import socket
import base64
import select
import ssl
import json
import argparse
import os
import shutil

from email.parser import Parser
from email.policy import default

CRLF = b'\r\n'


class Config:
	def __init__(self, user, password, server, port, letters_dir, use_ssl):
		self.user = user
		self.password = password
		self.server = server
		self.port = port
		self.letters_dir = letters_dir
		self.use_ssl = use_ssl


def load_config(filename):
	with open(filename, 'r') as config_file:
		d = json.load(config_file)

		return Config(d['user'], d['password'], d['server'], d['port'], d['letters_dir'], d['use_ssl'])


def parse_args():
	parser = argparse.ArgumentParser(description='simple pop3 client')
	parser.add_argument('--config', required=False, default='mail_config.json', help='config file', type=str)
	parser.add_argument('--count', required=False, default=1, help='amount of letters to download', type=int)

	return parser.parse_args()


class Attachment:
	def __init__(self, name, data):
		self.name = name
		self.data = data


class LetterInfo:
	def __init__(self, text, subject, from_, to, date, attachments):
		self.text = text
		self.subject = subject
		self.from_ = from_
		self.to = to
		self.date = date
		self.attachments = attachments

	def save_at(self, path):
		if os.path.isdir(path):
			shutil.rmtree(path)

		os.mkdir(path)

		with open(os.path.join(path, 'letter.txt'), 'w') as letter_file:
			letter_file.write(f'From: {self.from_}\n')
			letter_file.write(f'To: {self.to}\n')
			letter_file.write(f'Date: {self.date}\n')
			letter_file.write(f'Subject: {self.subject}\n')
			letter_file.write(f'Attachments: {" ".join(map(lambda x: x.name, self.attachments))}\n')
			letter_file.write(f'Text:\n{self.text}\n')

		os.mkdir(os.path.join(path, 'attachments'))

		for attachment in self.attachments:
			with open(os.path.join(path, 'attachments', attachment.name), 'wb') as attachment_file:
				attachment_file.write(attachment.data)


class Pop3Response:
	def __init__(self, successful, data):
		self.successful = successful
		self.data = data

	def __str__(self):
		if self.successful:
			return f'[SUCCESSFUL RESPONSE]\n{self.data}'
		return f'[FAILED RESPONSE]\n{self.data}'


class Pop3Client:
	def __init__(self, host, port, user, password, use_ssl):
		self.__sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
		if use_ssl:
			self.__sock = ssl.wrap_socket(self.__sock, ssl_version=ssl.PROTOCOL_SSLv23)

		self.__sock.connect((host, port))
		self.__sock.settimeout(10)

		self._login(user, password)

	def _login(self, user, password):
		print(f'Login for {user}...')

		_ = self._read_single_line()

		user_response = self.execute_raw('USER', [user])

		if not user_response.successful:
			raise ValueError(f'User command failed: {user_response.data}')

		pass_response = self.execute_raw('PASS', [password])

		if not pass_response.successful:
			raise ValueError(f'Password command failed: {pass_response.data}')

		print(f'Successfully login for: {user}')

	def __enter__(self):
		return self

	def __exit__(self, e, et, tb):
		self.__sock.close()
		return False

	def retr(self, i):
		resp = self.execute_raw('RETR', [i], is_long_cmd=True)

		if not resp.successful:
			print(resp.data)
			return

		headers = Parser(policy=default).parsestr(resp.data)

		from_ = headers['From']
		to = headers['To']
		date = headers['Date']
		subject = headers['Subject']

		parts = list(headers.iter_parts())

		text = parts[0].get_payload()
		attachments = []

		for i in range(1, len(parts)):
			attachment = self._read_attachment(parts[i])
			if attachment:
				attachments.append(attachment)

		return LetterInfo(text, subject, from_, to, date, attachments)

	def _read_attachment(self, h):
		name = ''

		if h['Content-Type'].maintype != 'image' or h['Content-Transfer-Encoding'].cte != 'base64':
			print(f'Cant read attachment of type: {h["Content-Type"].content_type} and cte {h["Content-Transfer-Encoding"].cte}')
			return None

		for p in h['Content-Type'].split(';'):
			if p.find('name=') == -1:
				continue

			pp = p.split('=')
			name = pp[1].strip('"')
			break

		data = base64.b64decode(''.join(h.get_payload().split()))

		return Attachment(name, data)


	def execute_raw(self, command, args=None, is_long_cmd=False):
		cmd = command.encode()
		if args:
			cmd += b' ' + b' '.join(map(lambda x: str(x).encode(), args))

		if not cmd.endswith(CRLF):
			cmd += CRLF

		self.__sock.sendall(cmd)

		if not is_long_cmd:
			return self._read_response_with_single_line()

		return self._read_long_response()

	def _read_long_response(self):
		resp = self._read_response_with_single_line()
		lines = []

		if not resp.successful:
			return resp

		line = self._read_single_line()

		while line != b'.':
			if not line.startswith(b'..'):
				lines.append(line)
			else:
				lines.append(b'.')
			line = self._read_single_line()

		return Pop3Response(True, '\n'.join(map(lambda x: x.decode(), lines)))

	def _read_response_with_single_line(self):
		line = self._read_single_line().decode()
		successful = line.startswith('+OK')
		data = (line[4:] if len(line) > 3 else line[3:]) if successful else (line[5:] if len(line) > 4 else line[4:])

		return Pop3Response(successful, data)

	def _read_single_line(self):
		line = bytearray()

		while True:
			line.extend(self.__sock.recv(1))

			if line.endswith(CRLF):
				break

		return line[:-2]


def main():
	try:
		args = parse_args()
		config = load_config(args.config)

		if not os.path.isdir(config.letters_dir):
			os.mkdir(config.letters_dir)

		with Pop3Client(config.server, config.port, config.user, config.password, config.use_ssl) as client:
			for i in range(args.count):
				letter = client.retr(i + 1)

				letter.save_at(os.path.join(config.letters_dir, str(i + 1)))
	except (FileNotFoundError, KeyError):
		print('Invalid config file')
	except socket.timeout:
		print('Network operation timeout')


if __name__ == "__main__":
	main()