
  ABNORMAL = 6;
}