package store

import (
	"fmt"
	"io"
	"log"
	"os"
	"path"

	"git.phc.dm.unipi.it/phc/storage/utils"
)

const RandomIdSize = 32

func split(baseDir string, prefixSize int, id string) (prefix, rest string) {
	return id[:prefixSize], id[prefixSize:]
}

func Create(baseDir string) error {
	return os.Mkdir(baseDir, os.ModePerm)
}

func CreateObject(baseDir string, prefixSize int, r io.Reader) (string, error) {
	id := utils.GenerateRandomString(RandomIdSize)
	prefix, rest := split(baseDir, prefixSize, id)

	os.MkdirAll(path.Join(baseDir, prefix), os.ModePerm)

	f, err := os.Create(path.Join(baseDir, prefix, rest))
	if err != nil {
		return "", err
	}

	if _, err := io.Copy(f, r); err != nil {
		return "", err
	}

	return id, nil
}

func ReadObject(baseDir string, prefixSize int, id string, w io.Writer) error {
	prefix, rest := split(baseDir, prefixSize, id)

	f, err := os.Open(path.Join(baseDir, prefix, rest))
	if err != nil {
		return err
	}

	if _, err := io.Copy(w, f); err != nil {
		return err
	}

	return nil
}

func AllObjects(baseDir string) ([]string, error) {
	entries, err := os.ReadDir(baseDir)
	if err != nil {
		return nil, err
	}

	objects := []string{}

	for _, e := range entries {
		if !e.IsDir() {
			return nil, fmt.Errorf(`invalid store structure`)
		}

		objectsEntries, err := os.ReadDir(path.Join(baseDir, e.Name()))
		if err != nil {
			return nil, err
		}

		for _, obj := range objectsEntries {
			if obj.IsDir() {
				return nil, fmt.Errorf(`invalid store structure`)
			}

			objects = append(objects, e.Name()+obj.Name())
		}
	}

	return objects, nil
}

func UpdateObject(baseDir string, prefixSize int, id string, r io.Reader) error {
	panic("TODO: Not implemented")
}

func DeleteObject(baseDir string, prefixSize int, id string) error {
	prefix, rest := split(baseDir, prefixSize, id)
	err := os.Remove(path.Join(baseDir, prefix, rest))
	if err != nil {
		return err
	}

	// Silently tries to remove the "<prefix>/" directory if empty
	if err := os.Remove(path.Join(baseDir, prefix)); err != nil {
		log.Panicf(`Tried to remove "%s/" folder, got: %s`, prefix, err.Error())
	}

	return nil
}