package main

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

var database map[string]string

func main() {
	database = make(map[string]string)

	listener, err := net.Listen("tcp", ":6379")
	if err != nil {
		fmt.Println("error starting server: ", err)
		os.Exit(1)
	}
	defer listener.Close()
	fmt.Println("Redis clone listening on port 6379...")

	for {
		conn, err := listener.Accept()
		if err != nil {
			fmt.Println("Error accepting connection:", err)
			continue
		}
		go handleConnection(conn)
	}
}

func handleGet(conn net.Conn, key string) {
	value, exists := database[key]
	if exists {
		// Redis protocol format for a string reply
		conn.Write([]byte("+" + value + "\r\n"))
	} else {
		// Redis protocol format for a Nil/Null response
		conn.Write([]byte("$-1\r\n"))
	}
}

func handleSet(conn net.Conn, key, value string) {
	database[key] = value
	conn.Write([]byte("+OK\r\n"))
}

func handleConnection(conn net.Conn) {
	defer conn.Close()
	fmt.Println("Client connected:", conn.RemoteAddr())

	reader := bufio.NewReader(conn)
	for {
		message, err := reader.ReadString('\n')
		if err != nil {
			fmt.Println("Client disconnected:", conn.RemoteAddr())
			return
		}

		message = strings.TrimSpace(message)

		fmt.Printf("Received: %s\n", message)
		
		args := strings.Fields(message)
		if len(args) == 0 {
			continue
		}

		command := strings.ToUpper(args[0])

		switch {
		case command == "GET" && len(args) == 2:
			handleGet(conn, args[1])
		case command == "SET" && len(args) == 3:
			handleSet(conn, args[1], args[2])
		default:
			conn.Write([]byte("-ERR unknown command or wrong arguments\r\n"))
		}
	}
}