package ocean

import (
	"os"
	"path/filepath"
	"strings"
)

// DirectoryStorage creates a directory and stores every record in a separate file.
type DirectoryStorage[T any] struct {
	collection *collection[T]
	directory  string
}

// Init loads all existing records from the directory.
func (ds *DirectoryStorage[T]) Init(c *collection[T]) error {
	ds.collection = c
	ds.directory = filepath.Join(c.root, c.name)
	os.Mkdir(ds.directory, 0700)
	return ds.loadFromDisk()
}

// Set saves the value in a file.
func (ds *DirectoryStorage[T]) Set(key string, value *T) error {
	return ds.writeFileToDisk(key, value)
}

// Delete deletes the file for the given key.
func (ds *DirectoryStorage[T]) Delete(key string) error {
	return os.Remove(ds.keyFile(key))
}

// keyFile returns the file path for the given key.
func (ds *DirectoryStorage[T]) keyFile(key string) string {
	return filepath.Join(ds.directory, key+".json")
}

// loadFromDisk loads the collection data from the disk.
func (ds *DirectoryStorage[T]) loadFromDisk() error {
	dir, err := os.Open(ds.directory)

	if err != nil {
		return err
	}

	defer dir.Close()
	files, err := dir.Readdirnames(0)

	for _, fileName := range files {
		fileError := ds.loadFileFromDisk(fileName)

		if fileError != nil {
			return fileError
		}
	}

	return err
}

// loadFileFromDisk loads a single file from the disk.
func (ds *DirectoryStorage[T]) loadFileFromDisk(fileName string) error {
	file, err := os.Open(filepath.Join(ds.directory, fileName))

	if err != nil {
		return err
	}

	value := new(T)
	decoder := NewDecoder(file)
	err = decoder.Decode(value)

	if err != nil {
		file.Close()
		return err
	}

	key := strings.TrimSuffix(fileName, ".json")
	ds.collection.data.Store(key, value)
	return file.Close()
}

// writeFileToDisk writes the value for the key to disk as a JSON file.
func (ds *DirectoryStorage[T]) writeFileToDisk(key string, value *T) error {
	fileName := ds.keyFile(key)
	file, err := os.OpenFile(fileName, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0600)

	if err != nil {
		return err
	}

	encoder := NewEncoder(file)
	err = encoder.Encode(value)

	if err != nil {
		file.Close()
		return err
	}

	return file.Close()
}