#! /usr/bin/python3
# -*- test-case-name: twisted.mail.test.test_pop3client -*-

# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.


import sys

from twisted.internet import reactor
from twisted.internet.protocol import Factory
from twisted.protocols import basic

USER = "test"
PASS = "twisted"

PORT = 1100

SSL_SUPPORT = True
UIDL_SUPPORT = True
INVALID_SERVER_RESPONSE = False
INVALID_CAPABILITY_RESPONSE = False
INVALID_LOGIN_RESPONSE = False
DENY_CONNECTION = False
DROP_CONNECTION = False
BAD_TLS_RESPONSE = False
TIMEOUT_RESPONSE = False
TIMEOUT_DEFERRED = False
SLOW_GREETING = False

"""Commands"""
CONNECTION_MADE = b"+OK POP3 localhost v2003.83 server ready"

CAPABILITIES = [b"TOP", b"LOGIN-DELAY 180", b"USER", b"SASL LOGIN"]

CAPABILITIES_SSL = b"STLS"
CAPABILITIES_UIDL = b"UIDL"


INVALID_RESPONSE = b"-ERR Unknown request"
VALID_RESPONSE = b"+OK Command Completed"
AUTH_DECLINED = b"-ERR LOGIN failed"
AUTH_ACCEPTED = b"+OK Mailbox open, 0 messages"
TLS_ERROR = b"-ERR server side error start TLS handshake"
LOGOUT_COMPLETE = b"+OK quit completed"
NOT_LOGGED_IN = b"-ERR Unknown AUHORIZATION state command"
STAT = b"+OK 0 0"
UIDL = b"+OK Unique-ID listing follows\r\n."
LIST = b"+OK Mailbox scan listing follows\r\n."
CAP_START = b"+OK Capability list follows:"


class POP3TestServer(basic.LineReceiver):
    def __init__(self, contextFactory=None):
        self.loggedIn = False
        self.caps = None
        self.tmpUser = None
        self.ctx = contextFactory

    def sendSTATResp(self, req):
        self.sendLine(STAT)

    def sendUIDLResp(self, req):
        self.sendLine(UIDL)

    def sendLISTResp(self, req):
        self.sendLine(LIST)

    def sendCapabilities(self):
        if self.caps is None:
            self.caps = [CAP_START]

        if UIDL_SUPPORT:
            self.caps.append(CAPABILITIES_UIDL)

        if SSL_SUPPORT:
            self.caps.append(CAPABILITIES_SSL)

        for cap in CAPABILITIES:
            self.caps.append(cap)
        resp = b"\r\n".join(self.caps)
        resp += b"\r\n."

        self.sendLine(resp)

    def connectionMade(self):
        if DENY_CONNECTION:
            self.disconnect()
            return

        if SLOW_GREETING:
            reactor.callLater(20, self.sendGreeting)

        else:
            self.sendGreeting()

    def sendGreeting(self):
        self.sendLine(CONNECTION_MADE)

    def lineReceived(self, line):
        """Error Conditions"""

        uline = line.upper()
        find = lambda s: uline.find(s) != -1

        if TIMEOUT_RESPONSE:
            # Do not respond to clients request
            return

        if DROP_CONNECTION:
            self.disconnect()
            return

        elif find(b"CAPA"):
            if INVALID_CAPABILITY_RESPONSE:
                self.sendLine(INVALID_RESPONSE)
            else:
                self.sendCapabilities()

        elif find(b"STLS") and SSL_SUPPORT:
            self.startTLS()

        elif find(b"USER"):
            if INVALID_LOGIN_RESPONSE:
                self.sendLine(INVALID_RESPONSE)
                return

            resp = None
            try:
                self.tmpUser = line.split(" ")[1]
                resp = VALID_RESPONSE
            except BaseException:
                resp = AUTH_DECLINED

            self.sendLine(resp)

        elif find(b"PASS"):
            resp = None
            try:
                pwd = line.split(" ")[1]

                if self.tmpUser is None or pwd is None:
                    resp = AUTH_DECLINED
                elif self.tmpUser == USER and pwd == PASS:
                    resp = AUTH_ACCEPTED
                    self.loggedIn = True
                else:
                    resp = AUTH_DECLINED
            except BaseException:
                resp = AUTH_DECLINED

            self.sendLine(resp)

        elif find(b"QUIT"):
            self.loggedIn = False
            self.sendLine(LOGOUT_COMPLETE)
            self.disconnect()

        elif INVALID_SERVER_RESPONSE:
            self.sendLine(INVALID_RESPONSE)

        elif not self.loggedIn:
            self.sendLine(NOT_LOGGED_IN)

        elif find(b"NOOP"):
            self.sendLine(VALID_RESPONSE)

        elif find(b"STAT"):
            if TIMEOUT_DEFERRED:
                return
            self.sendLine(STAT)

        elif find(b"LIST"):
            if TIMEOUT_DEFERRED:
                return
            self.sendLine(LIST)

        elif find(b"UIDL"):
            if TIMEOUT_DEFERRED:
                return
            elif not UIDL_SUPPORT:
                self.sendLine(INVALID_RESPONSE)
                return

            self.sendLine(UIDL)

    def startTLS(self):
        if SSL_SUPPORT and self.ctx is not None:
            self.sendLine(b"+OK Begin TLS negotiation now")
            self.transport.startTLS(self.ctx)
        else:
            self.sendLine(b"-ERR TLS not available")

    def disconnect(self):
        self.transport.loseConnection()


usage = """popServer.py [arg] (default is Standard POP Server with no messages)
no_ssl  - Start with no SSL support
no_uidl - Start with no UIDL support
bad_resp - Send a non-RFC compliant response to the Client
bad_cap_resp - send a non-RFC compliant response when the Client sends a 'CAPABILITY' request
bad_login_resp - send a non-RFC compliant response when the Client sends a 'LOGIN' request
deny - Deny the connection
drop - Drop the connection after sending the greeting
bad_tls - Send a bad response to a STARTTLS
timeout - Do not return a response to a Client request
to_deferred - Do not return a response on a 'Select' request. This
              will test Deferred callback handling
slow - Wait 20 seconds after the connection is made to return a Server Greeting
"""


def printMessage(msg):
    print("Server Starting in %s mode" % msg)


def processArg(arg):
    if arg.lower() == "no_ssl":
        global SSL_SUPPORT
        SSL_SUPPORT = False
        printMessage("NON-SSL")

    elif arg.lower() == "no_uidl":
        global UIDL_SUPPORT
        UIDL_SUPPORT = False
        printMessage("NON-UIDL")

    elif arg.lower() == "bad_resp":
        global INVALID_SERVER_RESPONSE
        INVALID_SERVER_RESPONSE = True
        printMessage("Invalid Server Response")

    elif arg.lower() == "bad_cap_resp":
        global INVALID_CAPABILITY_RESPONSE
        INVALID_CAPABILITY_RESPONSE = True
        printMessage("Invalid Capability Response")

    elif arg.lower() == "bad_login_resp":
        global INVALID_LOGIN_RESPONSE
        INVALID_LOGIN_RESPONSE = True
        printMessage("Invalid Capability Response")

    elif arg.lower() == "deny":
        global DENY_CONNECTION
        DENY_CONNECTION = True
        printMessage("Deny Connection")

    elif arg.lower() == "drop":
        global DROP_CONNECTION
        DROP_CONNECTION = True
        printMessage("Drop Connection")

    elif arg.lower() == "bad_tls":
        global BAD_TLS_RESPONSE
        BAD_TLS_RESPONSE = True
        printMessage("Bad TLS Response")

    elif arg.lower() == "timeout":
        global TIMEOUT_RESPONSE
        TIMEOUT_RESPONSE = True
        printMessage("Timeout Response")

    elif arg.lower() == "to_deferred":
        global TIMEOUT_DEFERRED
        TIMEOUT_DEFERRED = True
        printMessage("Timeout Deferred Response")

    elif arg.lower() == "slow":
        global SLOW_GREETING
        SLOW_GREETING = True
        printMessage("Slow Greeting")

    elif arg.lower() == "--help":
        print(usage)
        sys.exit()

    else:
        print(usage)
        sys.exit()


def main():
    if len(sys.argv) < 2:
        printMessage("POP3 with no messages")
    else:
        args = sys.argv[1:]

        for arg in args:
            processArg(arg)

    f = Factory()
    f.protocol = POP3TestServer
    reactor.listenTCP(PORT, f)
    reactor.run()


if __name__ == "__main__":
    main()
