ATM low level design (#7)

* Added meeting scheduler low level design

* Added mutex and Getroom

* Add feedback and readme for meeting scheduler design

* Update IsFree method for room

* ATM LLD

* added atm LLD feeback for improvement

* added enter pin in atm state floe

Author: codeimmortal

README.md

@@ -110,6 +110,15 @@ The sixth project in this repository is a Meeting Scheduler, a system that simul
 - Room calendar management, tracking when a room is booked or available.
 - Concurrency control, preventing scheduling conflicts in real time.
 
+## ATM
+
+The seventh project in this repository is a ATM machine, a system that simulates ATM. It demonstrates the following concepts:
+
+- State design pattern for different state of ATM.
+- Chain of responsibility principle for withdrawing cash.
+- Template pattern for handling error of each place in one place.
+- Concurrency control, preventing atm to conflict.
+
 ### Features
 
 - Book and cancel meetings seamlessly.

atm-machine/atm/Account.go

@@ -0,0 +1,42 @@
+package atm
+
+import "errors"
+
+type Account interface {
+	GetBalance() float64
+}
+
+type AccountType string
+
+const (
+	Saving  AccountType = "SAVING"
+	Current AccountType = "CURRENT"
+)
+
+func AccountFactory(accType AccountType) (Account, error) {
+	switch accType {
+	case Current:
+		return &CurrentAccount{}, nil
+	case Saving:
+		return &SavingAccount{}, nil
+	default:
+		return nil, errors.New("Not a valid account type")
+	}
+}
+
+type BaseAccount struct {
+	acctNo  string
+	balance float64
+}
+
+func (b *BaseAccount) GetBalance() float64 {
+	return b.balance
+}
+
+type SavingAccount struct {
+	BaseAccount
+}
+
+type CurrentAccount struct {
+	BaseAccount
+}

atm-machine/atm/atm.go

@@ -0,0 +1,134 @@
+package atm
+
+import (
+	"atm-machine/model"
+	"fmt"
+	"sync"
+)
+
+type WithdrawNote struct {
+	FiveHundred int
+	Hundred     int
+	Left        int
+}
+
+type ATM struct {
+	countOfNotes    map[string]int
+	card            model.Card
+	account         Account
+	uiOption        []string
+	WithdrawAs      *WithdrawNote
+	insertPin       ATMState
+	insertCard      ATMState
+	readCard        ATMState
+	selectAccount   ATMState
+	dispenserAmount ATMState
+	currentState    ATMState
+	mu              sync.RWMutex
+}
+
+func (a *ATM) SetState(s ATMState) {
+	a.currentState = s
+}
+
+func (a *ATM) CleanPreviousAtmTransaction() {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	a.WithdrawAs = &WithdrawNote{}
+	a.card = model.Card{}
+	a.account = nil
+}
+
+func (a *ATM) PrintMoney() {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	fmt.Printf("\n500 note present:%d, 100 not present:%d", a.countOfNotes["500"], a.countOfNotes["100"])
+}
+
+func (a *ATM) StateName() string {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.currentState.StateName()
+}
+
+func (a *ATM) InsertCard() error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.currentState.InsertCard()
+}
+
+func (a *ATM) GetCardDetail() error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.currentState.GetCardDetail()
+}
+
+func (a *ATM) InsertPin() error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.currentState.InsertPin()
+}
+
+func (a *ATM) DispenserAmount() error {
+	a.mu.Lock()
+	if err := a.currentState.DispenserAmount(); err != nil {
+		return err
+	}
+
+	a.mu.Unlock()
+
+	a.CleanPreviousAtmTransaction()
+
+	return nil
+}
+
+func (a *ATM) SelectAccount() error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.currentState.SelectAccount()
+}
+
+func (a *ATM) Execute(operation func() error) {
+	err := operation()
+	if err != nil {
+		a.CleanPreviousAtmTransaction()
+		a.SetState(a.insertCard)
+		fmt.Println("All operation will be nil operation:")
+		fmt.Println("Error while operation:", err.Error())
+	}
+}
+
+func NewATM() *ATM {
+	atm := &ATM{
+		countOfNotes: map[string]int{
+			"500": 1000,
+			"200": 2000,
+			"100": 1000,
+		},
+		WithdrawAs: &WithdrawNote{},
+	}
+
+	atm.insertCard = &InsertCard{
+		atm: atm,
+	}
+
+	atm.readCard = &ReadCard{
+		atm: atm,
+	}
+
+	atm.insertPin = &InsertPin{
+		atm: atm,
+	}
+
+	atm.selectAccount = &SelectAccount{
+		atm: atm,
+	}
+
+	atm.dispenserAmount = &DispenserAmount{
+		atm: atm,
+	}
+
+	atm.SetState(atm.insertCard)
+
+	return atm
+}

atm-machine/atm/atm_state.go

@@ -0,0 +1,42 @@
+package atm
+
+type ATMState interface {
+	StateName() string
+	InsertCard() error
+	InsertPin() error
+	SelectAccount() error
+	GetCardDetail() error
+	DispenserAmount() error
+}
+
+type ATMAbstract struct{}
+
+func (s *ATMAbstract) InsertCard() error {
+	return nil
+}
+
+func (s *ATMAbstract) InsertPin() error {
+	return nil
+}
+
+func (s *ATMAbstract) AuthticateCard() error {
+	return nil
+}
+
+func (s *ATMAbstract) DispenserAmount() error {
+	return nil
+}
+
+func (s *ATMAbstract) SelectAccount() error {
+	return nil
+
+}
+
+func (s *ATMAbstract) GetCardDetail() error {
+	return nil
+
+}
+
+func (s *ATMAbstract) StateName() string {
+	return "ATMAbstract"
+}

atm-machine/atm/card_reader.go

@@ -0,0 +1,34 @@
+package atm
+
+import "atm-machine/model"
+
+const (
+	InvalidCard = "invalid"
+)
+
+// This will be actuall implementation of card reader // i am returning a card from here
+type CardReader struct {
+}
+
+func NewCardReader() CardReader {
+	return CardReader{}
+}
+
+// for now it will return some dummy card depend of input for acting as multiple car
+func (c CardReader) ReadCard(cardType string) model.Card {
+	switch cardType {
+	case InvalidCard:
+		return model.Card{
+			Status: model.NoCard,
+		}
+	default:
+		return model.Card{
+			BankName:  "hdfc",
+			CardNo:    "34567-sd55498459",
+			AccountNo: "bshy4859-sdhhj66",
+			Status:    model.Active,
+			UserName:  "Himanshu sharma"}
+
+	}
+
+}

atm-machine/atm/insert_card.go

@@ -0,0 +1,15 @@
+package atm
+
+type InsertCard struct {
+	atm *ATM
+	ATMAbstract
+}
+
+func (d *InsertCard) InsertCard() error {
+	d.atm.SetState(d.atm.readCard)
+	return nil
+}
+
+func (d *InsertCard) StateName() string {
+	return "InsertCard"
+}

atm-machine/atm/insert_pin.go

@@ -0,0 +1,31 @@
+package atm
+
+import (
+	"errors"
+	"fmt"
+)
+
+type InsertPin struct {
+	atm *ATM
+	ATMAbstract
+}
+
+func (s *InsertPin) InsertPin() error {
+	// logic to valid pin, we can call api client inside it, i will return sucess and error depend on input
+	fmt.Println("Enter 4 letter pin for card:\n")
+
+	var pin string
+
+	fmt.Scanf("%s", &pin)
+
+	if pin == "1111" {
+		s.atm.SetState(s.atm.selectAccount)
+		return nil
+	} else {
+		return errors.New("Pin is not valid")
+	}
+}
+
+func (d *InsertPin) StateName() string {
+	return "InsetPin"
+}

atm-machine/atm/read_card.go

@@ -0,0 +1,20 @@
+package atm
+
+type ReadCard struct {
+	atm *ATM
+	ATMAbstract
+}
+
+func (d *ReadCard) GetCardDetail() error {
+	card := NewCardReader().ReadCard("valid")
+	if card.CardNo == "" {
+		d.atm.SetState(d.atm.insertCard)
+	}
+	d.atm.card = card
+	d.atm.SetState(d.atm.insertPin)
+	return nil
+}
+
+func (d *ReadCard) StateName() string {
+	return "ReadCard"
+}

atm-machine/atm/select_account.go

@@ -0,0 +1,32 @@
+package atm
+
+import (
+	"fmt"
+)
+
+type SelectAccount struct {
+	atm *ATM
+	ATMAbstract
+}
+
+func (s *SelectAccount) SelectAccount() error {
+
+	var accountType string
+	var err error
+
+	fmt.Println("Select account type SAVING OR CURRENT:\n")
+	fmt.Scanf("%s", &accountType)
+
+	if s.atm.account, err = AccountFactory(AccountType(accountType)); err != nil {
+		return err
+	}
+
+	s.atm.SetState(s.atm.dispenserAmount)
+
+	return nil
+
+}
+
+func (s *SelectAccount) StateName() string {
+	return "SelectAccount"
+}