M3O SDK Concept

examples/otp/handler/handler.go

@@ -0,0 +1,99 @@
+package handler
+
+import (
+	"crypto/rand"
+
+	otp "github.com/m3o/m3o-go/examples/otp/proto"
+	"github.com/m3o/m3o-go/context"
+	"github.com/m3o/m3o-go/errors"
+	"github.com/m3o/m3o-go/sms"
+	"github.com/m3o/m3o-go/store/keyvalue"
+)
+
+const (
+	otpChars  = "1234567890"
+	otpLength = 6
+	otpTTL = time.Minute * 5
+)
+
+var (
+	errMissingPhoneNumber = errors.BadRequest("Missing PhoneNumber")
+	errMissingCode 				= errors.BadRequest("Missing Code")
+	errInvalidCode 				= errors.BadRequest("Invalid Code")
+)
+
+// OTP satisfies the OTP handler interface. Note: this handler is an exampple and not intended for 
+// production use - the handler does not enforce verification limits so it would be possible to brute
+// force the verification process. It is advised to use a retry limit of 3 in real-world applications.
+type OTP struct {
+	SMS   sms.Service
+	Store keyvalue.Store
+}
+
+// Send a one time password to the phone number provided
+func (o *OTP) Send(ctx context.Context, req *otp.SendRequest) (*otp.SendResponse, error) {
+	// validate the request
+	if len(req.PhoneNumber) == 0 {
+		return nil, errMissingPhoneNumber
+	}
+
+	// generate and send the OPT
+	otp := generateOTP()
+	msg := fmt.Sprintf("Your M3O verification code is %v", otp
+	if err := o.SMS.Send(req.PhoneNumber, msg); err != nil {
+		return nil, err
+	}
+
+	// write the code to the store
+	err := o.Store.Write(req.PhoneNumber, otp, keyvalue.WriteOptions{
+		Expiry: time.Now().Add(otpTTL),
+	})
+	if err != nil {
+		return nil, errors.InternalServerError("Error writing OTP to the store")
+	}
+
+	// return no error, indicating the verification code send successfully
+	return &otp.SendResponse{}, nil
+}
+
+// Validate a one time password
+func (o *OTP) Verify(ctx context.Context, req *otp.VerifyRequest) (*otp.VerifyResponse, error) {
+	// validate the request
+	if len(req.PhoneNumber) == 0 {
+		return nil, errMissingPhoneNumber
+	}
+	if len(req.Code) == 0 {
+		return nil, errMissingCode
+	}
+
+	// lookup the phone number from the store
+	rec, err := o.Store.Read(req.PhoneNumber)
+	if err == keyvalue.ErrRecordNotFound {
+		return nil, errMissingCode
+	} else if err != nil {
+		return nil, errors.InternalServerError("Error reading OTP from the store")
+	}
+
+	// ensure the codes match
+	if rec.Value != req.Code {
+		return nil, errInvalidCode
+	}
+
+	// return no error, indicating the verification was successful
+	return &otp.VerifyResponse{}, nil
+}
+
+func generateOTP() (string, error) {
+	buffer := make([]byte, otpLength)
+	_, err := rand.Read(buffer)
+	if err != nil {
+		return "", err
+	}
+
+	otpCharsLength := len(otpChars)
+	for i := 0; i < otpLength; i++ {
+		buffer[i] = otpChars[int(buffer[i])%otpCharsLength]
+	}
+
+	return string(buffer), nil
+}