package practicecontent

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

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

type Service struct {
	questions ports.QuestionStore
	lms       ports.LmsPracticeStore
	examPrep  ports.ExamPrepPracticeStore
	personas  ports.LmsPersonaReader
}

func NewService(
	questions ports.QuestionStore,
	lms ports.LmsPracticeStore,
	examPrep ports.ExamPrepPracticeStore,
	personas ports.LmsPersonaReader,
) *Service {
	return &Service{
		questions: questions,
		lms:       lms,
		examPrep:  examPrep,
		personas:  personas,
	}
}

func (s *Service) validatePersona(ctx context.Context, id int64) error {
	if id <= 0 {
		return domain.ErrPersonaNotFound
	}
	_, err := s.personas.GetLmsPersonaByID(ctx, id)
	if errors.Is(err, pgx.ErrNoRows) {
		return domain.ErrPersonaNotFound
	}
	return err
}

func (s *Service) validateQuestionSet(ctx context.Context, id int64) error {
	_, err := s.questions.GetQuestionSetByID(ctx, id)
	if errors.Is(err, pgx.ErrNoRows) {
		return ErrQuestionSetNotFound
	}
	return err
}

func mergeQuestionSetInput(existing domain.QuestionSet, in *domain.FullUpdateQuestionSetInput) domain.CreateQuestionSetInput {
	out := domain.CreateQuestionSetInput{
		Title:            existing.Title,
		Description:      existing.Description,
		SetType:          existing.SetType,
		OwnerType:        existing.OwnerType,
		OwnerID:          existing.OwnerID,
		BannerImage:      existing.BannerImage,
		Persona:          existing.Persona,
		TimeLimitMinutes: existing.TimeLimitMinutes,
		PassingScore:     existing.PassingScore,
		ShuffleQuestions: &existing.ShuffleQuestions,
		Status:           &existing.Status,
		IntroVideoURL:    existing.IntroVideoURL,
	}
	if in == nil {
		return out
	}
	if in.Title != nil {
		out.Title = *in.Title
	}
	if in.Description != nil {
		out.Description = in.Description
	}
	if in.BannerImage != nil {
		out.BannerImage = in.BannerImage
	}
	if in.Persona != nil {
		out.Persona = in.Persona
	}
	if in.TimeLimitMinutes != nil {
		out.TimeLimitMinutes = in.TimeLimitMinutes
	}
	if in.PassingScore != nil {
		out.PassingScore = in.PassingScore
	}
	if in.ShuffleQuestions != nil {
		out.ShuffleQuestions = in.ShuffleQuestions
	}
	if in.Status != nil {
		out.Status = in.Status
	}
	if in.IntroVideoURL != nil {
		out.IntroVideoURL = in.IntroVideoURL
	}
	return out
}

func (s *Service) applySharedUpdates(
	ctx context.Context,
	questionSetID int64,
	in domain.FullUpdatePracticeInput,
) (domain.QuestionSet, []domain.QuestionWithDetails, error) {
	if in.QuestionSet != nil {
		existingSet, err := s.questions.GetQuestionSetByID(ctx, questionSetID)
		if err != nil {
			if errors.Is(err, pgx.ErrNoRows) {
				return domain.QuestionSet{}, nil, ErrQuestionSetNotFound
			}
			return domain.QuestionSet{}, nil, err
		}
		merged := mergeQuestionSetInput(existingSet, in.QuestionSet)
		if err := s.questions.UpdateQuestionSet(ctx, questionSetID, merged); err != nil {
			return domain.QuestionSet{}, nil, err
		}
	}

	var synced []domain.QuestionWithDetails
	if in.Questions != nil {
		var err error
		synced, err = s.syncQuestionsInSet(ctx, questionSetID, in.Questions)
		if err != nil {
			return domain.QuestionSet{}, nil, err
		}
	}

	set, err := s.questions.GetQuestionSetByID(ctx, questionSetID)
	if err != nil {
		return domain.QuestionSet{}, nil, err
	}

	if synced == nil && in.Questions == nil {
		items, err := s.questions.GetQuestionSetItems(ctx, questionSetID)
		if err != nil {
			return domain.QuestionSet{}, nil, err
		}
		synced = make([]domain.QuestionWithDetails, 0, len(items))
		for _, item := range items {
			q, err := s.questions.GetQuestionWithDetails(ctx, item.QuestionID)
			if err != nil {
				return domain.QuestionSet{}, nil, err
			}
			synced = append(synced, q)
		}
	}

	return set, synced, nil
}

// UpdateLmsPracticeFull updates an LMS practice shell, linked question set, and questions.
func (s *Service) UpdateLmsPracticeFull(ctx context.Context, practiceID int64, in domain.FullUpdatePracticeInput) (domain.FullUpdatePracticeResult, error) {
	practice, err := s.lms.GetLmsPracticeByID(ctx, practiceID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.FullUpdatePracticeResult{}, ErrPracticeNotFound
		}
		return domain.FullUpdatePracticeResult{}, err
	}

	questionSetID := practice.QuestionSetID
	if in.Practice != nil {
		if in.Practice.PersonaID != nil {
			if err := s.validatePersona(ctx, *in.Practice.PersonaID); err != nil {
				return domain.FullUpdatePracticeResult{}, err
			}
		}
		if in.Practice.QuestionSetID != nil {
			if err := s.validateQuestionSet(ctx, *in.Practice.QuestionSetID); err != nil {
				return domain.FullUpdatePracticeResult{}, err
			}
		}

		update := domain.UpdatePracticeInput{
			Title:            in.Practice.Title,
			StoryDescription: in.Practice.StoryDescription,
			StoryImage:       in.Practice.StoryImage,
			PersonaID:        in.Practice.PersonaID,
			QuestionSetID:    in.Practice.QuestionSetID,
			QuickTips:        in.Practice.QuickTips,
			PublishStatus:    in.Practice.PublishStatus,
		}
		practice, err = s.lms.UpdateLmsPractice(ctx, practiceID, update)
		if err != nil {
			if errors.Is(err, pgx.ErrNoRows) {
				return domain.FullUpdatePracticeResult{}, ErrPracticeNotFound
			}
			return domain.FullUpdatePracticeResult{}, err
		}
		questionSetID = practice.QuestionSetID
	}

	set, questions, err := s.applySharedUpdates(ctx, questionSetID, in)
	if err != nil {
		return domain.FullUpdatePracticeResult{}, err
	}

	return domain.FullUpdatePracticeResult{
		Practice:    practice,
		QuestionSet: set,
		Questions:   questions,
	}, nil
}

// UpdateExamPrepPracticeFull updates an exam-prep practice shell, linked question set, and questions.
func (s *Service) UpdateExamPrepPracticeFull(ctx context.Context, practiceID int64, in domain.FullUpdatePracticeInput) (domain.FullUpdatePracticeResult, error) {
	practice, err := s.examPrep.GetExamPrepLessonPracticeByID(ctx, practiceID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return domain.FullUpdatePracticeResult{}, ErrPracticeNotFound
		}
		return domain.FullUpdatePracticeResult{}, err
	}

	questionSetID := practice.QuestionSetID
	if in.Practice != nil {
		if in.Practice.PersonaID != nil {
			if err := s.validatePersona(ctx, *in.Practice.PersonaID); err != nil {
				return domain.FullUpdatePracticeResult{}, err
			}
		}
		if in.Practice.QuestionSetID != nil {
			if err := s.validateQuestionSet(ctx, *in.Practice.QuestionSetID); err != nil {
				return domain.FullUpdatePracticeResult{}, err
			}
		}

		update := domain.UpdateExamPrepPracticeInput{
			Title:            in.Practice.Title,
			StoryDescription: in.Practice.StoryDescription,
			StoryImage:       in.Practice.StoryImage,
			PersonaID:        in.Practice.PersonaID,
			QuestionSetID:    in.Practice.QuestionSetID,
			QuickTips:        in.Practice.QuickTips,
			PublishStatus:    in.Practice.PublishStatus,
		}
		practice, err = s.examPrep.UpdateExamPrepLessonPractice(ctx, practiceID, update)
		if err != nil {
			if errors.Is(err, pgx.ErrNoRows) {
				return domain.FullUpdatePracticeResult{}, ErrPracticeNotFound
			}
			return domain.FullUpdatePracticeResult{}, err
		}
		questionSetID = practice.QuestionSetID
	}

	set, questions, err := s.applySharedUpdates(ctx, questionSetID, in)
	if err != nil {
		return domain.FullUpdatePracticeResult{}, err
	}

	return domain.FullUpdatePracticeResult{
		Practice:    practice,
		QuestionSet: set,
		Questions:   questions,
	}, nil
}