ATM LLD

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 +1,43 @@
+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 SavingAccount struct {
+	acctNo  string
+	balance float64
+}
+
+func (s *SavingAccount) GetBalance() float64 {
+	return s.balance
+}
+
+type CurrentAccount struct {
+	acctNo  string
+	balance float64
+}
+
+func (c *CurrentAccount) GetBalance() float64 {
+	return c.balance
+}

atm-machine/atm/atm.go

@@ -0,0 +1,120 @@
+package atm
+
+import (
+	"atm-machine/model"
+	"fmt"
+	"sync"
+)
+
+type WithdrawNote struct {
+	FiveHundread int
+	Hundread     int
+	Left         int
+}
+
+type ATM struct {
+	countOFNotes    map[string]int
+	card            model.Card
+	account         Account
+	uiOption        []string
+	WithdrawAs      *WithdrawNote
+	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) ResetAtm() {
+	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) DispenserAmount() error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.currentState.DispenserAmount()
+}
+
+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.ResetAtm()
+		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.selectAccount = &SelectAccount{
+		atm: atm,
+	}
+
+	atm.readCard = &ReadCard{
+		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 +1,30 @@
+package atm
+
+import "atm-machine/model"
+
+// 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 "invalid":
+		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 +1,30 @@
+package atm
+
+import (
+	"errors"
+	"fmt"
+)
+
+type InsetPin struct {
+	atm *ATM
+	ATMAbstract
+}
+
+func (s *InsetPin) 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" {
+		return nil
+	} else {
+		return errors.New("Pin is not valid")
+	}
+}
+
+func (d *InsetPin) 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.selectAccount)
+	return nil
+}
+
+func (d *ReadCard) StateName() string {
+	return "ReadCard"
+}

atm-machine/atm/select_account.go

@@ -0,0 +1,30 @@
+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)
+
+	s.atm.account, err = AccountFactory(AccountType(accountType))
+
+	s.atm.SetState(s.atm.dispenserAmount)
+
+	return err
+
+}
+
+func (s *SelectAccount) StateName() string {
+	return "SelectAccount"
+}

atm-machine/atm/withdraw.go

@@ -0,0 +1,34 @@
+package atm
+
+type Withdraw interface {
+	ProcessAmount(atm *ATM, atmamount float64)
+}
+
+func NewWithDrawPipeline() Withdraw {
+	return fiveHundreadWithdraw{
+		next: hundreadHundreadWithdraw{},
+	}
+}
+
+type fiveHundreadWithdraw struct {
+	next Withdraw
+}
+
+func (f fiveHundreadWithdraw) ProcessAmount(atm *ATM, atmamount float64) {
+	div := atmamount / 500
+	rem := int(atmamount) % 500
+	atm.WithdrawAs.FiveHundread = int(div)
+	f.next.ProcessAmount(atm, float64(rem))
+}
+
+type hundreadHundreadWithdraw struct {
+	next Withdraw
+}
+
+func (h hundreadHundreadWithdraw) ProcessAmount(atm *ATM, atmamount float64) {
+	div := atmamount / 100
+	rem := int(atmamount) % 100
+	atm.WithdrawAs.Hundread = int(div)
+	atm.WithdrawAs.Left = rem
+
+}