user_store.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"strings"
)

//An interface
type UserStore interface {
	Find(string) (*User, error)
	FindByEmail(string) (*User, error)
	FindByUsername(string) (*User, error)
	Save(User) error
}

//Globa variable UserStore (representing the interface)
var globalUserStore UserStore

/**
* Post Condition:
* - globalUserStore global variable initialized for use
 */
func init() {
	store, err := NewFileUserStore("./data/users.json")
	if err != nil {
		panic(fmt.Errorf("Error creating user store: %s", err))
	}
	globalUserStore = store
}

//A FileUserStore represents the intreface to store users in files (json)
type FileUserStore struct {
	filename string
	Users    map[string]User
}

/**
*
 */
func NewFileUserStore(filename string) (*FileUserStore, error) {

	store := &FileUserStore{
		Users:    map[string]User{},
		filename: filename,
	}

	contents, err := ioutil.ReadFile(filename)

	if err != nil {
		// If it's a matter of the file not existing, that's ok
		if os.IsNotExist(err) {
			return store, nil
		}
		return nil, err
	}
	err = json.Unmarshal(contents, store)
	if err != nil {
		return nil, err
	}
	return store, nil
}

/**
* Function used to save the user
*
 */
func (store FileUserStore) Save(user User) error {
	store.Users[user.ID] = user

	contents, err := json.MarshalIndent(store, "", "  ")
	if err != nil {
		return err
	}

	return ioutil.WriteFile(store.filename, contents, 0660)
}

/**
*
*
 */
func (store FileUserStore) Find(id string) (*User, error) {
	user, ok := store.Users[id]
	if ok {
		return &user, nil
	}
	return nil, nil
}

/**
*
*
 */
func (store FileUserStore) FindByUsername(username string) (*User, error) {
	if username == "" {
		return nil, nil
	}

	for _, user := range store.Users {
		if strings.ToLower(username) == strings.ToLower(user.Username) {
			return &user, nil
		}
	}
	return nil, nil
}

/**
*
*
 */
func (store FileUserStore) FindByEmail(email string) (*User, error) {
	if email == "" {
		return nil, nil
	}

	for _, user := range store.Users {
		if strings.ToLower(email) == strings.ToLower(user.Email) {
			return &user, nil
		}
	}
	return nil, nil
}