/* diodemail - send-only smtp server
 * Copyright (c) 2024 Gnarwhal
 *
 * This file is part of SSHare.
 *
 * SSHare is free software: you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * SSHare is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * SSHare. If not, see <https://www.gnu.org/licenses/>.
 */

package smtp

import (
	"fmt"
	"strings"
)

type Command struct {
	name string
	Exec func(Connection)([]Command, error)
}

func (self Command) Name() string {
	return self.name
}

func (self Command) Check(message string) bool {
	return strings.HasPrefix(message, self.name)
}

func (self Connection) Chain() error {
	commands, err := Greet(self)
	if err != nil {
		return err
	}
	for {
		message, err := self.Read()
		if err != nil {
			return err
		}

		command_found := false
		for _, command := range commands {
			if command.Check(message) {
				commands, err = command.Exec(self)
				if err != nil {
					return err
				}
				command_found = true
				break
			}
		}
		if !command_found {
			expected := make([]string, len(commands))
			for index, command := range commands {
				expected[index] = command.Name()
			}
			return fmt.Errorf("Expected one of %v, but got: %v", expected, message)
		}

		if len(commands) == 0 {
			break
		}
	}
	return nil
}

/* --- GREETING RESPONSE --- */

func Greet(connection Connection) ([]Command, error) {
	err := connection.Write(
		"220 localhost ESMTP diodemail -- Service ready" + "\n",
	)
	if err != nil {
		return nil, err
	}

	return []Command{
		Command{ "HELO", Hello },
		Command{ "EHLO", Hello },
	}, nil
}

/* --- HELO/EHLO RESPONSE --- */

func Hello(connection Connection) ([]Command, error) {
	err := connection.Write(
		fmt.Sprintf("250 %v is shy", connection.connection.LocalAddr()) + "\n",
	)
	if err != nil {
		return nil, err
	}

	return []Command{}, nil
}