package file

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

	"git.andreafazzi.eu/andrea/probo/pkg/store"
)

type IndexDirFunc[T FileStorable, K store.Storer[T]] func(s *FileStore[T, K]) error

var (
	ErrorMetaHeaderIsNotPresent = errors.New("Meta header was not found in file.")
)

type FileStorable interface {
	store.Storable

	Marshal() ([]byte, error)
	Unmarshal([]byte) error
}

type FileStorer[T FileStorable] interface {
	// store.Storer[T]
	Create(T, ...string) (T, error)
	ReadAll() []T
	Read(string) (T, error)
	Update(T, string) (T, error)
	Delete(string) (T, error)
}

type FilePathConfig struct {
	Dir        string
	FilePrefix string
	FileSuffix string
}

type FileStoreConfig[T FileStorable, K store.Storer[T]] struct {
	FilePathConfig
	IndexDirFunc     func(*FileStore[T, K]) error
	CreateEntityFunc func() T
	NoIndexOnCreate  bool
}

type FileStore[T FileStorable, K store.Storer[T]] struct {
	*FileStoreConfig[T, K]

	Storer K

	lock  sync.RWMutex
	paths map[string]string
}

func DefaultIndexDirFunc[T FileStorable, K store.Storer[T]](s *FileStore[T, K]) error {
	if s.CreateEntityFunc == nil {
		return errors.New("CreateEntityFunc cannot be nil!")
	}

	files, err := os.ReadDir(s.Dir)
	if err != nil {
		return err
	}

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

	for _, file := range files {
		filename := file.Name()
		if !file.IsDir() && strings.HasSuffix(filename, s.FileSuffix) {
			entityFiles = append(entityFiles, file)
		}
	}

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

		fileInfo, err := os.Stat(fullPath)
		if err != nil {
			panic(err)
		}

		if fileInfo.Size() > 0 {
			content, err := os.ReadFile(fullPath)
			if err != nil {
				return err
			}

			entity := s.CreateEntityFunc()

			err = entity.Unmarshal(content)
			if err != nil {
				return fmt.Errorf("An error occurred unmarshalling %v: %v", filename, err)
			}

			mEntity, err := s.Create(entity, fullPath)
			if err != nil {
				return err
			}

			s.SetPath(mEntity, fullPath)
		}
	}

	return nil

}

func NewFileStore[T FileStorable, K store.Storer[T]](config *FileStoreConfig[T, K], storer K) (*FileStore[T, K], error) {
	store := &FileStore[T, K]{
		FileStoreConfig: config,
		Storer:          storer,
		paths:           make(map[string]string, 0),
	}

	if !config.NoIndexOnCreate {
		err := store.IndexDir()
		if err != nil {
			return nil, err

		}
	}

	return store, nil
}

func (s *FileStore[T, K]) Create(entity T, path ...string) (T, error) {
	e, err := s.Storer.Create(entity)
	if err != nil {
		return e, err
	}

	data, err := e.Marshal()
	if err != nil {
		return e, err
	}

	if len(path) == 0 {
		path = append(path, filepath.Join(s.Dir, fmt.Sprintf("%s_%v%s", s.FilePrefix, e.GetID(), s.FileSuffix)))
	}

	file, err := os.Create(path[0])
	if err != nil {
		return e, err
	}

	defer file.Close()

	_, err = file.Write(data)
	if err != nil {
		return e, err
	}

	s.SetPath(e, path[0])

	return e, nil
}

func (s *FileStore[T, K]) Update(entity T, id string) (T, error) {
	e, err := s.Storer.Update(entity, id)
	if err != nil {
		return e, err
	}

	filePath := s.GetPath(e)

	data, err := e.Marshal()
	if err != nil {
		return e, err
	}

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

	defer file.Close()

	_, err = file.Write(data)
	if err != nil {
		return e, err
	}

	return e, nil
}

func (s *FileStore[T, K]) Read(id string) (T, error) {
	return s.Storer.Read(id)
}

func (s *FileStore[T, K]) ReadAll() []T {
	return s.Storer.ReadAll()
}

func (s *FileStore[T, K]) Delete(id string) (T, error) {
	e, err := s.Storer.Delete(id)
	if err != nil {
		return e, err
	}

	err = os.Remove(s.GetPath(e))
	if err != nil {
		return e, err
	}

	return e, nil
}

func (s *FileStore[T, K]) IndexDir() error {
	return s.IndexDirFunc(s)
}

func (s *FileStore[T, K]) GetPath(entity T) string {
	s.lock.RLock()
	defer s.lock.RUnlock()

	return s.paths[entity.GetID()]
}

func (s *FileStore[T, K]) SetPath(entity T, path string) string {
	s.lock.Lock()
	defer s.lock.Unlock()

	s.paths[entity.GetID()] = path

	return path
}