package service

import (
	"context"
	"errors"
	"sno/internal/models"
	"sno/internal/repository"
)

// QuestionService defines the interface for question-related business logic.
type QuestionService interface {
	CreateQuestion(ctx context.Context, question *models.Question) (*models.Question, error)
	GetQuestionByID(ctx context.Context, id int) (*models.Question, error)
	UpdateQuestion(ctx context.Context, id int, question *models.Question) (*models.Question, error)
	DeleteQuestion(ctx context.Context, id int) error
}

// questionService implements the QuestionService interface.
type questionService struct {
	questionRepo repository.QuestionRepository
}

// NewQuestionService creates a new instance of a question service.
func NewQuestionService(questionRepo repository.QuestionRepository) QuestionService {
	return &questionService{questionRepo: questionRepo}
}

// CreateQuestion handles the business logic for creating a new question.
func (s *questionService) CreateQuestion(ctx context.Context, question *models.Question) (*models.Question, error) {
	// Basic validation
	if question.Text == "" {
		return nil, errors.New("question text cannot be empty")
	}
	if len(question.Options) < 2 {
		return nil, errors.New("question must have at least two options")
	}

	correctAnswers := 0
	for _, opt := range question.Options {
		if opt.IsCorrect {
			correctAnswers++
		}
	}

	if correctAnswers == 0 {
		return nil, errors.New("question must have at least one correct answer")
	}
	if question.Type == models.Single && correctAnswers > 1 {
		return nil, errors.New("single choice question cannot have multiple correct answers")
	}

	return s.questionRepo.Create(ctx, question)
}

// GetQuestionByID retrieves a question by its ID.
func (s *questionService) GetQuestionByID(ctx context.Context, id int) (*models.Question, error) {
	return s.questionRepo.GetByID(ctx, id)
}

// UpdateQuestion handles the business logic for updating an existing question.
func (s *questionService) UpdateQuestion(ctx context.Context, id int, question *models.Question) (*models.Question, error) {
	// Basic validation
	if question.Text == "" {
		return nil, errors.New("question text cannot be empty")
	}
	if len(question.Options) < 2 {
		return nil, errors.New("question must have at least two options")
	}

	correctAnswers := 0
	for _, opt := range question.Options {
		if opt.IsCorrect {
			correctAnswers++
		}
	}

	if correctAnswers == 0 {
		return nil, errors.New("question must have at least one correct answer")
	}
	if question.Type == models.Single && correctAnswers > 1 {
		return nil, errors.New("single choice question cannot have multiple correct answers")
	}

	return s.questionRepo.Update(ctx, id, question)
}

// DeleteQuestion handles the business logic for deleting a question.
func (s *questionService) DeleteQuestion(ctx context.Context, id int) error {
	return s.questionRepo.Delete(ctx, id)
}