package protocol

import (
	"bytes"
)

// The required prefix for the SSH protocol identification line.
const (
	ssh199Prefix = "SSH-1.99-"
	ssh20Prefix  = "SSH-2.0-"
)

func init() {
	Register(Both, "", detectSSH)
}

func detectSSH(dir Direction, data []byte, srcPort, dstPort int) (proto *Protocol, confidence float64) {
	// The data must be at least as long as the prefix itself.
	if len(data) < len(ssh20Prefix) {
		return nil, 0
	}

	if dstPort == 22 || dstPort == 2200 || dstPort == 2222 {
		confidence = .1
	}

	// The protocol allows for pre-banner text, so we have to check all lines.
	for _, line := range bytes.Split(data, []byte{'\n'}) {
		line = bytes.TrimSuffix(line, []byte{'\r'})
		if bytes.HasPrefix(line, []byte(ssh20Prefix)) {
			return &Protocol{
				Name: ProtocolSSH,
				Version: Version{
					Major: 2,
					Minor: 0,
					Patch: -1,
					Extra: string(line[len(ssh20Prefix):]),
				},
			}, confidence + 0.75
		}
		if bytes.HasPrefix(line, []byte(ssh199Prefix)) {
			return &Protocol{
				Name: ProtocolSSH,
				Version: Version{
					Major: 1,
					Minor: 99,
					Patch: -1,
					Extra: string(line[len(ssh20Prefix):]),
				},
			}, confidence + 0.75
		}
	}

	return nil, 0
}