#!/usr/bin/env python2
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2011 thomasv@gitorious
#
# This program 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.
#
# This program 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 this program. If not, see <http://www.gnu.org/licenses/>.


import copy, re, errno, os
import threading, traceback, sys, time, Queue
import socket
import ssl

import requests
ca_path = requests.certs.where()

import util
import x509
from version import ELECTRUM_VERSION, PROTOCOL_VERSION
from simple_config import SimpleConfig


def Interface(server, response_queue, config = None):
    """Interface factory function.  The returned interface class handles the connection
    to a single remote electrum server.  The object handles all necessary locking.  It's
    exposed API is:

    - Inherits everything from threading.Thread.
    - Member functions send_request(), stop(), is_connected()
    - Member variable server.
    
    "server" is constant for the object's lifetime and hence synchronization is unnecessary.
    """
    host, port, protocol = server.split(':')
    if protocol in 'st':
        return TcpInterface(server, response_queue, config)
    else:
        raise Exception('Unknown protocol: %s'%protocol)

# Connection status
CS_OPENING, CS_CONNECTED, CS_FAILED = range(3)

class TcpInterface(threading.Thread):

    def __init__(self, server, response_queue, config = None):
        threading.Thread.__init__(self)
        self.daemon = True
        self.config = config if config is not None else SimpleConfig()
        # Set by stop(); no more data is exchanged and the thread exits after gracefully
        # closing the socket
        self.disconnect = False
        self._status = CS_OPENING
        self.debug = False # dump network messages. can be changed at runtime using the console
        self.message_id = 0
        self.response_queue = response_queue
        self.request_queue = Queue.Queue()
        self.unanswered_requests = {}
        # request timeouts
        self.request_time = time.time()
        self.ping_time = 0
        # parse server
        self.server = server
        self.host, self.port, self.protocol = self.server.split(':')
        self.host = str(self.host)
        self.port = int(self.port)
        self.use_ssl = (self.protocol == 's')

    def print_error(self, *msg):
        util.print_error("[%s]"%self.host, *msg)

    def process_response(self, response):
        if self.debug:
            self.print_error("<--", response)

        msg_id = response.get('id')
        error = response.get('error')
        result = response.get('result')

        if msg_id is not None:
            method, params, _id, queue = self.unanswered_requests.pop(msg_id)
            if queue is None:
                queue = self.response_queue
        else:
            # notification
            method = response.get('method')
            params = response.get('params')
            _id = None
            queue = self.response_queue
            # restore parameters
            if method == 'blockchain.numblocks.subscribe':
                result = params[0]
                params = []
            elif method == 'blockchain.headers.subscribe':
                result = params[0]
                params = []
            elif method == 'blockchain.address.subscribe':
                addr = params[0]
                result = params[1]
                params = [addr]

        if method == 'server.version':
            self.server_version = result
            return

        if error:
            queue.put((self, {'method':method, 'params':params, 'error':error, 'id':_id}))
        else:
            queue.put((self, {'method':method, 'params':params, 'result':result, 'id':_id}))


    def get_simple_socket(self):
        try:
            l = socket.getaddrinfo(self.host, self.port, socket.AF_UNSPEC, socket.SOCK_STREAM)
        except socket.gaierror:
            self.print_error("cannot resolve hostname")
            return
        for res in l:
            try:
                s = socket.socket(res[0], socket.SOCK_STREAM)
                s.connect(res[4])
                s.settimeout(2)
                s.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
                return s
            except BaseException as e:
                continue
        else:
            self.print_error("failed to connect", str(e))


    def get_socket(self):
        if self.use_ssl:
            cert_path = os.path.join( self.config.path, 'certs', self.host)
            if not os.path.exists(cert_path):
                is_new = True
                s = self.get_simple_socket()
                if s is None:
                    return
                # try with CA first
                try:
                    s = ssl.wrap_socket(s, ssl_version=ssl.PROTOCOL_SSLv23, cert_reqs=ssl.CERT_REQUIRED, ca_certs=ca_path, do_handshake_on_connect=True)
                except ssl.SSLError, e:
                    s = None
                if s and check_host_name(s.getpeercert(), self.host):
                    self.print_error("SSL certificate signed by CA")
                    return s

                # get server certificate.
                # Do not use ssl.get_server_certificate because it does not work with proxy
                s = self.get_simple_socket()
                if s is None:
                    return
                try:
                    s = ssl.wrap_socket(s, ssl_version=ssl.PROTOCOL_SSLv23, cert_reqs=ssl.CERT_NONE, ca_certs=None)
                except ssl.SSLError, e:
                    self.print_error("SSL error retrieving SSL certificate:", e)
                    return

                dercert = s.getpeercert(True)
                s.close()
                cert = ssl.DER_cert_to_PEM_cert(dercert)
                # workaround android bug
                cert = re.sub("([^\n])-----END CERTIFICATE-----","\\1\n-----END CERTIFICATE-----",cert)
                temporary_path = cert_path + '.temp'
                with open(temporary_path,"w") as f:
                    f.write(cert)
            else:
                is_new = False

        s = self.get_simple_socket()
        if s is None:
            return

        if self.use_ssl:
            try:
                s = ssl.wrap_socket(s,
                                    ssl_version=ssl.PROTOCOL_SSLv23,
                                    cert_reqs=ssl.CERT_REQUIRED,
                                    ca_certs= (temporary_path if is_new else cert_path),
                                    do_handshake_on_connect=True)
            except ssl.SSLError, e:
                self.print_error("SSL error:", e)
                if e.errno != 1:
                    return
                if is_new:
                    rej = cert_path + '.rej'
                    if os.path.exists(rej):
                        os.unlink(rej)
                    os.rename(temporary_path, rej)
                else:
                    with open(cert_path) as f:
                        cert = f.read()
                    try:
                        x = x509.X509()
                        x.parse(cert)
                    except:
                        traceback.print_exc(file=sys.stderr)
                        self.print_error("wrong certificate")
                        return
                    try:
                        x.check_date()
                    except:
                        self.print_error("certificate has expired:", cert_path)
                        os.unlink(cert_path)
                        return
                    self.print_error("wrong certificate")
                return
            except BaseException, e:
                self.print_error(e)
                if e.errno == 104:
                    return
                traceback.print_exc(file=sys.stderr)
                return

            if is_new:
                self.print_error("saving certificate")
                os.rename(temporary_path, cert_path)

        return s

    def send_request(self, request, response_queue = None):
        '''Queue a request.  Blocking only if called from other threads.'''
        self.request_time = time.time()
        self.request_queue.put((copy.deepcopy(request), response_queue), threading.current_thread() != self)

    def send_requests(self):
        '''Sends all queued requests'''
        while self.is_connected() and not self.request_queue.empty():
            request, response_queue = self.request_queue.get()
            method = request.get('method')
            params = request.get('params')
            r = {'id': self.message_id, 'method': method, 'params': params}
            try:
                self.pipe.send(r)
            except socket.error, e:
                self.print_error("socket error:", e)
                self.stop()
                return
            if self.debug:
                self.print_error("-->", r)
            self.unanswered_requests[self.message_id] = method, params, request.get('id'), response_queue
            self.message_id += 1

    def is_connected(self):
        '''True if status is connected'''
        return self._status == CS_CONNECTED and not self.disconnect

    def stop(self):
        if not self.disconnect:
            self.disconnect = True
            self.print_error("disconnecting")

    def maybe_ping(self):
        # ping the server with server.version
        if time.time() - self.ping_time > 60:
            self.send_request({'method':'server.version', 'params':[ELECTRUM_VERSION, PROTOCOL_VERSION]})
            self.ping_time = time.time()
        # stop interface if we have been waiting for more than 10 seconds
        if self.unanswered_requests and time.time() - self.request_time > 10 and self.pipe.idle_time() > 10:
            self.print_error("interface timeout", len(self.unanswered_requests))
            self.stop()

    def get_and_process_response(self):
        if self.is_connected():
            try:
                response = self.pipe.get()
            except util.timeout:
                return
            # If remote side closed the socket, SocketPipe closes our socket and returns None
            if response is None:
                self.disconnect = True
                self.print_error("connection closed remotely")
            else:
                self.process_response(response)

    def run(self):
        s = self.get_socket()
        if s:
            self.pipe = util.SocketPipe(s)
            s.settimeout(0.1)
            self.print_error("connected")
            self._status = CS_CONNECTED
            # Indicate to parent that we've connected
            self.notify_status()
            while self.is_connected():
                self.maybe_ping()
                self.send_requests()
                self.get_and_process_response()
            s.shutdown(socket.SHUT_RDWR)
            s.close()

        # Also for the s is None case 
        self._status = CS_FAILED
        # Indicate to parent that the connection is now down
        self.notify_status()

    def notify_status(self):
        '''Notify owner that we have just connected or just failed the connection.
        Owner determines which through e.g. testing is_connected()'''
        self.response_queue.put((self, None))


def _match_hostname(name, val):
    if val == name:
        return True

    return val.startswith('*.') and name.endswith(val[1:])


def check_host_name(peercert, name):
    """Simple certificate/host name checker.  Returns True if the
    certificate matches, False otherwise."""
    # Check that the peer has supplied a certificate.
    # None/{} is not acceptable.
    if not peercert:
        return False
    if peercert.has_key("subjectAltName"):
        for typ, val in peercert["subjectAltName"]:
            if typ == "DNS" and _match_hostname(name, val):
                return True
    else:
        # Only check the subject DN if there is no subject alternative
        # name.
        cn = None
        for attr, val in peercert["subject"]:
            # Use most-specific (last) commonName attribute.
            if attr == "commonName":
                cn = val
        if cn is not None:
            return _match_hostname(name, cn)
    return False


def check_cert(host, cert):
    try:
        x = x509.X509()
        x.parse(cert)
    except:
        traceback.print_exc(file=sys.stdout)
        return

    try:
        x.check_date()
        expired = False
    except:
        expired = True

    m = "host: %s\n"%host
    m += "has_expired: %s\n"% expired
    util.print_msg(m)


def test_certificates():
    config = SimpleConfig()
    mydir = os.path.join(config.path, "certs")
    certs = os.listdir(mydir)
    for c in certs:
        print c
        p = os.path.join(mydir,c)
        with open(p) as f:
            cert = f.read()
        check_cert(c, cert)

if __name__ == "__main__":
    test_certificates()
