package network

import (
	"bufio"
	"fmt"
	"io"
	"net"
	"strings"

	"git.uwushka.cc/nzx056/nzx056/nzx_tmpmail/loggingshit"
)

type Session struct {
	Conn        net.Conn
	Reader      *bufio.Reader
	Writer      *bufio.Writer
	MailFrom    string
	RcptTo      []string
	RemoteAddr  string
	hasMailFrom bool
	hasRcptTo   bool
}

func init() {
	loggingshit.Log("lmtp init", 1)
	ln, err := net.Listen("tcp", "127.0.0.1:2525")
	if err != nil {
		loggingshit.Log("lmtp init failed with error %v", 3, err)
	}

	for {
		conn, err := ln.Accept()
		if err != nil {
			loggingshit.Log("failed to accept connection with error %v, skipping", 2, err)
			continue
		}

		go handle_conn(conn)
	}
}

func handle_conn(conn net.Conn) {
	defer conn.Close()

	s := &Session{
		Conn:       conn,
		Writer:     bufio.NewWriter(conn),
		Reader:     bufio.NewReader(conn),
		RemoteAddr: conn.RemoteAddr().String(),
	}

	s.reply("220 nzx056.love LMTP ready")

	for {
		l, err := s.readline()
		if err != nil {
			if err != io.EOF {
				loggingshit.Log("readline failed for %s with error: %v", 2, s.RemoteAddr, err)
			}
			loggingshit.Log("caught EOF from %s, closing conn", 2, s.RemoteAddr)
			return
		}

		upper := strings.ToUpper(l)

		switch {
		case strings.HasPrefix(upper, "LHLO "):
			s.reply("250-nzx056.love")
			s.reply("250-8BITMIME")
			s.reply("250 PIPELINING")
		case strings.HasPrefix(upper, "MAIL FROM:"):
			s.MailFrom = extractSender(l[len("MAIL FROM:"):])
			s.hasMailFrom = true
			s.RcptTo = nil
			s.reply("250 2.1.0 Ok")
		case strings.HasPrefix(upper, "RCPT TO:"):
			rcpt := strings.ToLower(extractSender(l[len("RCPT TO:"):]))
			s.hasRcptTo = true

			if !strings.HasSuffix(rcpt, "@nzx056.love") {
				s.reply("550 5.1.1 User unknown")
				loggingshit.Log("got an email for unknown domain %s, skipping", 1, rcpt)
				continue
			}

			s.RcptTo = append(s.RcptTo, rcpt)
			s.reply("250 2.1.5 Ok")
		case upper == "DATA":
			if !s.hasMailFrom {
				s.reply("503 5.5.1 Need MAIL FROM first")
				continue
			}

			if !s.hasRcptTo {
				s.reply("503 5.5.1 Need RCPT TO first")
				continue
			}

			s.reply("354 End data with <CR><LF>.<CR><LF>")
		}
	}
}

func extractSender(s string) string {
	s = strings.TrimSpace(s)
	if strings.HasPrefix(s, "<") {
		end := strings.Index(s, ">")
		if end >= 0 {
			return s[1:end]
		}
	}

	fields := strings.Fields(s)
	if len(fields) == 0 {
		return ""
	}

	return strings.Trim(fields[0], "<>")
}

func (s *Session) readline() (string, error) {
	l, err := s.Reader.ReadString('\n')
	if err != nil {
		return "", err
	}

	l = strings.TrimRight(l, "\r\n")
	loggingshit.Log("readline %s from %s", 1, l, s.RemoteAddr)
	return l, nil
}

func (s *Session) reply(st string) {
	loggingshit.Log("write to %s: %s", 1, s.RemoteAddr, st)
	fmt.Fprintf(s.Writer, "%s\r\n", st)
	s.Writer.Flush()
}