package protocol

import (
	"bufio"
	"bytes"
	"fmt"
	"net/http"
)

func init() {
	Register(Client, "", detectHTTPRequest)
	Register(Server, "HTTP/?.", detectHTTPResponse)
}

func detectHTTPRequest(dir Direction, data []byte, srcPort, dstPort int) (proto *Protocol, confidence float64) {
	// A minimal request "GET / HTTP/1.0\r\n" is > 8 bytes.
	if len(data) < 8 {
		return nil, 0
	}

	switch dstPort {
	case 80, 8080: // Common HTTP ports
		confidence = +.1
	case 3128: // Common HTTP proxy port
		confidence = -.1
	}

	if Strict {
		var (
			b = append(data, '\r', '\n')
			r = bufio.NewReader(bytes.NewReader(b))
		)
		if request, err := http.ReadRequest(r); err == nil {
			return &Protocol{
				Name: ProtocolHTTP,
				Version: Version{
					Major: request.ProtoMajor,
					Minor: request.ProtoMinor,
					Patch: -1,
				},
			}, confidence + .85
		}
		return nil, 0
	}

	crlfIndex := bytes.IndexFunc(data, func(r rune) bool {
		return r == '\r' || r == '\n'
	})
	if crlfIndex == -1 {
		return nil, 0
	}

	// A request has three, space-separated parts.
	part := bytes.Split(data[:crlfIndex], []byte(" "))
	if len(part) != 3 {
		return nil, 0
	}

	// The last part starts with "HTTP/".
	if !bytes.HasPrefix(part[2], []byte("HTTP/1")) {
		return nil, 0
	}

	var version = Version{Patch: -1}
	fmt.Sscanf(string(part[2]), "HTTP/%d.%d ", &version.Major, &version.Minor)

	return &Protocol{
		Name:    ProtocolHTTP,
		Version: version,
	}, confidence + .75
}

func detectHTTPResponse(dir Direction, data []byte, srcPort, dstPort int) (proto *Protocol, confidence float64) {
	if !dir.Contains(Server) {
		return nil, 0
	}

	// A minimal response "HTTP/1.0 200 OK\r\n" is > 8 bytes.
	if len(data) < 8 {
		return nil, 0
	}

	switch srcPort {
	case 80, 8080: // Common HTTP ports
		confidence = +.1
	case 3128: // Common HTTP proxy port
		confidence = -.1
	}

	if Strict {
		var (
			b = append(data, '\r', '\n')
			r = bufio.NewReader(bytes.NewReader(b))
		)
		if response, err := http.ReadResponse(r, nil); err == nil {
			return &Protocol{
				Name: ProtocolHTTP,
				Version: Version{
					Major: response.ProtoMajor,
					Minor: response.ProtoMinor,
					Patch: -1,
				},
			}, confidence + .85
		}
		return nil, 0
	}

	var version = Version{Patch: -1}
	fmt.Sscanf(string(data), "HTTP/%d.%d ", &version.Major, &version.Minor)

	return &Protocol{
		Name:    ProtocolHTTP,
		Version: version,
	}, confidence + .75
}