package main

// 24 Aug 2026: Added support for the "finger://host[/user]" URL format
//              Maintained original author's commenting style
// Original by: https://github.com/Lindax28/finger-client
// Updates by:  https://640kb.neocities.org/fingerverse
//              go build -o lindax2


import (
	"fmt"
	"net"
	"os"
	"strings"
	"unicode"
)

func main() {
	// Verify number of arguments is correct
	if len(os.Args) != 2 {
		fmt.Println("Usage: finger [user@hostname | finger://hostname(/user)]")
		os.Exit(1)
	}

	// Parse the argument - support both formats
	user, hostname, err := parseFingerArgument(os.Args[1])
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	// Verify username is in ASCII format (if provided)
	if user != "" {
		for _, char := range user {
			if char > unicode.MaxASCII {
				fmt.Println("Username must be in ASCII format")
				os.Exit(1)
			}
		}
	}

	// Connect to host on port 79
	conn, err := net.Dial("tcp", hostname+":79")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	defer conn.Close()

	// Write user data to the connection, ended with CRLF
	// If user is empty, just send CRLF to query all users
	conn.Write([]byte(user + "\r\n"))

	// Read data from the connection
	response := make([]byte, 0)
	tmp := make([]byte, 256)
	for {
		n, err := conn.Read(tmp)
		if err != nil {
			break
		}
		response = append(response, tmp[:n]...)
	}
	fmt.Println(string(response))
}

// parseFingerArgument parses either "user@host" or "finger://host[/user]" format
func parseFingerArgument(arg string) (user, hostname string, err error) {
	// Check for finger:// format
	if strings.HasPrefix(arg, "finger://") {
		// Remove the "finger://" prefix
		withoutPrefix := strings.TrimPrefix(arg, "finger://")
		
		// Split by "/" - could be host/user or just host
		parts := strings.SplitN(withoutPrefix, "/", 2)
		
		if len(parts) == 1 {
			// Just hostname - query all users
			hostname = parts[0]
			if hostname == "" {
				return "", "", fmt.Errorf("Invalid finger:// format. Use: finger://hostname[/user]")
			}
			return "", hostname, nil
		}
		
		// host/user format
		hostname = parts[0]
		user = parts[1]
		
		if hostname == "" {
			return "", "", fmt.Errorf("Invalid finger:// format. Use: finger://hostname[/user]")
		}
		
		return user, hostname, nil
	}
	
	// Try user@host format
	parts := strings.SplitN(arg, "@", 2)
	if len(parts) != 2 {
		return "", "", fmt.Errorf("Proper Usage is: finger user@hostname")
	}
	
	user = parts[0]
	hostname = parts[1]
	
	// Validate we got something
	if user == "" || hostname == "" {
		return "", "", fmt.Errorf("Proper Usage is: finger user@hostname")
	}
	
	return user, hostname, nil
}