package courses

import (
	"Yimaru-Backend/internal/domain"
	"Yimaru-Backend/internal/ports"
	"Yimaru-Backend/internal/services/programs"
	"context"
	"errors"

	"github.com/jackc/pgx/v5"
)

var ErrCourseNotFound = errors.New("course not found")

type Service struct {
	courses  ports.CourseStore
	programs ports.ProgramStore
}

func NewService(courses ports.CourseStore, programs ports.ProgramStore) *Service {
	return &Service{courses: courses, programs: programs}
}

func (s *Service) Create(ctx context.Context, programID int64, input domain.CreateCourseInput) (domain.Course, error) {
	if _, err := s.programs.GetProgramByID(ctx, programID); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.Course{}, programs.ErrProgramNotFound
		}
		return domain.Course{}, err
	}
	return s.courses.CreateCourse(ctx, programID, input)
}

func (s *Service) GetByID(ctx context.Context, id int64) (domain.Course, error) {
	c, err := s.courses.GetCourseByID(ctx, id)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.Course{}, ErrCourseNotFound
		}
		return domain.Course{}, err
	}
	return c, nil
}

func (s *Service) ListByProgram(ctx context.Context, programID int64, limit, offset int32) ([]domain.Course, int64, error) {
	if _, err := s.programs.GetProgramByID(ctx, programID); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, 0, programs.ErrProgramNotFound
		}
		return nil, 0, err
	}
	if limit <= 0 {
		limit = 20
	}
	if limit > 200 {
		limit = 200
	}
	if offset < 0 {
		offset = 0
	}
	return s.courses.ListCoursesByProgramID(ctx, programID, limit, offset)
}

func (s *Service) Update(ctx context.Context, id int64, input domain.UpdateCourseInput) (domain.Course, error) {
	c, err := s.courses.UpdateCourse(ctx, id, input)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.Course{}, ErrCourseNotFound
		}
		return domain.Course{}, err
	}
	return c, nil
}

func (s *Service) Delete(ctx context.Context, id int64) error {
	if _, err := s.courses.GetCourseByID(ctx, id); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ErrCourseNotFound
		}
		return err
	}
	return s.courses.DeleteCourse(ctx, id)
}