main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"sync"

	"github.com/jcelliott/lumber"
)

const Version = "1.0.0"

type (
	Logger interface {
		Fatal(string, ...interface{})
		Error(string, ...interface{})
		Warn(string, ...interface{})
		Info(string, ...interface{})
		Debug(string, ...interface{})
		Trace(string, ...interface{})
	}

	Driver struct {
		mutex   sync.Mutex
		mutexes map[string]*sync.Mutex
		dir     string
		log     Logger
	}
)

type Options struct {
	Logger
}

// Creates a database and returns the Driver we can use to interact with the DB
func New(dir string, options *Options) (*Driver, error) {
	dir = filepath.Clean(dir)

	opts := Options{}
	if options != nil {
		opts = *options
	}

	//creating a Logger
	if opts.Logger == nil {
		opts.Logger = lumber.NewConsoleLogger(lumber.INFO)
	}

	//creating a driver of type Driver
	driver := Driver{
		dir:     dir,
		mutexes: make(map[string]*sync.Mutex),
		log:     opts.Logger,
	}

	//check if database exists by passing the name of the directory
	if _, err := os.Stat(dir); err == nil {
		opts.Logger.Debug("Using '%s' (database already exists)\n", dir)
		return &driver, nil
	}

	//database does not exists
	opts.Logger.Debug("Creating the database at '%s' ...\n", dir)
	return &driver, os.MkdirAll(dir, 0755)

}

func (d *Driver) Write(collection, resource string, v interface{}) error {

	if collection == "" {
		return fmt.Errorf("Missing collection!")
	}

	if resource == "" {
		return fmt.Errorf("Missing resource!")
	}

	//only when the write function is completed then only it is unlock otherwise it wont allow anything to work with database
	mutex := d.getOrCreateMutex(collection)
	mutex.Lock()
	defer mutex.Unlock()

	dir := filepath.Join(d.dir, collection)
	finalPath := filepath.Join(dir, resource+".json")
	tempPath := finalPath + ".tmp"

	if err := os.MkdirAll(dir, 0755); err != nil {
		return err
	}

	b, err := json.MarshalIndent(v, "", "\t")
	if err != nil {
		return err
	}
	b = append(b, byte('\n'))

	if err := ioutil.WriteFile(tempPath, b, 0644); err != nil {
		return err
	}

	return os.Rename(tempPath, finalPath)
}

func (d *Driver) Read(collection, resource string, v interface{}) error {
	if collection == "" {
		return fmt.Errorf("Missing collection")
	}

	if resource == "" {
		return fmt.Errorf("Missing resource")
	}

	record := filepath.Join(d.dir, collection, resource)

	if _, err := stat(record); err != nil {
		return err
	}

	b, err := ioutil.ReadFile(record + ".json")
	if err != nil {
		return err
	}

	return json.Unmarshal(b, &v)
}

func (d *Driver) ReadAll(collection string) ([]string, error) {
	if collection == "" {
		return nil, fmt.Errorf("Missing collection")
	}

	dir := filepath.Join(d.dir, collection)

	if _, err := stat(dir); err != nil {
		return nil, err
	}

	files, _ := ioutil.ReadDir(dir)

	var records []string

	for _, file := range files {
		b, err := ioutil.ReadFile(filepath.Join(dir, file.Name()))
		if err != nil {
			return nil, err
		}

		records = append(records, string(b))
	}

	return records, nil
}

func (d *Driver) Delete(collection, resource string) error {
	path := filepath.Join(collection, resource)
	mutex := d.getOrCreateMutex(collection)
	mutex.Lock()
	mutex.Unlock()

	dir := filepath.Join(d.dir, path)

	switch fi, err := stat(dir); {
	case fi == nil, err != nil:
		return fmt.Errorf("Unable to find file or directory %v\n", path)
	case fi.Mode().IsDir():
		return os.RemoveAll(dir)
	case fi.Mode().IsRegular():
		return os.RemoveAll(dir + ".json")
	}
	return nil
}

func (d *Driver) getOrCreateMutex(collection string) *sync.Mutex {

	d.mutex.Lock()
	defer d.mutex.Unlock()

	m, ok := d.mutexes[collection]

	if !ok {
		m = &sync.Mutex{}
		d.mutexes[collection] = m
	}
	return m
}

//checks for files with a .json extension
func stat(path string) (fi os.FileInfo, err error) {
	if fi, err = os.Stat(path); os.IsNotExist(err) {
		fi, err = os.Stat(path + ".json")
	}
	return
}

type Address struct {
	City string
	// State string
	// Country string
	Pincode json.Number
}

type User struct {
	Name    string
	Age     json.Number
	Contact string
	Company string
	Address Address
}

func main() {

	dir := "./"

	db, err := New(dir, nil)
	if err != nil {
		fmt.Println("Error", err)
	}

	employees := []User{
		{"Linux", "12", "42567567", "linux", Address{"not appropriate", "12"}},
		{"GoLang", "13", "12232343", "golang", Address{"not appropriate", "34"}},
		{"K8s", "14", "41432343", "k8s", Address{"not appropriate", "56"}},
		{"Docker", "15", "89982343", "docker", Address{"not appropriate", "78"}},
	}

	for _, value := range employees {
		db.Write("users", value.Name, User{
			Name:    value.Name,
			Age:     value.Age,
			Contact: value.Contact,
			Company: value.Company,
			Address: value.Address,
		})
	}

	records, err := db.ReadAll("users")
	if err != nil {
		fmt.Println("Error", err)
	}
	fmt.Println(records)

	allUsers := []User{}

	for _, value := range records {
		employeeFound := User{}
		if err := json.Unmarshal([]byte(value), &employeeFound); err != nil {
			fmt.Println("Error", err)
		}
		allUsers = append(allUsers, employeeFound)
	}
	fmt.Println(allUsers)

	if err := db.Delete("users", "Linux"); err != nil {
		fmt.Println("Error", err)
	}

	// if err := db.DeleteAll("user", ""); err != nil {
	// 	fmt.Println("Error", err)
	// }
}