package protocol

import (
	"bytes"
	"fmt"
)

func init() {
	Register(Server, "\x0a", detectMySQL)
}

func detectMySQL(dir Direction, data []byte, srcPort, dstPort int) (proto *Protocol, confidence float64) {
	if len(data) < 7 {
		return nil, 0
	}

	// The first byte of the handshake packet is the protocol version.
	// For MySQL, this is 10 (0x0A).
	if data[0] != 0x0A {
		return nil, 0
	}

	if srcPort == 3306 {
		confidence = .1
	}

	// After the protocol version, there is a null-terminated server version string.
	// We search for the null byte starting from the second byte (index 1).
	nullIndex := bytes.IndexByte(data[1:], 0x00)

	// If no null byte is found, it's not a valid banner.
	if nullIndex == -1 {
		return nil, 0
	}

	// The position of the null byte is relative to the start of the whole slice.
	// It's 1 (for the protocol byte) + nullIndex.
	serverVersionEndPos := 1 + nullIndex

	// After the null-terminated version string, there must be at least 4 bytes
	// for the connection ID, plus more data for capabilities, auth, etc.
	// We'll check for the 4-byte connection ID as a minimum requirement.
	const connectionIDLength = 4
	if len(data) < serverVersionEndPos+1+connectionIDLength {
		return nil, 0
	}

	var version Version
	_, _ = fmt.Sscanf(string(data[1:serverVersionEndPos]), "%d.%d.%d-%s", &version.Major, &version.Minor, &version.Patch, &version.Extra)

	return &Protocol{
		Type:    TypeMySQL,
		Version: version,
	}, confidence + .75
}