package file

import (
	"errors"
	"fmt"
	"io/fs"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"git.andreafazzi.eu/andrea/probo/client"
	"git.andreafazzi.eu/andrea/probo/hasher/sha256"
	"git.andreafazzi.eu/andrea/probo/models"
	"git.andreafazzi.eu/andrea/probo/store/memory"
)

type FileProboCollectorStore struct {
	Dir string

	memoryStore *memory.MemoryProboCollectorStore
	paths       map[string]string

	// A mutex is used to synchronize read/write access to the map
	lock sync.RWMutex
}

func NewFileProboCollectorStore(dirname string) (*FileProboCollectorStore, error) {
	s := new(FileProboCollectorStore)

	s.Dir = dirname

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

	return s, nil
}

func (s *FileProboCollectorStore) Reindex() error {
	files, err := ioutil.ReadDir(s.Dir)
	if err != nil {
		return err
	}

	s.paths = make(map[string]string)

	markdownFiles := make([]fs.FileInfo, 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.")
	}

	s.memoryStore = memory.NewMemoryProboCollectorStore(
		sha256.NewDefault256Hasher(sha256.DefaultSHA256HashingFn),
	)

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

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

		s.SetPath(q, fullPath)
	}

	return nil
}

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) GetPath(quiz *models.Quiz) (string, error) {
	s.lock.RLock()
	defer s.lock.RUnlock()

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

func (s *FileProboCollectorStore) SetPath(quiz *models.Quiz, path string) string {
	s.lock.Lock()
	defer s.lock.Unlock()
	s.paths[quiz.ID] = path
	return path
}

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, error) {
	lines := strings.Split(markdown, "\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, fmt.Errorf("Question text should not be empty.")
	}

	if len(answers) < 2 {
		return 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, nil
}

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

	fn, _ := s.GetPath(quiz)
	if fn == "" {
		fn = filepath.Join(s.Dir, fmt.Sprintf("quiz_%v.%s", time.Now().Unix(), "md"))
	}

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

	defer file.Close()

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

	s.SetPath(quiz, fn)

	return nil
}