package ident

import (
	"fmt"
	"net"
	"regexp"
	"strconv"
)

// Request is an ident protocol request, as seen by the client or server.
type Request struct {
	// ClientPort is the port number on the client side of the indent protocol,
	// ie. the port local to the ident client.
	ClientPort uint16
	// ServerPort is the port number on the server side of the ident protocol,
	// ie. the port local to the ident server.
	ServerPort uint16

	// ClientAddress is the address of the ident protocol client. This is set
	// by the ident Server before invoking handlers, and is ignored by the
	// ident protocol Client.
	// In handlers this can be used to ensure that responses are only returned
	// to clients who are running on the remote side of the connection that
	// they are querying about.
	ClientAddress net.Addr
}

// encode encodes ths Request as per RFC1413, including the terminating \r\n.
func (r *Request) encode() []byte {
	return []byte(fmt.Sprintf("%d,%d\r\n", r.ServerPort, r.ClientPort))
}

var (
	// reRequest matches request from RFC1413, but allows extra whitespace
	// between significant tokens.
	reRequest = regexp.MustCompile(`^\s*(\d{1,5})\s*,\s*(\d{1,5})\s*$`)
)

// decodeRequest parses the given bytes as an ident request. The data must be
// stripped of the trailing \r\n.
func decodeRequest(data []byte) (*Request, error) {
	match := reRequest.FindStringSubmatch(string(data))
	if match == nil {
		return nil, fmt.Errorf("unparseable request")
	}
	serverPort, err := strconv.ParseUint(match[1], 10, 16)
	if err != nil {
		return nil, fmt.Errorf("invalid server port: %w", err)
	}
	clientPort, err := strconv.ParseUint(match[2], 10, 16)
	if err != nil {
		return nil, fmt.Errorf("invalid client port: %w", err)
	}
	return &Request{
		ClientPort: uint16(clientPort),
		ServerPort: uint16(serverPort),
	}, nil
}