import os, socket, time
import threading
from OpenSSL import SSL
from netlib import tcp, http, certutils, http_status, http_auth
import utils, flow, version, platform, controller


TRANSPARENT_SSL_PORTS = [443, 8443]

KILL = 0


class ProxyError(Exception):
    def __init__(self, code, msg, headers=None):
        self.code, self.msg, self.headers = code, msg, headers

    def __str__(self):
        return "ProxyError(%s, %s)"%(self.code, self.msg)


class Log:
    def __init__(self, msg):
        self.msg = msg


class ProxyConfig:
    def __init__(self, certfile = None, cacert = None, clientcerts = None, no_upstream_cert=False, body_size_limit = None, reverse_proxy=None, forward_proxy=None, transparent_proxy=None, authenticator=None):
        self.certfile = certfile
        self.cacert = cacert
        self.clientcerts = clientcerts
        self.no_upstream_cert = no_upstream_cert
        self.body_size_limit = body_size_limit
        self.reverse_proxy = reverse_proxy
        self.forward_proxy = forward_proxy
        self.transparent_proxy = transparent_proxy
        self.authenticator = authenticator
        self.certstore = certutils.CertStore()


class ServerConnection(tcp.TCPClient):
    def __init__(self, config, scheme, host, port, sni):
        tcp.TCPClient.__init__(self, host, port)
        self.config = config
        self.scheme, self.sni = scheme, sni
        self.requestcount = 0
        self.tcp_setup_timestamp = None
        self.ssl_setup_timestamp = None

    def connect(self):
        tcp.TCPClient.connect(self)
        self.tcp_setup_timestamp = time.time()
        if self.scheme == "https":
            clientcert = None
            if self.config.clientcerts:
                path = os.path.join(self.config.clientcerts, self.host.encode("idna")) + ".pem"
                if os.path.exists(path):
                    clientcert = path
            try:
                self.convert_to_ssl(cert=clientcert, sni=self.sni)
                self.ssl_setup_timestamp = time.time()
            except tcp.NetLibError, v:
                raise ProxyError(400, str(v))

    def send(self, request):
        self.requestcount += 1
        d = request._assemble()
        if not d:
            raise ProxyError(502, "Cannot transmit an incomplete request.")
        self.wfile.write(d)
        self.wfile.flush()

    def terminate(self):
        if self.connection:
            try:
                self.wfile.flush()
            except tcp.NetLibDisconnect: # pragma: no cover
                pass
            self.connection.close()



class RequestReplayThread(threading.Thread):
    def __init__(self, config, flow, masterq):
        self.config, self.flow, self.channel = config, flow, controller.Channel(masterq)
        threading.Thread.__init__(self)

    def run(self):
        try:
            r = self.flow.request
            server = ServerConnection(self.config, r.scheme, r.host, r.port, r.host)
            server.connect()
            server.send(r)
            httpversion, code, msg, headers, content = http.read_response(
                server.rfile, r.method, self.config.body_size_limit
            )
            response = flow.Response(
                self.flow.request, httpversion, code, msg, headers, content, server.cert, 
                server.rfile.first_byte_timestamp
            )
            self.channel.ask("response", response)
        except (ProxyError, http.HttpError, tcp.NetLibError), v:
            err = flow.Error(self.flow.request, str(v))
            self.channel.ask("error", err)


class HandleSNI:
    def __init__(self, handler, client_conn, host, port, key):
        self.handler, self.client_conn, self.host, self.port = handler, client_conn, host, port
        self.key = key

    def __call__(self, client_connection):
        try:
            sn = client_connection.get_servername()
            if sn:
                self.handler.get_server_connection(self.client_conn, "https", self.host, self.port, sn)
                dummycert = self.handler.find_cert(self.client_conn, self.host, self.port, sn)
                new_context = SSL.Context(SSL.TLSv1_METHOD)
                new_context.use_privatekey_file(self.key)
                new_context.use_certificate(dummycert.x509)
                client_connection.set_context(new_context)
                self.handler.sni = sn.decode("utf8").encode("idna")
        # An unhandled exception in this method will core dump PyOpenSSL, so
        # make dang sure it doesn't happen.
        except Exception: # pragma: no cover
            pass


class ProxyHandler(tcp.BaseHandler):
    def __init__(self, config, connection, client_address, server, channel, server_version):
        self.channel, self.server_version = channel, server_version
        self.config = config
        self.proxy_connect_state = None
        self.sni = None
        self.server_conn = None
        tcp.BaseHandler.__init__(self, connection, client_address, server)

    def get_server_connection(self, cc, scheme, host, port, sni, request=None):
        """
            When SNI is in play, this means we have an SSL-encrypted
            connection, which means that the entire handler is dedicated to a
            single server connection - no multiplexing. If this assumption ever
            breaks, we'll have to do something different with the SNI host
            variable on the handler object.

            `conn_info` holds the initial connection's parameters, as the
            hook might change them. Also, the hook might require an initial
            request to figure out connection settings; in this case it can
            set require_request, which will cause the connection to be
            re-opened after the client's request arrives.
        """
        sc = self.server_conn
        if not sni:
            sni = host
        conn_info = (scheme, host, port, sni)
        if sc and (conn_info != sc.conn_info or (request and sc.require_request)):
            sc.terminate()
            self.server_conn = None
            self.log(
                cc,
                "switching connection", [
                    "%s://%s:%s (sni=%s) -> %s://%s:%s (sni=%s)"%(
                        scheme, host, port, sni,
                        sc.scheme, sc.host, sc.port, sc.sni
                    )
                ]
            )
        if not self.server_conn:
            try:
                self.server_conn = ServerConnection(self.config, scheme, host, port, sni)

                # Additional attributes, used if the server_connect hook
                # needs to change parameters
                self.server_conn.request = request
                self.server_conn.require_request = False

                self.server_conn.conn_info = conn_info
                self.channel.ask("serverconnect", self.server_conn)
                self.server_conn.connect()
            except tcp.NetLibError, v:
                raise ProxyError(502, v)
        return self.server_conn

    def del_server_connection(self):
        if self.server_conn:
            self.server_conn.terminate()
        self.server_conn = None

    def handle(self):
        cc = flow.ClientConnect(self.client_address)
        self.log(cc, "connect")
        self.channel.ask("clientconnect", cc)
        while self.handle_request(cc) and not cc.close:
            pass
        cc.close = True
        self.del_server_connection()

        cd = flow.ClientDisconnect(cc)
        self.log(
            cc, "disconnect",
            [
                "handled %s requests"%cc.requestcount]
        )
        self.channel.tell("clientdisconnect", cd)

    def handle_request(self, cc):
        try:
            request, err = None, None
            request = self.read_request(cc)
            if request is None:
                return
            cc.requestcount += 1

            request_reply = self.channel.ask("request", request)
            if request_reply is None or request_reply == KILL:
                return
            elif isinstance(request_reply, flow.Response):
                request = False
                response = request_reply
                response_reply = self.channel.ask("response", response)
            else:
                request = request_reply
                if self.config.reverse_proxy:
                    scheme, host, port = self.config.reverse_proxy
                elif self.config.forward_proxy:
                    scheme, host, port = self.config.forward_proxy
                else:
                    scheme, host, port = request.scheme, request.host, request.port

                # If we've already pumped a request over this connection,
                # it's possible that the server has timed out. If this is
                # the case, we want to reconnect without sending an error
                # to the client.
                while 1:
                    sc = self.get_server_connection(cc, scheme, host, port, self.sni, request=request)
                    sc.send(request)
                    if sc.requestcount == 1: # add timestamps only for first request (others are not directly affected)
                        request.tcp_setup_timestamp = sc.tcp_setup_timestamp
                        request.ssl_setup_timestamp = sc.ssl_setup_timestamp
                    sc.rfile.reset_timestamps()
                    try:
                        peername = sc.connection.getpeername()
                        if peername:
                            request.ip = peername[0]
                        httpversion, code, msg, headers, content = http.read_response(
                            sc.rfile,
                            request.method,
                            self.config.body_size_limit
                        )
                    except http.HttpErrorConnClosed:
                        self.del_server_connection()
                        if sc.requestcount > 1:
                            continue
                        else:
                            raise
                    except http.HttpError:
                        raise ProxyError(502, "Invalid server response.")
                    else:
                        break

                response = flow.Response(
                    request, httpversion, code, msg, headers, content, sc.cert,
                    sc.rfile.first_byte_timestamp
                )
                response_reply = self.channel.ask("response", response)
                # Not replying to the server invalidates the server
                # connection, so we terminate.
                if response_reply == KILL:
                    sc.terminate()

            if response_reply == KILL:
                return
            else:
                response = response_reply
                self.send_response(response)
                if request and http.connection_close(request.httpversion, request.headers):
                    return
                # We could keep the client connection when the server
                # connection needs to go away.  However, we want to mimic
                # behaviour as closely as possible to the client, so we
                # disconnect.
                if http.connection_close(response.httpversion, response.headers):
                    return
        except (IOError, ProxyError, http.HttpError, tcp.NetLibError), e:
            if hasattr(e, "code"):
                cc.error = "%s: %s"%(e.code, e.msg)
            else:
                cc.error = str(e)

            if request:
                err = flow.Error(request, cc.error)
                self.channel.ask("error", err)
                self.log(
                    cc, cc.error,
                    ["url: %s"%request.get_url()]
                )
            else:
                self.log(cc, cc.error)
            if isinstance(e, ProxyError):
                self.send_error(e.code, e.msg, e.headers)
        else:
            return True

    def log(self, cc, msg, subs=()):
        msg = [
            "%s:%s: "%cc.address + msg
        ]
        for i in subs:
            msg.append("  -> "+i)
        msg = "\n".join(msg)
        l = Log(msg)
        self.channel.tell("log", l)

    def find_cert(self, cc, host, port, sni):
        if self.config.certfile:
            with open(self.config.certfile, "rb") as f:
                return certutils.SSLCert.from_pem(f.read())
        else:
            sans = []
            if not self.config.no_upstream_cert:
                conn = self.get_server_connection(cc, "https", host, port, sni)
                sans = conn.cert.altnames
                if conn.cert.cn:
                    host = conn.cert.cn.decode("utf8").encode("idna")
            ret = self.config.certstore.get_cert(host, sans, self.config.cacert)
            if not ret:
                raise ProxyError(502, "Unable to generate dummy cert.")
            return ret

    def establish_ssl(self, client_conn, host, port):
        dummycert = self.find_cert(client_conn, host, port, host)
        sni = HandleSNI(
            self, client_conn, host, port, self.config.certfile or self.config.cacert
        )
        try:
            self.convert_to_ssl(dummycert, self.config.certfile or self.config.cacert, handle_sni=sni)
        except tcp.NetLibError, v:
            raise ProxyError(400, str(v))

    def get_line(self, fp):
        """
            Get a line, possibly preceded by a blank.
        """
        line = fp.readline()
        if line == "\r\n" or line == "\n": # Possible leftover from previous message
            line = fp.readline()
        return line

    def read_request(self, client_conn):
        self.rfile.reset_timestamps()
        if self.config.transparent_proxy:
            return self.read_request_transparent(client_conn)
        elif self.config.reverse_proxy:
            return self.read_request_reverse(client_conn)
        else:
            return self.read_request_proxy(client_conn)

    def read_request_transparent(self, client_conn):
        orig = self.config.transparent_proxy["resolver"].original_addr(self.connection)
        if not orig:
            raise ProxyError(502, "Transparent mode failure: could not resolve original destination.")
        self.log(client_conn, "transparent to %s:%s"%orig)

        host, port = orig
        if port in self.config.transparent_proxy["sslports"]:
            scheme = "https"
        else:
            scheme = "http"

        return self._read_request_origin_form(client_conn, scheme, host, port)

    def read_request_reverse(self, client_conn):
        scheme, host, port = self.config.reverse_proxy
        return self._read_request_origin_form(client_conn, scheme, host, port)

    def read_request_proxy(self, client_conn):
        # Check for a CONNECT command.
        if not self.proxy_connect_state:
            line = self.get_line(self.rfile)
            if line == "":
                return None
            self.proxy_connect_state = self._read_request_authority_form(line)

        # Check for an actual request
        if self.proxy_connect_state:
            host, port, _ = self.proxy_connect_state
            return self._read_request_origin_form(client_conn, "https", host, port)
        else:
            # noinspection PyUnboundLocalVariable
            return self._read_request_absolute_form(client_conn, line)

    def _read_request_authority_form(self, line):
        """
        The authority-form of request-target is only used for CONNECT requests.
        The CONNECT method is used to request a tunnel to the destination server.
        This function sends a "200 Connection established" response to the client
        and returns the host information that can be used to process further requests in origin-form.
        An example authority-form request line would be:
            CONNECT www.example.com:80 HTTP/1.1
        """
        connparts = http.parse_init_connect(line)
        if connparts:
            self.read_headers(authenticate=True)
            # respond according to http://tools.ietf.org/html/draft-luotonen-web-proxy-tunneling-01 section 3.2
            self.wfile.write(
                'HTTP/1.1 200 Connection established\r\n' +
                ('Proxy-agent: %s\r\n'%self.server_version) +
                '\r\n'
            )
            self.wfile.flush()
        return connparts

    def _read_request_absolute_form(self, client_conn, line):
        """
        When making a request to a proxy (other than CONNECT or OPTIONS),
        a client must send the target uri in absolute-form.
        An example absolute-form request line would be:
            GET http://www.example.com/foo.html HTTP/1.1
        """
        r = http.parse_init_proxy(line)
        if not r:
            raise ProxyError(400, "Bad HTTP request line: %s"%repr(line))
        method, scheme, host, port, path, httpversion = r
        headers = self.read_headers(authenticate=True)
        self.handle_expect_header(headers, httpversion)
        content = http.read_http_body(
            self.rfile, headers, self.config.body_size_limit, True
        )
        r = flow.Request(
            client_conn, httpversion, host, port, scheme, method, path, headers, content,
            self.rfile.first_byte_timestamp, utils.timestamp()
        )
        r.set_live(self.rfile, self.wfile)
        return r

    def _read_request_origin_form(self, client_conn, scheme, host, port):
        """
        Read a HTTP request with regular (origin-form) request line.
        An example origin-form request line would be:
            GET /foo.html HTTP/1.1

        The request destination is already known from one of the following sources:
        1) transparent proxy: destination provided by platform resolver
        2) reverse proxy: fixed destination
        3) regular proxy: known from CONNECT command.
        """
        if scheme.lower() == "https" and not self.ssl_established:
            self.establish_ssl(client_conn, host, port)

        line = self.get_line(self.rfile)
        if line == "":
            return None

        r = http.parse_init_http(line)
        if not r:
            raise ProxyError(400, "Bad HTTP request line: %s"%repr(line))
        method, path, httpversion = r
        headers = self.read_headers(authenticate=False)
        self.handle_expect_header(headers, httpversion)
        content = http.read_http_body(
            self.rfile, headers, self.config.body_size_limit, True
        )
        r = flow.Request(
            client_conn, httpversion, host, port, scheme, method, path, headers, content,
            self.rfile.first_byte_timestamp, utils.timestamp()
        )
        r.set_live(self.rfile, self.wfile)
        return r

    def handle_expect_header(self, headers, httpversion):
        if "expect" in headers:
            if "100-continue" in headers['expect'] and httpversion >= (1, 1):
                #FIXME: Check if content-length is over limit
                self.wfile.write('HTTP/1.1 100 Continue\r\n'
                                 '\r\n')
                del headers['expect']

    def read_headers(self, authenticate=False):
        headers = http.read_headers(self.rfile)
        if headers is None:
            raise ProxyError(400, "Invalid headers")
        if authenticate and self.config.authenticator:
            if self.config.authenticator.authenticate(headers):
                self.config.authenticator.clean(headers)
            else:
                raise ProxyError(
                            407,
                            "Proxy Authentication Required",
                            self.config.authenticator.auth_challenge_headers()
                       )
        return headers

    def send_response(self, response):
        d = response._assemble()
        if not d:
            raise ProxyError(502, "Cannot transmit an incomplete response.")
        self.wfile.write(d)
        self.wfile.flush()

    def send_error(self, code, body, headers):
        try:
            response = http_status.RESPONSES.get(code, "Unknown")
            html_content = '<html><head>\n<title>%d %s</title>\n</head>\n<body>\n%s\n</body>\n</html>'%(code, response, body)
            self.wfile.write("HTTP/1.1 %s %s\r\n" % (code, response))
            self.wfile.write("Server: %s\r\n"%self.server_version)
            self.wfile.write("Content-type: text/html\r\n")
            self.wfile.write("Content-Length: %d\r\n"%len(html_content))
            if headers:
                for key, value in headers.items():
                    self.wfile.write("%s: %s\r\n"%(key, value))
            self.wfile.write("Connection: close\r\n")
            self.wfile.write("\r\n")
            self.wfile.write(html_content)
            self.wfile.flush()
        except:
            pass


class ProxyServerError(Exception): pass


class ProxyServer(tcp.TCPServer):
    allow_reuse_address = True
    bound = True
    def __init__(self, config, port, address='', server_version=version.NAMEVERSION):
        """
            Raises ProxyServerError if there's a startup problem.
        """
        self.config, self.port, self.address = config, port, address
        self.server_version = server_version
        try:
            tcp.TCPServer.__init__(self, (address, port))
        except socket.error, v:
            raise ProxyServerError('Error starting proxy server: ' + v.strerror)
        self.channel = None

    def start_slave(self, klass, channel):
        slave = klass(channel, self)
        slave.start()

    def set_channel(self, channel):
        self.channel = channel

    def handle_connection(self, request, client_address):
        h = ProxyHandler(self.config, request, client_address, self, self.channel, self.server_version)
        h.handle()
        h.finish()


class DummyServer:
    bound = False
    def __init__(self, config):
        self.config = config

    def start_slave(self, *args):
        pass

    def shutdown(self):
        pass


# Command-line utils
def certificate_option_group(parser):
    group = parser.add_argument_group("SSL")
    group.add_argument(
        "--cert", action="store",
        type = str, dest="cert", default=None,
        help = "User-created SSL certificate file."
    )
    group.add_argument(
        "--client-certs", action="store",
        type = str, dest = "clientcerts", default=None,
        help = "Client certificate directory."
    )



def process_proxy_options(parser, options):
    if options.cert:
        options.cert = os.path.expanduser(options.cert)
        if not os.path.exists(options.cert):
            return parser.error("Manually created certificate does not exist: %s"%options.cert)

    cacert = os.path.join(options.confdir, "mitmproxy-ca.pem")
    cacert = os.path.expanduser(cacert)
    if not os.path.exists(cacert):
        certutils.dummy_ca(cacert)
    body_size_limit = utils.parse_size(options.body_size_limit)
    if options.reverse_proxy and options.transparent_proxy:
        return parser.error("Can't set both reverse proxy and transparent proxy.")

    if options.transparent_proxy:
        if not platform.resolver:
            return parser.error("Transparent mode not supported on this platform.")
        trans = dict(
            resolver = platform.resolver(),
            sslports = TRANSPARENT_SSL_PORTS
        )
    else:
        trans = None

    if options.reverse_proxy:
        rp = utils.parse_proxy_spec(options.reverse_proxy)
        if not rp:
            return parser.error("Invalid reverse proxy specification: %s"%options.reverse_proxy)
    else:
        rp = None

    if options.forward_proxy:
        fp = utils.parse_proxy_spec(options.forward_proxy)
        if not fp:
            return parser.error("Invalid forward proxy specification: %s"%options.forward_proxy)
    else:
        fp = None

    if options.clientcerts:
        options.clientcerts = os.path.expanduser(options.clientcerts)
        if not os.path.exists(options.clientcerts) or not os.path.isdir(options.clientcerts):
            return parser.error(
                    "Client certificate directory does not exist or is not a directory: %s"%options.clientcerts
                )

    if (options.auth_nonanonymous or options.auth_singleuser or options.auth_htpasswd):
        if options.auth_singleuser:
            if len(options.auth_singleuser.split(':')) != 2:
                return parser.error("Invalid single-user specification. Please use the format username:password")
            username, password = options.auth_singleuser.split(':')
            password_manager = http_auth.PassManSingleUser(username, password)
        elif options.auth_nonanonymous:
            password_manager = http_auth.PassManNonAnon()
        elif options.auth_htpasswd:
            try:
                password_manager = http_auth.PassManHtpasswd(options.auth_htpasswd)
            except ValueError, v:
                return parser.error(v.message)
        authenticator = http_auth.BasicProxyAuth(password_manager, "mitmproxy")
    else:
        authenticator = http_auth.NullProxyAuth(None)

    return ProxyConfig(
        certfile = options.cert,
        cacert = cacert,
        clientcerts = options.clientcerts,
        body_size_limit = body_size_limit,
        no_upstream_cert = options.no_upstream_cert,
        reverse_proxy = rp,
        forward_proxy = fp,
        transparent_proxy = trans,
        authenticator = authenticator
    )