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- package models
- import (
- "crypto/sha256"
- "errors"
- "fmt"
- "io"
- "sort"
- "strings"
- "gopkg.in/yaml.v2"
- )
- type Quiz struct {
- Meta
- Hash string `json:"hash"`
- Question *Question `json:"question" gorm:"foreignKey:ID"`
- Answers []*Answer `json:"answers" gorm:"many2many:quiz_answers"`
- Tags []*Tag `json:"tags" yaml:"-" gorm:"-"`
- Correct *Answer `json:"correct" gorm:"foreignKey:ID"`
- CorrectPos uint `gorm:"-"` // Position of the correct answer during quiz creation
- Type int `json:"type"`
- }
- func MarkdownToQuiz(quiz *Quiz, markdown string) error {
- meta, remainingMarkdown, err := ParseMetaHeaderFromMarkdown(markdown)
- if err != nil {
- return err
- }
- lines := strings.Split(remainingMarkdown, "\n")
- questionText := ""
- answers := []*Answer{}
- for _, line := range lines {
- if strings.HasPrefix(line, "*") {
- answerText := strings.TrimPrefix(line, "* ")
- answer := &Answer{Text: answerText}
- answers = append(answers, answer)
- } else {
- if questionText != "" {
- questionText += "\n"
- }
- questionText += line
- }
- }
- questionText = strings.TrimRight(questionText, "\n")
- if questionText == "" {
- return fmt.Errorf("Question text should not be empty.")
- }
- if len(answers) < 2 {
- return fmt.Errorf("Number of answers should be at least 2 but parsed answers are %d.", len(answers))
- }
- question := &Question{Text: questionText}
- quiz.Question = question
- quiz.Answers = answers
- //quiz = &Quiz{Question: question, Answers: answers, CorrectPos: 0}
- if meta != nil {
- quiz.Meta = *meta
- }
- return nil
- }
- func QuizToMarkdown(quiz *Quiz) (string, error) {
- if quiz.Question == nil {
- return "", errors.New("Quiz should contain a question but it wasn't provided.")
- }
- if len(quiz.Answers) < 2 {
- return "", errors.New("Quiz should contain at least 2 answers but none was provided.")
- }
- quiz.Correct = quiz.Answers[quiz.CorrectPos]
- if quiz.Correct == nil {
- return "", errors.New("Quiz should contain a correct answer but not was provided.")
- }
- correctAnswer := "* " + quiz.Correct.Text
- var otherAnswers string
- for pos, answer := range quiz.Answers {
- if quiz.CorrectPos != uint(pos) {
- otherAnswers += "* " + answer.Text + "\n"
- }
- }
- markdown := quiz.Question.Text + "\n\n" + correctAnswer + "\n" + otherAnswers
- return markdown, nil
- }
- func (q *Quiz) GetHash() string {
- return q.calculateHash()
- }
- func (q *Quiz) Marshal() ([]byte, error) {
- result, err := QuizToMarkdown(q)
- return []byte(result), err
- }
- func (q *Quiz) Unmarshal(data []byte) error {
- return MarkdownToQuiz(q, string(data))
- }
- func (q *Quiz) calculateHash() string {
- result := make([]string, 0)
- result = append(result, q.Question.GetHash())
- for _, a := range q.Answers {
- result = append(result, a.GetHash())
- }
- orderedHashes := make([]string, len(result))
- copy(orderedHashes, result)
- sort.Strings(orderedHashes)
- return fmt.Sprintf("%x", sha256.Sum256([]byte(strings.Join(orderedHashes, ""))))
- }
- func ParseMetaHeaderFromMarkdown(markdown string) (*Meta, string, error) {
- reader := strings.NewReader(markdown)
- var sb strings.Builder
- var line string
- var err error
- for {
- line, err = readLine(reader)
- if err != nil {
- if err == io.EOF {
- break
- }
- return nil, "", err
- }
- if strings.TrimSpace(line) == "---" {
- break
- }
- }
- for {
- line, err = readLine(reader)
- if err != nil {
- if err == io.EOF {
- break
- }
- return nil, "", err
- }
- if strings.TrimSpace(line) == "---" {
- break
- }
- sb.WriteString(line)
- }
- if sb.String() == "" {
- return nil, markdown, nil
- }
- var meta Meta
- err = yaml.Unmarshal([]byte(sb.String()), &meta)
- if err != nil {
- return nil, markdown, err
- }
- remainingMarkdown := markdown[strings.Index(markdown, "---\n"+sb.String()+"---\n")+len("---\n"+sb.String()+"---\n"):]
- return &meta, remainingMarkdown, nil
- }
- func readLine(reader *strings.Reader) (string, error) {
- var sb strings.Builder
- for {
- r, _, err := reader.ReadRune()
- if err != nil {
- if err == io.EOF {
- return sb.String(), io.EOF
- }
- return "", err
- }
- sb.WriteRune(r)
- if r == '\n' {
- break
- }
- }
- return sb.String(), nil
- }
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