Write the bank API

Write the bank API

For now, we won’t use a database to persist data, so we’ll have to create a global variable to store all the accounts in memory

Set up an account in memory

In bankapi/main.go, we’ll create the global variable accounts to store all the accounts in memory. We will add a first account on it.

package main

import (
    "github.com/msft/bank"
)

// map of accounts
// key: number
// value: direction of the account
var accounts = map[float64]*bank.Account{}

func main() {
    accounts[1001] = &bank.Account{
        Customer: bank.Customer{
            Name:    "John",
            Address: "Los Angeles, California",
            Phone:   "(213) 555 0147",
        },
        Number: 1001,
    }
}

Expose the statement method (API endpoint)

We need the net/http package for it. We also need the HandleFunc and ListenAndserve method from the http package.

In bankapi/main.go, we’ll create the statement method.

func statement(w http.ResponseWriter, req *http.Request) {
    // get the account number from the URL
    numberqs := req.URL.Query().Get("number")

    if numberqs == "" {
        fmt.Fprintf(w, "Account number is missing!")
        return
    }

    if number, err := strconv.ParseFloat(numberqs, 64); err != nil {
        fmt.Fprintf(w, "Invalid account number!")
    } else {
        account, ok := accounts[number]
        if !ok {
            fmt.Fprintf(w, "Account with number %v can't be found!", number)
        } else {
            fmt.Fprintf(w, account.Statement())
        }
    }
}

Let’s add the statement method in the main():

func main() {
    accounts[1001] = &bank.Account{
        Customer: bank.Customer{
            Name:    "John",
            Address: "Los Angeles, California",
            Phone:   "(213) 555 0147",
        },
        Number: 1001,
    }


    http.HandleFunc("/statement", statement) //handle GET requests like http://localhost:8000/statement?number=1001
    log.Fatal(http.ListenAndServe("localhost:8000", nil))
}

For testing it, we just can to open a browser and go to http://localhost:8000/statement?number=1001 or curl http://localhost:8000/statement\?number=1001

Expose the deposit method (API endpoint)

func deposit(w http.ResponseWriter, req *http.Request) {
    numberqs := req.URL.Query().Get("number")
    amountqs := req.URL.Query().Get("amount")

    // This a very common check... we should extract this, right?
    if numberqs == "" {
        fmt.Fprintf(w, "Account number is missing!")
        return
    }

    if number, err := strconv.ParseFloat(numberqs, 64); err != nil {
        fmt.Fprintf(w, "Invalid account number!")
    } else if amount, err := strconv.ParseFloat(amountqs, 64); err != nil {
        fmt.Fprintf(w, "Invalid amount number!")
    } else {
        account, ok := accounts[number]
        if !ok {
            fmt.Fprintf(w, "Account with number %v can't be found!", number)
        } else {
            err := account.Deposit(amount)
            if err != nil {
                fmt.Fprintf(w, "%v", err)
            } else {
                fmt.Fprintf(w, account.Statement())
            }
        }
    }
}

Then, we update the main():

//...
  http.HandleFunc("/statement", statement)
  http.HandleFunc("/deposit", deposit)
  log.Fatal(http.ListenAndServe("localhost:8000", nil))

To test it: http://localhost:8000/deposit?number=1001&amount=100 in url or curl http://localhost:8000/deposit\?number=1001&amount=100

Expose the withdraw method (API endpoint)

func withdraw(w http.ResponseWriter, req *http.Request) {
    numberqs := req.URL.Query().Get("number")
    amountqs := req.URL.Query().Get("amount")

    if numberqs == "" {
        fmt.Fprintf(w, "Account number is missing!")
        return
    }

    if number, err := strconv.ParseFloat(numberqs, 64); err != nil {
        fmt.Fprintf(w, "Invalid account number!")
    } else if amount, err := strconv.ParseFloat(amountqs, 64); err != nil {
        fmt.Fprintf(w, "Invalid amount number!")
    } else {
        account, ok := accounts[number]
        if !ok {
            fmt.Fprintf(w, "Account with number %v can't be found!", number)
        } else {
            err := account.Withdraw(amount)
            if err != nil {
                fmt.Fprintf(w, "%v", err)
            } else {
                fmt.Fprintf(w, account.Statement())
            }
        }
    }
}

Add that into the main() method

Then, test it with http://localhost:8000/withdraw?number=1001&amount=100 or curl http://localhost:8000/withdraw\?number=1001&amount=100

Next: part IV