source: server/cli.go

package main

import (
        "bufio"
        "fmt"
        "os"
        "strings"
)

// Session holds the currently-logged-in user, if any.
type Session struct {
        UserID   string
        Username string
}

var stdin = bufio.NewReader(os.Stdin)

func prompt(label string) string {
        fmt.Print(label)
        line, err := stdin.ReadString('\n')
        // On EOF (Ctrl-D, or the end of a piped script) ReadString keeps returning
        // an error forever. Without this the menu loop would spin printing
        // "Unknown option." indefinitely instead of ending.
        if err != nil && strings.TrimSpace(line) == "" {
                fmt.Println("\nInput closed. Goodbye.")
                os.Exit(0)
        }
        return strings.TrimSpace(line)
}

func RunCLI() {
        fmt.Println("=========================================")
        fmt.Println("  EduBerza - Crypto Exchange Simulation")
        fmt.Println("=========================================")

        var s Session
        for {
                if s.UserID == "" {
                        anonymousMenu(&s)
                } else {
                        authenticatedMenu(&s)
                }
        }
}

func anonymousMenu(s *Session) {
        fmt.Println()
        fmt.Println("[1] Register")
        fmt.Println("[2] Login")
        fmt.Println("[3] Browse markets")
        fmt.Println("[0] Exit")
        switch prompt("> ") {
        case "1":
                Register()
        case "2":
                Login(s)
        case "3":
                ListMarkets()
        case "0":
                fmt.Println("Goodbye.")
                os.Exit(0)
        default:
                fmt.Println("Unknown option.")
        }
}

func authenticatedMenu(s *Session) {
        fmt.Printf("\n--- Logged in as %s ---\n", s.Username)
        fmt.Println("[1] View balance")
        fmt.Println("[2] Deposit virtual funds")
        fmt.Println("[3] Browse markets")
        fmt.Println("[4] Place BUY order")
        fmt.Println("[5] Place SELL order")
        fmt.Println("[6] View portfolio")
        fmt.Println("[7] View transaction history")
        fmt.Println("[8] Manage watchlist")
        fmt.Println("[9] Logout")
        fmt.Println("[10] Report: top traders")
        fmt.Println("[11] Report: market performance")
        fmt.Println("[12] Order book")
        fmt.Println("[13] My open orders")
        fmt.Println("[14] Cancel an order")
        fmt.Println("[0] Exit")
        switch prompt("> ") {
        case "1":
                ShowBalance(s)
        case "2":
                Deposit(s)
        case "3":
                ListMarkets()
        case "4":
                PlaceOrder(s, "buy")
        case "5":
                PlaceOrder(s, "sell")
        case "6":
                ShowPortfolio(s)
        case "7":
                ShowTransactions(s)
        case "8":
                ManageWatchlist(s)
        case "10":
                ShowTopTraders(s)
        case "11":
                ShowMarketPerformance(s)
        case "12":
                ShowOrderBook()
        case "13":
                ShowMyOrders(s)
        case "14":
                CancelOrder(s)
        case "9":
                s.UserID = ""
                s.Username = ""
                fmt.Println("Logged out.")
        case "0":
                fmt.Println("Goodbye.")
                os.Exit(0)
        default:
                fmt.Println("Unknown option.")
        }
}