package main

import (
	"errors"
	"fmt"
	"log"
	"net"
	"regexp"
	"strings"
)

type client struct {
	c    net.Conn
	name string
}

func isValidName(name string) bool {
	pattern := "^[a-zA-Z0-9]+$"
	nameReg, err := regexp.Compile(pattern)
	if err != nil {
		log.Fatalln(err)
	}
	return nameReg.MatchString(name)
}

func cleanString(buf []byte) string {
	s := string(buf)
	idx := strings.Index(s, "\n")
	if idx != -1 {
		s = s[:idx]
	}
	return s
}

func newClient(c net.Conn) (*client, error) {
	cl := &client{
		c:    c,
		name: "",
	}

	cl.sendMessageString("Welcome to budgetchat! What shall I call you?")

	r := make(chan string, 1)
	var err error = nil
	go func() {
		for {
			buf := make([]byte, 32)
			_, err = c.Read(buf)
			if err != nil {
				c.Close()
				r <- ""
				return
			}
			name := cleanString(buf)

			// Check legality
			if !isValidName(name) {
				cl.sendMessageString("The name %s is invalid", string(name))
				err = errors.New("name invalid")
				c.Close()
				r <- name
				return
			}

			// Check for duplicate name
			for _, cls := range room {
				if cls.name == name {
					cl.sendMessageString("The name %s is already taken", string(name))
					err = errors.New("name already taken")
					c.Close()
					r <- name
					return
				}
			}
			r <- name
			return
		}
	}()

	cl.name = <-r
	if err != nil {
		return nil, err
	}
	return cl, nil
}

func (cl *client) sendMessage(m []byte) {
	_, err := cl.c.Write(m)
	if err != nil {
		log.Fatalln(err)
	}
}

func (cl *client) sendMessageString(m string, vars ...any) {
	cl.sendMessage([]byte(fmt.Sprintf(m, vars...) + "\n"))
}