// Copyright (c) 2021 VMware, Inc. or its affiliates. All Rights Reserved.
// Copyright (c) 2012-2021, Sean Treadway, SoundCloud Ltd.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package amqp091

import (
	"bytes"
	"fmt"
)

// Authentication interface provides a means for different SASL authentication
// mechanisms to be used during connection tuning.
type Authentication interface {
	Mechanism() string
	Response() string
}

// PlainAuth is a similar to Basic Auth in HTTP.
type PlainAuth struct {
	Username string
	Password string
}

// Mechanism returns "PLAIN"
func (auth *PlainAuth) Mechanism() string {
	return "PLAIN"
}

// Response returns the null character delimited encoding for the SASL PLAIN Mechanism.
func (auth *PlainAuth) Response() string {
	return fmt.Sprintf("\000%s\000%s", auth.Username, auth.Password)
}

// AMQPlainAuth is similar to PlainAuth
type AMQPlainAuth struct {
	Username string
	Password string
}

// Mechanism returns "AMQPLAIN"
func (auth *AMQPlainAuth) Mechanism() string {
	return "AMQPLAIN"
}

// Response returns an AMQP encoded credentials table, without the field table size.
func (auth *AMQPlainAuth) Response() string {
	var buf bytes.Buffer
	table := Table{"LOGIN": auth.Username, "PASSWORD": auth.Password}
	if err := writeTable(&buf, table); err != nil {
		return ""
	}
	return buf.String()[4:]
}

// ExternalAuth for RabbitMQ-auth-mechanism-ssl.
type ExternalAuth struct{}

// Mechanism returns "EXTERNAL"
func (*ExternalAuth) Mechanism() string {
	return "EXTERNAL"
}

// Response returns an AMQP encoded credentials table, without the field table size.
func (*ExternalAuth) Response() string {
	return "\000*\000*"
}

// Finds the first mechanism preferred by the client that the server supports.
func pickSASLMechanism(client []Authentication, serverMechanisms []string) (auth Authentication, ok bool) {
	for _, auth = range client {
		for _, mech := range serverMechanisms {
			if auth.Mechanism() == mech {
				return auth, true
			}
		}
	}

	return
}
