package practicecontent

import (
	"Yimaru-Backend/internal/domain"
	"context"
	"fmt"
	"strings"
)

func normalizeRuntimeQuestionType(v string) string {
	return strings.ToUpper(strings.TrimSpace(v))
}

func optionalTrimmedString(s *string) string {
	if s == nil {
		return ""
	}
	return strings.TrimSpace(*s)
}

func resolveStoredQuestionText(questionType string, explicit *string, payload *domain.DynamicQuestionPayload, existing string) (string, error) {
	exp := optionalTrimmedString(explicit)
	if err := domain.ValidateQuestionTextNotAllowedForDynamic(questionType, exp); err != nil {
		return "", err
	}
	if domain.UsesDynamicQuestionPayload(questionType) {
		return domain.ResolveDynamicStoredQuestionText(payload, existing)
	}
	if exp == "" {
		if strings.TrimSpace(existing) != "" {
			return strings.TrimSpace(existing), nil
		}
		return "", fmt.Errorf("question_text is required")
	}
	return exp, nil
}

func buildQuestionInput(
	item domain.FullUpdatePracticeQuestionItem,
	existing *domain.Question,
	getDefinition func(id int64) (domain.QuestionTypeDefinition, error),
) (domain.CreateQuestionInput, error) {
	var questionType string
	if existing != nil {
		questionType = existing.QuestionType
	}
	if item.QuestionType != nil {
		questionType = normalizeRuntimeQuestionType(*item.QuestionType)
	}
	if questionType == "" {
		return domain.CreateQuestionInput{}, fmt.Errorf("%w: question_type is required for new questions", ErrInvalidQuestionItem)
	}

	effectiveDefinitionID := (*int64)(nil)
	if existing != nil {
		effectiveDefinitionID = existing.QuestionTypeDefinitionID
	}
	if item.QuestionTypeDefinitionID != nil {
		effectiveDefinitionID = item.QuestionTypeDefinitionID
	}

	effectiveDynamicPayload := (*domain.DynamicQuestionPayload)(nil)
	if existing != nil {
		effectiveDynamicPayload = existing.DynamicPayload
	}
	if item.DynamicPayload != nil {
		effectiveDynamicPayload = item.DynamicPayload
	}

	if effectiveDefinitionID != nil {
		def, err := getDefinition(*effectiveDefinitionID)
		if err != nil {
			return domain.CreateQuestionInput{}, fmt.Errorf("invalid question_type_definition_id: %w", err)
		}
		if questionType == "" {
			questionType = "DYNAMIC"
		}
		if questionType != "DYNAMIC" {
			return domain.CreateQuestionInput{}, fmt.Errorf("%w: question_type must be DYNAMIC when question_type_definition_id is provided", ErrInvalidQuestionItem)
		}
		if effectiveDynamicPayload == nil {
			return domain.CreateQuestionInput{}, fmt.Errorf("%w: dynamic_payload is required for dynamic questions", ErrInvalidQuestionItem)
		}
		if err := domain.ValidateDynamicPayloadAgainstDefinition(*effectiveDynamicPayload, def); err != nil {
			return domain.CreateQuestionInput{}, err
		}
	}
	if effectiveDefinitionID == nil && item.DynamicPayload != nil {
		return domain.CreateQuestionInput{}, fmt.Errorf("%w: dynamic_payload requires question_type_definition_id", ErrInvalidQuestionItem)
	}

	switch questionType {
	case "MCQ", "TRUE_FALSE", "SHORT_ANSWER", "AUDIO", "DYNAMIC":
	default:
		return domain.CreateQuestionInput{}, fmt.Errorf("%w: question_type must be one of MCQ, TRUE_FALSE, SHORT_ANSWER, AUDIO, DYNAMIC", ErrInvalidQuestionItem)
	}
	if questionType == "DYNAMIC" && effectiveDefinitionID == nil {
		return domain.CreateQuestionInput{}, fmt.Errorf("%w: question_type_definition_id is required for DYNAMIC question_type", ErrInvalidQuestionItem)
	}

	existingText := ""
	if existing != nil {
		existingText = existing.QuestionText
	}
	questionText, err := resolveStoredQuestionText(questionType, item.QuestionText, effectiveDynamicPayload, existingText)
	if err != nil {
		return domain.CreateQuestionInput{}, err
	}

	return domain.CreateQuestionInput{
		QuestionText:             questionText,
		QuestionType:             questionType,
		QuestionTypeDefinitionID: effectiveDefinitionID,
		DynamicPayload:           effectiveDynamicPayload,
		DifficultyLevel:          coalesceStringPtr(item.DifficultyLevel, existingDifficulty(existing)),
		Points:                   coalesceInt32Ptr(item.Points, existingPoints(existing)),
		Explanation:              coalesceStringPtr(item.Explanation, existingExplanation(existing)),
		Tips:                     coalesceStringPtr(item.Tips, existingTips(existing)),
		VoicePrompt:              coalesceStringPtr(item.VoicePrompt, existingVoicePrompt(existing)),
		SampleAnswerVoicePrompt:  coalesceStringPtr(item.SampleAnswerVoicePrompt, existingSampleVoice(existing)),
		ImageURL:                 coalesceStringPtr(item.ImageURL, existingImageURL(existing)),
		Status:                   coalesceStringPtr(item.Status, existingStatus(existing)),
		Options:                  item.Options,
		ShortAnswers:             item.ShortAnswers,
		AudioCorrectAnswerText:   item.AudioCorrectAnswerText,
	}, nil
}

func existingDifficulty(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	return q.DifficultyLevel
}

func existingPoints(q *domain.Question) *int32 {
	if q == nil {
		return nil
	}
	p := q.Points
	return &p
}

func existingExplanation(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	return q.Explanation
}

func existingTips(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	return q.Tips
}

func existingVoicePrompt(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	return q.VoicePrompt
}

func existingSampleVoice(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	return q.SampleAnswerVoicePrompt
}

func existingImageURL(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	return q.ImageURL
}

func existingStatus(q *domain.Question) *string {
	if q == nil {
		return nil
	}
	s := q.Status
	return &s
}

func coalesceStringPtr(in *string, existing *string) *string {
	if in != nil {
		return in
	}
	return existing
}

func coalesceInt32Ptr(in *int32, existing *int32) *int32 {
	if in != nil {
		return in
	}
	return existing
}

func displayOrderForItem(item domain.FullUpdatePracticeQuestionItem, index int) int32 {
	if item.DisplayOrder != nil && *item.DisplayOrder > 0 {
		return *item.DisplayOrder
	}
	return int32(index + 1)
}

func (s *Service) replaceQuestionChildren(ctx context.Context, questionID int64, input domain.CreateQuestionInput) error {
	if err := s.questions.DeleteOptionsByQuestionID(ctx, questionID); err != nil {
		return err
	}
	for _, opt := range input.Options {
		if _, err := s.questions.CreateQuestionOption(ctx, questionID, opt.OptionText, opt.OptionOrder, opt.IsCorrect); err != nil {
			return err
		}
	}

	if err := s.questions.DeleteShortAnswersByQuestionID(ctx, questionID); err != nil {
		return err
	}
	for _, sa := range input.ShortAnswers {
		if _, err := s.questions.CreateQuestionShortAnswer(ctx, questionID, sa.AcceptableAnswer, sa.MatchType); err != nil {
			return err
		}
	}
	return nil
}

func (s *Service) syncQuestionsInSet(ctx context.Context, setID int64, items []domain.FullUpdatePracticeQuestionItem) ([]domain.QuestionWithDetails, error) {
	currentItems, err := s.questions.GetQuestionSetItems(ctx, setID)
	if err != nil {
		return nil, err
	}

	if len(items) == 0 {
		for _, it := range currentItems {
			if err := s.questions.RemoveQuestionFromSet(ctx, setID, it.QuestionID); err != nil {
				return nil, err
			}
		}
		return []domain.QuestionWithDetails{}, nil
	}

	currentInSet := make(map[int64]struct{}, len(currentItems))
	for _, it := range currentItems {
		currentInSet[it.QuestionID] = struct{}{}
	}

	getDefinition := func(id int64) (domain.QuestionTypeDefinition, error) {
		return s.questions.GetQuestionTypeDefinitionByID(ctx, id)
	}

	desiredIDs := make(map[int64]struct{}, len(items))
	orderedIDs := make([]int64, 0, len(items))

	for i, item := range items {
		order := displayOrderForItem(item, i)

		if item.ID != nil && *item.ID > 0 {
			questionID := *item.ID
			existing, err := s.questions.GetQuestionByID(ctx, questionID)
			if err != nil {
				return nil, fmt.Errorf("%w: %d", ErrQuestionNotFound, questionID)
			}

			input, err := buildQuestionInput(item, &existing, getDefinition)
			if err != nil {
				return nil, err
			}
			if err := s.questions.UpdateQuestion(ctx, questionID, input); err != nil {
				return nil, err
			}
			if err := s.replaceQuestionChildren(ctx, questionID, input); err != nil {
				return nil, err
			}

			if _, ok := currentInSet[questionID]; !ok {
				if _, err := s.questions.AddQuestionToSet(ctx, setID, questionID, &order); err != nil {
					return nil, err
				}
			} else if err := s.questions.UpdateQuestionOrder(ctx, setID, questionID, order); err != nil {
				return nil, err
			}

			desiredIDs[questionID] = struct{}{}
			orderedIDs = append(orderedIDs, questionID)
			continue
		}

		input, err := buildQuestionInput(item, nil, getDefinition)
		if err != nil {
			return nil, err
		}
		created, err := s.questions.CreateQuestion(ctx, input)
		if err != nil {
			return nil, err
		}
		if _, err := s.questions.AddQuestionToSet(ctx, setID, created.ID, &order); err != nil {
			return nil, err
		}
		desiredIDs[created.ID] = struct{}{}
		orderedIDs = append(orderedIDs, created.ID)
	}

	for _, it := range currentItems {
		if _, keep := desiredIDs[it.QuestionID]; !keep {
			if err := s.questions.RemoveQuestionFromSet(ctx, setID, it.QuestionID); err != nil {
				return nil, err
			}
		}
	}

	out := make([]domain.QuestionWithDetails, 0, len(orderedIDs))
	for _, id := range orderedIDs {
		q, err := s.questions.GetQuestionWithDetails(ctx, id)
		if err != nil {
			return nil, err
		}
		out = append(out, q)
	}
	return out, nil
}