package lessons

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

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

var ErrLessonNotFound = errors.New("lesson not found")

type Service struct {
	lessons ports.LessonStore
	modules ports.ModuleStore
}

func NewService(lessons ports.LessonStore, modules ports.ModuleStore) *Service {
	return &Service{lessons: lessons, modules: modules}
}

func (s *Service) getModuleOrErr(ctx context.Context, moduleID int64) error {
	_, err := s.modules.GetModuleByID(ctx, moduleID)
	if err == nil {
		return nil
	}
	if errors.Is(err, pgx.ErrNoRows) {
		return modules.ErrModuleNotFound
	}
	return err
}

func (s *Service) Create(ctx context.Context, moduleID int64, input domain.CreateLessonInput) (domain.Lesson, error) {
	if err := s.getModuleOrErr(ctx, moduleID); err != nil {
		return domain.Lesson{}, err
	}
	return s.lessons.CreateLesson(ctx, moduleID, input)
}

func (s *Service) GetByID(ctx context.Context, id int64) (domain.Lesson, error) {
	l, err := s.lessons.GetLessonByID(ctx, id)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.Lesson{}, ErrLessonNotFound
		}
		return domain.Lesson{}, err
	}
	return l, nil
}

func (s *Service) ListByModule(ctx context.Context, moduleID int64, publishedOnly bool, limit, offset int32) ([]domain.Lesson, int64, error) {
	if err := s.getModuleOrErr(ctx, moduleID); err != nil {
		return nil, 0, err
	}
	if limit <= 0 {
		limit = 20
	}
	if limit > 200 {
		limit = 200
	}
	if offset < 0 {
		offset = 0
	}
	return s.lessons.ListLessonsByModuleID(ctx, moduleID, publishedOnly, limit, offset)
}

func (s *Service) Update(ctx context.Context, id int64, input domain.UpdateLessonInput) (domain.Lesson, error) {
	l, err := s.lessons.UpdateLesson(ctx, id, input)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.Lesson{}, ErrLessonNotFound
		}
		return domain.Lesson{}, err
	}
	return l, nil
}

func (s *Service) Delete(ctx context.Context, id int64) error {
	if _, err := s.lessons.GetLessonByID(ctx, id); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ErrLessonNotFound
		}
		return err
	}
	return s.lessons.DeleteLesson(ctx, id)
}