package file

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"os"
	"path"
	"path/filepath"
	"strings"
	"time"

	"git.andreafazzi.eu/andrea/probo/client"
	"git.andreafazzi.eu/andrea/probo/models"
	"github.com/go-yaml/yaml"
)

func (s *FileProboCollectorStore) GetQuizzesDir() string {
	return s.quizzesDir
}

func (s *FileProboCollectorStore) SetQuizPath(quiz *models.Quiz, path string) string {
	s.lock.Lock()
	defer s.lock.Unlock()

	s.quizzesPaths[quiz.ID] = path

	return path
}

func (s *FileProboCollectorStore) ReadAllQuizzes() ([]*models.Quiz, error) {
	return s.memoryStore.ReadAllQuizzes()
}

func (s *FileProboCollectorStore) CreateQuiz(r *client.CreateUpdateQuizRequest) (*models.Quiz, error) {
	quiz, err := s.memoryStore.CreateQuiz(r)
	if err != nil {
		return nil, err
	}

	err = s.createOrUpdateMarkdownFile(quiz)
	if err != nil {
		return nil, err
	}

	err = s.Reindex()
	if err != nil {
		return nil, err
	}

	return s.memoryStore.ReadQuizByHash(quiz.Hash)
}

func (s *FileProboCollectorStore) UpdateQuiz(r *client.CreateUpdateQuizRequest, id string) (*models.Quiz, error) {
	quiz, updated, err := s.memoryStore.UpdateQuiz(r, id)
	if err != nil {
		return nil, err
	}

	if updated { // Update and re-index only if quiz hash is changed
		err = s.createOrUpdateMarkdownFile(quiz)
		if err != nil {
			return nil, err
		}

		err = s.Reindex()
		if err != nil {
			return nil, err
		}
	}
	return s.memoryStore.ReadQuizByHash(quiz.Hash)
}

func (s *FileProboCollectorStore) DeleteQuiz(r *client.DeleteQuizRequest) (*models.Quiz, error) {
	quiz, err := s.memoryStore.DeleteQuiz(&client.DeleteQuizRequest{ID: r.ID})
	if err != nil {
		return nil, err
	}

	path, err := s.GetQuizPath(quiz)
	if err != nil {
		return nil, err
	}

	err = os.Remove(path)
	if err != nil {
		return nil, err
	}

	err = s.Reindex()
	if err != nil {
		return nil, err
	}

	return quiz, nil
}

func (s *FileProboCollectorStore) GetQuizPath(quiz *models.Quiz) (string, error) {
	if quiz == nil {
		return "", errors.New("Quiz object passed as argument is nil!")
	}

	s.lock.RLock()
	defer s.lock.RUnlock()

	path, ok := s.quizzesPaths[quiz.ID]
	if !ok {
		return "", errors.New(fmt.Sprintf("Path not found for quiz ID %v", quiz.ID))
	}
	return path, nil
}

func MarkdownFromQuiz(quiz *models.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.")
	}

	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 _, answer := range quiz.Answers {
		if quiz.Correct.ID != answer.ID {
			otherAnswers += "* " + answer.Text + "\n"
		}
	}

	markdown := quiz.Question.Text + "\n\n" + correctAnswer + "\n" + otherAnswers

	return markdown, nil
}

func QuizFromMarkdown(markdown string) (*client.Quiz, *models.Meta, error) {
	meta, remainingMarkdown, err := parseMetaHeaderFromMarkdown(markdown)
	if err != nil {
		return nil, nil, err
	}

	lines := strings.Split(remainingMarkdown, "\n")

	questionText := ""
	answers := []*client.Answer{}

	for _, line := range lines {
		if strings.HasPrefix(line, "*") {
			answerText := strings.TrimPrefix(line, "* ")
			correct := len(answers) == 0
			answer := &client.Answer{Text: answerText, Correct: correct}
			answers = append(answers, answer)
		} else {
			if questionText != "" {
				questionText += "\n"
			}
			questionText += line
		}
	}

	questionText = strings.TrimRight(questionText, "\n")

	if questionText == "" {
		return nil, nil, fmt.Errorf("Question text should not be empty.")
	}

	if len(answers) < 2 {
		return nil, nil, fmt.Errorf("Number of answers should be at least 2 but parsed answers are %d.", len(answers))
	}

	question := &client.Question{Text: questionText}
	quiz := &client.Quiz{Question: question, Answers: answers}

	return quiz, meta, nil
}

func (s *FileProboCollectorStore) ReadMetaHeaderFromFile(filename string) (*models.Meta, error) {
	data, err := os.ReadFile(path.Join(s.quizzesDir, filename))
	if err != nil {
		return nil, err
	}
	meta, _, err := parseMetaHeaderFromMarkdown(string(data))
	if err != nil {
		return nil, err
	}
	return meta, nil
}

func (s *FileProboCollectorStore) WriteMetaHeaderToFile(filename string, meta *models.Meta) (*models.Meta, error) {
	readMeta, err := s.ReadMetaHeaderFromFile(filename)
	if err != nil {
		return nil, err
	}
	if readMeta == nil {
		_, err := writeMetaHeader(path.Join(s.quizzesDir, filename), meta)
		if err != nil {
			return nil, err
		}
	}

	return meta, nil
}

func (s *FileProboCollectorStore) reindexQuizzes() error {
	files, err := os.ReadDir(s.quizzesDir)
	if err != nil {
		return err
	}

	markdownFiles := make([]fs.DirEntry, 0)

	for _, file := range files {
		filename := file.Name()
		if !file.IsDir() && strings.HasSuffix(filename, ".md") {
			markdownFiles = append(markdownFiles, file)
		}
	}

	if len(markdownFiles) == 0 {
		return fmt.Errorf("The directory is empty.")
	}

	for _, file := range markdownFiles {
		filename := file.Name()
		fullPath := filepath.Join(s.quizzesDir, filename)

		content, err := os.ReadFile(fullPath)
		if err != nil {
			return err
		}
		quiz, meta, err := QuizFromMarkdown(string(content))
		if err != nil {
			return err
		}
		q, err := s.memoryStore.CreateQuiz(&client.CreateUpdateQuizRequest{
			Quiz: quiz,
			Meta: meta,
		})
		if err != nil {
			return err
		}

		if meta == nil {
			s.WriteMetaHeaderToFile(filename, &models.Meta{
				ID:        q.ID,
				CreatedAt: time.Now(),
			})
		}
		s.SetQuizPath(q, fullPath)
	}

	return nil
}

func (s *FileProboCollectorStore) removeMetaFromFile(filename string) (*models.Meta, error) {
	file, err := os.Open(path.Join(s.quizzesDir, filename))
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var buffer bytes.Buffer

	reader := bufio.NewReader(file)

	var meta models.Meta
	var line string
	var sb strings.Builder
	for {
		line, err = reader.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				break
			}
			return nil, err
		}

		if strings.TrimSpace(line) == "---" {
			break
		}
	}

	for {
		line, err = reader.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				break
			}
			return nil, err
		}

		if strings.TrimSpace(line) == "---" {
			break
		}

		sb.WriteString(line)
	}

	err = yaml.Unmarshal([]byte(sb.String()), &meta)
	if err != nil {
		return nil, err
	}

	_, err = io.Copy(&buffer, reader)
	if err != nil {
		return nil, err
	}

	file, err = os.Create(path.Join(s.quizzesDir, filename))
	if err != nil {
		return nil, err
	}
	defer file.Close()

	_, err = io.Copy(file, &buffer)
	if err != nil {
		return nil, err
	}

	return &meta, nil
}

func (s *FileProboCollectorStore) createOrUpdateMarkdownFile(quiz *models.Quiz) error {
	markdown, err := MarkdownFromQuiz(quiz)
	if err != nil {
		return err
	}

	fn, _ := s.GetQuizPath(quiz)
	if fn == "" {
		fn = filepath.Join(s.quizzesDir, fmt.Sprintf("quiz_%v.%s", quiz.ID, "md"))
	}

	file, err := os.Create(fn)
	if err != nil {
		return err
	}

	defer file.Close()

	markdownWithMetaHeader, err := addMetaHeaderToMarkdown(markdown, &quiz.Meta)
	if err != nil {
		return err
	}

	_, err = file.Write([]byte(markdownWithMetaHeader))
	if err != nil {
		return err
	}

	s.SetQuizPath(quiz, fn)

	return nil
}

func addMetaHeaderToMarkdown(content string, meta *models.Meta) (string, error) {
	var buffer bytes.Buffer

	header, err := yaml.Marshal(meta)
	if err != nil {
		return "", err
	}
	_, err = buffer.WriteString("---\n" + string(header) + "---\n")
	if err != nil {
		return "", err
	}

	_, err = buffer.WriteString(content)
	if err != nil {
		return "", err
	}

	return buffer.String(), nil
}

func parseMetaHeaderFromMarkdown(markdown string) (*models.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 models.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
}

func writeMetaHeader(filename string, meta *models.Meta) (*models.Meta, error) {
	// Apri il file in lettura
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	// Crea un buffer in memoria
	var buffer bytes.Buffer

	// Scrivi l'intestazione YAML nel buffer
	header, err := yaml.Marshal(meta)
	if err != nil {
		return nil, err
	}
	_, err = buffer.WriteString("---\n" + string(header) + "---\n")
	if err != nil {
		return nil, err
	}

	// Copia il contenuto del file originale nel buffer
	_, err = io.Copy(&buffer, file)
	if err != nil {
		return nil, err
	}

	// Riapri il file in scrittura
	file, err = os.Create(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	// Scrivi il contenuto del buffer nel file
	_, err = io.Copy(file, &buffer)
	if err != nil {
		return nil, err
	}

	return meta, nil
}