Example (Go) - Bank

module example.com/bank

go 1.21.6

package main

import (
	"errors"
	"fmt"
	"os"
	"strconv"
)

const accountBalanceFile string = "balance.txt"

func writeBalanceToFile(balance float64) {
	var balanceText string = fmt.Sprint(balance)
	os.WriteFile(accountBalanceFile, []byte(balanceText), 0644) // 0644 = read and write
}

func getBalanceFromFile() (float64, error) {
	data, err := os.ReadFile(accountBalanceFile)
	if err != nil {
		return 1000, errors.New("Failed to find/read file.")
	}

	var balanceText string = string(data)
	balance, err := strconv.ParseFloat(balanceText, 64)
	if err != nil {
		return 1000, errors.New("Failed to parse balance.")
	}

	return balance, nil
}

func main() {
	accountBalance, err := getBalanceFromFile()
	if err != nil {
		fmt.Println("Error:", err)
        // panic("Cannot continue, sorry.")
        fmt.Println("Continuing with default balance of $1000.00")
	}

	fmt.Println("Welcome to Go Bank!")

	// for i := 0; i < 2; i++ {
	for {
		fmt.Println("=====================")

		fmt.Println("What do you want to do?")
		fmt.Println("1. Check Balance")
		fmt.Println("2. Deposit Money")
		fmt.Println("3. Withdraw Money")
		fmt.Println("4. Exit")

		var choice int
		fmt.Print("Select Option: ")
		fmt.Scan(&choice)
		fmt.Println("You Chose: ", choice)

		if choice == 1 {
			fmt.Printf("Your balance is $%.2f\n", accountBalance)
		} else if choice == 2 {
			fmt.Print("Enter amount to deposit: ")
			var depositAmount float64
			fmt.Scan(&depositAmount)

			if depositAmount <= 0 {
				fmt.Println("Invalid amount. Amount must be greater than 0.")
				continue
			}

			accountBalance += depositAmount
			fmt.Printf("Your new balance is $%.2f\n", accountBalance)
			writeBalanceToFile(accountBalance)
		} else if choice == 3 {
			fmt.Print("Enter amount to withdraw: ")
			var withdrawAmount float64
			fmt.Scan(&withdrawAmount)

			if withdrawAmount <= 0 {
				fmt.Println("Invalid amount. Amount must be greater than 0.")
				continue
			}
			if withdrawAmount > accountBalance {
				fmt.Println("Insufficient funds.")
				continue
			}

			accountBalance -= withdrawAmount
			fmt.Printf("Your new balance is $%.2f\n", accountBalance)
			writeBalanceToFile(accountBalance)
		} else {
			fmt.Println("Exiting...")
			break
		}

		//! ====In Go, the break statement cannot exit the loop from inside a switch statement====
		//! ====this is because the break statement simply breaks the switch statement====
		// switch choice {
		// case 1:
		// 	fmt.Printf("Your balance is $%.2f\n", accountBalance)
		// case 2:
		// 	fmt.Print("Enter amount to deposit: ")
		// 	var depositAmount float64
		// 	fmt.Scan(&depositAmount)
		//
		// 	if depositAmount <= 0 {
		// 		fmt.Println("Invalid amount. Amount must be greater than 0.")
		// 		continue
		// 	}
		//
		// 	accountBalance += depositAmount
		// 	fmt.Printf("Your new balance is $%.2f\n", accountBalance)
		// case 3:
		// 	fmt.Print("Enter amount to withdraw: ")
		// 	var withdrawAmount float64
		// 	fmt.Scan(&withdrawAmount)
		//
		// 	if withdrawAmount <= 0 {
		// 		fmt.Println("Invalid amount. Amount must be greater than 0.")
		// 		continue
		// 	}
		// 	if withdrawAmount > accountBalance {
		// 		fmt.Println("Insufficient funds.")
		// 		continue
		// 	}
		//
		// 	accountBalance -= withdrawAmount
		// 	fmt.Printf("Your new balance is $%.2f\n", accountBalance)
		// default:
		// 	fmt.Println("Exiting...")
		// 	return
		// }
	}
}